Light Pruning on Toy Story 4



Vaibhav Vavilala

July 2019



Pixar films have recently seen drastically rising light counts via procedural generation, resulting in longer render times and slower interactive workflows. Here we present a fully automated, scalable, and error-free light pruning pipeline deployed on Toy Story 4 that reduces final render times by 15-50% in challenging cases, accelerates interactive ... more



Paper (PDF)







Reduced Boundary Viscosity for Smoke



Alexis Angelidis

June 2019



We propose a method to reduce viscosity at the boundaries of incompressible flows. Our method allows artists to control the amount of boundary viscosity by mixing a new slip boundary solution with an existing no-slip solution. The cost of our method is an additional pre-computation and a post-computation that can ... more



Paper (PDF)



Available as Pixar Technical Memo #19-02







Art-Directed Surface Tearing Simulation



Leon Jeong Wook Park

January 2019



A key sequence in Pixar's Cars 3 includes dramatic surface tearing effects on Lightning McQueen's new body suit. Controlling and stylizing physically-based simulation is one of the hardest topics in CGI productions. To achieve our director's specific vision, we developed an art-directable surface tearing simulation framework. This talk presents our ... more



Paper (PDF)



Available as Pixar Technical Memo #19-01







Progressive Sampling Strategies for Disk Light Sources



Per Christensen

June 2018



This technical memo compares six different strategies for sampling a disk area light source. We test padding the domain with zero values, rejection sampling, polar mapping, concentric mapping, and two new strategies we call polar4 and concentric4 mapping. We test the six strategies with nine different sample sequences ... more



Paper (PDF)



Available as Pixar Technical Memo #18-02







Deep Compositing Using Lie Algebras



Tom Duff

July 2017



Deep compositing is an important practical tool in creating digital imagery, but there has been little theoretical analysis of the underlying mathematical operators. Motivated by finding a simple formulation of the merging operation on OpenEXR-style deep images, we show that the Porter-Duff over function is the operator of a Lie group. In its corresponding ... more



Paper (PDF)



To appear in ACM Transactions on Graphics







Importance Resampling for BSSRDF



Ryusuke Villemin, Christophe Hery, Per Christensen

November 2016



We present a method to improve BSSRDF rendering, which reduces variance due to sampling of the scattering exit point. By using importance resampling, we are able to sample any arbitrary diffusion model, taking into account the geometry of the object at the same time. The new method is trivial to implement ... more



Paper (PDF)



Available as Pixar Technical Memo #16-05







The Path to Path-Traced Movies



Per H. Christensen, Wojciech Jarosz

October 2016



Path tracing is one of several techniques to render photorealistic images by simulating the physics of light propagation within a scene. The roots of path tracing are outside of computer graphics, in the Monte Carlo simulations developed for neutron transport. A great strength of path tracing is that it is conceptually, mathematically, and often-times algorithmically ... more



Paper (PDF)



Appeared as: Foundation and Trends in Computer Graphics and Vision, volume 10, number 2, pages 103-175.







Vorticle Fluid Simulation



Alexis Angelidis

February 2015



We present a Lagrangian method for simulating incompressible gases in 3 dimensions. Using the vorticity equation with Lagrangian particles, we create, modify and delete vortices of varying size in a manner that handles buoyancy, boundaries, viscosity and collision with deformable objects using monopoles. Our method scales linearly for parallel processing and provides user controls at varying ... more



Paper (PDF)



Available as Pixar Technical Memo #15-01







Physically Based Lighting at Pixar



Christophe Hery, Ryusuke Villemin

July 2013



We recently participated in the Siggraph 2013 Physically Based Shading course, with all notes and documents stored at http://blog.selfshadow.com/publications/s2013-shading-course. We provide here direct access to our own chapter, describing the Physically Based System we designed at Pixar (on top of RenderMan) for the movie Monsters University and the short film ... more



Paper (PDF)







