KAIST Computer Science
Global illumination for
PIXAR® movie production
20100121
Jaehyun Jang
KAIST Computer Science
• Global illumination for movie production
• Current Lighting Computation Methods
• Point-based Glo...
KAIST Computer Science
• The first 3D animation used global illumination - Shrek 2 (2004)
Global illumination for movie pr...
KAIST Computer Science
• Faking it : adding extra light sources
labour intensive
• Ray Tracing : requires many rays + shad...
KAIST Computer Science
Current : Physically-based Ray Tracing
Fig 2. Monster University
[Photograph]. Retrieved from http:...
KAIST Computer Science
Past : Point-based Global Illumination Techniques
Fig 3. Toy Story 3
[Photograph]. Retrieved from h...
KAIST Computer Science
• First introduced this technique in ‘Point-Based Approximate Color Bleeding’, (2008).
• Background...
KAIST Computer Science
Point-Based GI for Movie Production (2010)
• Point Cloud
Each point : position, normal, radius, col...
KAIST Computer Science
Point-Based GI for Movie Production (2010)
• Compute octree
A bottom-up computation
Consisting a no...
KAIST Computer Science
Point-Based GI for Movie Production (2010)
Fig 4. Rasterization onto six raster cube faces
[Photogr...
KAIST Computer Science
Point-Based GI for Movie Production (2010)
Fig 5. Rendering with PRMan, baked radiosity value of po...
KAIST Computer Science
Point-Based GI for Movie Production (2010)
• Variation and extensions
Area light sources and soft s...
KAIST Computer Science
Point-Based GI for Movie Production (2010)
Fig 6. Textured and displaced area light sources
[Photog...
KAIST Computer Science
Point-Based GI for Movie Production (2010)
Fig 7. Point cloud, Ambient occlusion, Reflection Occlusi...
KAIST Computer Science
• The lighting pipeline at PIXAR was completely rewritten
and switched to a physically based and ra...
KAIST Computer Science
• Break down the rendering equation, each part will be solved by different
coshaders(defined in RSL...
KAIST Computer Science
Fig 8. Light reflection
[Photograph]. Retrieved from http://content.gpwiki.org/index.php/D3DBook:
(L...
KAIST Computer Science
• Direct Lighting Integrator (Coshader)
1.Sample from lobes using BRDF coshaders
2.Sample from ligh...
KAIST Computer Science
Fig 9. Structures communicates data between three coshaders consisting of Direct Light Integrator
[...
KAIST Computer Science
Algorithm 1. (Light Integration)
Several algorithms in the paper : http://graphics.pixar.com/librar...
KAIST Computer Science
Fig 10. Various luminaries in this shot, The Blue Umbrella
[Photograph]. Retrieved from http://grap...
KAIST Computer Science
Fig 11. Physically-based lighting in Monster University
[Photograph]. Retrieved from http://blog.se...
KAIST Computer Science
Fig 12. Physically-based lighting in Monster University
[Photograph]. Retrieved from http://blog.se...
KAIST Computer Science
• Based on PIXAR online library (from 2011 - now)
• Sampling
Importance sampling
1. A statistical f...
KAIST Computer Science
• Caching
1. Multiresolution Radiosity Caching for Efficient Preview and Final Quality
Global Illum...
KAIST Computer Science
• Physically-based rendering is production standard.
• Current PRMan® pipeline, RSL 2.0 supports ph...
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Global illumination for PIXAR movie production

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Global illumination for PIXAR movie production

  1. 1. KAIST Computer Science Global illumination for PIXAR® movie production 20100121 Jaehyun Jang
  2. 2. KAIST Computer Science • Global illumination for movie production • Current Lighting Computation Methods • Point-based Global Illumination for Movie Production • Physically-based Lighting at PIXAR • Global illumination researches in PIXAR® • Rendering Pipeline in Production (as a Rendering TD) Contents
  3. 3. KAIST Computer Science • The first 3D animation used global illumination - Shrek 2 (2004) Global illumination for movie production Fig 1. Shrek 2. [Photograph]. Retrieved from http://www.awn.com/vfxworld/illuminating-global-illumination Courtesy of Paramount Pictures.
