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Order by: Date  | Author  | Title  | Index of all authors  | Index of Pixar Technical Memos

Kernel-Predicting Convolutional Networks for Denoising Monte Carlo Renderings

Steve Bako, Thijs Vogels, Brian McWilliams, Mark Meyer, Jan Novak, Alex Harvill, Pradeep Sen, Tony DeRose, Fabrice Rousselle
July 2017

Regression-based algorithms have shown to be good at denoising Monte Carlo (MC) renderings by leveraging its inexpensive by-products (e.g., feature buffers). However, when using higher-order models to handle complex cases, these techniques often overfit to noise in the input. For this reason, supervised learning methods have been proposed that ... more

Paper (PDF)

To appear in SIGGRAPH 2017

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

Regularized Kelvinlets: Sculpting Brushes based on Fundamental Solutions of Elasticity

Fernando de Goes, Doug L. James
May 2017

We introduce a new technique for real-time physically based volume sculpting of virtual elastic materials. Our formulation is based on the elastic response to localized force distributions associated with common modeling primitives such as grab, scale, twist, and pinch. The resulting brush-like displacements correspond to the regularization of fundamental solutions ... more

Paper (PDF)

Video: Regularized Kelvinlets

Video: Additional example with ~2M triangles

Additional materials: [multiScaleDerivation.pdf], [gradDerivation.pdf]


Available as Pixar Technical Memo #17-03

Eulerian Solid-Fluid Coupling

Yun Teng, David I.W. Levin, Theodore Kim
December 2016

We present a new method that achieves a two-way coupling between deformable solids and an incompressible fluid where the underlying geometric representation is entirely Eulerian. Using the recently developed Eulerian Solids approach [Levin et al. 2011], we are able to simulate multiple solids undergoing complex, frictional contact while simultaneously interacting ... more

Paper (PDF)

Optimal Voronoi Tessellations with Hessian-based Anisotropy

Max Budninskiy, Beibei Liu, Fernando de Goes, Yiying Tong, Pierre Alliez, Mathieu Desbrun
December 2016

This paper presents a variational method to generate cell complexes with local anisotropy conforming to the Hessian of any given convex function and for any given local mesh density. Our formulation builds upon approximation theory to offer an anisotropic extension of Centroidal Voronoi Tessellations which can be seen as a ... more

Paper (PDF)

Additional materials: [BLdG+16_SuppMat.pdf]

SIGGRAPH Asia 2016

Dispersion Kernels for Water Wave Simulation

Jose Angel Canabal, David Miraut, Nils Thuerey, Theodore Kim, Javier Portilla, Miguel Otaduy
December 2016

We propose a method to simulate the rich, scale-dependent dynamics of water waves. Our method preserves the dispersion properties of real waves, yet it supports interactions with obstacles and is computationally efficient. Fundamentally, it computes wave accelerations by way of applying a dispersion kernel as a spatially variant filter, which ... more

Paper (PDF)

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.

Towards Bidirectional Path Tracing at Pixar

Christophe Hery, Ryusuke Villemin, Florian Hecht
July 2016

On Finding Dory and Piper, we were faced with rendering a lot of water, or creatures and sets seen through water and glass. We worked with production artists to give controls for resolving these difficult light transports. We also learned to cheat these effects where appropriate. In these course notes, ... more

Paper (PDF)

Compressing Fluid Subspaces

Aaron Demby-Jones, Pradeep Sen, Theodore Kim
May 2016

Subspace fluid simulations, also known as reduced-order simulations, can be extremely fast, but also require basis matrices that consume an enormous amount of memory. Motivated by the extreme sparsity of Laplacian eigenfunctions in the frequency domain, we design a frequency-space codec that is capable of compressing basis matrices by up ... more

Paper (PDF)

Subdivision Exterior Calculus for Geometry Processing

Fernando de Goes, Mathieu Desbrun, Mark Meyer, Tony DeRose
April 2016

This paper introduces a new computational method to solve differential equations on subdivision surfaces. Our approach adapts the numerical framework of Discrete Exterior Calculus (DEC) from the polygonal to the subdivision setting by exploiting the refinability of subdivision basis functions. The resulting Subdivision Exterior Calculus (SEC) provides significant improvements in ... more

