GDML USER'S GUIDE
Contents
1. So m 4 will be evaluated to 6 Matrices can of course be used inside loops there is where they are actually most useful We will see how to do this in section 3 5 1 Page 11 of 50 3 3 Materials 3 3 1 Isotopes Isotopes can be defined using a very simple contsruct lt isotope name its name Z atomic number N num of nucleons gt The following shows and example lt isotope name U235 Z 92 N 235 gt lt atom type A value 235 01 gt lt isotope gt lt isotope name U238 Z 92 N 238 gt lt atom type A value 235 03 gt lt isotope gt 3 3 2 Elements Elements can be defined using this very self explanatory construct lt element Z 8 formula 0 name Oxygen gt lt atom value 16 gt lt element gt Instead of an atomic number being used on a child node of the element declaration a fraction of an isotope can be used using lt fraction ref isotope name n fraction gt This is implemented as the following shows lt element name enriched_uranium gt lt fraction ref U235 n 0 9 gt lt fraction ref U238 n 0 1 gt lt element gt Page 12 of 50 3 3 3 Materials Materials can be defined in three ways The material can be defined directly from an element created from previously defined elements or materials on number of atoms and finally created as a fractional mixture of previously defined elements or materials2. material name A1 Z 13 0 gt lt D value 2 70 gt lt atom value 26 98 gt lt material gt lt material name Water formula H20 gt lt D value 1 0 gt composite n 2 ref Hydrogen gt lt composite n 1 ref Oxygen gt lt material gt lt material formula air name Air gt D value 0 0012899999999999999 fraction n 0 7 ref Nitrogen gt fraction n 0 3 ref Oxygen gt lt material gt Page 13 of 50 3 4 Solids 3 4 1 Box The GDML box is formed using the three standard dimensions x y and z The box therefore has 4 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a box made from the above dimensions lt box name thebox x 30 y 30 z 30 lunit mm gt 3 4 2 Cone Segment The GDML Cone Segment is formed using 7 dimensions rmin1 inner radius at base of cone rmax1 outer radius at base of cone rmin2 inner radius at top of cone rmax2 outer radius at top of cone Z height of cone segment startphi start angle of the segment deltaphi angle of the segment The cone segment therefore has 8 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a co
3. Finally the lt setup gt lt setup gt block serves to specify the top volume of the geometry tree It is possible to define several setups within one file allowing testing different subparts or different configurations included in the same file of the geometry tree without changing the GDML file Page 7 of 50 3 1 1 Splitting GDML file using ENTITY Any GDML file can be split into several files which are combined together during the parsing by using the ENTITY statement The files included in such a way are not standalone GDML files they simply contain parts of the GDML description and in general are meaningful only when put all together In order to use such a mechanism one has to first declare the given ENTITY just after the lt xml gt tag lt DOCTYPE gdml lt ENTITY materials SYSTEM materials xml 1 gt where materials xml is the name of the file to be included and materials is the ENTITY name that we have assigned to it The entity can be then used anywhere inside the GDML description lt gdml gt materials lt gdml gt The materials line is then replaced during parsing by the contents of materials xm1 file 3 1 2 Multiple GDML files It is also possible to define the geometry in the form of several standalone GDML files each one representing a module of the setup we want to describe Each GDML file would contain only the materials the solids and the vol
4. finclude G4GDMLParser hh 2 Instantiate a Geant4 parser object G4GDMLParser parser 3 Call the parse method G4LogicalVolume STW parser ParseST filename med mat geo mat This method takes three parameters the first one is a string which specifies the name without file extension for the geom and tree files assumed to have the same names and be located in the current directory It returns a pointer of a generated mother volume with med mat material pointer associated including the imported tessellated geometry with geom mat material pointer associated Common vertices will not be repeated in the define section i e facets sharing the same vertex will refer to the same vertex name defined at the beginning of the GDML file In this case there will not be any two vertices with the same coordinates During a test a input geom file of 9 5 MB could be saved in a GDML output file of 10 5 MB the same input file would have become a 33 MB GDML output file with repetition of common vertices 4 Call the dump method parser Write output gdml STW phys The same method of the parser for writing the GDML output file can be used by passing the placed physical volume pointer of such geometry The result is a GDML file corresponding to the geom and tree files previously taken as input 5 User extensions to GDML using Geant4 The GDML syntax is defined in an XML schema Inside the schema are all the definitions of
5. startPhi start angle of the segment openPhi angle of the segment numRZ number of zplanes forming polycone numSide number of sides zplane inner radius outer radius and z coordinate of each plane The following example illustrates its construction lt polycone dimensions startPhi 30 openPhi 60 numRZ 2 numSide 3 lunit mm aunit deg lt zplane rmin 0 rmax 2 z 10 gt lt zplane rmin 0 rmax 4 z 20 polycone dimensions gt 3 5 3 13 Dimensions of Parametrised Ellipsoid The GDML dimensions of a parameterised general tellipsoid are given using ax length of semi axis in x direction by length of semi axis in y direction CZ length of semi axis in z direction zcut1 lower cut plane level at z solid lies above this plane zcut2 upper cut plane level at z solid lies below this plane Page 38 of 50 The following example illustrates its construction lt ellipsoid dimensions ax 30 by 60 cz 20 zcutl 30 zcut2 30 lunit mm gt 3 5 4 GDML Modules GDML modules are GDML files used in the definition of complex geometries They allow an easier to understand view of big geometries as they split it into smaller and therefore more readable pieces A GDML module is a normal GDML file and it is completely independent from all the other modules also from its mother module it contains all the information definitions materials solids and volumes it needs to be fully
6. 3 5 1 Loops Loops can be used to avoid tedious repetitions of definitions To use a loop you need to define a variable first section 3 2 1 Suppose you defined a variable x with 0 initial value variable name x value 0 then you can use it inside a loop statement loop for x to 8 step 2 lt loop gt The code within the loop tags will we executed 5 times in this case because the variable x starting from the initial value of 0 as in its definition will be increased by 2 according to the step value for each loop until it reaches the value of 8 as stated in the to attribute Loops are very useful to access elements of matrices see section 3 2 2 for example wan variable name i value 1 matrix name m coldim 3 values 0 4 9 126 8 5 T 21 34 6 7 B os loop for i to 3 step 1 sm 4 us loop We are able to access the three elements of the first row of the matrix i e 0 4 9 and 126 Loops can be used when defining solids logical volumes and physical volumes let s see how this is done in practice Suppose we want to create the following structure Page 30 of 50 We need to write the code for 5 boxes 5 logical volumes that refer to the boxes and 5 physical volumes that refer to the 5 logical volumes The code would be the following lt solids gt Xbox name boxl x 10 yz 5 zz e 5 gt Xbox name box2 x 9 y 4
7. the tags and the rules associated to those tags The GDML schema can be extended as XML is a fully extendable mark up language This section will discuss how to add custom elements to GDML This could be useful if certain information is required to be contained in the GDML file for an application of GDML The extension can be defined as such to contain a new tag and values within whichever chosen part of the GDML file It may be the case that within the binding to GDML being used there are methods already in place for information not supported by the GDML schema in which case the user extension facility will help implementing that An example of a user extension is implemented in Geant4 and can be found in the directory geant4 examples persistency gdm1 G03 This example will be used as a point of reference throughout this section Page 47 of 50 The Schema The first step in extending GDML is to redefine the GDML schema It needs to include the custom elements of the extension The extension is done in a separate schema file that imports the original schema as opposed to adding new parts to the old one The schema for example c03 is found in a subdirectory of the example SimpleExtensionSchema SimpleExtension xsd The original main GDML schema is imported from its local relative location within your GDML directory The new schema file normally will need to contain two main parts 5 1 A redefine element This element uses t