Correlated Multi-Jittered Sampling



Andrew Kensler

March 2013



We present a new technique for generating sets of stratified samples on the unit square. Though based on jittering, this method is competitive with low-discrepancy quasi-Monte Carlo sequences while avoiding some of the structured artifacts to which they are prone. An efficient implementation is provided that allows repeatable, ... more



Paper (PDF)



Available as Pixar Technical Memo #13-01







Porting RSL to C++



Ryusuke Villemin, Christophe Hery

November 2012



In a modern renderer, relying on recursive ray-tracing, the number of shader calls increases by one or two order of magnitude compared to a straighforward rasterizer dealing only with camera visible objects. Recognizing the potential overhead of RSL parsing in all these shader calls, this report evaluates different C++ pre-compiled ... more



Paper (PDF)



Available as Pixar Technical Memo #12-08







Coherent Noise for Non-Photorealistic Rendering



Michael Kass, Davide Pesare

July 2011



A wide variety of non-photorealistic rendering techniques make use of random variation in the placement or appearance of primitives. In order to avoid the "shower-door" effect, this random variation should move with the objects in the scene. Here we present coherent noise tailored to this purpose. We compute the coherent ... more



Paper (PDF)



Available in the Proceedings of SIGGRAPH 2011







Smoothed Local Histogram Filters



Michael Kass, Justin Solomon

May 2010



Local image histograms contain a great deal of information useful for applications in computer graphics, computer vision and computational photography. Making use of that information has been challenging because of the expense of computing histogram properties over large neighborhoods. Efficient algorithms exist for some specific computations like the bilateral filter, but not others. ... more



Paper (PDF)



To appear in the Proceedings of SIGGRAPH 2010



Available as Pixar Technical Memo #10-02







Point-Based Approximate Color Bleeding



Per H. Christensen

July 2008



This technical memo describes a fast point-based method for computing diffuse global illumination (color bleeding). The computation is 4-10 times faster than ray tracing, uses less memory, has no noise, and its run-time does not increase due to displacement-mapped surfaces, complex shaders, or many complex light sources. These properties make the method suitable ... more



Paper (PDF)



Additional materials: [SlidesFromAnnecy09.pdf]



Available as Pixar Technical Memo #08-01







Rat-Sized Water Effects in Ratatouille



Gary Bruins, Jon Reisch

May 2007



A particularly heavy effects sequence in the film Ratatouille depicts a colony of rats fleeing their home and crossing a long narrow river in several makeshift boats during a rainy afternoon. Nearly the entire sequence was photographed inches above the ground from a s perspective. Although this perspective provided a very interesting point of view ... more



Paper (PDF)



Available as Pixar Technical Memo #07-14







Effective Toon-Style Rendering Control Using Scalar Fields



Alex Harvill

May 2007



An illustration of Gusteau comes to life and introduces a new facet of the film Ratatouille. To do this, a technique was needed to convert an animated 3D character into a 2D illustration. Existing renderman shaders based on normal and depth maps were difficult to control. Post processing per gprim id ... more



Paper (PDF)



Available as Pixar Technical Memo #07-08







3D Paint Baking Proposal



Robert L. Cook

May 2007



3d paint has long been one of the most expensive parts of rendering at Pixar. This proposal is for a new baking technique that would greatly reduce the run-time cost of 3d paint and require no changes to the existing workflow. The implementation makes heavy use of existing code, which ... more



Paper (PDF)



Available as Pixar Technical Memo #07-16







500 Million and Counting: Hair Rendering on Ratatouille



David Ryu

May 2007



Featuring plush rats, well-groomed humans, and a colony of rodents numbering a thousand strong, Ratatouille had shots where the original scene descriptions contained many hundreds of millions of hairs. To make these shots renderable, we developed many new technologies to optimize our RenderMan-based hair rendering pipeline, including caching to speed up runtime sculpting, a technique ... more



Paper (PDF)



Available as Pixar Technical Memo #07-09







Articulating the Appeal



Sonoko Konishi, Michael Venturini

May 2007



It's difficult. In our society, rodents are usual portrayed in a negative manner. To overcome this, every department on Ratatouille strove to create appeal. In this sketch we will focus on how this was achieved through articulation.



