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TrueGrid ® Tutorial

1. In case of a mistake deactivate the projection command by pressing the Undo button in the Edit button group of the Environment Window History Resume Pressing the Undo button will undo the last active meshing command So pressing the Undo button many times will undo many meshing commands The Undo feature does not apply to graphics commands There are more sophisticated ways to selectively deactivate meshing commands Such techniques will be discussed later Copyright 2001 by XYZ Scientific Applications Inc It should not be difficult to finish this problem There are four other projection commands required The minimum 1 face should be projected to the plane on the left surface definition 2 The maximum 1 face should be projected to the plane on the right surface definition 3 The minimum j face bottom should be projected to the bottom sphere surface definition 4 The maximum j face top should be projected to the top sphere surface definition 5 Keep in mind that the F2 KEY clears the computational selection and that Undo will reverse the effects of any meshing command such as a projection In the next sections there is more about the activating and deactivating commands more about the computational highlighting system and information concerning how this single block mesh is handled internally All of these sections reference this example TrueGrid Tutorial 27 More
2. When TrueGrid reaches another interrupt command or the end of the input file another interactive session begins The new session file produced will contain all the interactive and input file commands in the order in which they were issued The interrupt commands will be removed TrueGrid Tutorial The Session and Input File Format The session file is an ASCH file that is easily edited Only the first 80 characters of a line are considered by TrueGrid Within a session file it is permissible to Use upper or lower case letters Insert a comment anywhere Use any format for numbers Insert extra spaces anywhere Break a command across lines Insert graphics commands or Insert interrupt commands SWAN RWN Comments are placed in the input file by placing a single c or C either at the beginning of the line or sandwiched between at least one space All characters after the c and on the same line are treated as part of the comment A comment may be inserted in the middle of a command For example TrueGrid has no problem processing c Create the Block Part DLOCK c Determine the Node G Distr Lour ron L Oe aeoe Oe 36 alse to 868 kage c Specify the Coordinates A A X COOrOtMaces 6 p lt c y CoOordinatLes 2 2 BZ Coordina eE TrueGrid uses a flexible format for numbers as well For example if TrueGrid is looking for a floating point number then any of the following will work
3. 3 The name of the file used with either the igesfile or iges command must be exactly the same as when saveiges was issued IGES Levels Layers and Groups The layer or level feature commonly found in CAD systems can be used to organize the geometry for TrueGrid use The associativity instance is used for grouping the entities into levels TrueGrid preserves this level structure TrueGrid Tutorial Interactive Graphics Mouse Selection of Geometry Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial 13 TrueGrid Graphics TrueGrid provides dynamic control for rotating translating and zooming Also provided is readily accessible control over what curves surfaces regions etc are in the picture and whether or not they are labeled Example Run TrueGrid using the command t g with no command line options There is no graphics capability in the Control Phase of the code so issue the command merge to enter the Merge Phase of the code Next create a couple of surfaces using the Surface Definition command sa l gyli 2 000 0 sd 2 plan 1 00 1 1 0 0 0 The first surface is a right circular cylinder of radius 2 whose axis of rotation passes through 0 0 0 and is parallel to 0 1 0 The second surface is a plane passing through 1 0 0 and normal to 1 0 0 The current picture in the Physical Window should appear similar to the one below Even though the plane is actually
4. The final interactive positioning commands are used to initialize the isolated block of the mesh near the cylindrical pipe Issue these graphics commands to center the right end of the cylindrical pipe in the picture REST L O04359 D 04175 ZF 20 60 Copyright 2001 by XYZ Scientific Applications Inc Right End of the Small Pipe The resulting Physical picture is shown below The goal is to position the edges on the right side of the isolated block of the mesh around the perimeter of the cylindrical pipe An edge of the mesh is highlighted when a single dot is highlighted on each of two index bars and when only segments are highlighted on the other index bar The two dots determine two planes The intersection of the two planes is an edge Choosing segments in the other direction serves to restrict the edge Many mesh edges can be selected at once but all edges in a single selection must be aligned in the same direction Mesh edges are highlighted blue The first edge to be moved is pictured below Use the Screen Plane option to position this edge near Point A of the previous diagram TrueGrid Tutorial A N W AN W NO I 2 3 Gann Y Position this Edge Near Point A Highlight the next edge to be moved by altering the current selection deactivate the third j index dot and activate the second jJ index dot instead Use the Screen Plane option and position this edge near Point B All points of
5. Removing an Object from the picture is done by highlighting the object using the label highlighting feature described above and then by pressing the Remove button with the left mouse button To Remove All Objects Except One highlight the object to remain using the label highlighting feature described above 18 Copyright 2001 by XYZ Scientific Applications Inc and then press the Show Only button with the left mouse button Remove All Objects of the Specified Class by pressing the Show None button with the left mouse button Removing all surfaces for example makes the mesh easier to view Add All Objects of the Specified Class to the picture by pressing the Show All button with the left mouse button The Add Feature also works on selected objects Using the Computational Highlighting System for the mesh in the Part Phase it is possible to select a region of the mesh that is not in the picture Such a region is then added to the picture by pressing the Add button with the left mouse button Notice that the Region button is grayed out in the Merge Phase because it is not possible to point to a region of the mesh in this phase of the code TrueGrid Tutorial Controlling the Picture From the Command Line All of the interactive functions presented so far except for the frame feature correspond to commands that can be issued from the text and menu window of TrueGrid On the other hand there are graphics comm
6. The effects of perspective are detrimental to such alignment So turn perspective off with angle 0 Frame the lower end of the pipe by issuing these graphics commands REOT RX 90 D 0 19 ZF l2 The REST command puts the picture in a default position first The other commands Rotate the picture about the X axis translate the picture Left and Zoom Forward Copyright 2001 by XYZ Scientific Applications Inc A Close Up of the Lower Pipe End Use the Frame graphics option to isolate the intersection of the left alignment marker with the semi circular edge of the elbow pipe surface Display the labels of points on defined surfaces press the Surf Point button in the Labels dialogue of the Environment Window 47 31 47 30 747 29 7 28 1 22 77 47 21 1 21 79 x Surface Point Labels Near the Left Alignment Mark The point corresponding to a label is indicated with a small Choose the label of the point on the surface edge nearest the vertical alignment mark For the version of TrueGrid used while making this tutorial TrueGrid Tutorial 55 the alignment mark intersects the surface edge at a point whose label is 1 47 28 Make arecord of the label number you found Use the Move graphics feature of TrueGrid to move the picture left until the yellow alignment mark on the right appears Choose the label of the point on the edge of the elbow pipe surface nearest the vertical alignment mark For v
7. Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Supported Geometry Importing IGES Files 10 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Internal Geometry Library TrueGrid can create a wide variety of surface types such as sphere plane cylinder cone torus surface of revolution ruled surface Swept surface using skinning extruded surface general cylinders surface interpolated between two other surfaces tabulated surface consisting of a 2D array of points surface composed of multi sided polygons pipe surface from a 3D curve surface given by equations cubic spline surface B spline surface NURBS surface Stereo Lithography surfaces compositions of any of the above An extensive set of options for building 2D and 3D curves is also provided within TrueGrid For more information issue the help command for Id in the 2D CURVE sub menu sd is the SURFACE sub menu or curd in the 3D CURVE sub menu Importing IGES Entities TrueGrid can extract most surface and curve entities from an IGES file We presently support the following IGES Entities 100 Circular Arc 102 Composite Curve 104 Conic Arc 108 Plane 110 Line 112 Parametric Spline Curve 114 Parametric Spline Surface 118 Ruled Surface 120 Surface of Revolution 122 Tabulated Cylinder 124 Transformation Matrix 126 NURBS Curve 128 NURBS Surf
8. add and remove surfaces Pick Move Pts DER one hit Labels Apply Action to Material Show Only Curve Part Show All Point Region Action Show None BB Copyright 2001 by XYZ Scientific Applications Inc Press the Region button under the Apply Action To category Then press the Show Only button under the Action category TrueGrid now shows only the highlighted selection Nothing has been deleted only removed from the picture Because the current selection consists of the faces of the hole projected to the sphere only these faces are shown Now clear the highlighting by pressing the F2 KEY Activate the second dot on the j index bar corresponding to the second J partition While the Region button is still pressed press the Add button in the Action category The Physical Picture which contains the actual mesh appears as below Only Part of the Mesh TrueGrid Tutorial 43 By activating only the second dot on the j index bar you selected the entire second jJ partition Then by pressing the Add button you added this entire partition to the picture Notice how easy it is to point to a region that is not in the picture and add it to the picture With no other object is this possible For in order to point to another type of object that object must already be in the picture About the Mesh Each of the 27 blocks i
9. and remove the menu press the upward pointing arrow appearing on the right of the text menu window or press the Page Up key or the Up Arrow key on the keyboard while the cursor is in the text window Any of these actions indicate to TrueGrid that you wish to view more of the previous text In such cases the text area expands to fill the window thereby making more of the previous text visible To scroll through the text either use the Page Up Page Down Up Arrow or Down Arrow keyboard keys or use the scroll bar Pressing the left mouse button on the arrows above the scroll bar moves text by pages Pressing the middle mouse button on the arrows moves the text by lines Getting Help For a Main Menu In the main menu area of the text menu window there are two grey buttons the HELP button and the EXIT button Press the EXIT button with the left mouse button to quit TrueGrid without confirmation Toe ae ba mi eee ee Pe ECO T E i PPLE Cia A ED T a ria raar T Eal e a T t _ ne f A Loe d ME ee Ae re BLD Bae ae eee eee Press the HELP button to activate the help system Normally pressing the left mouse button on an entry of the main menu causes a submenu to appear However when the HELP button is on pressing the left mouse button on a main menu entry calls up a Help Window containing information about all the commands in the given category TrueGrid Tutorial 5 echo a Do character niring bo ihe E
10. highlighted These faces can be simultaneously selected for just this purpose The Computational Highlighting System of TrueGrid is the general purpose tool for selecting and examining parts of the mesh Copyright 2001 by XYZ Scientific Applications Inc The first component of this unique highlighting system is a Slicing Plane illustrated below The slicing plane feature is activated whenever the mouse is moved into the Computational Window near one of the dots of the index bars The dot near the mouse turns white and a corresponding block TrueGrid Tutorial 25 face in the Computational Window is highlighted in white I 2 dA The Minimum k Slicing Plane The corresponding mesh face in the Physical Window is also highlighted in white MSNS SSSSSSSS iit mi ON a HITT Y Te HEN jii i Sl A N SASSA N AAA a n ee wns T Corresponding Physical Mesh Face Notice that in this example when the mouse is near the left most dot of the upper index bar that the back face of mesh is highlighted Dots on the lower index bar correspond to faces where the 1 index is held constant dots on the right index bar correspond to constant j index faces dots on the top index bar correspond to constant k index faces By 26 Copyright 2001 by XYZ Scientific Applications Inc convention the actual values of fixed indices increase from left to right and bottom to top Now select the bac
11. is AN AHH AHT W WY AN mae L Z Z EPF ER EZ LESS LI S 22 HAHH aih N SA KSS w AS ADH AY HH HIT TT ZEEE i LG MMM SSN ZL 7 YD WO WN XY N NN N N AT LLL L LL MUE NG K at 7 a WN WS NN S Zz G72 if O N NY GZ WY W M j W VA N N N NNN A Intersecting Pipes with Node Clustering Toward Walls Getting Started Run TrueGrid with no input file Enter the Merge Phase by typing the command merge followed by areturn This allows you to view the geometry for the problem as it is created The Geometry The geometry for this problem is more complex than for previous examples The elbow pipe is created using a technique of skinning whereby 2D cross sections of the pipe are specified along a 2D curve A dialogue box for the 2D Line Definition command is accessed by moving to the 2D CURVE submenu and then by pressing the left mouse button on the LD button TrueGrid Tutorial 51 Lists are sometimes too long to fit fully within the dialogue window The Page Up Page Down Up Arrow and Down Arrow keys can be used to scroll Or the arrows at the top can be used to scroll the text Press the left mouse button on an arrow to scroll a page at a time Press the middle mouse button on an arrow to scroll a line at a time There is yet another option for the dialog
12. whenever a new picture is generated Also if the user changes the type of picture to be drawn Wire Hide Fill option a new picture is not automatically redrawn the user needs to tell TrueGrid to redraw the picture There are three basic ways to regenerate the picture The first uses the Draw option Invoking the Draw option by pressing the Draw button with the left mouse button causes the code to execute all buffered commands and to generate a picture of the specified type Wire Hide or Fill in the same position and orientation as the previous picture The Center option is used to adjust the picture so that all objects are fully visible within the window The Center command leaves the rotational orientation of the picture the same as for the previous picture TrueGrid Tutorial The Restore option also makes sure all objects are visible However the Restore command puts the picture back to the home default rotational orientation The Center and Rest commands are especially useful when objects are added or removed from the picture or if the user gets lost in the picture Locating Objects Using Labels Pick Move Pts Display List PARA Beams Part Surface Shells BB Surf Edge Q Shells Node Surf Point Bricks Curve _ Q Bricks Off Curve Point Labels play an important role in interactive mesh g