8. v2y 2 v3x 3 v3y 3 v4x 4 v4y 4 v5x 10 v5y 10 v6x 11 voy 11 v7x 12 v7y 12 v8x 13 v8y 13 dz 20 lunit mm gt 3 4 26 Tessellated solid NB supported only by Geant4 The GDML tessellated solid can be made of any number of triangular and or quadrangular facets forming a closed space Each facet is defined by specifying references to names of three for the triangular one or four for the quadrangular one vertices The vertices are standard position elements and should be declared beforehand within the define section If a referenced vertex is not defined an error message is displayed By looking from the outside of the tessellated solid vertices are listed in the anti clockwise order for each of the facets There are two ways of defining vertices ABSOLUTE default and RELATIVE In the first case each vertex coordinates are considered to be absolute coordinates in the reference system of the solid In the second case only the first listed vertex has absolute coordinates while the remaining ones are considered to be translations from the first one The tessellated solid has only one attribute name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The sub elements of tessellated solid element are all of FacetType in other words they are the triangular and or quadrangular facets the solid is made of The triangular quadrangular facet element contains three four
9. 3 7 Dimensions of Parameterised Hype The GDML dimensions of a parameterised hype are given using rmin inside radius rmax outside radius Z length ihst inner stereo outst outer stereo The following example illustrates its construction hype dimensions rmin 30 rmax 60 z 160 lunit mm inst 3 outst 4 gt 3 5 3 8 Dimensions of Parameterised Parallelepiped The GDML dimensions of a parameterised parallelepiped are given using x length of x y length of y Z length of z alpha angle between x and z plane theta polar angle of the line joining the centre of the faces z amp z in z phi azimuthal angle of the line joining the centre of the faces z amp z in z The following example illustrates its construction Page 36 of 50 lt para_dimensions x 30 y 60 z 60 alpha 1 theta 1 phi 1 lunit mm aunit rad gt 3 5 3 9 Dimensions of Parameterised Trapezoid The GDML dimensions of a parameterised trapezoid are given using x1 x length at z x2 x length at z y1 y length at z y2 y length at z Z z length The following example illustrates its construction trd dimensions x1 30 x2 60 yl 20 y2 40 z 30 lunit mm 3 5 3 10 Dimensions of Parameterised General Trapezoid The GDML dimensions of a parameterised general trapezoid are given using x1 length along x at side y y1 of the face at z x2 length along x at side y y1 of the face at
10. 6 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a twisted tube segment made from the above dimensions lt twistedtubs name twisttube endinnerrad 1 endouterrad 4 zlen 20 phi 3 twistedangle 1 aunit rad lunit mm gt 3 4 24 Extruded Solid The GDML Extruded Solid Xtru is formed using 2 attributes twoDimVertex vertices of an unbound blueprint polygon section z sections The twoDimVertex element is required to be used at least 3 times and the section element is required to be used at least twice You can use both as many times as you like The twoDimVertex is formed using the 2 attributes shown below X x coordinate of the vertex y y coordinate of the vertex The section is formed using the 5 attributes shown below zOrder index of the section must be between 0 and n 1 where n is the number of sections zPosition distance from the plane z 0 xOffset x offset from centre point of original plane yOffset y offset from centre point of original plane scalingFactor proportion to original blueprint Page 24 of 50 The Xtru therefore has a minimum of 17 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of an Xtru made from the a
11. attributes vertex1 vertex2 vertex3 vertex4 being references to the vertices defined beforehand of the facet and an optional attribute t ype indicated whether the coordinates of the vertices are ABSOLUTE default or RELATIVE The following example illustrates the construction of a simple tessellated solid made from a square base and six triangular walls We first define the vertices define position name v1 x 10 y 10 z 0 unit m gt lt position name v2 x 10 y 10 z 0 unit m gt lt position name v3 x 10 y 10 z 0 unit m gt lt position name v4 x 10 y 10 z 0 unit m gt position name v5 x 7 y 3 z 20 unit m gt position name v6 x 3 y 7 zz 5 unit m gt lt define gt and then we build the tessellated solid out of them lt tessellated name pyramid gt triangular vertexl v1 vertex2 v2 vertex3 v6 type ABSOLUTE gt triangular vertexl v2 vertex2 v3 vertex3 v6 type ABSOLUTE gt triangular vertexl v3 vertex2 v4 vertex3 v5 type ABSOLUTE gt triangular vertexl v4 vertex2 v1 vertex3 v5 type ABSOLUTE gt triangular vertexl v1 vertex2 v6 vertex3 v5 type ABSOLUTE gt triangular vertexl v6 vertex2 v3 vertex3 v5 type ABSOLUTE gt lt quadrangular vertexl v4 vertex2 2 v3 vertex3 v2 vertex4 v1 type ABSOLUTE tessellated Page 26 of 5
12. ref TrackerinWorldrot gt lt physvol gt lt volume gt lt structure gt lt setup name Default version 1 0 gt lt world ref World gt lt setup gt gdml1 One can distinguish there five parts each holding specific type of data The define define block contains numerical values of different constants positions rotations and scales that will be used later on in the geometry construction The materials lt materials gt block contains definitions of all the materials used in the given geometry The supported forms are simple materials which are made from one element as well as mixtures Mixtures can be composed on the basis of fraction of mass or atom count The soiids solids block is the collection of all solid definitions which are used in the given geometry description The presently supported solids are described in Section 3 4 Page 6 of 50 Composite solids made using Boolean operation union subtraction intersection are also supported The structure lt structure gt block contains the actual implementation of the geometry tree together with the assignment of solids and materials The hierarchy of volumes is defined by specifying the daughter volumes physvol positioned inside a volume Constructions like assembly volumes reflections replicas and divisions are possible A more detailed discussion of the structure block can be found in Section 3 5
13. 0 e 5 Gs 6 yi 3 47 5 4 O 10 10 0 1 10 10 0 92 10 10 0 Figure graphical representation of the tessellated solid as described in the example 3 4 27 Tetrahedron The tetrahedron solid in GDML is defined by specifying the coordinates of the four vertices In order for the solid not to be degenerated the four points must not lie on the same surface The tet solid element contains the standard name attribute and four attributes being references to the vertices namely vertex1 vertex2 vertex3 and vertex4 These vertices are standard position elements which must be defined beforehand within the define part The following example illustrates the construction of the tetrahedron lt define gt position name v1 x 10 y 10 z 0 gt position name v2 x 10 y 10 z 0 gt position name v3 x 10 y 10 z 0 gt lt position name v4 x 0 y 0 z 10 gt lt define gt tet name halfpyramid vertexl v1 vertex2 v2 vertex3 v3 vertex4 v4 Page 27 of 50 3 4 28 Using loops for solids Suppose you want to define a set of solids with the same shape but with dimensions varying according to a particular function In this case loops are very useful because the avoid repetition of solids definitions For a more detailed discussion on loops please refer to Section 3 5 1 The following example shows you how to use a loop to define a set 10 of boxes
14. 15 dz 20 aunit rad lunit mm 3 4 8 Parallelepiped The GDML Parallelepiped is formed using 6 dimensions x length of x y length of y Z length of z alpha angle between x and z planes theta polar angle of the line joining the centres of the faces at z amp z in z phi azimuthal angle of the line joining the centres of faces at z amp z in z The Parallelepiped therefore has 7 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a parallelepiped made from the above dimensions Page 16 of 50 lt para name thepara x 10 y 10 z 10 alpha 1 theta 1 phi 1 aunit rad lunit mm gt 3 4 9 Polycone The GDML Polycone can be described in two ways as Polycone using zplanes with rmin and rmax and as Generic Polycone using vertices with r z coordinates The GDML Polycone is described using the following information startphi start angle of the segment if not given 0 0 is defaulted deltaphi angle of the segment zplane see below The zplane element is required to be used at least once You can use it as many times as you like The zplane is formed using the 3 attributes shown above rmin inner radius of cone at this point if not given 0 0 is defaulted rmax outer radius of cone at this point Z z coordinate of the plane The Polycone therefore ha