Paper (PDF)



Available as Pixar Technical Memo #07-12







Statistical Acceleration for Animated Global Illumination



Mark Meyer, John Anderson

January 2006



Global illumination provides important visual cues to an animation, however its computational expense limits its use in practice. In this paper, we present an easy to implement technique for accelerating the computation of indirect illumination for an animated sequence using stochastic ray tracing. We begin by computing a quick but noisy solution using a ... more



Paper (PDF)



Additional materials: [ShotRender.mov]



To appear in SIGGRAPH 2006



Available as Pixar Technical Memo #06-03







Wavelet Noise



Robert L. Cook, Tony DeRose

August 2005



Noise functions are an essential building block for writing procedural shaders in 3D computer graphics. The original noise function introduced by Ken Perlin is still the most popular because it is simple and fast, and many spectacular images have been made ... more



Paper (PDF)



Additional materials: [RapLyrics.txt]



Available in the Proceedings of SIGGRAPH 2005







Untangling Cloth



David Baraff, Andrew Witkin, Michael Kass

August 2003



Deficient cloth-to-cloth collision response is the most serious shortcoming of most cloth simulation systems. Past approaches to cloth-cloth collision have used history to decide wheter nearby cloth regions have interpenetrated. The biggest pitfall of history-based methods is that an error anywhere along the way can give rise to persistent tangles...This ... more



Paper (PDF)



Available in the Proceedings of SIGGRAPH 2003







Adjoints and Importance in Rendering: an Overview



Per H. Christensen

July 2003



This survey gives an overview of the use of importance, an adjoint of light, in speeding up rendering. The importance of a light distribution indicates its contribution to the region of most interest --- typically the directly visible parts of a scene. Importance can therefore be used to concentrate global illumination and ray ... more



Paper (PDF)



Available as IEEE Transactions on Visualization and Computer Graphics (TVCG), Volume 9, Number 3, pages 329-340. IEEE, July 2003.







Deep Shadow Maps



Tom Lokovic, Eric Veach

August 2000



We introduce deep shadow maps, a technique that produces fast, high-quality shadows for primitives such as hair, fur, and smoke. Unlike traditional shadow maps, which store a single depth at each pixel, deep shadow maps store a representation of the fractional visibility through a pixel at all possible depths. Deep ... more



Paper (PDF)



Available in the Proceedings of SIGGRAPH 2000.







Texture On Demand



Darwyn Peachey

January 1990



Texture On Demand (TOD) is a technique for organizing large amounts of stored texture data in disk files and accessing it efficiently. Simply reading entire texture images into memory is not a good solution for real memory systems or for virtual memory systems. Texture data should be read from disk files only on ... more



Paper (PDF)



Available as Pixar Technical Memo #217







Stochastic Sampling in Computer Graphics



Robert L. Cook

January 1986



Ray tracing, ray casting, and other forms of point sampling are important techniques in computer graphics, but their usefulness has been undermined by aliasing artifacts. In this paper it is shown that these artifacts are not an inherent part of point sampling, but a consequence of ... more



Paper (PDF)



Available in ACM Transactions on Graphics, Volume 6, Number 1, January 1996.







Compositing Digital Images



Thomas Porter, Tom Duff

July 1984



Most computer graphics pictures have been computed all at once, so that the rendering program takes care of all computations relating to the overlap of objects. There are several applications, however, where elements must be rendered separately, relying on compositing techniques for the anti-aliased accumulation of the full image. This ... more



Paper (PDF)



Available in the Proceedings of SIGGRAPH 1984.