13. Square Peg in a Round Hole An example of a double butterfly mesh is shown at the end of this section The butterfly mesh is much better near the boundaries of the pipes However some simulation codes cannot deal with the complicated structure of the double butterfly More importantly implementing a butterfly mesh in this example would have made it more complicated than appropriate for a beginner s tutorial Everywhere except near where block corners are folded out to lie on the pipe the mesh is quite good The mesh is even better if the ends of the pipes are relaxed and then solid regions are relaxed For example try these commands emer 2 Ves Or aed oe ur iO a tmei i 22 Ask 3330 0 1 The first Thomas Mbiddlecoff Elliptic relaxation command smooths the two ends of the elbow pipe The second smooths the interior using the walls of the pipe as boundary conditions Each performs 30 iterations of the relaxation method The tmei command is better than usual techniques of elliptic relaxation for problems where elements need to be nearly orthogonal to the boundary Furthermore this type of smoothing tends to better respect zoning requirements than other elliptic relaxation TrueGrid Tutorial methods Note that TrueGrid also supports equi potential relaxation relax Part Replication Most simulation codes deal nicely with planes of symmetry Therefore this half model is good enough in most cases However it is
14. and reactivated 3 TrueGrid is a WYSIWYG What you see is what you get the actual mesh is shown at all times 4 The most frequently used mesh generation commands can be performed using the mouse 5 The mesh can be interactively refined 6 TrueGrid produces clean session files that can be easily edited rerun and interrupted for interactive mesh editing TrueGrid Tutorial The Phases of TrueGrid TrueGrid behaves in different ways depending on what commands have been issued so far When the command tg is first issued a text and menu window appears on the screen in the upper left corner The initial title of this window is Control Phase The title of this particular window will always indicate the current phase of TrueGrid Because the current phase depends on the commands issued the text and menu window title changes depending on the commands issued interactively and or read from a batch file The Control Phase the initial phase of the code is where output options are chosen material models defined geometry created and where parameters governing the final mesh output file are set No graphical capabilities are available in the Control Phase The Part Phase is entered as soon as a block mesh is created using either the block or cylinder command Three new windows appear in the Part Phase the Computational Window used for displaying logical blocks of the mesh the Physical Window used for display
15. demonstrates that a block structured mesh of the intersecting pipe problem can be created which does not suffer from the side effect of putting a square peg into a round role This example file is called dblbtrf Try a little zoning and relaxation on the model Examine the block structure It s an interesting example The Double Butterfly Mesh 70 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial 71 ee SSS SS SS Be a SS D aa TEER Scientific Applications Inc 1324 Concannon Blvd Livermore CA 94550 925 373 0628 SS SS A f f f IA SD T N W j i B M4 3 K X N 9 LY y o 1 i ae N XN y S 4 SPVA KOI LON RUIN SSH Ne SY OS J y l f Nall s N X 5 wi i W 4 W aN WK Ni Hes 4 XY LZ KITT a SA SSIS SLS STETA AA E ERN EN ENEA NRA RO NSN N SES x W XI i Sh SK SSS 9077 yA x re LA ii a rb P PIRN QQ KI QY N NAAN ERAN LIQ WY D NNN TrueGrid Tutorial Copyright 2001 by XYZ Scientific Applications Inc 72
16. lie Then TrueGrid equally spaces these nodes along this intersection curve because there are no clustering requirements in this case Step 3 Edges are Projected TrueGrid Tutorial 29 Step 4 Using the edges all faces of the mesh are now interpolated Many faces end up by accident in their final positions For example the faces that must lie on planes have edges that already lie on planes and consequently the interpolated faces end up on planes However the top and bottom ends of the rod are not correctly positioned The top and bottom ends are required to be on spheres Step 4 Interpolate Block Faces Step 5 The interior nodes of faces of the mesh are now projected onto the surfaces on which they are required to lie Nearly all nodes were already correctly positioned by accident Only the top and bottom ends of the rod which must lie on spheres end up being repositioned At this point the mesh appears to be finished However there is no telling where the interior nodes may be at this point Because the interior nodes of the block not pictured have never been touched it is even possible that some of these nodes now lie outside the volume of the actual problem 30 Copyright 2001 by XYZ Scientific Applications Inc Project the Face TrueGrid display Z Step 5 Block Faces are Projected Step 6 As a final step the interior nodes of the block are interpolated using the positions of the n
17. menu category A submenu is viewed by pressing the left mouse button on a category of the main menu Aie Tara rel Ham ER ee ee ee a a A A L Me ee fO DEd g e ae g PE n T F 6 Copyright 2001 by XYZ Scientific Applications Inc while the HELP button is off ee ee ees E ee ee Oe Me ee ee ee i Th au Each submenu contains two grey buttons a MAIN MENU button and a HELP button Press the MAIN MENU button to return to the main menu The HELP button of a submenu works the same as that of the main menu Each submenu also contains as its first entry a red button which indicates the name of the current submenu The red button is not an active button Getting Help For a Submenu Item When the mouse is moved onto a command button in the submenu a bar appears above the text menu window with a short description of that command oe be m Se Ree Fle _ e Ca nip ME ee ee ee eee ee The help system works the same as for the main menu but the Help Window for a command in a submenu is far more specific The first part of the help for a command is in white with black print This part is extracted from the main menu help i aii Wbp Gnl wan m amp pol Ar tar heh otii a feetore H the auriei The Ile uate at Tected bij Uhja comer Disi froga LPa VPS commer fred thee SE ei he Le HL ar AST options A Pasture m sien an on inter lor wipe That leterior mip are ie Pail ae wLim irn mipan of the mnh i
18. nearly ideal Such contours can be converted to 3D Curves in TrueGrid for just such a purpose When a contour used for graphical purposes is converted to a curve all points on that curve are written to the session file This is because the way that TrueGrid tiles a surface for graphical purposes may vary between versions However writing all points of the curve to the session file creates a permanent record of the curve The variation in graphics also creates a problem in describing how to locate the surface contours used in this example Our solution is to specify some 3D line segments that serve as markers The user is then asked to locate surface contours ending near these markers Create the markers for this problem with the 3D CUR ve Definition command curd Two such markers are required Curd gt Ipo 244s 3242 045 Se LAS S3I4Z S 0S curd 4 tps Za AIAGA 045 2 8495464 3 UF A A These commands define segments joining two 3D points The segments should align with the endpoints of certain contours on the elbow pipe However do not be alarmed if the alignment in this version is not so precise TrueGrid Tutorial Make sure all surfaces and curves are displayed use either the Display List dialogue in the Environment Window or dasd dacd The alignment marks are yellow and are located at the lower end of the elbow pipe Arrows Point to Alignment Marks Visual alignment is required in this example
19. of the block command Therefore there were just two partitions in each direction leading to a computational representation which was a single cube The Consequences of Having Partitions Each of the 27 blocks of the current mesh are treated as though they were single block meshes In particular it is not possible to delete only part of a block It is not possible to project only part of a block face onto a surface It is not possible to zone just part of a block edge Furthermore the same interpolation used to position the nodes within a single block mesh is used here The coordinates of corner nodes Copyright 2001 by XYZ Scientific Applications Inc of blocks are used to interpolate edge node coordinates Edge node positions are then used to interpolate face nodes Face node positions are used to interpolate interior nodes So even though only corner node coordinates of the 27 blocks were specified using the block command all nodes of the mesh have coordinates assigned to them Because of the way that individual blocks are treated any unaltered mesh created using the block command will always consist of rectangular boxes whose nodes are equally spaced in the 1 direction equally spaced in the j direction and equally spaced in the k direction However globally this need not be true because adjacent blocks do not necessarily contain the same number of nodes All that can be said in general is that all blocks betwee
20. perpendicular to the x y plane it appears somewhat slanted This is because perspective is added to the picture 1 e distant parts of the picture are smaller The various circular cross sections of the cylinder differ from each other for the same reason The perspective angle the angle between the center of the picture and the edge of the screen is controlled by the command angle angle_of_perspective 14 Copyright 2001 by XYZ Scientific Applications Inc The default angle of perspective is 23 degrees Setting the angle to 0 eliminates all effects of perspective Specifying the Type of Picture Hide Fill H W TrueGrid can create several types of pictures Which type of picture will be generated depends on the setting of the Picture button group in the Environment Window of TrueGrid shown above The initial setting of the picture type is a Hide drawing hidden lines are removed The other types are described below To choose a different picture type for all subsequently generated pictures press the left mouse button on the desired picture type button Wire Hide or Fill Changing the picture type does not cause a picture to be regenerated A picture is redrawn by pressing either the Draw Center or Restore button TrueGrid Tutorial The simplest type of picture is a Wire frame drawing of all objects in the picture the preceding picture is an example Objects that would be hidden by others in the re
21. redundant nodes are merged using the Standard Part Tolerance command stp 0 01 View the merged nodes within the part using the graphics command labels TOL 1 1 TrueGrid Tutorial A Square Peg in a Round Hole The Reason for the Butterfly Mesh The alternative to the butterfly mesh involves just projecting the blocks to the cylinder Actually the mesh could be a single block mesh Such a mesh is shown on this page Pay particular attention to the region near the corners of the block The angles of elements in this region are not good One of the corners of the block has been darkened to illustrate what goes wrong witha mesh of this type The outer two faces of the block at a corner of the mesh must be folded back to conform to the cylinder The result is that the elements near this corner have angles that are nearly 180 degrees Copyright 2001 by XYZ Scientific Applications Inc If the mesh is refined then the problem just gets worse This is because two points on a circle that are very close are connected by a segment whose slope is nearly the same as a tangent to the circle Therefore as the mesh is refined the elements at the corner end up with two faces that are very nearly tangent to the cylinder In other words the two faces of the corner elements align themselves with a tangent plane to the cylinder and thus with each other In general the fact that the mesh quality actually goes down as the me
22. the history table reports the status of the command you selected to be deactivated Reactivate the command by pressing the middle mouse button on the word deactivated and by pressing ENTER Again draw the picture to see that the top end of the rod is back on the sphere Pressing the History button will print a history table that reports the command status to be active Inactive commands cannot be deactivated Such commands only occur when usin certain very advanced features of TrueGrid No such examples occur in this tutorial TrueGrid Tutorial Interactively Changing the Mesh Density Modify SEQuence mseq The mseg command is used to change the mesh density For example the block command plock 1 97 1 10 I oj 2a 25 0 OF2 2 A creates the same mesh as these commands Diock L2 L27 L Ze gt A ee Omaa ZF mseq 1 7 mseq J 8 mseq k 6 The first mseq command adds 7 nodes in the i direction The next mseq command adds 8 nodes in the j direction The last mseq command adds 6 nodes in the k direction The mseq command can also be used to remove nodes in one direction by using a negative number Refining the Mesh of the Previous Example Just to illustrate how easy it is to refine the mesh without having to change any other commands try the command mseg J 10 To view the change regenerate the picture by pressing the draw button The effects of this command are reversed by the command After t
23. About the Part 28 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial How TrueGrid Built the Mesh The previous example provides a wonderful illustration of the projection method of TrueGrid For this previous example we describe the method used by TrueGrid to build the single block mesh Snapshots of the mesh in various unfinished states are used for illustration purposes You never actually see the intermediate pictures Step 1 TrueGrid begins with the corners of the block or blocks for a multiple block mesh In the case at hand each corner of the mesh is required to be on 3 different surfaces So TrueGrid first places each corner at the intersection of the 3 surfaces on which the corner is to lie Step 1 The Corners are Positioned Step 2 After the corners of a block are positioned the edges are interpolated using the default interpolation method of TrueGrid For edges this amounts to pulling the edges tight as though they were strings and then evenly spacing the nodes along the edges Copyright 2001 by XYZ Scientific Applications Inc Step 2 Interpolate Edges Step 3 The edges of the blocks are now projected to the surfaces on which they must lie In this example all edges are required to be on two different surfaces So TrueGrid places all the interior nodes of a given edge onto the intersection of the two surfaces on which these interior edge nodes are to
