Derek Jenson - 3d Artist
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Environment Sampling for Lightmaps

12/18/2010

 
There is a lot of flexibilty, production time-savings, and specific look development which can be gained by building lightmaps (for realtime engines) in passes. Using mental ray, these passes are fairly easy to setup and bake. However, while final gathering (FG) works great (result-wise) for radiosity sampling, it is only single threaded when used for rendermapping. Seeing as how FG is a screen space method for sampling, I don't know if this can be called a bug (definitely an oversight). This limitation is made worse when several computers are used via satellite rendering to generate a single lightmap (or lightmap pass). The other systems sit idle, while one machine (using one core) calculates the FG prepass.
To avoid this production slow down and get your systems rendering with full CPU power, an environment sampling shader can do the work FG would normally calculate. Using mental ray's ambient occlusion shader with the below parameters, I generated the environment sampling with satellite rendering using 100% of 24 cores.
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pass material setup
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environment sampling pass: using the occlusion shader for ambient lightmaps
Use this sampling method with interactive IBL light domes for a fast and iterative lighting solution.

Glass Shader

10/17/2010

 
Wired-up an interesting glass shader.
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Interactive IBL Domes

7/31/2010

 
Using an intergrated compositor (Blender, Softimage, Houdini) it is possible to create an interactive studio environment to drive the IBL in a 3d scene. By wiring a couple vector paint nodes together in Softimage I can create an interactive environment map; then I use the map as the source image for the final-gathering or environment sampling.  HDR Light Studio is a standalone product that does just that. Read about the setup in Softimage here.
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compositor feeds the IBL texture data to the environment shader
This environment sampling setup was used in two, full-scale production, Tony Hawk video game projects. 

Terrain Displacement

7/18/2010

 
A few terrain displacement tests. Used 3delight and mental ray to achive these results. The mental ray renders were enhanced with normal maps. Bump mapping wasn't necessary for rendering with 3delight; displacement results hold high detail with low render times.
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3delight displacement
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mental ray displacement + normal map
If you use CrazyBump or Xnormal to generate normal maps, I find this shader very helpful for the tuning process. It removes the need to 'tweak' parameters in a separate app. The author's (Felix Reichert) site is here. 
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modulating displacement & bump with weightmaps

Camera Projection Post FX

7/15/2010

 
Testing camera projecting into a 3d scene. The concept is to unload heavy math caluclations from the renderer by reprojecting the final composite onto the 3d geometry, and then quickly rendering depth of field and motion blur. Arnold makes such work-arounds obsolete, but in mental ray and other raytracers, these cheats go a long way.
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camera mapping the beauty pass back onto the geo; then activating lens and output shaders

Volume Lights

1/3/2010

 
Volume lighting tests with mental ray. Found this book very helpful. Its not an easy read (gets very technical) but contains an abundance of condensed knowledge that is difficult to find. If you use a version of Softimage prior to version 2011, download the .spdl files below for the required shaders.
volumeshaders.zip
File Size: 4 kb
File Type: zip
Download File

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setup
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volume scatter with an IES profile
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volume scatter via photons cast through refractive materials
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volume light scattering through transparent materials
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