  4. 4. KAIST Computer Science • Faking it : adding extra light sources labour intensive • Ray Tracing : requires many rays + shader evaluations Too much slow (at 2010!) • Radiosity Requires entire scene data on memory • Point-based Little memory, no shader evaluations Current Lighting Computation Method
  5. 5. KAIST Computer Science Current : Physically-based Ray Tracing Fig 2. Monster University [Photograph]. Retrieved from http://neogaf.com/forum/showthread.php?t=569821 Courtesy of Disney-PIXAR • PIXAR has been rendering their movie using physically based ray-tracing after Monster University (2013)
  6. 6. KAIST Computer Science Past : Point-based Global Illumination Techniques Fig 3. Toy Story 3 [Photograph]. Retrieved from http://graphics.pixar.com/library/PointBasedGlobalIlluminationForMovieProduction/ Courtesy of Disney-PIXAR • PIXAR uses point-based global illumination for rendering at 2010. At that time, ray- tracing cost is too high to render images.
  7. 7. KAIST Computer Science • First introduced this technique in ‘Point-Based Approximate Color Bleeding’, (2008). • Background : Ray-tracing based global illumination is still expensive. • Advantages using point-based : 1. Fast Computation 2. Noisy-Free • Disadvantages : 1.Multi-pass approach, it cannot guarantee results as precise as ray tracing. Point-Based GI for Movie Production (2010)
  8. 8. KAIST Computer Science Point-Based GI for Movie Production (2010) • Point Cloud Each point : position, normal, radius, color = a colored disk Color : the direct illumination at that surface position How to generate? : PRMan to tessellate the surfaces into small micropolygons, compute direct illumination from all light sources by using surface shader. —> This approach is “Baking the direct illumination” (TD Terminology)
  9. 9. KAIST Computer Science Point-Based GI for Movie Production (2010) • Compute octree A bottom-up computation Consisting a node similar normals Compute a spherical harmonic from leaf-node Leaf-node : the sums of the coefficients for the surfels in the node. Non-leaf-node : the sums of the coefficients of its child nodes.
  10. 10. KAIST Computer Science Point-Based GI for Movie Production (2010) Fig 4. Rasterization onto six raster cube faces [Photograph]. Retrieved from http:// graphics.pixar.com/library/ PointBasedGlobalIlluminationForMovieProducti on/ Courtesy of Disney-PIXAR • Compute diffuse, and glossy global illumination Traverse octree, visiting a node and rasterize the illumination from node. Rasterize colors contributing to a point : world “as seen” by that point (a low resolution fish-eye image) Convolution with the BRDF 1. loop over raster pixels and multiplying colors with the BRDF for the direction corresponding to that pixel. 2. Can deal with glossy global illumination
  11. 11. KAIST Computer Science Point-Based GI for Movie Production (2010) Fig 5. Rendering with PRMan, baked radiosity value of point cloud (700,000 points) (left), glossy reflection (right) [Photograph]. Retrieved from http://penguin.ewu.edu/RenderMan/RMS_2.0/pointbased.html Courtesy of Disney-PIXAR
  12. 12. KAIST Computer Science Point-Based GI for Movie Production (2010) • Variation and extensions Area light sources and soft shadows Environment illumination Multiple diffuse bounces Final gathering for photon mapping Ambient occlusion and reflection occlusion etc.
