Stupid RAT Tricks, Pixar User

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Stupid RAT Tricks, Pixar Users Group 2001The
RenderMan EasyBake Oven

• Jonathan Litt (presenting)
• Technical Director, ILM
• Dan Goldman
• CG Supervisor, ILM

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• Subject how can I pre-light my scene using MTOR?
• Date 15 Aug 2001 090513 -0700
• From harley_at_public1.ptt.js.cn (harley)
• Newsgroups comp.graphics.rendering.renderman
• Hello, i am using maya with renderman. I have
  a big scene with about 200 light. Nothing move in
  the scene. To speed up the rendering, i want to
  convert all the light effects on the object to
  textures. I think that mean "pre-light" . How can
  i do that.
• Thank you very much for your help!

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Shading Network Example
Texture
Color Adjust
Noise
Bump
Synthesis
Color
Lighting
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Shading Network with Baking
Texture
Color Adjust
bake
Noise
Bump
Synthesis
Baked Texture
Stub
Lighting
Color
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The Phantom Mesh

• Render flattened geometry
• Shade original (phantom) geometry

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Case Study A Bagel
Original Render Baked
Texture
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How does it work?Part 1 RIB Modifications

• Regular rib
• PatchMesh P ltpointsgt
• Replace vertices (P) with s/t coordinates
• (x,y,z) --gt (s,t,0)
• Attach original P as Pref (reference geometry)
• Baked rib
• CoordSysTransform NDC
• PatchMesh P (s,t,0) Pref ltpointsgt
• Render with orthographic camera

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How does it work?Part 2 Shader Modifications

• Do all shading on reference geometry
• Replace P with Pref at beginning of shader
• point oldP P
• P transform(object, Pref)
• P transform(world, current, P)
• N calculatenormal(P)
• Restore P at end of shader
• P oldP
• Beware of view-dependent shading

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A Non-Leaning Tower

• 121 lights
• Single patch
• Render time 3.5 minutes (resolution 600x750)

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Baked tower

• Bake time 15 minutes (1k x 1k)

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Rendered with Baked Texture

• Render time 10 seconds
• No more lights in scene

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Baking Antialiasing

• Got aliasing? Can use baking to oversample
• Only have to oversample once, then let texture
  filtering take care of the rest

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Next YearUsing RenderMan to Bake
DeliciousShortbread Cookies with Sprinkles