15. 5 zg 4 gt Xbox name box3 x 8 y 4 z 3 2 gt Xbox name box4 xz 7 y 3 57 z 2 56 Xbox name box5 x 6 y 3 z 2 048 lt solids gt lt structure gt volume name volbox1 gt lt solidref ref box1 gt lt materialref ref iron gt lt volume gt lt volume name volbox2 gt lt solidref ref box2 gt lt materialref ref iron gt lt volume gt volume name volbox3 lt solidref ref box3 gt lt materialref ref iron gt lt volume gt volume name volbox4 lt solidref ref box4 materialref ref iron volume volume name volbox5 gt lt solidref ref box5 gt lt materialref ref iron gt lt volume gt volume name world gt lt physvol gt lt volumeref ref volbox1 gt position x 5 yz 0 z 40 gt lt physvol gt lt physvol gt lt volumeref ref volbox2 gt position x 5 y 2 z 38 lt physvol gt lt physvol gt lt volumeref ref volbox3 gt position x 5 yz 3 5 z 36 gt physvol lt physvol gt lt volumeref ref volbox4 gt position x 5 yz 3 9 z 34 gt physvol lt physvol gt lt volumeref ref volbox5 gt position x 5 y 4 15 z 32 gt lt physvol gt lt volume gt lt structure gt Page 31 of 50 Of course th
16. E RE NRA RAR RARE EAEE ShA 19 DAS SSplete ain a a a a 19 34TA A o A HR A DV debe ta tra AE E 20 3 4 15 Trapezoid x amp y varying along A tt a 20 AO General Trapezoid ous e 20 Page 2 of 50 3 4 17 Tube with Hyperbolic Profile t ae ues Rb tatus 21 BAA Be et up rN Wad tocara Hrs abd ei Md et ue RN de luta e ped 21 S4 19 TORS Segno A A t ete ude nen Seca A ien enn 22 54420 JA BOX Lese be nd A 22 34 21 Twisted LtapeZOId o oiii a a aa R 23 3 4 22 Twisted General Trapezoid a ain cii cte dt 23 34203 Twisted T be Md iia 24 3424 Extruded Solide aede ut p tie leur O 24 3 4 25 Arbitrary Trapezoid CATS Lus a la 23 3 426 Tessollated Mis 26 3427 Tetrahedron susci eios dedico a ed in dus on brevedad Wea db pud aive 27 3 4 28 Using loops for sold edestedntwansetast cas cienea eee tasagedetaokaseaneeas 28 2429 OA da tl anata atta cet 28 e A IS 29 3 5 1 Eo Tr 30 3 5 2 R plicated Volumes tox eto e Net E lee desees E EE 32 3 5 3 Parameterised Volumes ia 33 3 5 3 1 Dimensions of Parameterised Box sss 34 3 5 3 2 Dimensions of Parameterised Tube essere 34 3 5 3 3 Dimensions of Parameterised Cone sse 35 3 5 3 4 Dimensions of Parameterised Orb e ete ee ovens 35 3 5 3 5 Dimensions of Parameterised Sphere oooocnnncciocococcconcnonnnconncconoconcconnncnnncnns 35 3 5 3 6 Dimensions of Parameterised Torus essere 36 3 5 3 7 Dimensions of Parameterised Hy
17. GDML USER S GUIDE Version 2 5 Page 1 of 50 Contents GDME USERS GUIDE pindi Sah So ak a eiusd a ae eti tate pedes 1 CONG TS PL HD EP 2 Ts JGR OAC EOIN iS 4 Ze tna 5 2 1 Installation of GDML in Geantd iiiuieee e errem te treten nne etae etra eren dida 5 2 2 Runing simple examples aaa 2 3e gt COMES COSI A alas 6 S41 t General St PU EO e 6 3 1 1 Splitting GDML file using ENTITY is 8 21 2 M ltiple CD NIE HIES ado 8 CNN A NS 9 3 2 1 COSAS A s Saga d RR en REN ta dane eun 9 3 2 2 Quantes ur ue IS o A 9 3 2 3 Variable a NE 9 3 2 4 POSITIONS e 9 3 2 5 A A A A EA 10 3 2 6 SodleSu ar E uA Eie 10 3 2 7 Matices aena A EE 10 3 37 Mat rialS nespala i stai poete esi ch ada Pe tata but aaa acit d ve ase aa a a etg 12 3 3 1 TOP ii 12 3 3 2 A e E E E ES 12 3 3 3 Matta a OS 13 BiB O MT 14 3 4 1 BOK A 14 3 4 2 CONG SE DIDI oo A oU M ie iM estat due T ae 14 3 4 3 A sacectsns icc eteccanatd seco home tedi sodes eas MO E EC D DUE 14 3 4 4 Elliptical Tb ia 15 3 4 5 Elliptical C O06 oder A Swedes aw DIMUS 15 3 4 6 jj sept PL NECEM 15 3 4 7 A E a 16 3 4 8 Paralleleplped edes tod eee p o 16 3 4 9 Polycone is 17 2d TU Generne Polyoofie sauce oe p ae Suas scelestus UE Sel a clay aa tes 17 JALE Polyhedron eee iino Vett um eu e asc s Roe ac mne 18 SAAD Genere Polyhedron nsoni nan n AE AE
18. anager GetTransportationManager gt GetNavigatorForTracking GetWorldVolume 3 Instantiate the parser and write to file G4GDMLParser parser parser Write output gdml W true path to GDML schema The last parameter is optional and refers to the GDML Schema path it is very important to set this right in order to allow for comparison with the Schema while reading the file back to Geant4 the path can either be an absolute directory path relative to the system schema location local to that system or an URL to the Schema By default the schema location points to the latest version of the GDML schema located in the GDML web site There exists also an optional third parameter which is a Boolean value set by default to TRUE This parameter tells how you would like the names of volumes as well as of solids materials and all entities to be formatted in your output GDML file true default The names will be concatenated with their logical address in hexadecimal format This is to avoid name duplication in the GDML output in fact Geant4 allows different volumes as well as materials and solids with the same name When you will read the GDML output file back into Geant4 the address part will be stripped off and you will have the original names This is almost always safe false The names will NOT be concatenated with anything So the names in the output file will correspond exactly to the ones you have in Gea
19. ave been tested with the ST Viewer can be found at http www steptools com ST Viewer uses intermediate files to store CAD geometry and structure information These files with geom and tree extensions respectively use an internal format that can be parsed and translated into GDML format using the functionalities provided by the Geant4 GDML plug in The geometry of the solids is defined by means of triangular facets i e every solid in the geom files is a tessellated solid made of only triangular facets Therefore the GDML output will be a collection of tessellated solids where each solid has its own set of facets that are in turn defined by a set of three vertices The vertices are named vectors of three values x y and z coordinates and are defined in the beginning of the GDML file The facets within a tessellated solid contain references to the names not the values of the three vertices they are made of for more information on how a tessellated solid is defined in GDML please refer to the GDML Solids Schema solids xsd Of course multiple facets may share a common vertex therefore in their definition there will be a reference to the same vertex name Again the actual values of the vertices vectors are stored in the first part the one enclosed by the lt define gt and lt define gt tags of the GDML file In order to use the parser in your own application you need to Page 46 of 50 1 Include the Geant4 parser header
20. bove dimensions lt xtru name lt xtru gt lt twoDimVertex x lt twoDimVertex x lt twoDimVertex x lt section zOrder lt section zOrder theXtru lunit M EA y 9 y 5 y zPosition 2 xOffset 5 zPosition 5 xOffset 3 mm gt gt gt yOffset 3 scalingFactor 3 gt yOffset 5 scalingFactor 1 gt 3 4 25 Arbitrary Trapezoid Arb8 The GDML Arb8 arbitrary trapezoid with less than 8 vertices is formed using 17 dimensions It s made up of two quadrilaterals sitting on parallel planes V1 to V4 define the vertices for the quadrilateral base situated at dz V5 to V8 define the vertices for the other quadrilateral situated at dx v1x vly v2x v2y v3x v3y v4x vertex 1 x position vertex 1 y position vertex 2 x position vertex 2 y position vertex 3 x position vertex 3 y position vertex 4 x position vertex 4 y position v8x dz vertex 5 x position vertex 5 y position vertex 6 x position vertex 6 y position vertex 7 x position vertex 7 y position vertex 8 x position vertex 8 y position half z length The Arb8 therefore has a minimum of 18 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of an Arb8 made from the above dimensions Page 25 of 50 lt arb8 name thearb8 vlx 1 vly 1 v2x 2
21. clared in the structure section structure World volume is declared percer d materialref ref Air solidref ref det volume Physical Volumes placed inside a Logical Volume with volume names Worlg s a specified position rotation materialref ref Air and scale lt solidref ref world lt physvol gt lt volumeref ref Detector gt lt positionref ref posl gt The top volume of the lt rotationref ref rot1 gt geometry is specified A ct Te dis Page 43 of 50 4 Importing and exporting GDML files 4 1 GDML Reading 4 1 1 Importing GDML files into Geant4 Geometry GDML files can be directly imported into Geant4 geometry using the GDML plug in facility in your Geant4 application Generally you will want to put the following lines into your DetectorCostruction Class In the class constructor as far as the initializations are concerned step 2 In the construct method steps 3 and 4 This can be done in four steps 1 Include the necessary header files include G4GDMLParser hh 2 Declare and initialize properly the parser G4GDMLParser parser source file gdml will be your GDML source file in case of multiple GDML files modules you should put the main GDML file there the main mother module 3 Run the parser parser Read source file gdml If solids or other entities with the same name are found in different modules a war