Paper (PDF)

Additional materials: [supplementalFigs.pdf], [supplemental.pdf]


Available as Pixar Technical Memo #16-01

Art and Technology at Pixar, from Toy Story to Today

Ryusuke Villemin, Christophe Hery, Sonoko Konishi, Takahito Tejima, David Yu
November 2015

Technology has always played an important part in Pixar's movie making process, starting with Toy Story over 20 years ago. This course will take you on a journey through that technical evolution, focusing on how story drove our technical designs and how we utilized new technical advancements to tell more appealing stories. Finally ... more

Paper (PDF)

SIGGRAPH Asia 2015 Course Notes.

Vector Field Processing on Triangle Meshes

Fernando de Goes, Mathieu Desbrun, Yiying Tong
August 2015

While scalar fields on surfaces have been staples of geometry processing, the use of tangent vector fields has steadily grown in geometry processing over the last two decades: they are crucial to encoding directions and sizing on surfaces as commonly required in tasks such as texture synthesis, non-photorealistic rendering, digital ... more

Paper (PDF)

SIGGRAPH Courses 2016, SIGGRAPH Asia Courses 2015

Convolutional Wasserstein Distances: Efficient Optimal Transportation on Geometric Domains

Justin Solomon, Fernando de Goes, Gabriel Peyre, Marco Cuturi, Adrian Butscher, Andy Nguyen, Tao Du, Leonidas Guibas
August 2015

This paper introduces a new class of algorithms for optimization problems involving optimal transportation over geometric domains. Our main contribution is to show that optimal transportation can be made tractable over large domains used in graphics, such as images and triangle meshes, improving performance by orders of magnitude compared to ... more

Paper (PDF)


Approximate Reflectance Profiles for Efficient Subsurface Scattering

Per H. Christensen, Brent Burley
July 2015

We present three useful parameterizations of a BSSRDF model based on empirical reflectance profiles. The model is very simple, but with the appropriate parameterization it matches brute-force Monte Carlo references better than state-of-the-art physically-based models (quantized diffusion and photon beam diffusion) for many common materials. Each reflectance profile is a sum of ... more

Paper (PDF)

Additional materials: [approxbssrdfslides.pdf], [SIGGRAPH_Tech_Talk.pdf]

Available as Pixar Technical Memo #15-04

Subspace Condensation: Full Space Adaptivity for Subspace Deformations

Yun Teng, Mark Meyer, Tony DeRose, Theodore Kim
May 2015

Subspace deformable body simulations can be very fast, but can behave unrealistically when behaviors outside the prescribed subspace, such as novel external collisions, are encountered. We address this limitation by presenting a fast, flexible new method that allows full space computation to be activated in the neighborhood of novel events ... more

Paper (PDF)

Additional materials: [paper_0089.mov]

To appear in SIGGRAPH 2015.

Available as Pixar Technical Memo #15-03

A Data-Driven Light Scattering Model for Hair

Leonid Pekelis, Christophe Hery, Ryusuke Villemin, Junyi Ling
May 2015

We present an implementation of the [Marschner et al. 2003] model for importance sampling light reflected from hair. The implemen- tation makes use of a version of Adaptive Importance Sampling (AIS), specialized to fit easily sampled distributions to BCSDFs. Our model is novel among importance sampling implementations in that it ... more

Paper (PDF)

Additional materials: [hairlock_eccentricity_100.mov], [hairlock_eccentricity_085.mov]

Available as Pixar Technical Memo #15-02

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

Geometry into Shading

Christophe Hery, Michael Kass, Junyi Ling
October 2014

Sometimes, when 3D CG objects are viewed from a distance, a great deal of geometry can end up inside a single pixel. When this happens, full-sized facets, or pixels in a displacement map should play the role of traditional micro-facets. Here we describe how to alter traditional shading calculations to ... more