24. Command The Butterfly Mesh ROUNGHIG a Comer e s 07 45 6004 Auli ccs eae OE Sdn Bale aed SOE RORY Oe Rar hoe wacRS 46 Prerequisites Description Creating the Part The Method The Geometry Cutting Corners Projecting to the Cylinder The Reason for the Butterfly Mesh Intersecting Pipes A More Challengen ProD 42 Gakuen teen Wiese sd taken R r E ea 50 Prerequisites Description Getting Started The Geometry Extracting Curves from Surfaces Making the Part Positioning Edges of the Mesh Along Curves and Surface Edges Interpolation of Intermediate Edges It s time to Project Adding More Nodes Clustering Nodes near the Pipe Walls Further Suggestions Part Replication Writing the Mesh File The Double Butterfly Version of the Mesh Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial An Overview Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Introduction to TrueGrid TrueGrid is a general purpose tool for creating a multiple block structured mesh Although the beginning of this Tutorial provides some introductory information the new user is strongly advised to read the first 2 chapters of the User s Manual before proceeding with this document The processes of creating a mesh and creatin geometry are separated within TrueGrid Surfaces and curves may be created internally or imported from a CAD CAM system via an IGES file A block mesh is then created and molded t
25. IGES Piles 202 021ge ht ones shee SU Ree hehe ek A eA ERE e ees 10 Internal Geometry Library Importing IGES Entities Interactive Graphics Mouse Selection of Geometry serseri 0 0 eee eee eens 13 Specifying the Type of Picture Moving Around Interactively Drawing a New Picture Locating Objects Using Labels Specifying What Objects Get Put in the Picture Controlling the Picture From the Command Line A SMe BIOCM Patt serari kaoewlods ke a a hae ee Ree ee Kae ed bade Kaen 21 Prerequisites Description Getting Started The Geometry The Block Command So Now TrueGrid is in the Part Phase Configure TrueGrid to Choose Surfaces by Label Highlight Faces of the Mesh to be Projected More A DOUUHMC UR All es aoee a ier Reto a coche esd oS anh ioe cela Gd 4 AA a cares 28 How TrueGrid Built the Mesh The History Table Turning Commands Off and On Interactively Changing the Mesh Density Clustering of Nodes Zoning Clustering of Nodes Zoning in both Directions Saving and Rerunning the Session File The Session and Input File Format Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Sphere in a Box A Multiple Block Mesh oi4 ccucce Bao tenes deat tedon tense adda im eRe es 38 Prerequisites Description Creating the Part What the Block Command is Doing The Consequences of Having Partitions Finishing the Mesh The Peel Commands About the Mesh The TrueGrid Challenge Mesh Diagnostics The MEASURE Command The ELM
26. Introduced Here Multiple Block Parts Diagnostics Deleting Blocks Graphical Peeling Prerequisites Familiarity with graphics labeling objects and choosing objects by label The single block example 1 Description 1 A multiple block mesh is constructed of the space inside a box and outside a Sphere contained within the box This mesh is created with just four commands that 3 3 3 Cut A Way View of the Final 27 Block Mesh l Create the multiple block part 2 Define the Sphere 3 Make a hole in the mesh where the What the Block Command is Doing spherical cavity will be and 4 Project the faces of the hole onto the The syntax of the block command is sphere block i list j list k list Creating the Part x list y list z list Run TrueGrid with no input file Instead of The i list j list and k list must be terminated entering the Merge Phase as before this time by a semicolon enter the block command straightaway block L oo tot 52 to 1 So Do 13 o L Sa T ee Sa a a This command creates a 27 block part The block boundaries are shown above Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial 39 In this case i list consists of the numbers 1 5 9 13 and x list consists of the numbers 3 1 1 3 Ifintermediate numbers are used in the i list 5 and 9 are intermediate in this case then TrueGrid will subdivide the mesh in the 1 direc
27. Shift key down while rotating Move The picture follows the mouse Zoom Only vertical mouse movement causes a change Move the mouse upward to enlarge the picture and downward to shrink the picture Moving the mouse half a window causes the picture to change by a factor of 10 Frame The Frame option is the fastest way to isolate some visible portion of the current 16 Copyright 2001 by XYZ Scientific Applications Inc picture This is done by positioning a rubber banded box around the part of the picture to be isolated the framed part of the picture is then expanded to fill the entire graphics window To frame part of the picture first make sure the Frame button is pressed Move the mouse into the graphics window and press the middle mouse button where you wish to place one corner of the framing box Keep the middle mouse button pressed and drag the mouse to a new position A rubber banded square box will appear Release the middle mouse button to view a wire frame a hidden line or a polygon fill picture of the contents of the framing box depending on the setting of the Wire Hide Fill buttons To abort a frame operation in progress drag the mouse outside of the graphics window and release the middle mouse button Drawing a New Picture It is sometimes necessary to tell TrueGrid to redraw the picture This is especially true in the Part Phase where commands are buffered all buffered commands are executed
28. TrueGrid A quality mesh in a fraction of the time Version 2 1 A Tutorial Copyright 2001 by XYZ Scientific Applications Inc All rights reserved TrueGrid the TrueGrid Manual and related products of XYZ Scientific Applications Inc are copyrighted and distributed under license agreements Under copyright laws they may not be copied in whole or in part without prior written approval from XYZ Scientific Applications Inc The license agreements further restrict use and redistribution XYZ Scientific Applications Inc makes no warranty regarding its products or their use and reserves the right to change its products without notice This manual is for informational purposes only and does not represent a commitment by XYZ Scientific Applications Inc XYZ Scientific Applications Inc accepts no responsibility or liability for any errors or inaccuracies in this document or any of its products TrueGrid is a registered trademark of XYZ Scientific Applications Inc Table of Contents ATOV OW 5 6 2 a5 base Ba he Oo ee eaten ee a EG Aa Ha Oe a eee eee 1 Introduction to TrueGrid The Phases of TrueGrid Menus Dialogue Boxes and Help lt 4 644005 sac0 44 nev de ast tava ens dae dealst baw ae 4 The Main Menu Getting Help For a Main Menu Sub Menus Getting Help For a Submenu Item Dialogue Boxes Moving the Cursor in a Dialogue Box Lists in Dialogue Boxes Executing a Dialogue Box Supported Geometry Importing
29. ace 140 Offset Surface 142 Curve on a Parametric Spline Surface 144 Trimmed Parametric Spline Surface 402 Associativity Instance Extracting All IGES Entities All supported entities are extracted from an IGES file with the single command iges IGES_file_name m n Copyright 2001 by XYZ Scientific Applications Inc Issuing this command causes the specified IGES input file to be read and all curves and surfaces to be extracted You can find this command in the CAD sub menu The surfaces are assigned TrueGrid surface definition numbers beginning with m and the curves are assigned TrueGrid curve definition numbers beginning with n where m and n are integers Note that curves used to construct others are not processed Selectively Extracting IGES Entities Entities can be selectively extracted from an IGES file using a two step process First specify the IGES file using the command also in the CAD sub menu igesfile IGES_ file name Second use either the igescd igessd or nurbsd command to extract curves surfaces or NURBS surfaces respectively These commands are all found in the CAD sub menu as well TrueGrid Tutorial 11 Example igesfile airplane igs Dir sd sb 24 gt ay igessda 1L 15 25 igescd 1 87 2 will cause TrueGrid to a read the IGES file airplane igs b to extract the first 24 NURBS surfaces and to create TrueGrid surface definitions 1 to 24 c to extract t
30. ach the three edges on the opposite side of the large rectangular block to surface edge 1 1 beginning with for example the edge shown below Half of the attach commands are finished The remaining 6 attach commands involve curves instead of surface edges So make sure all curves are showing use the Display List dialogue box of the Environment Window And label curves instead of surface edges using the Labels dialogue box of the Environment Window Attachments will involve only curve definitions 1 and 2 The other two curves were for alignment purposes only Begin by attaching the edge pictured below to curve number 2 D N OD Res Attach to Curve Number 2 The situation here is analogous to the previous where three block edges were attached to a surface edge Attach to curve definition 2 the remaining two block edges of the top right edge of the large rectangular region Now attach to curve definition 1 the three edges along the top left edge of the large rectangular region TrueGrid Tutorial 63 Interpolation of Intermediate Edges The mesh constructed so far is shown below Notice the highlighted portion in the picture This 1s the composite edge of the mesh formed by intersecting the first 1 partition and the last j partition The reason this segment is not well positioned is that little has been done to the block corners along the second k partition Most corners along the first and third k partitions
31. adios quit Otherwise TrueGrid will exit without pausing for an interactive session There are times when you may wish to rerun the session file without any interactive session In this case leaving an exit command in the file is appropriate When TrueGrid is finished processing the input file the user interface becomes active A prompt appears in the text menu window to indicate this fact TrueGrid will not automatically draw a picture unless a draw command has been placed in the input file The new session file will contain the lines from the original input file as well as any commands issued interactively after processing the input file 36 Copyright 2001 by XYZ Scientific Applications Inc Mixing Batch and Interactive Processing TrueGrid allows you to interrupt an input file at any point even in the middle of a command by placing interrupt in the input file When TrueGrid reaches the interrupt command the user interface becomes active A prompt appears in the text menu window upper left corner to signal this fact To process all the input file commands up to the next interrupt or to the end of input file whichever comes first issue the command resume Alternatively if TrueGrid is stopped in either the Part or Merge Phase then the Resume button in the Environment Window can be used the Environment Window does not exist in the Control Phase Undo History Resume
32. al world are not hidden in a Wire picture TrueGrid Draw Mh ee Hi Wy Nyy Hasan i vi if NS Sing ind i INP ae W NI Py pe H OAA NY WH i NANA VV W f Y i 2 Picture Type Wire The Hide option is used for creating pictures whose hidden lines are removed TrueGrid display Picture Type Hide The Fill option is used to create a picture where all polygons are filled and all hidden Copyright 2001 by XYZ Scientific Applications Inc surfaces are removed For all but the PC Version a two source lighting model is used along with dithering to create a very smoothly lighted picture when only 8 bit plane graphics is available Picture Type Fill When the picture type is set to Fill several options concerning the lighting model can be changed via a pop up menu which is accessed with the right mouse button in the Physical Window not applicable to the PC version Hardware Graphics We currently support hardware graphics features only for SGI versions of TrueGrid To invoke the graphics hardware features lighting fogging material models etc press the H W button using the left mouse When hardware is invoked the Wire option is the same as before except that lighting and fogging models now apply The Hide and Fill options no longer function differently both set the picture type to a Fill type Many parameters of the hardware model can be interactively changed using the ri
33. along curves or surface edges The sdint off command just issued shows just the edges of the surfaces It is not necessary to issue this command to position mesh edges along surface edges in this case it just cleans up the picture Using the Labels dialogue of the Environment Window choose the option to label all surface edges by pressing the Surf Edge button Reconfigure TrueGrid to choose objects by label This is done by 62 Copyright 2001 by XYZ Scientific Applications Inc pressing the Label button in the Pick dialogue of the Environment Window Highlight surface edge 1 3 This is the upper edge of the elbow pipe Now highlight the mesh edge shown below u y K 2 3 4 3 2 J 2 3 S Edge to be Initialized to Edge 1 3 Press the Attach button and TrueGrid will reposition the nodes of the selected edge along the highlighted surface edge Right now there are no intermediate nodes along the highlighted edge this will change So only the endpoints can be repositioned The next edge is highlighted by modifying the current selection deactivate the segment between the third and fourth dots of the j index bar and active the segment between the second and third dots of the j index bar This can be done in one step because segments toggle on and off press the mouse on the fourth dot of the j index bar and drag the mouse to the second before releasing the mouse This toggles the top se
34. and to see the refined mesh A hidden line version of the picture is probably called for The surfaces will interfere with such a picture Therefore it is best to first remove all the surfaces using the Display List dialogue in the Environment Window On the other hand you may wish to leave the surfaces in the picture to convince yourself that the faces projected to the pipe surfaces are actually projected It will take some time to see the new picture because the mesh must be rebuilt and now there are many more nodes in the mesh The need for another linear interpolation command becomes apparent at this time now that there are many more nodes Notice that the node distribution on the block faces 66 Copyright 2001 by XYZ Scientific Applications Inc pictured below is not ideal the edges of these block faces are darkened et MEG EESeaBeseil SSS SSS SESS What happened Of the three darkened edges shown above only the two outside edges were positioned One was placed along a curve and the other along the edge of the elbow pipe surface The middle edge was positioned before projection using the default interpolation Therefore the middle block edge was before projection a straight line segment connecting a point somewhere on the bend of the pipe to a point on the lower end of the pipe You can see this by deactivating the projection command of faces onto the elbow pipe Be sure to reactivate the command afterwar