22. defined It defines a logical volume which corresponds to its world volume which can be referenced by physical volumes of other modules which are called mother modules To include a GDML module say child gdml in a mother module say mother gdml in the structure section of the mother module you should add a physical volume which points to the child module as in the following example Instead of having one file mother gdml lt volume name child gt lt materialref ref Alluminium gt lt solidref ref ChildBox gt lt volume gt lt volume name mother gt lt materialref ref Iron gt lt solidref ref MotherBox gt lt physvol gt lt volumeref ref child gt lt positionref ref center gt lt rotationref ref identity gt lt physvol gt lt volume gt You can define child logical volume in a different GDML file so you will have two files mother gdml lt volume name mother gt lt materialref ref Iron gt lt solidref ref MotherBox gt lt physvol gt file name child gdml gt lt positionref ref center gt lt rotationref ref identity gt lt physvol gt lt volume gt child gdml lt volume name child gt lt materialref ref Alluminium gt lt solidref ref ChildBox gt lt volume gt Page 39 of 50 So in the general case instead of writing lt volumeref ref logical volume gt You wil
23. defined they can be referenced in place where scales are expected Scale can be used to implement reflection and has no units A scale can be defined as in the following example scale name my reflection x 1 yz 1 zz 1 3 2 7 Matrices A matrix definition allows you to store values in matrix format The definition of a matrix is very simple matrix name name coldim number of columns values space separated values gt A simple example follows matrix name m coldim 3 values 0 4 9 126 8 5 7 21 34 6 7 9 Or you could also write it like this visually clearer matrix name m coldim 3 values 0 4 9 126 8 55 y 21 34 6 7 9 The elements of a matrix can be accessed anywhere after the definition of the matrix itself just variables To access them you have to use the following syntax matrix name row number column number For example Page 10 of 50 m 3 1 will be evaluated to 34 6 You can also put variables inside the square brackets like this m y y So if y 3 this will be evaluated to 9 Just be sure that the values of the variables don t exceed the matrix dimensions otherwise you will get an error when processing the file A matrix with coldim 1 is a vector and its elements may be accessed using only one index as in the following example matrix name m coldim 1 values 4 9 12 6 7 9
24. e auxiliary information block It is important to stress here that the GDML parser does not interpret in any way the auxiliary attributes The auxiliary attributes are stored in memory and available to the user once the parsing is done The auxiliary tags are placed within a volume like this volume name main gt materialref ref Iron lt solidref ref Box lt physvol gt Page 40 of 50 lt volumeref ref world gt lt positionref ref center gt lt rotationref ref identity gt lt physvol gt auxiliary auxtype SensDet auxvalue veloSD1 auxiliary auxtype Color auxvalue blue gt lt volume gt In Geant4 an additional GDML file example is auxiliary gdm1 located in example G01 provided in the Geant4 distribution the same example also provides a snippet of code in its main program showing how to retrieve the auxiliary information Example co4 instead shows how to define a sensitive detector associated to a logical volume using the Auxiliary Information field 0 Auxiliary User Information Since version 3 1 2 of the schema it is possible to specify an optional auxiliary block userinfo lt userinfo gt after the structure lt structure gt block where a generic list of auxiliary tags can be included to describe specific features of a model which are then properly treated by the client code Here is an example on how to represent geometrical reg
25. ef union rotation lt union gt Another way to describe Union Solid is by using the MultiUnion construct which offers possibility to make union of many solids The following example illustrates the construction of a MultiUnion structure Page 28 of 50 Xbox name box first x 1 y 5 z 20 Xbox name box second x 4 yz 4 5 z 18 gt multiUnion name multiUnion multiUnionNode name node 1 solid ref box first gt multiUnionNode multiUnionNode name node 2 solid ref box second gt lt positionref ref union position gt lt rotationref ref union rotation gt lt multiUnionNode gt lt multiUnion gt 3 5 Structure The structure section is where volumes in the geometry are defined Volumes are referenced to solids and materials defined earlier to form the shape and composition of that volume This volume is then a logical volume Volumes can be placed within this logical volume these volumes are called physical volumes They can be positioned and rotated how you wish within the logical volume An example of the GDML for this is below lt volume name World gt lt materialref ref Air gt lt solidref ref WorldBox gt lt physvol gt lt volumeref ref vol0 gt lt positionref ref center gt lt rotationref ref identity gt lt physvol gt lt volume gt Page 29 of 50
26. eneral Trapezoid NB supported only by Geant4 The GDML Twisted General Trapezoid is formed using 11 dimensions PhiTwist twist angle Z length along z axis Theta polar angle to faces joining at z Phi azimuthal angle of line joining centre of z face to centre of z face y1 length along y at the face z x1 length along x at side y y1 of the face at z x2 length along x at side y y1 of the face at z y2 length along y at the face z x3 length along x at side y y1 of the face at z x4 length along x at side y y1 of the face at z Alph angle with respect to the y axis from the centre of the side The Twisted General Trapezoid therefore has a minimum of 12 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a General Twisted Trapezoid made from the above dimensions Page 23 of 50 lt twistedtrap name twisttrap PhiTwist 1 z 10 Theta 1 Phi 2 yl 15 x1 10 x2 10 y2 15 x3 10 x4 10 Alph 1 aunit rad lunit mm gt 3 4 23 Twisted Tube Segment NB supported only by Geant4 The GDML Twisted Tube Segment is formed using 5 dimensions endinnerrad inside radius of segment endouterrad outside radius of segment zlen z length of tube segment twistedangle twist angle phi phi angle of segment The Twisted Tube segment therefore has a minimum of
27. eref ref Chamber parameterised position size parameters number 1 position name positionCopyl x 0 y 0 z 1500 gt Xbox dimensions x 240 yz 240 z 100 lt parameters gt lt parameters number 2 lt position name positionCopy2 x 0 y 0 zz 700 Xbox dimensions x 672 yz 672 z 100 lt parameters gt lt parameterised position size paramvol volume lt structure gt For giving the dimensions of each parameterised solid in GDML a special syntax is used 3 5 3 1 Dimensions of Parameterised Box The GDML dimensions of a parameterised box have the following form with 3 standard dimensions x y and z Example Xbox dimensions x 30 y 30 z 30 lunit mm gt 3 5 3 2 Dimensions of Parameterised Tube The GDML dimensions of a parameterised tube are given using INR inside radius of segment OutR outside radius of segment hz z length of tube segment StartPhi starting phi position angle of segment DeltaPhi delta angle of segment The following example illustrates its construction lt tube dimensions InR 30 OutR 60 hz 30 lunit mm StartPhi 60 DeltaPhi 30 aunit deg gt Page 34 of 50 3 5 3 3 Dimensions of Parameterised Cone The GDML dimensions of a parameterised cone are given using rmin1 inside radius at base of cone rmax1 outside radius at base of cone rmin2 inside radius at top of cone rmax2 outside rad
28. es as you like The rzpoint is formed using the 2 attributes shown above r r coordinate of this point z coordinate of this point The Generic Polyhedra therefore has a minimum of 6 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a polyhedra made from the above dimensions lt genericPolyhedra name thepolyhedra startphi 1 deltaphi 4 numsides 10 aunit rad lunit mm gt rzpoint r 1 z 10 lt rzpoint r 3 z 12 rzpoint r 1 z 12 lt genericPolyhedra gt 3 4 13 Sphere The GDML Sphere is formed using 6 dimensions rmin inner radius if not given 0 0 is defaulted rmax outer radius startphi starting angle of the segment if not given 0 0 is defaulted deltaphi delta angle of the segment starttheta starting angle of the segment if not given 0 0 is defaulted deltatheta delta angle of the segment The Sphere therefore has a minimum of 7 attributes the other being name which is standard for any solidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a sphere made from the above dimensions Page 19 of 50 lt sphere name thesphere rmin 1 rmax 4 deltaphi 1 deltatheta 1 aunit rad lunit mm gt 3 4 14 Torus Segment The GDML Tor