Paper (PDF)

Available as Pixar Technical Memo #14-04

Multithreading for Visual Effects

Martin Watt, Erwin Coumans, George ElKoura, Ronald Henderson, Manuel Kraemer, Jeff Lait, James Reinders
August 2014

In this book, developers from the visual effects industry, including George ElKoura and Manuel Kraemer from Pixar, provide practical advice on multithreading techniques used in popular visual effects software. Concrete examples show how multithreading paradigms are applied to achieve high performance computation for visual effects in the challenging world ... more

Paper (PDF)

Computing Smooth Surface Contours with Accurate Topology

Pierre Benard, Aaron Hertzmann, Michael Kass
March 2014

This paper introduces a method for accurately computing the visible contours of a smooth 3D surface for stylization. This is a surprisingly difficult problem, and previous methods are prone to topological errors, such as gaps in the outline. Our approach is to generate, for each viewpoint, a new triangle mesh with contours that are topologically-equivalent ... more

Paper (PDF)

To appear in ACM Transactions on Graphics

A statistical framework for comparing importance sampling methods, and an application to rectangular lights

Leonid Pekelis, Christophe Hery
February 2014

Importance sampling methods for ray tracing are numerous. One reason is due to the lack of a robust, quantitative method for comparison. This tech memo takes strides to provide a framework for comparing sampling methods on fair ground. We define a simple, mathematical notion of strictly preferring one method to ... more

Paper (PDF)

Available as Pixar Technical Memo #14-01

Subspace Clothing Simulation using Adaptive Bases

Fabian Hahn, Bernhard Thomaszewski, Stelian Coros, Robert W. Sumner, Forrester Cole, Mark Meyer, Tony DeRose, Markus Gross
January 2014

We present a new approach to clothing simulation using low-dimensional linear subspaces with temporally adaptive bases. Our method exploits full-space simulation training data in order to construct a pool of low-dimensional bases distributed across pose space. For this purpose, we interpret the simulation data as offsets from a kinematic deformation ... more

Paper (PDF)

Additional materials: [SubspaceClothingSiggraph2.mp4]

Available as Pixar Technical Memo #14-03

Large Scale Geometric Visibility Culling on Brave

Zachary Repasky, Patrick Schork, Kevin McNamara, Susan Fong
August 2013

Disney/Pixar's Brave is visually complex, containing fully clothed and articulated crowds characters, a forest full of vegetation, ruins littered with debris, and a full fledged castle. In fact, it is so complex that our previous methods to remove unnecessary geometry are no longer adequate in keeping the renders feasible.

On ... more

Paper (PDF)

Additional materials: [visibilityCullingOnBrave.mov]

Available as Pixar Technical Memo #13-05

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)

Artistic Simulation of Curly Hair

Hayley Iben, Mark Meyer, Lena Petrovic, Olivier Soares, John Anderson, Andrew Witkin
July 2013

Artistic simulation of hair presents many challenges - ranging from incorporating artistic control to dealing with extreme motions of characters. Additionally, in a production environment, the simulation needs to be fast and results need to be usable "out of the box" (without extensive parameter modifications) in order to produce ... more

Paper (PDF)

Additional materials: [tazVideo-SCA.mov]

Available in the Proceedings of the Symposium on Computer Animation 2013.

Available as Pixar Technical Memo #12-03b

Other versions:

Mass Preserving Multi-Scale SPH

Christopher Jon Horvath, Barbara Solenthaler
July 2013

We present a method for performing very high resolution, incompressible fluid simulations at multiple resolutions of detail, simultaneously.