  13. 13. KAIST Computer Science Point-Based GI for Movie Production (2010) Fig 6. Textured and displaced area light sources [Photograph]. Retrieved from http://penguin.ewu.edu/RenderMan/RMS_2.0/pointbased.html Courtesy of Disney-PIXAR
  14. 14. KAIST Computer Science Point-Based GI for Movie Production (2010) Fig 7. Point cloud, Ambient occlusion, Reflection Occlusion, additional environment reflection [Photograph]. Retrieved from http://penguin.ewu.edu/RenderMan/RMS_2.0/pointbased.html Courtesy of Disney-PIXAR
  15. 15. KAIST Computer Science • The lighting pipeline at PIXAR was completely rewritten and switched to a physically based and ray-traced system. • Rendering Equation L : radiance, f : BRDF 2 parts working in tandem : 1.Physically correct lights emitting energy in the scene 2.Physically correct BRDFs bouncing energy in the scene Physically based rendering pipeline (2013)
  16. 16. KAIST Computer Science • Break down the rendering equation, each part will be solved by different coshaders(defined in RSL 2.0) called integrators (http://renderman.pixar.com/view/ coshaders) • ! ! • direct lighting integrator + indirect diffuse integrator + indirect specular integrator Physically based rendering pipeline (2013)
  17. 17. KAIST Computer Science Fig 8. Light reflection [Photograph]. Retrieved from http://content.gpwiki.org/index.php/D3DBook: (Lighting)_Foundation_and_theory Courtesy of Wikimedia
  18. 18. KAIST Computer Science • Direct Lighting Integrator (Coshader) 1.Sample from lobes using BRDF coshaders 2.Sample from lights using light coshaders 3.Combine samples using Multiple Importance Sampling (Ryusuke Villemin, et al. 2013). Physically based rendering pipeline (2013)
  19. 19. KAIST Computer Science Fig 9. Structures communicates data between three coshaders consisting of Direct Light Integrator [Photograph]. Retrieved from http://graphics.pixar.com/library/PhysicallyBasedLighting/paper.pdf Courtesy of Disney-PIXAR
  20. 20. KAIST Computer Science Algorithm 1. (Light Integration) Several algorithms in the paper : http://graphics.pixar.com/library/PhysicallyBasedLighting/paper.pdf
  21. 21. KAIST Computer Science Fig 10. Various luminaries in this shot, The Blue Umbrella [Photograph]. Retrieved from http://graphics.pixar.com/library/PhysicallyBasedLighting/paper.pdf Courtesy of Disney-PIXAR
  22. 22. KAIST Computer Science Fig 11. Physically-based lighting in Monster University [Photograph]. Retrieved from http://blog.selfshadow.com/publications/s2013-shading-course/pixar/ s2013_pbs_pixar_slides.pdf Courtesy of Disney-PIXAR
  23. 23. KAIST Computer Science Fig 12. Physically-based lighting in Monster University [Photograph]. Retrieved from http://blog.selfshadow.com/publications/s2013-shading-course/pixar/ s2013_pbs_pixar_slides.pdf Courtesy of Disney-PIXAR
  24. 24. KAIST Computer Science • Based on PIXAR online library (from 2011 - now) • Sampling Importance sampling 1. A statistical framework for comparing importance sampling methods, and an application to rectangular lights (Leonid Pekelis, et al. 2014). 2. Multiple Importance Sampling for Emissive Effects (Ryusuke Villemin, et al. 2013). 3. Importance Sampling of Reflections from Hair Fibers (Christophe Hery, et al. 2011). Stratified Sampling 1. Correlated Multi-Jittered Sampling (Andrew Kensler, 2013). Global Illumination Researches in PIXAR
  25. 25. KAIST Computer Science • Caching 1. Multiresolution Radiosity Caching for Efficient Preview and Final Quality Global Illumination in Movies (Per H. Christensen, et al. 2012) • Summary PIXAR researches physically-based ray tracing, their rendering pipeline running on monte-carlo ray tracing, and it needs to develop proper sampling techniques for BRDF and etc. Global Illumination Researches in PIXAR
  26. 26. KAIST Computer Science • Physically-based rendering is production standard. • Current PRMan® pipeline, RSL 2.0 supports physically plausible shaders. • For rendering technical directors, these kind of techniques are tremendously demanded. • — All is commented by technical director in PIXAR. Rendering Pipeline in Production
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