35. and will be treated equivalently T0 10E 01 10e1 TOs OE 01 I If TrueGrid is looking for an integer any of the above will be interpreted as 1 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid also understands FORTRAN expressions so long as they are enclosed by square brackets All FORTRAN intrinsic functions are supported including trigonometric functions and their inverses All angles are assumed to be in degrees For example these are valid floating point numbers Peat atanz 21y 3 ES eS 5 ey aS sore 2 sore 2 ae eae oR Parameters are defined using the para command and are referenced by preceding the parameter name with a sign The syntax for the para command calls for pairs of items parameter name followed by a value followed by a terminating For example after the command para xl 10 Za 12 X3 24 then sqrt x is a valid expression whose value is 12 Note that parameters can be used as soon as they are defined In particular para XL ALG 232 eo he results in a value of 20 for the parameter named x2 A single parameter can be referenced without brackets For example TrueGrid understand x1 by itself but it does not understand x1 x1 is however understood by TrueGrid TrueGrid Tutorial 37 Sphere in a Box A Multiple Block Mesh 38 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial A Multiple Block Part
36. ands that have no interactive counterparts For Generate a New Picture Generate a line drawing draw Generate a hidden line drawing disp Generate a polygon fill drawing EMY Center the picture do not change the rotational orientation Center Center the picture in the default orientation with no rotations rest or restore Rotate Translate Zoom Rotate the picture about a horizontal line parallel to the screen plane rx angle_in_degrees Rotate the picture about a vertical line parallel to the screen plane ry angle_in_degrees Rotate the picture about a line perpendicular to the screen plane rz angle_in_degrees Zoom Forward by a factor that can be less than 1 z zoom_factor Zoom Backward by a factor that can be greater than 1 zb inverse_zoom_factor Label Objects in the Picture labels option where option can be sd to label surfaces crv to label curves sdedge to label surface edges Copyright 2001 by XYZ Scientific Applications Inc example there is no interactive command to add a surface curve etc to the picture Presented below is a list of TrueGrid commands that are analogous to the interactive functions presented so far sdpt to label points on surfaces crvpt to label points on curves off toremove all labels Specify the Surfaces Shown Display All Surface Definitions dasd Remove All Surface Definitions rasd Display a single Surface Definition dsd_surface_definit
37. command In fact all but the simplest meshes built with TrueGrid will tend to be multiple block meshes And for multiple block meshes the Computational Highlighting and Selection system is a powerful tool for both mesh editing and setting boundary conditions Physical Window The Physical Window contains a picture of the actual mesh To distinguish between geometry and mesh mesh lines are green surfaces are red and curves are yellow Of course highlighting changes the color of the highlighted object The green mesh lines are not just a rough representation of the mesh Any time the user redraws the physical window all buffered commands are executed and the actual mesh is displayed TrueGrid Tutorial Both Comp Setting the Window Because there are two graphics windows in the Part Phase it is necessary to inform TrueGrid which window is to be acted upon This is done by pressing the left mouse button on either the Physical Computational or Both button When either the Draw Center or Restore buttons is pressed the appropriate window is redrawn The same is true of manually issued commands such as rx ry rz etc The user should also be aware that commands such as those to reset the angle of perspective are also directed to the window indicated by the setting of Phys Both and Comp button group Configure TrueGrid to Choose Surfaces by Label Move Pts Display List Labels Lasso Surface Cur
38. ct by label selecting the nearest vertex and moving regions All functions performed with the left mouse are indicated by a picture of the mouse with an X over the left button Set up TrueGrid so parts of the mesh can be moved interactively To do this press the Move Pts button in the Environment Window The dialogue shown above appears WARNING Be careful while TrueGrid is configured to move points of the mesh Pressing the left mouse button while in this mode can cause trouble Use the Undo button to deactivate an unintended move command The object is to move the previously highlighted region to the center of the lower edge of the elbow pipe Choose the Screen Plane option for this example This option is used to restrict movement of the points to plane s parallel to the screen plane Now press and hold the left mouse button down in the physical window As soon as the mouse is moved a cross hair appears and a line is drawn from the center of the highlighted region to this cross hair The highlighted region is redrawn centered at the new cross hair Move the mouse until the cross hair is centered along the lower edge of the elbow pipe Release the mouse button All of the mesh except for the two faces just repositioned is still sitting at the origin The two highlighted faces are still collapsed to a Copyright 2001 by XYZ Scientific Applications Inc single point just a different point than the remaining pa
39. d can be entered on one line or split across lines as shown TrueGrid Tutorial 23 So Now TrueGrid is in the Part Phase This block command creates a single block mesh with 9 nodes in the 1 direction 10 nodes in the j direction and 8 nodes in the k direction The x coordinates of these nodes are evenly spaced between 2 and 2 the y coordinates evenly spaced between 6 and 6 and the z coordinates evenly spaced between 2 and 2 As soon as the block command is finished TrueGrid switches to the Part Phase A new window with a tithe Computational appears in the upper right corner of the screen The Computational and Physical pictures will not be drawn until the user tells TrueGrid to draw these pictures Te K 2 I 2 Gree L Computational Window The Computational Window contains a block representation of the mesh Along the lower upper and right borders of the window are index bars These index bars provide a means by which the user can select any corner edge or face of the block as well as the solid block Such a selection can then be used directly in any command requiring a description of part of the mesh as one of its arguments The computational picture would not be so useful if all that could be created within 24 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid was a single block mesh However TrueGrid allows the user to create a three dimensional array of blocks using the block
40. ds Projection moved each node on the intermediate edge to its closest point on the elbow pipe Nodes that were well inside the pipe were therefore moved closer to the top of the elbow pipe The way to correct this situation is to apply an interpolation command across the two block faces sharing the intermediate edge Then TrueGrid will treat the two faces as though they were one block face and the intermediate edge will be interpolated between the two outer edges before projection Then because the nodes of the combined face are all rather close to the pipe the final distribution of nodes is much nicer TrueGrid Tutorial Actually there are four composite faces of the mesh that can benefit from additional interpolation Highlight the faces pictured below and issue the Lini command for these faces use the F1 Key to convert the selection to a numeric representation A W h D Composite Faces to be Interpolated The final interpolation command is Lina A O saji 2 O0 o dyl oF Clustering Nodes near the Pipe Walls The Re spacing command was discussed in the context of the single block example Recall that this command is used to space nodes in a particular direction in such a way that the ratio between adjacent pairs of nodes in the specified direction is a given number The re spacing command only applies to mesh edges A re spacing command for a face or a solid is converted to several re spacing commands
41. e applied to all solid blocks So for example pressing the Copyright 2001 by XYZ Scientific Applications Inc Delete button when the selection is NULL causes the entire mesh to be deleted TrueGrid Tutorial 57 There is only one other piece of the mesh to be deleted That piece is pictured below q mW z 3 4 3 2 J The Other Part of the Mesh to be Deleted The final computational block structure is shown below QE K 2 3 4 3 2 J 2 3 Final Computational Picture The next stage of building this mesh requires interactively moving parts of the mesh so that it resembles the final shape Bottom faces of the bottom blocks are positioned first near the bottom end of the elbow pipe Use either the Frame option to 58 Copyright 2001 by XYZ Scientific Applications Inc focus on the lower end of the pipe or the commands RES D O09 U 0 25 AE 10 These graphics commands roughly center the lower edge of the elbow pipe in the picture The First Interactive Move involves the Lower End of the Elbow Pipe The region to be positioned along the edge of the lower end of the elbow pipe needs to be highlighted pictured below W NO ts The Region to be Moved to the Lower End of the Elbow Pipe TrueGrid Tutorial Pick DEALA Display List Labels Interactive Positioning is Done The left mouse performs several different functions in the Physical Window such as selecting an obje
42. e the same procedure described in the example of the res command NOTE If you have already issued the res command of the previous example there is no need to deactivate that command Zoning commands for a region override previously issued zoning commands for that region Copyright 2001 by XYZ Scientific Applications Inc Double Zoning in all D efined Surfaces TrueGrid DISPLAY D irections a a A _ Ca 7 ae Sd z2 L7 Y TT g lt 7 a2 7 Z7 E L R LL IOGT L LL LL d cn 7 LLI ssa 1 aw Double Zoning in all 3 Directions TrueGrid Tutorial 35 Saving and Rerunning the Session File A TrueGrid session file is written every time that TrueGrid is run If no session file name is specified on the command line using the s option then the session file is named tsave and is placed in the current working directory If the session file is named tsave then make sure to rename the session file when finished or it will be over written the next time TrueGrid is run Rerunning the Session File A session file can be rerun as an input file using the i option Running the session file as an input file is a good way to pick up where you left off the last time TrueGrid was run To run the session file as an input file first remove the final command used to exit TrueGrid which canbe end exit
43. ed and yet natural Now highlight the largest rectangular section of the mesh by highlighting only the segment between the first and second 1 partitions Next type res on the command line press the F1 Key to convert the selection to a numeric description and add k 1 1 1 to the command line to obtain res tL 1i 12 4 3 k 1 1 1 Square braces are required whenever an expression involving arithmetic or FORTRAN functions is issued To save time issue more re spacing commands before drawing the picture The current res command zones the edges of the region inside the elbow pipe in the k direction 1 e from the symmetry plane to the TrueGrid Tutorial 67 top of the pipe As k increases the distance between nodes decreases the specified ratio is less than 1 Consequently the nodes cluster toward the top wall of the pipe Next restrict the current selection in the j direction to the top third of the blocks That is highlight the j index bar segment between the third and fourth j partitions This time apply the res command in the j direction with aratio of 1 1 res 131243 5 1 1 This command causes nodal distances to increase with increasing j Thus nodes cluster near the elbow in the upper section of the elbow pipe Now apply the re spacing command to the lower third of the blocks in the elbow pipe Use a ratio of 1 1 1 to cluster oppositely res Tt tO DS g Pit This command also cause
44. eneration TrueGrid allows the user to reference an object by pointing to its label TrueGrid never draws overlapping labels and within this restriction tries to center the label on the object Furthermore TrueGrid highlights the object corresponding to a particular label when the user points to that label Assuming that the user has selected the Labels option under the Pick menu These features make it easy to find a particular object by its label even when there are many objects in the picture Only one class of objects is labeled at any given time The user selects the class of objects to be labeled by first selecting the Labels Dialogue of the Environment Window by pressing the Labels button with the left mouse button Then the user presses the button corresponding to the class of objects to be labeled Pressing the Off button removes all labels Example Continuing with the current example Press the Surface button to display labels for the plane and cylinder in the picture Move the mouse into the Physical Window and press the left mouse button on one of the two labels in the picture Pointing in this fashion to label 1 highlights surface definition 1 which is the cylinder Similarly pointing to label 2 highlights the sphere Pressing the left Copyright 2001 by XYZ Scientific Applications Inc mouse button anywhere else in the picture clears the highlighting Next press the Surf Point button Poi
45. entries disappear from sight The hidden entries reappear if the selected entry is deselected Executing a Dialogue Box Press the EXECute button at the bottom of the dialogue box to issue the command Any number of error conditions will prevent execution of the dialogue a Not all input fields are filled in b Not all input fields have been flagged as complete Pressing ENTER causes the field to be checked for completeness Complete fields have red cursors at the end c No entry has been chosen for a list that requires a choice to be made d TrueGrid is in a state where a command is in progress If a or b occur then the input field will be moved just below the top of the dialogue and the prompt for the first offending field is colored blue If c occurs then the first entry of the offending list appears near the top of the dialogue and the marker either gt or o is colored blue If d occurs the EXECute button is colored red TrueGrid Tutorial To EXECute and QUIT the dialogue box use the EXEC QUIT button This button is usually the best choice because it requires the least number of mouse actions Note Pictures are not automatically redrawn when commands are issued in TrueGrid To insure that a new picture is drawn press the EXEC button or the EXEC QUIT button using the middle mouse button instead of the left mouse button Doing so causes a draw command to be issued with the command
46. ersion 1 1 0 of TrueGrid the alignment mark intersects the surface edge at a point whose label is 1 47 64 1 30 78 1 31 78 1 32 78 Surface Point Labels Near the Right Alignment Mark Notice these labels have two components in common The first part of the label is the surface definition number in this case 1 The second and third parts are indices into a grid of points used to draw the surface Both points lie on a common edge of the surface and therefore have the same value for one of the last two indices The corresponding points on the other end of the elbow pipe surface have labels Llel 2Z2s8 and Le ee 56 Copyright 2001 by XYZ Scientific Applications Inc The two curves we wish to construct lie on the elbow pipe surface and have endpoints with labels 1 1 28 1 47 28 and 1 1 64 1 47 64 respectively these numbers may depend on the version number of TrueGrid The required 3D curves are created with two applications of the curd command curd contour L lsve 11 47 2037 c rd 2 contour 1 1 604 12 47 6044 Alternatively use a dialogue box for the curd command located in the 3D CURVE submenu Choose the dialogue box option gt Begin With A Surface Contour The 3D curves just created are shown below The contour curves are darkened for emphasis These 3D curves appear yellow on the computer screen SA SK TE RRS ROA lt aAA aant T The F