The particle-based method supports user-defined regions of refinement and can handle complex collision boundary conditions while remaining smooth and stable. Conservation of mass in refined detail levels is handled explicitly, overcoming mass-loss ... more

Paper (PDF)

Additional materials: [MultiScaleSPH_PixarTechMemo13.04_July19_2013.mov]

Available as Pixar Technical Memo #13-04

Photon Beam Diffusion: A Hybrid Monte Carlo Method for Subsurface Scattering

Ralf Habel, Per H. Christensen, Wojciech Jarosz
June 2013

We present photon beam diffusion, an efficient numerical method for accurately rendering translucent materials. Our approach interprets incident light as a continuous beam of photons inside the material. Numerically integrating diffusion from such extended sources has long been assumed computationally prohibitive, leading to the ubiquitous single-depth dipole approximation and the recent analytic sum-of-Gaussians approach employed ... more

Paper (PDF)

Additional materials: [supplemental-theory.pdf], [PBD_matlab_v1.03.zip]

Published in Computer Graphics Forum (Proceedings of the Eurographics Symposium on Rendering 2013), volume 32, number 4. Eurographics / Blackwell Publishers, June 2013. (Zaragoza, Spain, June 19-21.). Equation 13 amended July 2013.

Stylizing Animation By Example

Pierre Benard, Forrester Cole, Michael Kass, Igor Mordatch, James Hegarty, Martin Sebastian Senn, Kurt Fleischer, Davide Pesare, Katherine Breeden
April 2013

Skilled artists, using traditional media or modern computer painting tools, can create a variety of expressive styles that are very appealing in still images, but have been unsuitable for animation. The key difficulty is that existing techniques lack adequate temporal coherence to animate these styles effectively. Here we augment the ... more

Paper (PDF)

Additional materials: [ComputerGraphicsWorldArticle.pdf], [PaintTweenWorkingSets.tgz], [mainVideo.mov], [PaintTweenDistro.tgz], [additionalResults.mov]

Available in the proceedings of SIGGRAPH 2013.

Available as Pixar Technical Memo #13-03

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

Multiple Importance Sampling for Emissive Effects

Ryusuke Villemin, Christophe Hery
January 2013

We present a method for creating and sampling volumetric light sources directly using the volumetric data, obtaining high quality results with any mirror, glossy or diffuse objects, and integrating with any global illumination framework.

Paper (PDF)

Additional materials: [volumeCornell.mov], [volumeMIS.mov]

Published version available as http://jcgt.org/published/0002/02/10/

Available as Pixar Technical Memo #13-02

Texture mapping for the Better Dipole model

Christophe Hery
December 2012

We derive an exact diffuse integral for Eugene D"Eon"s new Better Dipole model and we provide the code for numerically inverting it, leading to easy texture mapping for translucency effects.

Paper (PDF)

Available as Pixar Technical Memo #12-11

Multiresolution Radiosity Caching for Efficient Preview and Final Quality Global Illumination in Movies

Per H. Christensen, George Harker, Jonathan Shade, Brenden Schubert, Dana Batali
July 2012

We present a multiresolution radiosity caching method that allows global illumination to be computed efficiently in a single pass in complex CG movie production scenes.

For distribution ray tracing in production scenes, the bottleneck is the time spent evaluating complex shaders at the ray hit points. We speed up this shader ... more

Paper (PDF)

Additional materials: [siggraphtalk.pdf], [subsurf.m4v], [globillum.m4v], [siggraphslides.pdf]

Available as Pixar Technical Memo #12-06

Tone Mapping High Dynamic Range Videos using Wavelets

Qi Shan, Mark Meyer, Tony DeRose, John Anderson
January 2012

We propose a novel 3D wavelet based tone mapping framework for high dynamic range videos. Still image tone mapping methods can be applied to videos in a frame by frame fashion, but they often exhibit haloing artifacts and do not guarantee temporal coherence, resulting in flickering. Directly extending wavelet analysis/synthesis ... more

Paper (PDF)

Available as Pixar Technical Memo #12-01

Proton: Multitouch Gestures as Regular Expressions

Kenrick Kin, Bjoern Hartmann, Tony DeRose, Maneesh Agrawala
January 2012

Current multitouch frameworks require application developers to write recognition code for custom gestures; this code is split across multiple event-handling callbacks. As the number of custom gestures grows it becomes increasingly difficult to 1) know if new gestures will conflict with existing gestures, and 2) know how to extend existing ... more