29. he default file is color extension gdml which defines a single colored box in the world volume Page 50 of 50
30. he extension schema to modify existing GDML elements by adding additional content This is called by this line which gives the location of the schema to redefine lt xs redefine schemaLocation schema gdml xsd gt In most cases the extension will consist in defining new objects like color to a volume etc In such case the redefine needs to add a ReferenceType to the base it needs to be added to lt xs extension base VolumeType gt lt xs sequence gt lt xs element minOccurs 0 maxOccurs 1 name colourref type ReferenceType gt lt xs sequence gt lt xs extension gt 5 2 New Elements The new schema will need to define the new element that the ReferenceType will be referencing to In the example of adding a color reference to a volume the element color will need to be defined When elements are defined attributes of that element are defined within it but if tags within the element contain more than one attribute a type needs to be defined and then referenced to This is implemented in the c03 schema file All the new elements can t be contained inside the lt gdm1 gt tag as they are not part of the original schema there needs to be a new container defined that contains the new elements AND replaces the original gam1 tag we call it here lt gdml_simple extension A new special tag lt extension gt is used to include all new tags to be considered as extension to the original GDML schema in our e
31. ions with energy cuts associated to logical volumes in Geant4 userinfo auxiliary auxtype Region auxvalue DefaultRegionForTheWorld auxiliary auxtype volume auxvalue World gt auxiliary auxtype gamcut auxunit mm auxvalue 0 7 auxiliary auxtype ecut auxunit mm auxvalue 0 7 auxiliary auxtype poscut auxunit mm auxvalue 0 7 auxiliary auxtype pcut auxunit mm auxvalue 0 7 auxiliary auxiliary auxtype Region auxvalue CalorA auxiliary auxtype volume auxvalue CalorA auxiliary auxtype gamcut auxunit mm auxvalue 0 2 auxiliary auxtype ecut auxunit mm auxvalue 0 2 auxiliary auxtype poscut auxunit mm auxvalue 0 2 auxiliary auxtype pcut auxunit mm auxvalue 0 2 auxiliary auxiliary auxtype Region auxvalue CalorB auxiliary userinfo Page 41 of 50 3 6 Setup The top volume of the geometry needs to be specified This is done using the setup section The following GDML is the generic and most common for the setup section setup name Testl version 1 0 gt world ref World setup The only part you should need to change is the world ref name to the volume name of the top volume of your geometry Only one setup is defined here however it is possible define multiple geometry setups choosing different volumes as world volumes from all the already defined v
32. is is always possible but using the loop tags and combining them properly with matrices you would have the same result with fewer code lines and less complexity Here s the equivalent code using the loop and matrix tags lt define gt matrix name m coldim 5 values 9 4 15 56 2 048 gt variable name x value 1 gt variable name x1 value 0 gt variable name x2 value 0 define solids loop for x to 5 step 1 gt Xbox name box x 10 x 1 y 5 x 1 2 z m 2 x lt loop gt lt solids gt lt structure gt loop for x1 toz 4 step 1 gt volume name volbox lt solidref ref box materialref ref iron volume lt loop gt volume name world gt lt loop for x2 to 8 step 2 lt physvol gt lt volumeref ref volbox gt lt position x 5 y m 1 x2 2 1 z 40 x2 gt lt physvol gt lt loop gt lt volume gt lt structure gt In this example we only looped 5 times but just think if we needed to loop 100 times or more the difference in terms of code lines between the two approaches would be enormous Now two important rules you need to follow when using loops 1 Always use a different and properly initialized variable for each loop tag in our example x x1 x2 for the three loops 2 When you use linked loop triples oop triple 3 loop tags as we did in o
33. ius at top of cone Zz z length of cone startphi starting phi position of segment deltaphi delta angle of segment The following example illustrates its construction cone dimensions rminl 30 rmaxl 60 rmin2 20 rmax2 60 z 30 lunit mm startphi 60 deltaphi 30 aunit deg gt 3 5 3 4 Dimensions of Parameterised Orb The GDML dimensions of a parameterised orb have the following form with 1 standard dimension x radius Example orb dimensions r 30 lunit mm gt 3 5 3 5 Dimensions of Parameterised Sphere The GDML dimensions of a parameterised sphere are given using rmin inside radius rmax outside radius startphi starting phi position of segment deltaphi delta angle of segment starttheta starting theta position of segment deltatheta delta theta angle of segment The following example illustrates its construction sphere dimensions rmin 30 rmax 60 lunit mm starttheta 0 deltatheta 40 startphi 60 deltaphi 30 aunit deg gt Page 35 of 50 3 5 3 6 Dimensions of Parameterised Torus The GDML dimensions of a parameterised torus are given using rmin inside radius rmax outside radius rtor swept radius of torus startphi starting phi position of segment deltaphi delta angle of segment The following example illustrates its construction torus dimensions rmin 30 rmax 60 rtor 160 lunit mm startphi 60 deltaphi 30 aunit deg 3 5
34. l need to write file name logical volume gdml And then define 1ogical volume inside 1ogical volume gdml In the example given above the mother module will only contain the material Iron and the solid MotherBox while the child module will contain only the material Aluminium and the solid ChildBox thus enhancing readability and modularity Some advises While it is not useful to have a module for every single volume of the geometry it is good to have one for each group of volumes that you would consider as a module in the real world see par Multiple GDML files Modules should have low coupling i e they should be as independent as possible from other modules this improves reusability dramatically Modules should have high cohesion i e they should contain all and only the volumes that contribute to the geometry of the corresponding real world modules this improves readability 3 5 5 Volume Auxiliary Information Volumes can have auxiliary information attached to them through GDML The auxiliary tags look like this auxiliary auxtype SensDet auxvalue veloSD1 They have two attributes auxtype and auxvalue which are meant to specify what kind of auxiliary information it is and what is its value An additional optional attribute auxunit is also possible since version 3 1 2 of the schema the new schema also allows for inserting recursive auxiliary tags as part of a singl
35. lid can be referenced by The following example illustrates the construction of a tube segment made from the above dimensions tube name thetube rmin 1 rmax 4 z 20 deltaphi 3 startphi 1 aunit rad lunit mm gt 3 4 20 Twisted Box NB supported only by Geant4 The GDML Twisted box is formed using the three standard dimensions x y and z and one added dimension PhiTwist The box therefore has 5 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a box made from the above dimensions Page 22 of 50 lt twistedbox name twistbox PhiTwist 1 x 30 y 30 z 30 aunit rad lunit mm gt 3 4 21 Twisted Trapezoid NB supported only by Geant4 The GDML Twisted Trapezoid is formed using 6 dimensions PhiTwist Twist Angle x1 x length at z x2 x length at z y1 y length at z y2 y length at z Z z length The Twisted Trapezoid therefore has a minimum of 7 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a Twisted Trapezoid made from the above dimensions lt twistedtrd name twisttrd PhiTwist 1 x1 9 x2 8 yl 6 y2 5 z 10 aunit rad lunit mm gt 3 4 22 Twisted G
36. lt replicavol number 8 volumeref ref lvCube replicate along axis direction x 1 width value 100 unit mm offset value 0 unit mm lt replicate along axis lt replicavol gt lt volume gt lt structure gt 3 5 3 Parameterised Volumes NB supported only by Geant4 Parameterised volumes in GDML correspond to the parameterised physical volumes in Geant4 with the difference that in GDML only parameterisation of dimension and placement is supported Parameterisation of type of solid or its material is not supported by current implementation however it can be implemented as possible extension to the GDML schema Parameterised volumes are repeated volumes in the case in which the multiple copies of a volume can be different in size and position Examples of GDML files describing parameterised volumes are parameterized gdml and pTube gdml located in the example G01 distributed with Geant4 The following example illustrates the construction of parameterised volumes lt solids gt Xbox name tracker x 4800 y 4800 z 4800 Xbox name chamber x 2000 yz 2000 z 2000 solids structure volume name Chamber gt lt solidref ref chamber materialref ref XenonGas Page 33 of 50 lt volume gt volume name Tracker lt solidref ref tracker gt materialref ref Air gt lt paramvol ncopies 2 volum
