Make Your Own Environment Maps And Light Probes
Contents
1. gt Filters gt Gaussian Blur DO NOT be tempted to blur the LDR images in GIMP first as the HDR results will be completely wrong Google HDR blur to understand why Page 9 of 10 Issue 1 0 17 May 2013 A Note On Render Size And Resolution The render size for the unregistered 1 e free version of Terragen Classic is limited to 1280x960 As we need a square image we are limited to 960x960 And since this represents a 90 field of view a quick calculation gives us a 360 x180 equirectanglar latitude longitude mapped image of 3840x1920 7 3 Mpixels But what does this mean for the level of detail we can get in our background image Everybody s familiar with what the moon looks like so it s a very good test case The moon only covers slightly over 0 5 of sky check any astronomy book so if it was visible in our 960x960 render it would have a diameter of only 5 6 pixels The image image below left gives you an idea of the level of detail this represents i Ei ah 3840x1920 7680x3840 15360x7680 30720x15360 The other three images show the moon with the resolution doubled each time 10 20 and 40 pixels respectively To get the moon at this resolution in our renders would require 90 x90 renders of 1920x1920 2880x2880 and 5760x5760 respectively And to get these levels of detail from an equirectangular image they would have to be 7680x3840 29 Mpixels 15360x7680 118 Mpixels and 30720x15360 471 Mp2. use a scene name plus n e s w u d for north east south west up and down e g Scenel n Do the same with head set to 90 east and 270 west But for head 180 south also set bank 180 this will make the image upside down which is what we need for the vertical cross cube map we re making We also need a straight up and straight down render Set head 0 and bank 0 and then do the up render with pitch 90 and the down render with pitch 90 Don t forget to save each render Page 4 of 10 Issue 1 0 17 May 2013 3 Create A Vertical Cross Map Tools GIMP I found that the Terragen Classic renders fit perfectly together both in terms of colour and detail So it s only necessary to position them correctly and to add a bit to the edges to avoid white black curves on the angular equirectangular maps where the edges are I found the easiest way to do it was with a primary colours PNG or other lossless format NOT JPG template like the one shown here Each of the six squares is 960x960 or whatever size your renders are Simply open it with GIMP and create a new layer this 1s where you Il paste your renders Colour select one of the six squares on the original layer and then select the new layer Open the appropriate render in GIMP as a separate image and copy it Go back to the template on your empty layer and do Paste Into Do the same for each render in the appropriate square You should end up with so
3. you can click the buttons with the picture of a monitor top left and the button below it with the green hill respectively If any other panes are open just close them by clicking the red X at the top right of each pane It s not necessary but it reduces clutter On the Landscape pane click the Generate Terrain button This opens a new Terrain Genesis pane Click the Generate Terrain button on this pane The black square on the Landscape pane will turn into a random black grey and white pattern That s it You ve generated your new world with ground sky sun clouds water and atmospheric effects Page 1 of 10 Issue 1 0 17 May 2013 Now you ll probably want to see what it looks like On the Terrain Genesis pane click the Close button In the Camera section of the Rendering Control pane set a few of the camera parameters those marked in yellow on the image below and the click the Render Preview button With luck the grey rectangle top left will become a blocky but recogniseable landscape like in this screenshot Rendering Control Lamera B i units Metres y z alt Camera Position Crea ea 1 62 1m Fixed Height Above Surface w am Target Position 3840 m 7680 1m 162 1m Fired Height Above Surbace 301m ee head pitch bank 7 Unentation Render Preview Use Mouse Buttons mw Land Ww Sky to describe the S camera s view Detail Left button postions Render Setti
4. Issue 1 0 17 May 2013 Creating Your Own Environment Map Light Probe Set Please note that everything in this document is based on my very limited understanding and I may well be wrong on many points I ve already used this procedure to create several sets of LDR JPG images I believe that it can also be used to create HDR images see the Appendix The software you ll need all free e Terragen Classic v0 9 43 http planetside co uk products terragen classic e GIMP http www gimp org downloads e HDRShop Version 1 Link from here http www hdrlabs com tools links html 1 Create An Imaginary World Tools Terragen Classic Canam E mE D Tana so Haz E Gamer C Teenus Nun all H zis W zie Canen Pon air Ore ar 1a Pani n tru Caran Parion 0n 340m lin pal Height boar iaia Tira ligt Abon iaaa e FrodHeight Abova duaa fe iir Tapi Panin itn iin iih Fro Height Abram iuan fF im e arpa Empat Som Saad eas Sbd lepe asin wa i i High tolara phelacharsca Bu orignal E Emeki wdy rp began een a D erake keten tahing be Eman A oN mrana aOR al Shakur casd Tato 15 Don t worry if you can t read the writing on the screenshots above they re just to help you check that what you see on your computer looks about right Start the program by default it opens with two panes already displayed Rendering Control and Landscape slightly overlaid If they re not open