Paper (PDF)

To appear in CHI 2012

Available as Pixar Technical Memo #12-02

Feature Adaptive GPU Rendering of Catmull-Clark Subdivision Surfaces

Matthias Niessner, Charles Loop, Mark Meyer, Tony DeRose
January 2012

We present a novel method for high-performance GPU-based rendering of Catmull-Clark subdivision surfaces. Unlike previous methods, our algorithm computes the true limit surface up to machine precision, and is capable of rendering surfaces that conform to the full RenderMan specification for Catmull-Clark surfaces. Specifically, our algorithm can accommodate base meshes ... more

Paper (PDF)

Available in ACM Transactions on Graphics, January 2012.

Importance Sampling of Reflections from Hair Fibers

Christophe Hery, Ravi Ramamoorthi
December 2011

Hair and fur are increasingly important visual features in production rendering, and physically-based light scattering models are now commonly used. In this paper, we enable efficient Monte Carlo rendering of reflections from hair fibers by describing a simple and practical importance sampling strategy for the reflection term in the Marschner hair model. Our ... more

Paper (PDF)

Available as Pixar Technical Memo #11-07

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

Eden: A Professional Multitouch Tool for Constructing Virtual Organic Environments

Kenrick Kin, Tom Miller, Bjoern Bollensdorff, Tony DeRose, Bjoern Hartmann, Maneesh Agrawala
January 2011

Set construction is the process of selecting and positioning virtual geometric objects to create a virtual environment used in a computer-animated film. Set construction artists often have a clear mental image of the set composition, but find it tedious to build their intended sets with current mouse and keyboard interfaces. We investigate whether multitouch input can ... more

Paper (PDF)

To appear in the proceedings of SIGCHI 2011

Available as Pixar Technical Memo #11-04

Point-Based Global Illumination for Movie Production

Per H. Christensen
July 2010

This course note describes a fast point-based method for computing diffuse and glossy global illumination, area light illumination and soft shadows, HDRI environment map illumination, multiple diffuse reflection bounces, final gathering for photon mapping, ambient occlusion, reflection occlusion, and volume scattering. The results are free of noise and the ... more

Paper (PDF)

Additional materials: [Slides.pdf]

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

Determining the Benefits of Direct-Touch, Bimanual, and Multifinger Input on a Multitouch Workstation

Kenrick Kin, Maneesh Agrawala, Tony DeRose
May 2009

Multitouch workstations support direct-touch, bimanual, and multifinger interaction. Previous studies have separately examined the benefits of these three interaction attributes over mouse-based interactions. In contrast, we present an empirical user study that considers these three interaction attributes together for a single task, such that we can quantify and compare the performances of each attribute. In our ... more

Paper (PDF)

To appear in Graphics Interface 2009

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

Animating Oscillatory Motion With Overlap: Wiggly Splines

Michael Kass, John Anderson
June 2008

Oscillatory motion is ubiquitous in computer graphics, yet existing animation techniques are ill-suited to its authoring. We introduce a new type of spline for this purpose, known as a ``Wiggly Spline.'' The spline generalizes traditional piecewise cubics when its resonance and damping are set to zero, but creates oscillatory animation when its resonance and damping ... more

Paper (PDF)

Available in SIGGRAPH 2008

Available as Pixar Technical Memo #06-06a

Other versions:

Volume Conserving Finite Element Simulations of Deformable Models

Geoffrey Irving, Craig Schroeder, Ronald Fedkiw
August 2007

We propose a numerical method for modeling highly deformable nonlinear incompressible solids that conserves the volume locally near each node in a finite element mesh. Our method works with arbitrary constitutive models, is applicable to both passive and active materials (e.g. muscles), and works with simple tetrahedra without the need for multiple quadrature points ... more

Paper (PDF)

Available in the proceedings of SIGGRAPH 2007.