47. ess the middle mouse button on the word deactivated A command is generated on the command which when issued will reactivate the given command Press return to issue this command Multiple commands can be issued at one time Redraw the picture to see the result Example Use the history highlighting feature to isolate the command requiring the TrueGrid Tutorial 31 top end of the rod to be projected The progression line of that command appears as progression 1 27 2 27 2 On the line just above the progression description press the middle mouse button on the word active A command such as decmd 5 appears on the command line of the text menu window Press ENTER to issue this command A picture is not automatically regenerated so press the Draw button in the environment window The Top Cap is no longer Projected TrueGrid DISPLAY Defined Surfaces The Top End is not Projected to the Sphere Anymore Notice that the top end of the bar is no longer projected to the sphere Press the History button again to see the new history table HIS ft OR IT ABLE active 2 surface projection progression 1 2 1 2 1 0 2 active 3 surface projection Progression i 17 L 27 ay active 4 surface projection Progression 2 2 L27 lL 27 deactivated 5 Sur itace projection 32 Copyright 2001 by XYZ Scientific Applications Inc progression L 27 2 2 1 27 active 6 surface projection Progression L 27 1 1 1 23 Notice that
48. f the six collections of block faces surrounding this rectangular piece have been selected This is Copyright 2001 by XYZ Scientific Applications Inc a standard technique for selecting multiple block faces All Faces to be Projected to the Elbow Pipe Faces to be Projected to the Small Cylindrical Pipe Use the same procedure to highlight the block faces to be placed on the cylindrical pipe Then highlight surface number 2 and press the Project button As a check this region is pictured below TrueGrid Tutorial 65 Adding More Nodes Two things are required to finish the mesh add some nodes and issue re spacing commands to cluster the nodes near the walls of the pipe Nodes should be added before clustering is done otherwise the effects of clustering commands will hardly be noticed Just how many nodes to add is a question of the simulation to be performed We add 15 nodes to two ends of the elbow pipe in the direction of the pipe j direction and add 2 nodes to the center section of the elbow pipe This is done using the command mseq J 15 2 15 The mesh is not automatically redrawn Next we add 15 nodes across the pipe and 10 nodes along the length of the cylindrical pipe using the command mseg 1 15 10 Finally add 2 nodes to the bottom section of the pipe and consequently 2 to the entire cylindrical pipe and add 8 nodes to the top section with the command msegq k 2 8 Issue a draw comm
49. for all the edges in the face or solid If a re spacing command is applied to a composite edge then intermediate block corners on the composite edge are also re spaced In this regard the re spacing command is the same as the linear interpolation command Copyright 2001 by XYZ Scientific Applications Inc When a re spacing command is applied to an edge the nodes are reshuffled along the current curve of the edge This means in particular that re spacing will not change the shape of the curve on which the edge nodes currently lie By contrast recall that the linear interpolation command can be used to changed the shape of an edge we used the lini command to change the shape of an intermediate edge earlier The linear interpolation command can be used to determine the shape of an edge and then the re spacing command to determine the distribution of nodes along that edge An edge positioned along a curve or surface edge can also have a re spacing command applied to it Then nodes will be distributed along the curve or surface edge in such a way that they obey the zoning law An edge that must lie on one or more surfaces due to projection can also have a re spacing command applied to it In such a case both the projection and re spacing requirements will be satisfied All these considerations together show the versatility of the re spacing command The interaction of this command with others is quite sophisticat
50. ght mouse button to activate a pop up menu in the Physical Window TrueGrid Tutorial 15 Moving Around Interactively Move Zoom Frame The Middle Mouse Button is used to manipulate 3D graphics windows in TrueGrid The effect of pressing the middle mouse button in either the Physical or Computational window depends on which of the four buttons Rotate Move Zoom or Frame is pressed The buttons in this Motion button group of the Environment Window pictured above are reset by pressing the desired button using the left mouse button The Rotate Move and Zoom options are all similar in nature A dynamic operation is performed on the picture by moving the mouse to either the Physical or Computational Window pressing the middle mouse button and dragging the mouse to a new position while the middle mouse button remains pressed As the mouse is moved a minimal wire frame representation of the picture is redrawn as quickly as possible When the left mouse button is finally released a new picture is redrawn The type of the final picture is determined by the setting of the Wire Hide Fill button group Rotate Horizontal movement of the mouse causes a rotation about a vertical line parallel to the screen plane Vertical movement of the mouse causes a rotation about a horizontal line parallel to the screen plane When the picture is magnified rotations are reduced appropriately This effect is eliminated by holding the
51. gment off and the next to top segment on Select surface edge 1 3 again and press the Attach button TrueGrid Tutorial Modify the current selection again by deactivating the j index bar segment and activating the j index bar segment from the first j partition to the second Attach this edge to surface edge 1 3 as well You may be wondering why it is not possible to issue just one command to attach all three edges to surface edge 1 3 Actually this is possible However doing so would not yield the intended effect Issuing the command for all three edges at once would cause TrueGrid to treat the three edges as though they were part of a single block In particular TrueGrid would evenly distribute all nodes of the composite edge along surface edge 1 3 Breaking the attach command into three commands causes TrueGrid to deal with each block edge separately the endpoints of the edge are moved to the closest point on the surface edge 1 e projected and all intermediate edge points are evenly spaced along the surface edge The nodes along the composite edge do not end up evenly spaced along the surface edge Br ee Attach to Surface Edge 1 1 It is possible to attach the composite edge all at once and then use the double re spacing command to reposition the nodes But this Copyright 2001 by XYZ Scientific Applications Inc would be more trouble than issuing three separate attach commands Next att
52. have been positioned along curves or surface edges L The Mesh After All Attach Commands This points out a major difference between a single block mesh and a multiple block mesh interpolation is not automatically performed across block boundaries only within each block The solution is to apply interpolation to composite edges To do this first highlight the edges shown below Then type lini on the command line and press the F1 KEY or CTRL A to convert the current computational selection to a numerical description The command line will now be 64 Copyright 2001 by XYZ Scientific Applications Inc lini i 0 s2 1 0 43 1 3 w O Composite Edges to be Interpolated Before issuing a draw command carry out the same procedure for the highlighted region in the next picture as well o 07 _ Composite Edges to be Interpolated Now issue a draw command for the Physical Window Notice that there are no degenerate regions remaining There is one more linear interpolation command that will be useful The need for this command will be obvious once more nodes are added TrueGrid Tutorial It s time to Project The initial position of the mesh largely dictates the node distribution of a mesh after a projection The projection command in rough terms snaps nodes to the closest point of the surface to which the nodes are projected Though over simplified this explanation helps one to
53. he MSEQ Command msegq J 10 As before press the Draw button to view the changes to the mesh Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial 33 toward the bottom end of the bar issue the command TrueGrid converts the null selection to a description of the entire mesh Clustering of Nodes Zoning Relative Spacing Command res SYNTAX res 1i_minj_min k_min i_max J _max k_max direction ratio where direction can be either i j or k and ratio is a positive floating point number DESCRIPTION The nodes of all block edges of a specified region of the mesh are clustered in the specified direction The amount of clustering depends on the ratio The nodes are spaced so that the ratio of distances between adjacent nodes in the specified direction equals the given ratio Thus for example if re spacing is specified in the i direction with a ratio of 1 2 then the nodes with smaller 1 index values are closer together than those with larger 1 index value In particular for a fixed j and k index the distance between the nodes with 1 index 2 and 3 will be 1 2 times as large as the distance between nodes with i index and 2 So in this case nodes cluster in the negative 1 direction Zoning Toward the Bottom TrueGrid DISPLAY Defined Surfaces To cluster the nodes of the bar CTLAEVOo 4 14 I To avoid typing the region description first Ii ILAE p clear the comp
54. he first 15 surfaces other than NURBS and to create TrueGrid surface definition numbers 25 to 40 d to extract the first 87 curves from the IGES file and to create TrueGrid curve definition numbers 2 to 88 Saving Time Large IGES files may take some time to process within TrueGrid It can be time consuming to tile all the surfaces for graphics purposes Every time TrueGrid is rerun and consequently asked to read the same IGES file all this work must be repeated To eliminate the need for subsequent processings of an IGES file use the command Ssaveliges binary_output_file Example Suppose that after issuing the previous set of commands the command Saveliges airplane bin is issued Then the next time the same set of surfaces and curves are to be used issue the commands useiges airplane bin igesfile airplane igs nurbosd 1 24 IT rE Sd L 15 25 igescd 1 87 2 12 Copyright 2001 by XYZ Scientific Applications Inc The useiges command is also Found 17 the CAD Sub menu TrueGrid will process this set of commands many times faster than it was able to process the commands in the previous example Notes about saveiges 1 Only entities processed before the saveiges command are saved Entities are processed when eitherigessd igescd or nurbsd are issued 2 The name of the file used with the saveiges and the useiges commands must match exactly or the binary IGES file will not be used
55. id to merge all nodes that are within a distance of 0 01 of each other Merging is fast easy and versatile Furthermore you can interactively change the merging by simply issuing new merging commands Look at the help package for the MERGING category of commands The merged nodes are displayed using the LABELS dialogue in the GRAPHICS submenu Choose the following option to display the merged nodes gt Merged Parts Writing the Mesh File The final output file is written using the write command with no arguments The default output file name is trugrdo The name can be specified on the command line Some output options require selecting the type before creating the first part Others can be selected at the end For more information about output options look at the help package for the OUTPUT category of commands Help for an individual output option gives a list of all supported boundary conditions element types materials etc The commands used to set such conditions are also specified Boundary conditions are set in the Part Phase using the computational highlighting system to point to parts of the mesh Boundary conditions cannot be specified later TrueGrid Tutorial 69 The Double Butterfly Version of the Mesh As promised earlier a picture of a double butterfly version of the current example is shown Zoning has not yet been performed on the model shown Nor has any relaxation been done This picture
56. ific Applications Inc TrueGrid Tutorial Text Menu Window Menus Dialogue Boxes and Help The Main Menu Run TrueGrid with no input file using the command tg A single window appears in the upper left corner of the screen The main menu of TrueGrid appears in this text menu window This text menu window has a title indicating the current phase of the code either Control Phase Part Phase or Merge Phase Commands can be issued from this window and any output such as warnings or error messages is directed to this window oa ee ere Tae CERET Tee a et a eee Because of the limited screen space the text menu window is not particularly large This leaves room for other windows that appear in the other phases of the code Consequently when there is output from TrueGrid to the user the menu automatically disappears and the text portion of the text menu window 1s enlarged to fill the window For example enter the illegal command junk on the command line A message is issued indicating that junk is an illegal command Notice that the menu is no longer visible al Haa Ph bear pk Lal a ec eed a al To bring the menu back either press the Enter key or press the right mouse button 3 button mouse in the text menu window or Copyright 2001 by XYZ Scientific Applications Inc press the middle mouse button in the scroll bar area of the window To expand the text area to cover the window
57. inal Geometry 3D Curves are Darkened Making the Part The block command for this example may seem unusual at first because all coordinates are set to Q Block C 2S a 2 3s O 020 0 0 00 0 0 TrueGrid Tutorial The mesh will be interactively positioned so initial coordinates do not matter Notice that each block is only one element thick Elements will be added later The physical picture of the mesh is not very interesting because the entire mesh is collapsed to a point namely 0 0 0 The first two mesh commands delete portions of the mesh First highlight the region shown and press the Delete button in_ the environment window First Part of the Mesh to be Deleted There is acurious feature of the computational highlighting that should be mentioned If no dots or segments along an index bar are activated then TrueGrid treats this the same as if all segments were activated and all dots were not Consequently activating all segments in the k direction as shown above is the same as activating none All segments were activated here for clarity only There is one other curiosity concerning the highlighting If nothing is activated in any direction then this is equivalent to having chosen all solid blocks However the highlighting does not indicate this otherwise there would be no way to remove all highlighting But be aware that using a NULL selection will cause the command in which the selection is used to b