5. al Save it as an LDR JPG Close HDRShop That s it You now have an equirectangular map suitable for environment maps and reflection maps and an angular map suitable for use as a light probe for global illumination Page 6 of 10 Issue 1 0 17 May 2013 Appendices Extra Notes For Creating HDR Version Although opening any old LDR image with HDRShop converts it into an HDR image it s unlikely to be very good You really need to give HDRshop an HDR image to start with The SO Pack plugin for Terragen Classic http www terraproject de downloads view details terragen terragen classic plugins so pack html creates HDR renders but it seems to use different settings for each render so the six separate renders don t match up You could probably fix this in an HDR image editing program but I couldn t find a free one for Windows CinePaint The solution I found is to do several sets of cube map render at different exposures convert each set into a Vertical Cross and use HDRShop s Create gt Assemble HDR From Image Sequence to combine these Vertical Crosses into a single HDR image This does of course mean that you have to do the manual six separate renders to vertical cross image conversion for each exposure setting Think of it as an exercise in patience and calmness The main thing I haven t yet sorted out is how many which exposure settings to use in Terragen Classic The key is to use settings that give amostly black r
6. at that HDRShop will accept a e Although this all sounds a bit complicated tedious and error prone once you get used to the process it s actually quite quick and painless Page 5 of 10 Issue 1 0 17 May 2013 4 Convert The Cube Map To Equirectangular And Angular Formats Tools HDRShop This is very easy Open HDRShop Open the vertical cross image file you exported from GIMP drag and drop onto the HDRShop window Select the gamma curve you want I use the default 2 2 for computer monitors Not sure if I m correct Check your image is actually there use Ctrl to zoom out it s an HDR program so the and keys are for viewing different exposure settings and make sure you see your vertical cross If it s just black you probably used GIMP export options that HDRShop can t handle If you see your image then you are looking at an HDR version of it but see the note in the Appendix an HDR image created from a single LDR image will not be very good Select Image gt Panorama gt Panoramic Transformations set it up to convert your vertical cross to a 4096x2048 Latitude Longitude image and hit OK Save it as an LDR JPG Close the pane with the modified image Select Image gt Panorama gt Panoramic Transformations again and set it up to convert your vertical cross to a 1024x1024 Angular Map Light Probe image and hit OK Select Image gt Transform gt Flip Horizont
7. ender but with the sun still white at one end of the scale amostly white render except for the bits in deep shadow at the other end in between settings that provide the same number of F Stops between T Stop 4 0 T Stop 0 0 T Stop 4 0 You ll notice that there s no detail in the deep shadow even in the image on the right This seems to be because I had Lighting Conditions gt Background Light gt Single Colour Shadow Changing to Multiple and setting greys reverse 20 20 20 diffuse 30 30 30 above 40 40 40 improves it a bit Page 7 of 10 Issue 1 0 17 May 2013 T Stops F Stops And Focal Length When you create an HDR image from a series of LDR images HDRShop will ask you how many F Stops there are between images 1 2 or 3 But Terragen Classic works in T Stops F Stop from Poser 6 User Manual page 121 F Stop The F Stop number represents a lens aperture size The larger the number the smaller the aperture opening Each number is multiplied by a factor of approximately 1 4 as the scale rises giving standard values of 1 0 1 4 2 2 8 4 5 6 8 11 16 22 32 etc Each change either doubles or halves the amount of light transmitted by the lens to the film plane Basically f stop is calculated from the focal length of the camera lens divided by the diameter of the bundle of light rays entering the lens and passing through the aperture in the iris diaphragm On a physical camera this represents
8. ixels respectively So skydomes and such are probably only practical for smaller renders with fairly wide fields of view I think I said that before but it s worth repeating Page 10 of 10
9. mething like the second picture Save it as an XCF Vertical Cross Template If you export as is and convert using HDRShop you ll get curved lines where the unconnected cubemap edges get joined To avoid this you need to extend the edge pixels into the thin coloured strips that you can see in the two pictures I use simple masks not shown to select the row column of pixels that I wish to extend into the adjacent coloured areas a one pixel wide column for the red area a one pixel wide column for the cyan area a one pixel high row for the yellow area a one pixel high row for the green area ae Once you have the one pixel row column selected go to the layer where you have the pasted renders and Copy Paste As New Image Scale the new image in one dimension columns scale width to 500 rows scale height to 500 Create a new layer in the original image for the edge extensions Select the two coloured areas for the appropriate edge extension on the template layer then select the new layer and Paste into Do this for all four edges Save it as an XCF You don t want to redo all that Once saved you 4 six renders pasted in can safely delete the original renders With the vertical cross layer edge layer and template layer visible save the whole thing in a format suitable for HDRShop I decided to use a lossless format at this stage BMP R8 G8 B8 and no RLE or HDRShop won t like it You can use any form
10. ngs the eae Aight button Image Size 640 x 480 cal the paws Fender Image Animation E L Last Image View eee a I ae Zoom al R If your render preview has large black patches at the bottom or bits of terrain stopping in mid air just go back to the Landscape pane generate a new terrain check that the yellow camera parameters are still correct the same most of them should be but the Camera Orientation pitch bottom row may need to be reset to zero and do another render preview Do this until you get a reasonable render preview Now click the 3D preview button on the main Terragen window far left second from bottom with 3D written on it A progress indicator is diplayed while it sets things up and then a new 3D Page 2 of 10 Issue 1 0 17 May 2013 Preview window opens Simply click anywhere in the window and drag the mouse left or right you re rotating the camera in your 3D world ba a0 Preview You want to check that you can rotate a full 360 in azimuth left right without getting anything that seems as if you re looking through or underneath the terrain Looks like I ve got a problem in this 3D preview Simple answer you ve guessed already go back and generate a new terrain With luck you ll get a terrain that works after a few tries If not then you re probably thinking there must be another way to do this You ve probably also noticed that the camera is usually on a stee