High-Quality Rendering Using Ray Tracing and Photon Mapping

Henrik Wann Jensen, Per H. Christensen
August 2007

Detailed descriptions of the ray-tracing and photon-mapping algorithms for rendering complex scenes with indirect illumination, caustics, participating media, and subsurface scattering. The emphasis is on the practical insight necessary to use and implement these algorithms in production of high-quality image in movies, games, architecture, etc.

Paper (PDF)

Available as Siggraph 2007 course notes, Course Number 8

Anyone Can Cook -- Inside Ratatouille's Kitchen

Jun Han Cho, Athena Xenakis, Stefan Gronsky, Apurva Shah
July 2007

The passion for cooking and food are the central theme of Pixar's recent film - Ratatouille. This complex and multi-faceted problem posed many challenges that were solved using diverse computer graphics and production techniques. In this course we will comprehensively cover all aspects including modeling, dressing, shading, lighting and effects.

The ... more

Paper (PDF)

Available as Siggraph 2007 Course Notes, Course Number 30

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

Harmonic Coordinates for Character Articulation

Pushkar Joshi, Mark Meyer, Tony DeRose, Brian Green, Tom Sanocki
May 2007

In this paper we consider the problem of creating and controlling volume deformations used to articulate characters for use in high-end applications such as computer generated feature films. We introduce a method we call harmonic coordinates that significantly improves upon existing volume deformation techniques. Our deformations are controlled using a topologically flexible structure, called a cage, ... more

Paper (PDF)

Additional materials: [SiggraphSlides.pdf], [HarmonicCoordinates.divx]

Available in the proceedings of Siggraph 2007.

Available as Pixar Technical Memo #06-02b

Other versions:

Key Point Subspace Acceleration and Soft Caching

Mark Meyer, John Anderson
May 2007

Many applications in Computer Graphics contain computationally expensive calculations. These calculations are often performed at many points to produce a full solution, even though the subspace of reasonable solutions may be of a relatively low dimension. The calculation of facial articulation and rendering of scenes with global illumination are two example applications that ... more

Paper (PDF)

Additional materials: [SiggraphSlides.pdf], [softCaching.mov]

Available in the proceedings of Siggraph 2007

Available as Pixar Technical Memo #06-04b

Other versions:

Virtual Tailoring for Ratatouille: Clothing the Fattest Man in the World

Christine Waggoner, David Baraff
May 2007

He's fat. Enormously so. Essentially a clothed sphere. (A very deformable and complexly animated sphere, with legs, arms, and no neck.) For Ratatouille, creating dynamic costumes for every human character in the film required extensive development and innovation in Pixar's cloth pipeline, particularly for the character Gusteau. Modeling and shepherding ... more

Paper (PDF)

Available as Pixar Technical Memo #07-07

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

Chop It Up! Animation-Driven Modeling, Simulation, and Shading in the Kitchen

Patrick Coleman, Eric Froemling
May 2007

In Disney/Pixar's Ratatouille, the creation of believable cooking environments with all their complexity has been an important element in presenting a rich world that helps draw the audience into the story. Part of that complexity arises in the preparation of food before cooking. To create complex animations of food in preparation, we designed a system ... more

Paper (PDF)

Available as Pixar Technical Memo #07-13

Simulating Whitewater Rapids in Ratatouille

Eric Froemling, Tolga Goktekin, Darwyn Peachey
May 2007

In Pixar's Ratatouille, a key story point involves a rat being swept through the sewers of Paris, plummeting down waterfalls and along steeply sloping tunnels, through a series of high-speed S- bends which cause the torrent of water to bank up sharply on each turn. Bringing ... more

Paper (PDF)

Available as Pixar Technical Memo #07-03

Fast, Soft Reflections Using Radiance Caches

Apurva Shah, Justin Ritter, Chris King, Stefan Gronsky
May 2007

In Pixar's Ratatouille a lot of scenes take place inside the kitchen where reflective surfaces like counter tops, stoves, pots and pans abound. Furthermore, these surfaces were often burnished or covered with dents, scratches or other displacements, which meant that the reflections were soft and fuzzy. Physically accurate reflections are most ... more

Paper (PDF)