58. ing the actual mesh and any geometry and the Environment Window used to determine what is in a graphics window how itis displayed and how it can be manipulated using the mouse It is in the Part Phase where the mesh is constructed by positioning projecting deleting zoning refining and smoothing parts of the mesh as well as by performing other functions Boundary conditions for a part are also specified in the Part Phase The Merge Phase is where parts are assembled into one model by merging 1 e gluing nodes together that are within a specified tolerance of each other Only the Computational window of the Part Phase is missing Both the Physical and Environment windows are present in the Merge Phase Itis in the Merge Phase that the mesh output file is written There are features available in the Copyright 2001 by XYZ Scientific Applications Inc Merge Phase to view boundary conditions to diagnose the condition of the mesh and to view the highest quality images of the mesh and geometry As TrueGrid evolves the need for the Control Phase diminishes Eventually the Control Phase will be eliminated in favor of the Merge Phase This will make graphics capabilities available at all times within TrueGrid Most functionality once available only in the Control Phase has already been incorporated into the Merge Phase TrueGrid Tutorial 3 Menus Dialogue Boxes and Help 4 Copyright 2001 by XYZ Scient
59. ion_number Display a list of Surface DefinitionS dsds list_of_surface_definitions Add a Surface Definition asd _ surface_definition_number Remove a Surface Definition rsd surface_definition_number Specify the Curves Shown Display All Curve Definitions dacd Remove All Curve Definitions racd Display a single Curve Definition ded _ curve_definition_number Display a list of Curve DefinitionS deds list_of_curve_definition_numbers Add a Curve Definition acd curve_definition_number Remove a Curve Definition rcd curve_definition_number TrueGrid Tutorial 19 Specify the Parts Shown Display All Parts dap Display one particular Part p part_number Add a Part to the picture ap part_number Remove a Part from the picture rp part_number Specify the Materials Shown Display All Materials dam Display a specific Material m material_number Add a Material to the picture am material_number Remove a Material from the picture rm material_number Specify the Regions Shown These commands apply only in the Part Phase The distinction between a Region specification and an Index Progression specification are explained later Display All Regions darg Display a specific Region rg region Display a Region specified by Index Progression rgi progression Add a Region to the picture arg region Add a Region specified by Index Progression argi progression Remove a Region from the picture rrg region Remove a Region specified by Inde
60. is introduced for creating a good mesh of a rounded object using a block mesh in Cartesian coordinates The mesh is created using four commands Creating the Part Run TrueGrid with no input file Create a 9 block part using the block command block 1 gt 9 too 1 2 2 13 L teat L 2 The resulting mesh contains several collapsed blocks The first and second 1 partitions have the same x coordinates Likewise the second and third i partitions have the same x coordinates An analogous statement is true for the j direction and y coordinate Allin all only the center block of the mesh is not collapsed A good way to see that some regions are collapsed is to first draw both pictures and then explore the mesh using the Slicing Plane feature Copyright 2001 by XYZ Scientific Applications Inc The Butterfly Mesh a k a The Iron Cross The Method Notice that in the final mesh shown above there are only five blocks The center block is easy to spot Four other blocks surround this center block This mesh was created by first deleting the four corner blocks of the mesh Then the outside faces of the four outside blocks were projected in one command The Geometry The geometry for this problem consists of a single right circular cylinder created with the following Surface Definition command sd 1 cyli 000 001 3 TrueGrid Tutorial 47 Extra spaces were added for the sake of clarity you may omi
61. k face of the mesh by first highlighting that face as shown above and then by pressing the left mouse button while the minimum constant k slicing plane is active The back face of the computational block and the back face of the mesh will both turn yellow If you make a mistake while making the selection press the F2 KEY to clear the selection this will not clear any slicing plane Next move the mouse until the maximum k slicing plane is active equivalently when the right dot on the top index bar is white The highlighted face of the mesh is the front face Add this face to the current selection by pressing the left mouse button while the maximum k slicing plane is still active At this point both the front and back faces of the mesh will be highlighted in yellow The two dots of the upper index bar will be red The cylindrical surface you highlighted earlier should still be highlighted The final computational selection appears below K 2 2 J I 2 ie ET Front and Back Faces Selected TrueGrid Tutorial ee Se NS RNR SSS ON lin li Hn jji M p ii ii Mi ii ii I Front and Back Mesh Faces Now that the faces of the mesh to be projected and the surface to which they are to be projected are both highlighted then the required projection can be performed Perform the projection of the highlighted mesh faces to the highlighted surface by pressing the Project button Delete Attach SEES
62. lock Next press the Delete button in the Edit button group of the Environment Window Attach Project Recall that meshing commands can be deactivated using the History feature Alternatively use the Undo button to deactivate the last active command Notice that after the new pictures are drawn the highlighting of the center block has 42 Copyright 2001 by XYZ Scientific Applications Inc changed from cyan to magenta This is a feature of the computational highlighting system When part of a highlighted solid region is deleted then faces of the deleted region contained within the solid are colored magenta Another unique feature of the computational highlighting system any combination of the 6 faces of a highlighted block can be selected at once As soon as one dot on a highlighted segment is activated then the highlighting switches from solid to faces Faces are highlighted in yellow as opposed to cyan for solids SITE LPS NN NEES ST ONIS SEANN NLS SED NG SPSPSSES I 2 3 4 i Mmm Two Faces of The Center Block Notice the two activated dots on the 1 index bar in the above picture Activating these dots highlights the two corresponding 1 faces of the center block Similarly any or all of the remaining 4 faces of the center block can be added to the current selection We want to project all six faces of the center block onto the sphere So highlight all six faces by activating all si
63. mri wih ah Prieiqe Hemi cobrudeter print remilin of ay PORT A Sap Cae hi wha a D charsciar sirlig LS Che tat i i eo ad FOATA like ezpredeicon vijia Ln Lew tiile bF ther emun proibia heg irmi n OF oa cuset to be ligare isj MELAD Crnee promi o laa eeben Ei liaise ee tees oS a a immar or dot prekei oof ies weciore Wla bie fey te leer oe lirg bliin deling mipgibe t a a aa Soe pore lars Arii it L jji valg aia ja tee mai m a Daf inilio metar motiboa ie Efm ced 2 curves dor nibli makes oil lg tie eset PT ing Coren daf iai kien me habii ke a reed The Help Window contains a title bar with scroll arrows as required Pressing the left mouse button scrolls by page Pressing the middle mouse button scrolls by line The Page Up Page Up Up Arrow and Down Arrow keys can also be used for scrolling All command names in the category are highlighted in yellow A description of the options for each command and their purposes is stated Pressing the left mouse button on another category of the main menu replaces the contents of the current help window with information about the new category This feature allows for easy browsing through all categories of the menu To kill the Help Window either use window manager pop ups or turn the HELP button off Sub Menus Submenus contain a list of all the commands in a main menu category One uses a submenu to access detailed help or a dialogue box for each command in the main
64. n two adjacent i partitions have the Same number of nodes in the 1 direction etc Finishing the Mesh First create a sphere of radius 1 centered at the origin using the Surface Definition command sd 1 sphe 000 1 This sphere will not be visible using the Hide option because the sphere is fully contained within the physical mesh Second delete the center block of the 27 block part This is easy to do using the Computational Highlighting System TrueGrid Tutorial 41 To do this first highlight the solid center block as follows Move the mouse into the computational window close to the second dot on the 1 index bar bottom window border Press the left mouse button and drag the mouse to the third dot on the i1 index bar As you do this the middle segment of the 1 index bar turns red and all blocks between the second and third 1 partitions are highlighted in cyan Release the left mouse button Do the same in the j direction using the j index bar right border of the window This time only the blocks between the second and third 1 partitions and those between the second and third j partitions are highlighted in cyan Do the same in the k direction Now only the middle block is highlighted use the Wire option to see inside Note Pressing the F2 KEY clears all highlighting 3 4 Tis ain HO HA U I ra Sa EaR 3 SOS PREP Niners AT F I 2 3 4 po E OR re Highlight The Center B
65. not problem to duplicate the current model and glue the two sides together The Local Coordinate Transformation command lct allows the user to specify transformations to apply to a model Then the Local REplication command Irep is used to create copies of the current part using the local coordinate transformations In this example we create a mirror image part by reflecting the current part across the XY plane Create a dialogue box for the lct command by pressing the LCT button in the REPLICATION submenu Enter 1 for the NUMBER OF TRANSFORMATIONS Under the LIST O F TRANSFORMATIONS choose the reflection option gt Reflect about the x y plane End the current transformation and the list of transformations by selecting gt End Transformation and List Execute and Quit this dialogue box Issue the next command to replicate the current part rren G iy This command tells TrueGrid to preserve the part as it is transformation 0 and to replicate the part using the first defined local transformation As soon as the endpart command is issued TrueGrid creates the required copies of the current part Combine this with the command to enter the Merge Phase Copyright 2001 by XYZ Scientific Applications Inc endpart merge To complete the model we need to eliminate the duplicate nodes along the symmetry plane This is done using the Standard Part Tolerance command STE ao This command causes TrueGr
66. nts on the plane used mainly for graphical purposes are now labeled TrueGrid allows the user to attach points of the mesh directly to such surface points Zooming in on part of the picture will reveal more labels and points that can be used while building the mesh The Surf Edge button will label the edges of all defined surfaces in the picture Edges of the mesh can be directly placed on such surface edges When surfaces are infinite as in the example they have no useable edges their edges can be displayed and highlighted but cannot be used in interactive meshing This is because edges of infinite surfaces change depending on the size of the bounding box for the picture TrueGrid Tutorial 17 Specifying What Objects Get Put in the Picture Pick Move Pts DER oe Vanes Labels Apply Action to Surface Material Show Only Action Curve Part Show All Point Region BB Show None The Display List dialogue of the Environment Window provides an interactive way to add and remove objects from the picture Pressing the Display List button of the Environment Window activates this dialogue The group of buttons on the left is used to select the class of objects to which commands in this dialogue will apply The group of buttons on the right execute commands to selectively add objects to or remove objects from the picture
67. o imr imt Tete of th po ligans mife Th efli a chang FETH bii fo fhe mo inter bor apes defili ues and mele praqgter than IP TrueGrid Tutorial The second part of the help contains a complete syntax for the command All literal options are in upper case letters Other strings especially those containing underscores are meant to describe the type of data to be enter Semicolons should be regarded as literal Dialogue Boxes Dialogue boxes are available for every TrueGrid command To obtain a dialogue box for a particular command move to the submenu containing that command and press the left mouse button on the command name Make sure the HELP button 1s off TrueGrid dialogue boxes can contain incredibly complex decision trees especially for commands used to set options for output to a particular simulation code TrueGrid dialogue boxes may contain input fields and option lists as well as descriptions and or titles for such An input field consists of an optional description in white print prompts in light grey print and cursor boxes initially green 0 OLALOGLE SURFACE DEFINITION NUMBER T SURFACE TYPE POINT ON THE PLANE w s y z MORAAL VECTOR an ums zn There may be many input fields within a dialogue box The current active field the one to which text input is directed is always displayed with a filled green cursor The other active cursors are hollow green cursors Copyrigh
68. o the shape of the geometry Making a mesh with TrueGrid is analogous to sculpting A block mesh is created using the block command Pieces of the block mesh are removed so that its topology matches that of the object to be meshed Portions of the mesh are moved positioned along curves projected to surfaces etc Interpolation smoothing and zoning requirements are used to fine tune the mesh Parts created separately are glued merged together automatically by specifying a tolerance TrueGrid is based on a powerful technique known as the projection method The projection method allows faces edges and nodes of the mesh to be directly placed on surfaces Similarly edges and nodes of the mesh can be placed along curves In this sense TrueGrid is a constraint based mesh generator 2 Copyright 2001 by XYZ Scientific Applications Inc Additionally if TrueGrid is required to place two faces of the mesh sharing a common edge onto two different surfaces then it will automatically place the shared edge on the intersection of the two surfaces There is no need to construct the intersection curve of two surfaces TrueGrid will find the intersection curve automatically Likewise a vertex required to be on three surfaces will be placed at a common intersection point of all three surfaces Other notable features of TrueGrid include 1 TrueGrid is completely interactive 2 Any number of commands can be deactivated