37. n the Geant4 distribution in the G4INSTALL examples extended persistency gdml directory NOTE in case of using dynamic libraries one needs to set the LD LIBRARY PATH variable to point to all the necessary libraries CLHEP Geant4 and XercesC before running the examples Please refer to the examples README files for more information Page 5 of 50 3 GDMLSchema 3 1 General structure The GDML schema is a set of XSD files which define the structure of the GDML document and its legal elements The general structure of the GDML file can be seen below with some parts replaced by for brevity lt xml version 1 0 encoding UTF 8 gt lt gdml xsi noNamespaceSchemaLocation schema gdml xsd gt lt define gt position name TrackerinWorldpos unit mm x 0 y 0 z 100 gt lt define gt lt materials gt lt element name Nitrogen formula N Z 7 gt lt atom value 14 01 gt lt element gt lt material formula name Air gt lt D value 1 290 unit mg cm3 gt lt fraction n 0 7 ref Nitrogen gt lt fraction n 0 3 ref Oxygen gt lt material gt lt materials gt lt solids gt lt box lunit mm name Tracker x 50 y 50 z 50 gt lt solids gt lt structure gt lt volume name World gt lt materialref ref Air gt lt solidref ref world gt lt physvol gt lt volumeref ref Tracker gt lt positionref ref TrackerinWorldpos gt lt rotationref
38. ne segment made from the above dimensions lt cone name thecone rminl 10 rmax1 15 rmin2 15 rmax2 25 z 30 startphi 1 deltaphi 4 aunit rad lunit mm gt 3 4 3 Ellipsoid The GDML Ellipsoid is formed using 3 dimensions ax x semi axis by y semi axis CZ z semi axis There are 2 optional dimensions that can cut the ellipsoid zcutf will remove the specified value from the lower z axis effectively cutting a part of the bottom of the shape off zcut2 performs the same action but acts on the upper part of the z axis Page 14 of 50 The ellipsoid therefore has 4 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a ellipsoid made from the above dimensions lt ellipsoid name theellipsoid ax 10 by 15 cz 20 zcut2 4 lunit mm gt 3 4 4 Elliptical Tube The GDML Elliptical Tube is formed using 3 dimensions dx x semi axis dy y semi axis dz z semi axis The elliptical tube therefore has 4 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of an elliptical tube made from the above dimensions lt eltube name theeltube dx 10 dy 15 dz 20 lunit mm 3 4 5 Elliptical Cone NB supported only b
39. ning message is generated Usually this happens when different GDML modules define the same logical volume This is not a problem but it may suggest that the input GDML modules have a low cohesion therefore it maybe useful to review the way you have organized your geometry All names for solids volumes and other entities are by default stripped of possible strings concatenating their logical address in hexadecimal format it is possible to disable the name stripping by calling setstripFlag false available from the parser before reading By default when the parser reads a GDML file comparison with the GDML Schema from GDML Schema Location is made It is possible to switch off this comparison by setting to false second optional parameter in the Read parser Read source file gdml false 4 Get the World volume G4VphysicalVolume W parser GetWorldVolume world volume W gt GetLogicalVolume gt SetVisAttributes G4VisAttributes Invisible Page 44 of 50 The second line is optional but commonly used because you generally don t want to be able to see the World volume 4 2 GDML Writing 4 2 1 Exporting Geant4 Geometry Geant4 geometry can be exported into GDML files To do so you should do the following 1 Include the Geant4 header file of the parser include G4GDMLParser hh 2 Get the world volume from the geometry G4VphysicalVolume W G4TransportationM
40. nt4 This is the prettiest format although you have to be REALLY sure that you don t have name duplication inside Geant4 otherwise this will generate a GDML output with duplicated names which will be unreadable by any parser of course Page 45 of 50 4 Methods for dumping the geometry There are three ways of doing this a parser Write output gdml W Dumps all the geometry in a single GDML output file b parser AddModule physvol Dumps the geometry modularizing the output The generated module will include the geometry tree starting from the physical volume pointer physvol C parser AddModule depth Dumps the geometry modularizing the output The parameter in input is an integer indicating the depth in the geometry levels from where you wish to start modularization Any new sub tree at that depth level will become a module stored in a different GDML file the main tree binding all modules will include the geometry from the world volume down to that specified level and will be stored in a separate GDML file 4 2 2 Exporting ST Viewer CAD Geometry ST Viewer is an interactive tool for viewing 3D CAD information ST Viewer includes functions to display and relate product identification information assembly structure information and 3D geometry information ST Viewer implements the ISO STEP standard for product model data ST Viewer works with a very large range of CAD CAM CAE and PDM systems A list of systems that h
41. olumes Page 42 of 50 GDML file example XML Declaration GDML Namespace XML Schema Instance Namespace lt xml version 1 0 encoding UTF 8 gt GDML Schema Location A xmlns gdml http cern ch 2001 Schemas GDML xmlns xsi http www w3 org 2001 XMLSchema instance xsi noNamespaceSchemaLocation schema gdml xsd gt Declaration of constants positions rotations scalings tJ variables and matrices define constant name constl value 100 position name pos1 unit mm x 0 y 0 z 0 rotation name rot1 unit deg x constl y 0 z 0 gt scale name scll x 1 yz 41 zz 41 define Definition of elements materials isotopes etc Only materials can be referenced NI to volumes Waterials lt element Z 7 formula N name Nitrogen gt lt atom value 14 01 gt lt element gt lt element Z 8 formula 0 name Oxygen gt Simple material defined using atom value 16 fractions of elements defined element higher up material formula name Air gt D value 0 00128 fraction n 0 7 ref Nitrogen gt fraction n 0 3 ref Oxygen gt All solids to be used inside lt material gt the geometry defined here materials gt lt solids gt Xbox aunit radian lunit mm name world x 10000 y 10000 z 10000 Xbox aunit radian lunit mm name det x 2000 y 2000 z 2000 gt solids All volumes de
42. olyhedra can be described in two ways as Polyhedra using zplanes with rmin and rmax and as Generic Polyhedra using vertices with r z coordinates The GDML Polyhedron Polyhedra is described using the following information startphi start angle of the segment deltaphi angle of the segment numsides number of sides zplane see below The zplane element is required to be used at least once You can use it as many times as you like The zp1ane is formed using the 3 attributes shown above rmin inner radius of cone at this point if not given 0 0 is defaulted rmax outer radius of cone at this point Z z coordinate of the plane The Polyhedra therefore has a minimum of 6 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a polyhedra made from the above dimensions lt polyhedra name thepolyhedra startphi 1 deltaphi 4 numsides 10 aunit rad lunit mm gt lt zplane rmin 1 rmax 9 z 10 gt lt zplane rmin 3 rmax 5 z 12 gt lt polyhedra gt Page 18 of 50 3 4 12 Generic Polyhedron The GDML Generic Polyhedra is described using the following information startphi start angle of the segment deltaphi angle of the segment numsides number of sides rzpoint see below The rzpoint element is required to be used at least three times You can use it as many tim
43. oot binding for GDML is integrated within the Root framework the user should refer to the general Root manual for any information on importing and or exporting GDML files to from the Root geometry model The description of the GDMLSchema in Section 3 however is application independent and therefore is relevant for both Geant4 and Root users GDML Schema is distributed with GDML Geant4 binding Page 4 of 50 2 Getting started 2 1 Installation of GDML in Geant4 Building the GDML module in Geant4 is optional by default the GDML plug in is not built along with the rest of the Geant4 libraries In order to build the Geant4 module for GDML one needs to have The XercesC parser pre installed presently GDML uses XercesC 3 1 2 version The following environment variables set at the time the Geant4 libraries get built XERCESROOT specifying the path where the XercesC parser library and headers are installed in the system G4LIB BUILD GDML set to 1 Once the above setup is defined in the user s environment the GDML module in Geant4 will be built using the standard build procedure applicable for Geant4 2 2 Running simple examples The Geant4 binding for GDML comes with three examples which demonstrate the reading and writing out of different geometry configurations from to GDML files The examples also show how user can extend GDML and how to export ST Viewer CAD Geometry The directories containing these examples can be found i