11. ply sloping hillside and you get the problem when you look towards the up slope Here s a couple of hints before you get too frustrated Try increasing the Fixed Height Above Surface for the Camera from 2m to 10m 50m 100m 500m even that ll usually fix it I chose 2m purely because that s about eye level for a person standing on the terrain and that s usually a good camera height But remember that we re just creating a background image for an environment map light probe set so feel free to increase the height Alternatively try editing the terrain The View Sculpt and Modify buttons on the Landscape pane are a good place to start Or use the Generate features on existing terrain button of the Terrain Genesis pane Or you could just move the camera to a piece of flatter terrain the yellow camera parameters will change but by now you should understand which ones don treally need to be set as I stated Once you ve got a terrain that you think looks okay SAVE IT On the Landscape pane click the Save button and give it a name It ll be saved as a Terragen Terrain file with a ter extension As far as I know this file type can only be opened in Terragen Page 3 of 10 Issue 1 0 17 May 2013 N B You ve only saved the terrain here not the rest of the environment If you want to save the rest of the environment do this from the main Terragen window s menu bar World File gt Save World 2 C
12. reate Six Separate Cube Map Renders Tools Terragen Classic We continue within Terragen Classic On the Rendering Control pane click the Camera Settings button a new Camera Settings pane will open Change the Zoom Magnification setting from 1 414 to 1 and then Close the pane This has set the camera to a 90 field of view which we need to create the renders for our cubemap On the Rendering Control pane set all three Camera Orientation parameters head pitch bank to zero again and do a Render Preview Do the same with hedings of 90 180 and 270 If they all look okay then you re ready for the next step If any of them don t look right I think you know already I think you re getting familiar with the Terragen interface by now so I won t give as much detail for the rest of the instructions Next step is to create our six renders for the cube map On the Rendering Control set the Detail slider to maximum Image Size to 960x960 or any size you want but it must be square for your first try make it rather smaller say 400x400 ensure both Land and Sky are checked and then hit Render Image It ll take a while and gradually appear bit by bit but eventually a little box will pop up telling you it s complete The terrain will probably look like rock and hopefully you ll be surprised at just how realistic it looks SAVE THE RENDER TO DISK It ll be saved as a BMP Give it a meaningfull name I
13. the lens focal length see next bullet divided by the f stop value to determine the actual aperture size Enter your desired value in the F Stop field T Stop is apparently similar to an F Stop but it also takes into account light loss through the lenses Since our imaginary lenses are lossless I assume T Stop should equate to F Stop It looks to me as if Terragen Classic s Exposure Light Sensitivity setting is F Stop Here s a Exposure Light Sensitivity Corrected T Stop 0 125 3 most of the scene is black 0 177 2 5 0 25 2 0 354 1 5 0 5 1 0 707 0 5 1 0 1 414 0 5 default 2 1 2 828 1 5 4 2 5 657 2 5 8 3 most of the scene is white white Focal Length F field of view d dimension of sensor f focal length F 2atan d 2f approximates to F 180d af f 180d nF f 57 F For old 35mm film d 35mm For digital cameras d 12mm or thereabouts For an imaginary camera d Page 8 of 10 Issue 1 0 17 May 2013 What Is The Best Size For An Environment Map Light Probe Simple answer I don t know But consider these points If an environment map is intended for a skydome or similar then only a small part of it will appear in any individual render The purpose of a skydome is that you can point your camera anywhere set any field of view and the skydome will give you the correct bit of background sky If you want to do a 1024x1024 render with a 60 field of vie
14. w then a background of 6144x3072 1s needed to avoid losing resolution If you want a 1024x1024 render with a 10 field of view you d need a 36864x 18432 background image So skydomes and such are probably only practical for smaller renders with fairly wide fields of view An environment map intended for reflections can be a lot smaller it all depends how big the reflective objects in your scene are how much of the environment they ll reflect and of course how big your render is Light probes are rather different I don t think they need to be very big and 1024x1024 is probably far too large 512X512 or even 256x256 may be adequate But I m really just guessing here To Blur Or Not To Blur When a light probe image is used to provide global illumination in a scene I think that the image is always blurred first either by the rendering software or by providing a blurred light probe image If it s not blurred then in certain circumstances what you end up with can look more like a reflection But it seems such a shame to blur a beautiful image and most angular map light probe images do have a certain beauty that s taken so much work to produce I work on the basis that it s easy for an end user to blur an image but impossible to recreate the original from a blurred image So I don tnlur Note if you re creating an HDR light probe by combining LDR images in HDRShop then do the blurring in HDRShop with Image
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