69. odes on the block faces The mesh is complete Step 6 Interpolate Interior Block Nodes There is no difference between the last picture and the previous because interior nodes are not shown in either TrueGrid Tutorial The History Table Turning Commands Off and On A History Table of commands is kept by TrueGrid All the commands in the history table can be viewed by pressing the History button in the Edit button group of the Environment Window The history is also summoned by entering the ha story command at the text window prompt The history appears in the text menu window The entire history table will probably not be visible at one time There are several solutions to this problem Put the mouse in the text menu window and using the up arrow down arrow page up or page down keys to scroll the text Alternatively use the scroll bar on the right side of the window Another solution is to enlarge the window For the present example the history table contains all the projection commands The order of the commands in the table depends on the order in which they were issued Hilo TORI I ABLE active 2 surface projection progression L27 1 27 L 0 2 active 3 surface projection Progression Ly 1 27 I 27 active 4 surface projection Progression A 2 LA 1 2 active 5 surface projection Progression L 27 27 1I 25 active 6 surface projection Progression 1 A7 1 17 L 27 Each entr
70. on dialogue box and choose the same options as before Assign line definition number 3 to this final elliptic arc Enter the data for the line definition as shown below Copyright 2001 by XYZ Scientific Applications Inc length of first axis 0 25L length of second axis 0 25L x center 0L z center 0L beginning angle 0 ending angle 180L Angle between the major axis and the x axis rotation 0H View the two cross sections with cet 2 io S z TrueGrid 2D curves 6 00E 01 4 00E 01 2 00E 01 0 00E 00 2 00E 01 5 000E 01 1 000E 01 1 000E 01 3 000E 01 3 000E 01 x Cross Sections at the Ends of the Elbow Pipe To create the elbow pipe surface use a dialogue for the Surface Definition command Press the left mouse button on the SD button in the SURFACES submenu to create the dialogue box Enter 1 as the Surface Number Choose the option gt Sweep 2D Curves Along a 2D Curve The sweeping curve is curve definition 1 sweeping 2D curve number 1 Choose to place the cross sections on the left of the sweeping curve by selecting TrueGrid Tutorial 53 gt Sweep on left side of Sweeping curve The final surface is formed by placing 2D cross sections at various places along and orthogonal to the sweeping curve The position of a cross section along the sweeping curve 1s specified in terms of the arc length along the sweeping curve The arc length is always normalized so that O corresponds to the fir
71. rameter of the command You may enter as much of the command after the prompt as you wish even part of the next command TrueGrid Tutorial j N V Y Pressing the ESCape KEY in the middle of a command aborts that command Another way to correct any mistake is to simply redefine the surface Surface Definition 1 is a right circular cylinder of radius 2 whose axis of rotation passes through 0 0 0 and is parallel to 0 1 0 Both the front and back faces of the rod will lie on this cylinder Surface Definition 2 is a plane passing through the point 1 5 0 0 and perpendicular to 1 0 0 The left face of the rod will lie on this plane Surface Definition 3 is a plane passing through the point 1 5 0 0 and perpendicular to 1 0 0 The right side of the rod will lie on this plane Copyright 2001 by XYZ Scientific Applications Inc IED PEA i bounds the back face bounds the J top end Tem UT bf X bounds the front face the right side lies on this plane Surface Definition 4 is a sphere centered at O 3 0 and of radius 2 5 The bottom end of the rod will lie on this sphere Surface Definition 5 is a sphere centered at 0 3 0 and of radius 2 5 The top end of the rod will lie on this sphere The Block Command The actual mesh is now created using the block command At the merge gt prompt enter Block 1 9 1 407 1 A 27 0 O 2 The comman
72. rrent part The commands endpart merge will end the part and switch TrueGrid to the Merge Phase The computational window no longer exists because there may be several parts present in the Merge Phase Also nodes may be eliminated merged in this phase thereby destroyed the correspondence between the computational and physical domains No functions requiring the computational highlighting system are available including the peel commands Consequently the entire mesh is displayed after a draw command The MEASURE Command The measure command is in the DIAGNOSTICS submenu Move to that submenu and locate the measure command Press the left mouse button on the MEASURE button and a dialogue box appears In the measure dialogue choose the Orthogonal Test option by pressing the left mouse button anywhere on the string Execute the dialogue by pressing the EXECute button TrueGrid Tutorial Segments ELEMENT ORTHOGONALITY 25 00 5 00 15 00 15 00 De isolate elements whose measure is within a given range Either use a dialogue box to specify a range between 28 25 or directly issue the command elm 20 29 All the elements with angles between 62 and 65 degrees will be highlighted magenta The part can be removed from the picture using the command i Then only the selected elements remain in the picture Before trying another diagnostic command add the part back to the picture ap 1 This is nece
73. rt of the mesh The edges between the highlighted faces and the remaining part of the mesh are interpolated automatically So the mesh appears to be a single line segment Next faces of the mesh are positioned near the bend of the elbow pipe These graphics commands center the elbow of the pipe in the picture REST Ir O25 D 0 15 ZF 6 e a EE u a u os SST SEIN Wal a X RRNA I Wk 1 A Just Around the Bend Modify the computational selection just used by activating the second dot along the j index bar instead of the first The dots and segments toggle on and off So turn the first dot on the j index bar off by pressing the left mouse button on that dot again Use the TrueGrid Tutorial 59 Screen Plane option again to reposition the new region near Point A shown above The next region of interest is obtained by modifying the current selection so that the third dot on the j index bar is activated instead of the second With the Screen Plane option still in effect reposition the new region near Point B shown above The Screen Plane option is also the appropriate option for the next command Highlight the single block face shared by the larger and smaller rectangular blocks of the mesh Move this region so that it nearly aligns with Segment C shown above D Region to Place near Segment C Because blocks of the mesh are being pulled apart now the mesh is no longer one dimensional
74. s built the same way a single block mesh is built First the corners of the block are positioned Some corners are required to be on the sphere and others are not Those required to be on the sphere are projected to the closest point on the sphere relative to the corners initial position After all corners are positioned then block edges are interpolated This amounts to evenly distributing the edge nodes along a line connecting the corners Edges required to be on the sphere are projected to the sphere Next edge nodes are used to interpolate face nodes Faces required to be on the sphere are then projected to the sphere Finally interior nodes of each block are interpolated from the face nodes Notice that several blocks have some edges that are straight and others that are curved The faces interpolated from these edges are not simple surfaces 1 e non planar XO EF K K K K KK X Because of the way TrueGrid builds a block mesh there is no need to specify intermediate surfaces and curves between the sphere and the outer walls XO kK K K K Kk X The TrueGrid Challenge This mesh was built with just FOUR commands Try building a similar mesh using another mesh generator Compare the time it takes and the mesh quality 44 Copyright 2001 by XYZ Scientific Applications Inc Mesh Diagnostics Currently mesh diagnostics only exist in the Merge Phase You cannot directly enter the Merge Phase without ending the cu
75. s nodes to cluster near the elbow because nodal distances decrease from the bottom of the pipe to the elbow Now apply the double re spacing command to the entire region of the elbow pipe This time the clustering is done in the 1 direction to cluster nodes toward the sides of the pipe This command requires two ratios Use 1 1 2 for both ratios dro LL ha ee a ee eZ The first ratio causes distances to first increase with increasing i The second ratio has the opposite effect on the opposite side Therefore nodes cluster toward the sides near the pipe walls The last re spacing command is another double re spacing command This time highlight the middle third of the blocks of the elbow pipe Further restrict this selection to those about the cylindrical pipe 1 e between the second and third k partitions Use a double re spacing command to cluster nodes both toward the top of the pipe and toward the top of the cylindrical pipe 68 Copyright 2001 by XYZ Scientific Applications Inc Ges 2g 2s oa FT Ae aya Now draw the new picture Note Remember that clustering commands are translated to commands for edges Therefore these commands can be order dependent the last re spacing command applied to an edge is the one that ultimately applies Further Suggestions Clustering could also be done within the smaller cylindrical pipe The mesh in the pipes suffers from the same defect illustrated in the section Putting a
76. sh is refined is a classic symptom of a bad topology In these cases the user should consider a different topology for the mesh TrueGrid Tutorial 49 Intersecting Pipes A More Challenging Problem 50 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Intersecting Pipes TrueGrid display Used in this Example Technique of Skinning to build a Surface Extracting Curves from Surfaces Multi Block Part Interactive Placement of Regions of the Mesh Interactive Placement of Mesh Edges on a Curve or Surface Edge Interactive Mesh Refinement Mesh Zoning Part Replication Node Merging Prerequisites Familiarity with interactive graphics menus dialogue boxes single and multi block part examples Description The region inside two pipes that intersect 1s meshed One pipe is an elbow pipe with varying cross sections and the other pipe is a cylindrical pipe Zoning is performed to cluster nodes toward the walls of both pipes The symmetry of the problem is exploited only half of the model is constructed and the other half is created using part replication The mirror image part and the original part are glued together to form the final model Copyright 2001 by XYZ Scientific Applications Inc TULA AAN SA WW oN N A N N LA AZ JSS GLEE L7 LOT AT L M Q O se SoA a AL aly 04 UK Kes 3S se OO U Li ne LP 7
77. ssary because the measure command only measures those elements that the user has specified to be in the picture That is not to say only elements within the frame of the window are measured Orthogonality Test 2D Curve Windowy this command but all elements that are A new window whose title is 2D Curves appears In that window is a plot of the deviation angle from 90 degrees vs the number of segments The tallest peak is near 0 meaning that a substantial number of elements have nearly perfect 90 degree angles The absolute range of the test is printed in the text window measure ranges from 2st JOT CO 3 249846E 01 indicating that the element angles are roughly between 62 5 and 122 5 degrees The ELM Command The elm command is in the same DIAGNOSTICS submenu as the measure command The elm command allows you to Copyright 2001 by XYZ Scientific Applications Inc currently active and selected by the user To kill the 2D Curve Window use the window manager kill or quit option for the window TrueGrid Tutorial 45 The Butterfly Mesh Rounding a Corner 46 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Putting a Square Peg into a Round Hole Used in this example TrueGrid display Multiple Block Part Region Deletion Projection Node Merging Prerequisites Familiarity with interactive graphics and the previous multiple block example Description A technique
78. st end and to the other end number of 2D curve to be swept 2L relative arc length position O number of 2D curve to be swept 3L relative arc length position 1 No other cross sections are needed for this surface So choose gt End Swept Curve Surface Definition TrueGrid will smoothly interpolate between specified cross sections The cross sections of the swept surface are both semi circles and so the interpolated cross sections will also be semi circles Apply a transformation to the swept surface to bring it into position Under LIST OF TRANSFORMATIONS choose gt Rotate about the x axis and specify a rotation angle of 90 degrees angle degrees 90M Execute and quit the dialogue to define the upper half of the elbow pipe surface There are two more surfaces to be defined a cylinder and a plane of symmetry Define these surfaces using a dialogue box or by typing these commands SoU evils OOO LOO 1 54 Copyright 2001 by XYZ Scientific Applications Inc sd 3 plan 0 U 00 w Surface 2 is a cylinder of radius 0 1 whose axis is parallel to 1 0 0 and passes through 0 0 0 Surface 3 is a plane passing through 0 0 0 and whose normal is parallel to the vector 0 0 1 Extracting Curves from Surfaces It is sometimes convenient to have a curve along which to position an edge of the mesh In many such cases a contour of a surface used primarily for graphical purposes turns out to be
79. t 2001 by XYZ Scientific Applications Inc There are three types of input fields 1 Fields for entering a single number y coordinatea 2 Fields for entering a list of numbers lint of aurt aca definition rugibarsa 3 Fields for entering general strings PROBLEM TITLE In the first two cases input is checked as it is entered Characters that would create an invalid string are ignored Furthermore if just one number is required then TrueGrid will not allow a second number to be entered into that field Moving the Cursor in a Dialogue Box The active cursor can be repositioned to another character of the current field or to another field entirely using the left mouse button Press the left mouse button on the prompt itself to position the cursor at the end of the input field Alternatively press RETURN to move the cursor to the next available field If the current field is empty the cursor can always be moved from the field However if the current field is non empty and is not complete then TrueGrid will not allow the user to move the cursor from the current field For example 1 0e can be entered but is not complete TrueGrid informs the user of such problems by turning the active cursor blue The user must correct the problem before the cursor can be moved to another field The user can use the mouse to move the cursor to a previous character of the current field The backspace can be
80. t these when entering the command This creates a cylinder of radius 3 whose axis passes through 0 0 0 and is parallel to 0 0 1 Cutting Corners All four corner blocks can be highlighted and deleted at once Do this by activating the first and last segments of both the 1 and j index bars these are on the lower and right window borders respectively Then press the Delete button in the environment window re K 2 4 3 2 J I 2 3 4 U _Y Delete the Four Corner Blocks Projecting to the Cylinder Clear the current computational selection by pressing either the F2 KEY or CTRL D Now activate all segments on both the 1 and j index bars Activate all four endpoint dots of these index bars This selection consists of four block faces Use the Labels dialogue of the Environment Window to label the surface Use the Pick dialogue of the Environment Window to configure TrueGrid to choose objects by label Highlight the cylindrical surface by pressing the left mouse button on the label for this surface 48 Copyright 2001 by XYZ Scientific Applications Inc Finally press the Project button in the Environment Window to project the four highlighted faces to the cylinder T K 2 I 2 3 4 aoe aS Eee Faces Projected to the Cylinder The mesh is finished except for removing the redundant nodes on the block faces To do this end the part and change to the Merge Phase by issuing the commands endpart merge The