44. pe rmin 1 rmax 2 z 20 inst 3 outst 4 lunit mm gt 3 4 18 Cut Tube The GDML Cut Tube is formed using 11 dimensions Z length along z axis rmin inner radius if not given 0 0 is defaulted rmax outer radius startphi starting phi angle of segment if not given 0 0 is defaulted Page 21 of 50 deltaphi delta phi of angle lowX normal at lower z plane lowY normal at lower z plane lowZ normal at lower z plane highX normal at upper z plane highY normal at upper z plane highZ normal at upper z plane The cut Tube therefore has a minimum of 12 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a cut Tube made from the above dimensions lt cutTube name thecuttube z 20 rmin 1 rmax 5 startphi 1 deltaphi 4 lowxX 15 lowY 15 lowZ 15 highX 10 highY 10 highZ 10 aunit rad lunit mm 3 4 19 Tube Segment The GDML Tube Segment is formed using 5 dimensions rmin inside radius of segment if not given 0 0 is defaulted rmax outside radius of segment Z z length of tube segment startphi starting phi position angle of segment if not given 0 0 is defaulted deltaphi delta angle of segment The Tube segment therefore has a minimum of 6 attributes the other being name which is standard for any SolidType element and corresponds to the name the so
45. pe als 36 3 5 3 8 Dimensions of Parameterised Parallelepiped sss 36 3 5 3 9 Dimensions of Parameterised Trapezoid sss 37 3 5 3 10 Dimensions of Parameterised General Trapezoid sssse 37 3 5 3 11 Dimensions of Parametrised Polycone sse 38 3 5 3 12 Dimensions of Parametrised Polyhedron sss 38 3 5 3 13 Dimensions of Parametrised Ellipsoid sssssseeee 38 3 5 4 GDML Modules aestate bte rr o a vr selecta Desa mut doas ena tede aan 39 3 5 5 Volume Auxiliary InformatiOn No 40 3 5 6 Auxiliary User TInfOFffiatiOIL cue aeter eto ii nz 41 Sr M cis Peto cr PUDE IE 42 4 Importing and exporting GDML files sess 44 A 44 4 1 1 Importing GDML files into Geant4 Geometry see 44 AZ AGEL Writ eR ER 45 4 2 1 Exporting Geant4 Geometry dd dois 45 4 2 2 Exporting ST Viewer CAD Geometry iue etse a eese qi qns 46 5 User extensions to GDML using Geant4 sesssssssssseeseeeeeeneeeeeene nennen 47 S L AS Tedetine element al 48 527 New El MES eire od eo eer testet i ideo tiva ede dante 48 Page 3 of 50 1 Introduction The Geometry Description Markup Language GDML is a specialized XML based language designed as an application independent persistent format for describing the geometries of detectors associated with physics mea
46. s a minimum of 7 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a polycone made from the above dimensions lt polycone name thepolycone startphi 1 deltaphi 4 aunit rad lunit mm gt lt zplane rmin 1 rmax 9 z 10 gt lt zplane rmin 3 rmax 5 z 12 gt lt polycone gt 3 4 10 Generic Polycone The GDML Generic Polycone is described using the following information startphi start angle of the segment if not given 0 0 is defaulted deltaphi angle of the segment rzpoint see below The rzpoint element is required to be used at least three times You can use it as many times as you like The rzpoint is formed using the 2 attributes shown above r r coordinate of this point z coordinate of this point Page 17 of 50 The Generic Polycone therefore has a minimum of 7 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a generic polycone made from the above dimensions lt genericPolycone name thepolycone startphi 1 deltaphi 4 aunit rad lunit mm gt lt rzpoint r 1 z 5 gt lt rzpoint r 3 z 10 gt lt rzpoint r 1 z 12 gt lt genericPolycone gt 3 4 11 Polyhedron The GDML Polychedron P
47. surements It serves to implement geometry trees which correspond to the hierarchy of volumes a detector geometry can be composed of and to allow to identify the position of individual solids as well as to describe the materials they are made of Being pure XML GDML can be universally used and in particular it can be considered as the format for interchanging geometries among different applications GDML consists of two elements an XML definition part containing the set of rules and the list of the legal elements to be used in constructing any GDML document and the GDML generating and processing code implemented in the client tools The structure of the GDML document is defined through a set of XML Schema Definition XSD files which we call the GDMLSchema Any GDML geometry file must be valid with respect to the GDMLSchema The GDML file itself can be either written by hand in case GDML is used as the primary geometry source or generated automatically in case GDML is used as an exchange or persistency format out of the application specific in memory geometry tree using one of the GDML writers called by the user application The GDML reader is responsible for parsing the GDML file and creating the in memory representation of the geometry tree specific for the user application This manual will focus on the Geant4 binding to GDML which starting from release 9 2 of the simulation toolkit it is now integrated in Geant4 The R
48. th along x at side y y1 of the face at z x2 length along x at side y y1 of the face at z alpha1 angle with respect to the y axis from the centre of side at y y1 to centre of y y1 of the face at z y2 length along y at the face z x3 length along x at side y y1 of the face at z x4 length along x at side y y1 of the face at z alpha2 angle with respect to the y axis from the centre of side at y y2 to centre of y y2 of the face at z The General Trapezoid therefore has a minimum of 12 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a General Trapezoid made from the above dimensions trap name thetrap z 10 theta 1 phi 2 yl 15 x1 10 x2 10 alphal 1 y2 15 x3 10 x4 10 alpha2 1 aunit rad lunit mm gt 3 4 17 Tube with Hyperbolic Profile The GDML Tube with Hyperbolic Profile is formed using 5 dimensions rmin inside radius of tube rmax outside radius of tube inst inner stereo outst outer stereo Z z length The Hyperbolic Tube therefore has a minimum of 6 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a hyperbolic tube made from the above dimensions lt hype name thehy
49. umes the module is made of For example if one wants to describe a detector instead of creating a single detector gdm1 file with thousands of volumes and materials one could create smaller modules called tracker gdml calorimeter gdml beampipe gdml etc and a small main detector gdml file combining those modules This approach makes it easier to read and write the geometries and to apply changes Explanations and details on how GDML modules are defined and put together are given in the Section 3 5 Page 8 of 50 3 2 Definitions 3 2 1 Constants Constants are defined in the beginning of the GDML file in the define section Once defined they can be used anywhere inside the file A constant can be defined as in the following example constant name length value 6 25 3 2 2 Quantities Quantities are constants with units they are defined in the beginning of the GDML file in the define section Once defined they can be referenced where quantity is expected with the same type Example quantity name W Density type density value 1 unit g cm3 3 2 3 Variables Variables are defined in the beginning of the GDML file in the define section Once defined they can be used anywhere inside the file Their value will be evaluated each time they are used and it can change if they are used as loop variables see section 3 5 1 A variable can be defined as in the following example
50. ur example linked in the sense that we looped over a solid then we looped over a logical volume that referred to that solid and finally we looped over a physical volume that referred to that logical volume you always have to be sure that the number of steps is the same for every loop tag of that particular triple In our example that number was 5 from 1 to 5 in the first loop from O to 4 in the second loop and from O to 8 but with a step of 2 in the third loop 3 5 2 Replicated Volumes NB supported only by Geant4 Replicated volumes in GDML correspond to Geant4 Replicas Replica volumes are created along the specific direction of one of Cartesian or Cylindrical Axis The first replica is placed at the given position and rotated according to given rotation and others are placed using given distance This repeated Volumes technique is available for volumes described by Geant4 CSG Solids The following example illustrates the construction of replica volumes Page 32 of 50 along X Axis An example replicated gdml can be found in the G4INSTALL examples extended persistency gdml G01 girectory lt solids gt Xbox name Mother Cube x 800 yz 100 z 100 Xbox name Cube x 100 y z 100 zz 100 solids structure volume name lvCube solidref ref Cube materialref ref ALU volume volume name lvReplica lt solidref ref Mother Cube materialref ref AIR