81. ter two points for the first segment of the curve 0 0 and 2 0 xl z1 x2 z2 0 0 2 OC The second segment is an elliptic arc length of first axis 1 length of second axis 1 x_center 2 y_center 1 beginning angle 90L ending angle 0 Angle between the major axis and the x axis rotation 0L The last segment is drawn from the last point of the elliptic arc to the final point xl z1 x2 z2 3 35 Make sure to press RETURN after entering the final line this checks for completeness Now press the EXEC QUIT button The 1vi command can be used to display the curve just created E L 3 TrueGrid Tutorial z TrueGrid 2D curves The Sweeping Curve Curve 1 Curve is used as a sweeping curve Cross sections of the pipe are defined perpendicular to and along this curve Two line definition commands define the cross sections at the ends of the pipe The curves are single elliptic arcs Therefore the option to choose in each of the next two dialogue boxes for the 1d command is gt Append An Elliptic Arc For the first of the two elliptic arcs use line definition number 2 and specify the data as indicated below length of first axis 0 5L length of second axis 0 5 x center 0L z center 0L beginning angle 0 ending angle 180L Angle Between the major axis and the x axis rotation 0 Press the EXEC QUIT button to execute and quit this dialogue box Now open another line definiti
82. the mesh still lie on one plane The final interactive repositioning will move the region around the smaller pipe away from this plane So issue the graphics commands REST RY 90 L 025 D l6 ZF 29 to produce a picture looking straight down the cylindrical pipe Copyright 2001 by XYZ Scientific Applications Inc _ Looking Down the Cylindrical Pipe Toward the Elbow Pipe Highlight the top face of the isolated block of the mesh This face lies on the second k partition between the second and third 1 partitions and between the second and third J partitions T K 3 4 3 2 J 2 3 OoOo ee The Top Face of the Isolated Block The picture looking down the end of the cylindrical pipe shows the desired position of the final mesh Notice in particular the darkened line This is the desired position of the face that is currently highlighted TrueGrid Tutorial 61 Choose the Z option for moving the region instead of the Screen Plane option This option allows points only to move parallel to the global z axis notice the triad Proceed to reposition the highlighted face Put the mesh back in a rest position Turn off the display of interior lines of the surfaces by issuing the command SQIne Oli The Mesh So Far Note that the curves have also been removed from the picture for the sake of clarity Positioning Edges of the Mesh Along Curves and Surface Edges The next commands position certain edges of the mesh
83. tion at each place where the i index is equal to one of these intermediate numbers The corresponding intermediate values in the x list are used to set the x coordinates of the nodes at the subdivisions An analogous statement applies to the j and k directions TrueGrid Terminology If is a number in the i list then the face where the 1 index is held constant at n is called an 1 partition Similarly a jJ partition is a face where the J index is held constant and equal to a number in the j list of the block command And a k partition is a face where the k index is held constant and equal to a number in the k list Note The mesh partitions shown below can be highlighted using the slicing plane feature Sample Mesh Partitions Created by the Block Command 40 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial The Computational Window always contains just the partitions created using the block command The computational partitions are always shown a fixed distanced from each other and therefore each block in the computational picture is always a cube For the current example the computational picture contains 27 cubes the user must issue a draw command to see the initial computational and or physical pictures K 2 3 4 3 2 J I 2 3 4 2 a A The Computational Representation For the previous single block example no intermediate numbers were specified in either the i list j list or k list
84. ue box only press and hold the right mouse button down and drag the mouse vertically the text will follow An efficient way to use dialogue boxes is to first choose all applicable options using the mouse and then to enter all data using only the keyboard So first choose the gt Sequence of Coordinate Pairs option by pressing the left mouse button anywhere on the entry Recall that the red character gt preceding the entry indicates the option is part of an exclusive list As soon as this option is chosen the others disappear from sight and the chosen entry is highlighted in yellow Also recall that an option can be deselected by pressing the left mouse button on this entry again After the Sequence of Coordinate Pairs entry 1s selected a prompt appears with a hollow green cursor The cursor is hollow because this new input field is not the active input field Next choose the entry gt Append Another Segment This time for the type of segment choose gt Append an Elliptic Arc There is another segment to add to this curve So again choose gt Append Another Segment The final segment is another polygonal segment So choose the 32 Copyright 2001 by XYZ Scientific Applications Inc gt Append Sequence of Coordinate Pairs Enter 1 for the curve definition number Either press RETURN or the space bar The space bar functions as a return because only one number can be entered in this field En
85. understand why the initial position of the mesh before projection affects the final node distribution For example two nodes that start at the same position will after a projection end up in the same position Also if a mesh is initialized non symmetrically about a symmetric object the resulting mesh will not be symmetric The first projection command places the bottom of the mesh first k partition onto the plane surface definition 3 The command crn 4 Joly od gt will perform this projection A draw command is not automatically issued when the projection command is typed Recall that projections can also be done using point and click highlight the faces to be projected highlight the surface onto which the faces are to be place and press the Project button A picture is automatically redrawn Surfaces must be displayed and labeled to perform interactive projections Use the Display List dialogue to put all surfaces into the picture and the Labels dialogue to label all surfaces Make sure the Label button in the Pick dialogue is set otherwise left mouse button presses to highlight a surface by label may be misinterpreted Highlight surface number 1 the region shown below and press the Project button Notice if only the segments were activated the selection would consist of all blocks within the largest rectangular piece of the mesh Once dots are activated the selection will consist only of block faces Three o
86. used to delete a previous character Or CTRL X can be used to delete the character beneath the cursor TrueGrid Tutorial 7 When the user presses the ENTER key to end the current field and begin the next the current field is marked finished with a red cursor The cursor will not return to this field again without positioning the cursor using the mouse Lists in Dialogue Boxes There are two types of lists that occur in dialogue boxes exclusive choose one and non exclusive many items can be chosen Exclusive lists have entries that begin with a red gt character Non exclusive lists have entries that begin with a red o An option title description is in white above the list For example he Eo HIKES OPTIONS faa OF Tilen im Any number of items can be chosen E rj 150 Dialogas n Gidi ai HFAA Geass SFCTION hist ELONE E nA CHOS SECTION DEFITREITIOSN Sls PTEE tht HFT FELI MERE H Only one item can be chosen 8 Copyright 2001 by XYZ Scientific Applications Inc Choose an item of a list by pressing the left mouse button anywhere on the text of that entry The text of the chosen entry will be highlighted in yellow To deselect the entry press the left mouse button on the entry again D idi ere IEAA CROSS SECTION MURRER GOB PENA CROSS SECTION DEF IRETION LFT s bon EF ET arere m ea meri rer le ban Fare When an entry of an exclusive list is chosen the other
87. utational highlighting by Ii NT pressing the F2 KEY Then type res on the i T fi command line and press the F1 KEY A Int HT d ae iy J I TTH escription of the highlighted region is put NTH onto the command line following res NETH Because a null selection makes no sense in a Neem WHS HE v L Finish the command by entering j 1 1 Zoning in the j direction Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial Clustering of Nodes Zoning in both Directions Double Relative Spacing Command drs SYNTAX res 1i_minj_min k_min i_max J _max k_max direction ratiol ratio2 where direction can be either i or k ratiol is a positive floating point number ratio2 is a positive floating point number DESCRIPTION The nodes of the specified region are clustered in a given direction Zoning near the minimum index of the given direction is controlled by the first ratio Zoning near the maximum index of the given direction is controlled by the second ratio If the second ratio is the reciprocal of the first then drs works the same way as res Example The drs command is particularly useful for fluids problems where nodes need to be clustered toward the walls of a mesh in order to resolve the boundary layer To achieve such clustering for the current example issue the three commands drs 111222 ie 1 2 drs 111222 j 1 21 2 drs 111222 k 1 21 2 To avoid typing the region each time us
88. ve Edge BB Sets Nearest Node F9 or F7 Prints KA x mh Y Wh Zz Point by Projection Z Buffer There are three different functions for the left mouse in the Part Phase Physical Window The left mouse button can be used to choose objects by their labels to choose the nearest mesh vertex and to interactively move portions of the mesh You must explicitly tell TrueGrid which of these actions to perform There was no need to do this in the Merge Phase because the left mouse button was used only to highlight a labeled object Finishing the problem at hand requires a few interactive projections An interactive projection requires the user to highlight a face of the mesh and to highlight a surface Therefore for the purposes of projection press the Pick button in the Environment Window to obtain the Pick Dialogue pictured above Then press the Label button to inform TrueGrid that you wish the left mouse button to be used to pick an object by its label Notice the sketch of the mouse with the left mouse button marked All functions using the left mouse button in the Physical Window are clearly marked in this manner Now TrueGrid is set up to pick a surface by its label So highlight the cylinder by finding the appropriate label this is surface definition 1 Highlight Faces of the Mesh to be Projected The front and back faces of the mesh are to be projected to the cylinder that was just
89. x Progression rrgi region 20 Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial A Single Block Part Copyright 2001 by XYZ Scientific Applications Inc TrueGrid Tutorial 21 Making a Single Block Part Introduced Here The Block Command Projection Method Intersection Algorithm Computational Highlighting System Interpolation Prerequisites The previous sections on interactive graphics labeling objects and choosing objects by label Description A single block part is created Each of the six faces in projected to a different surface to form a rounded end rod TrueGrid automatically places the edges of the block along intersections of the surfaces The corners of the block are automatically placed at the intersections of three surfaces The default interpolation takes care of the interior nodes Getting Started Run TrueGrid with no input file Enter the Merge Phase by typing the command merge followed by areturn This allows you to view the geometry for this problem as it is being created 22 Copyright 2001 by XYZ Scientific Applications Inc rest view side view The Geometry The mesh is determined by just a few surfaces The commands to create the geometry are listed below sd 1 cyli 0 sd 2 1 sd 3 plan 1 sd 4 O sd 5 O As an experiment enter only part of a given command before pressing ENTER TrueGrid will prompt you for the next required pa
90. x endpoints of the activated segments Now everything is set up to project Instead of using a label to reference the sphere try the command line approach instead First enter sfi TrueGrid Tutorial on the command line in the text menu window Then press the F1 KEY to translate the highlighted selection into a numerical description of the selection The numerical description will be appended to the current command line to give Sti A 3542 sje a The 2 sand 3 sindicate the partition numbers second and third partitions in each direction The negative signs indicate that the dots at 2 and 3 in all directions were turned on If the segments connecting the dots had not be activated then a O would have been inserted between the 2 s and 3 s Finish the command by adding sda 1 to the command line and by pressing the ENTER key The final command is SCL 2 o A 37 2 3 sc L You must issue a draw command to view the results Meshing commands issued from the command line or using dialogue boxes do not cause the mesh to be automatically displayed This way the experienced user can issue many commands before viewing the next picture Furthermore TrueGrid does not have to recompute the mesh until a draw command is issued The Peel Commands Before clearing the highlighting try out the graphics peel commands Select the Display List dialogue within the Environment Window This is the same dialogue used to
91. y of the history is composed of two lines The first line of each entry begins with one of three words indicating the status of the Copyright 2001 by XYZ Scientific Applications Inc command active deactivated or inactive Immediately following the status is a command sequence number Command sequence numbers are assigned sequentially when the command is issued The last part of the first line contains a brief description of the command The next line begins either with region or progression indicating which of the two ways of specifying part of the mesh was used Highlighting the Part of the Mesh to which a Command Applies Press the middle mouse button anywhere on the second line of the history entry for a command to highlight the part of the mesh to which a command applies This line begins with either progression or region Notice that both the computational and physical windows are highlighted This highlighted region can be used in subsequent commands or modified and used in subsequent commands Deactivating and Reactivating Commands To deactivate a command whose status is active press the middle mouse button on the word active A command is generated on the command line which when issued will deactivate the given command Press return to issue this command Multiple commands can be issued at one time Redraw the picture to see the result To reactivate a command whose status is deactivated pr

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