51. us Segment is formed using 5 dimensions rmin inside radius of segment rmax outside radius of segment rtor swept radius of torus startphi starting phi position angle of segment deltaphi delta angle of segment The Torus segment therefore has a minimum of 6 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a torus segment made from the above dimensions torus name thetorus rmin 1 rmax 4 rtor 2 deltaphi 3 startphi 1 aunit rad lunit mm gt 3 4 15 Trapezoid x amp y varying along z The GDML Trapezoid is formed using 5 dimensions x1 x length at z x2 x length at z y1 y length at z y2 y length at z Z z length The Trapezoid therefore has a minimum of 6 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a Trapezoid made from the above dimensions lt trd name thetrd x1 9 x2 8 yl 6 y2 5 z 10 lunit mm 3 4 16 General Trapezoid The GDML General Trapezoid is formed using 11 dimensions Z length along z axis Page 20 of 50 theta polar angle to faces joining at z phi azimuthal angle of line joining centre of z face to centre of z face y1 length along y at the face z x1 leng
52. variable name x value 6 This simple code defines a variable with an initial value of 6 Of course previously defined variables may be used in variable definitions as in the following example WoW variable name x value 6 Wa variable name y value x 2 In this case variable y is set with an initial value of 3 You can now use your variable wherever you like for example in a box definition WoW Way Xbox name my box x2 x y y z xty gt 3 2 4 Positions Positions are usually defined in the beginning of the GDML file in the define section Once defined they can be referenced in place where positions are expected A position can be defined as in the following examples position name box position x 25 0 yz 50 0 zz 75 0 unit cm gt Page 9 of 50 constant name size value 25 0 position name position x 2 0 size y size z 75 0 unit m 3 2 5 Rotations Rotations are usually defined in the beginning of the GDML file in the define section Once defined they can be referenced in place where rotations are expected Positive rotations are expected to be right handed A rotation can be defined as in the following example rotation name RotateZ z 30 unit deg 3 2 6 Scales Scales are usually defined in the beginning of the GDML file in the define section Once
53. with different dimensions Without a loop you would write the following code Xbox name box0 x 1 y 5 z 20 gt Xbox name boxl x 4 yzc 4 5 g 18 gt Xbox name box2 x 7 y 4 z 16 gt Xbox name box3 x 10 y 3 5 zg 14 gt Xbox name box4 x 13 y 3 z 12 gt Xbox name box5 x 16 y 2 5 z 10 gt Xbox name box6 xz 19 y 2 z 8 gt Xbox name box7 x 22 y 1 5 z 6 gt Xbox name box8 xz 25 y 1 z 4 gt Xbox name box9 x 28 y 0 5 z 2 gt Using a loop you would only need four lines variable name x value 0 declared in the define section and loop for x to 9 step 1 Xbox name box x 1t x 3 y 5 x 2 z 20 2 x loop 3 4 29 Boolean Solids The GDML Boolean Solids can be described using following Boolean operations union subtraction and intersection As for Geant4 Boolean operations the second solid is placed with given position and rotation in the system coordinates of the first solid The following example illustrates the construction of Boolean solid using union operation Xbox name box first x 1 y 5 z 20 Xbox name box second x 4 yz 4 5 z 18 gt union name union first ref box first second ref box second lt positionref ref union position gt rotationref r
54. xample we have only one tag lt color gt which is part of the extension This is shown below lt xs element name gdml simple extension gt lt xs annotation gt lt xs documentation gt Page 48 of 50 New container for new element and gdml lt xs documentation gt lt xs annotation gt lt xs complexType gt lt xs sequence gt lt xs element ref extension minOccurs 0 maxOccurs 1 gt lt xs element ref gdml minOccurs 1 gt lt xs sequence gt lt xs complexType gt lt xs element gt This then means that a GDML file now takes the following structure based on the above lt gdml_simple extension xmlns gdml simple extension http www example org xmlns xs http www w3 org 2001 XMLSchema instance xs noNamespaceSchemaLocation SimpleExtensionSchema SimpleExtension xsd gt lt extension gt lt color name aColor R 1 0 G 0 0 B 0 0 A 1 0 gt lt extension gt lt structure gt lt volume gt lt materialref ref someMaterial gt lt solidref ref someSolid gt lt colorref ref aColor gt lt new reference type gt lt volume gt lt structure gt gdml simple extension In any GDML file you wish to use your extended schema in you will need to change the Namespace GDML Schema Location to your extended schema file and replace the original schema The new schema location must be relative to the location of the GDML file in question This will then import
55. y Geant4 The GDML Elliptical Cone is formed using 3 dimensions and one possible upper cut in Z dx x semi axis dy y semi axis zmax total z length without cut zcut upper cut in Z The elliptical cone therefore has 5 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of an elliptical cone made from the above dimensions lt elcone name theelcone dx 1 dy 1 5 zmax 2 zcut 1 5 lunit mm gt 3 4 6 Orb The GDML Orb is formed using only 1 dimension Page 15 of 50 r radius The orb is a simplified GDML Sphere with only the radius specified The orb therefore has 2 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of an orb made from the above dimensions orb name theorb r 10 lunit mm 3 4 7 Paraboloid The GDML Paraboloid is formed using 3 dimensions rlo radius at z rhi radius at z dz z length The paraboloid therefore has 4 attributes the other being name which is standard for any SolidType element and corresponds to the name the solid can be referenced by The following example illustrates the construction of a paraboloid made from the above dimensions lt paraboloid name theparab rlo 10 rhi
56. your new additions as well as the original GDML schema as shown above Customised Reader Once the GDML schema has been extended as wished the application making use of the extended GDML needs to provide the necessary instruments in order to properly handle the extensions This is done by implementing a specialized reader class whose instance will replace the standard reader inside the G4GDMLParser class in Geant4 The new class must inherit from G4GDMLStructureRead and override in this case two methods void ExtensionRead const xercesc DOMElement const element void VolumeRead const xercesc DOMElement const element The former will have to handle the top level parsing of the new tags in our case lt color gt while the latter will have to properly bound the new reference type lt colorref gt to the volume such that the new tag can be assigned as attribute to the volume entity In our example the class ColorReader implements such required functionality An instance of the reader must be dynamically created in the DetectorConstruction class and provided through pointer argument to the G4GDMLParser instance to be created as usual for importing GDML files in Geant4 Page 49 of 50 Try it To run the example application you simply need to build it using the standard procedure as for any Geant4 application Then from the G03 directory you can run the example using this command read ext filename gdml T
57. z x3 length along x at side y y1 of the face at z x4 length along x at side y y1 of the face at z alpha1 angle with respect to the y axis from the centre of side at y y1 to centre of y y1 of the face at z alpha2 angle with respect to the y axis from the centre of side at y y2 to centre of y y2 of the face at z theta polar angle of the line joining the centre of the faces z amp z in z phi azimuthal angle of the line joining the centre of the faces z amp z in z y1 y length at z y2 y length at z Z length along z axis The following example illustrates its construction trap dimensions x1 30 x2 60 yl 20 y2 40 x3 30 x4 60 z 30 lunit mm alphal 30 alpha2 2 30 phi 30 theta 60 aunit deg gt Page 37 of 50 3 5 3 11 Dimensions of Parametrised Polycone The GDML dimensions of a parameterised polycone are given using startPhi start angle of the segment openPhi angle of the segment numRZ number of zplanes forming polycone zplane inner radius outer radius and z coordinate of each plane The following example illustrates its construction lt polycone dimensions startPhi 30 openPhi 60 numRZ 2 lunit mm aunit deg lt zplane rmin 0 rmax 2 z 10 lt zplane rmin 0 rmax 4 z 20 polycone dimensions gt 3 5 3 12 Dimensions of Parametrised Polyhedron The GDML dimensions of a parameterised polyhedron polyhedra are given using
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