Available as Pixar Technical Memo #07-04

Extracting and Parametrizing Temporally Coherent Surfaces from Particles

Chen Shen, Apurva Shah
May 2007

From pouring sauces to sudsy sink water to violent sewer rapids, realistic animation of fluids presented interesting challenges in Ratatouille. The various fluid effects were simulated either using a physically-based solver or directly with generic particle systems. Although the simulated particles move as a whole like a fluid, the number ... more

Paper (PDF)

Available as Pixar Technical Memo #07-05

An Effects Recipe for Rolling Dough, Cracking Eggs and Pouring Sauce

Tolga Goktekin, Jon Reisch, Darwyn Peachey, Apurva Shah
May 2007

Creating the digital effects for cooking in Ratatouille posed a number of unique challanges. First we had to adopt efficient methods for simulating a wide variety of material behaviours. Second we needed to direct our simulations in order to match the expressiveness of the character's animation, e.g. forming specific shapes while the character pounds a ... more

Paper (PDF)

Available as Pixar Technical Memo #07-06

Acting with Contact in Ratatouille - Cartoon Collision and Response

Gordon Cameron, Robert Russ, Adam Woodbury
May 2007

Contact is natural in the real world but often avoided in 3D animated features. Animators tend to make acting decisions that minimise or avoid contact within and between their characters and the world, and when apparent contact does occur, it can tend to feel both "floaty" and unrealistic. "Ratatouille" called for dynamic, tactile characters that ... more

Paper (PDF)

Available as Pixar Technical Memo #07-10

Stochastic Simplification of Aggregate Detail

Robert L. Cook, John Halstead, Maxwell Planck, David Ryu
May 2007

Many renderers perform poorly on scenes that contain a lot of detailed geometry. The load on the renderer can be alleviated by simplification techniques, which create less expensive representations of geometry that is small on the screen. Current simplification techniques for high-quality surface-based rendering tend to work best with element ... more

Paper (PDF)

Additional materials: [SiggraphSlides.pdf], [WithAndWithoutSimplification.mov]

Available in the Proceedings of Siggraph 2007.

Available as Pixar Technical Memo #06-05a

Other versions:

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

Rivers of Rodents: An Animation-Centric Crowds Pipeline for Ratatouille

David Ryu, Paul Kanyuk
May 2007

One of the major technical challenges in the animated film Ratatouille was creating a believable rat colony. In numbers as high as a thousand, these rats participated in highly complex and coordinated behaviors ranging from chaotic swarming to gourmet cooking. Often, the colony was ... more

Paper (PDF)

Available as Pixar Technical Memo #07-02

Ray Tracing for the Movie 'Cars'

Per H. Christensen, Julian Fong, David M. Laur, Dana Batali
September 2006

This paper describes how we extended Pixar's RenderMan renderer with ray tracing abilities. In order to ray trace highly complex scenes we use multiresolution geometry and texture caches, and use ray differentials to determine the appropriate resolution. With this method we are able to efficiently ray trace scenes with much more geometry and ... more

Paper (PDF)

Available in Proceedings of the IEEE Symposium on Interactive Ray Tracing 2006, pages 1-6. IEEE 2006

Efficient Simulation of Large Bodies of Water by Coupling Two and Three Dimensional Techniques

Geoffrey Irving, Eran Guendelman, Frank Losasso, Ronald Fedkiw
January 2006

We present a new method for the efficient simulation of large bodies of water, especially effective when three-dimensional surface effects are important. Similar to a traditional two-dimensional height field approach, most of the water volume is represented by tall cells which are assumed to have linear pressure profiles. In order to avoid the limitations typically ... more

Paper (PDF)

Additional materials: [movie.avi]

Available in the proceedings of SIGGRAPH 2006

Interactive Depth of Field

Michael Kass, Aaron Lefohn, John Owens
January 2006

Accurate computation of depth-of-field effects in computer graphics rendering is generally very time consuming, creating a problematic workflow for film authoring. The computation is particularly challenging because it depends on large-scale spatially-varying filtering that must accurately respect complex boundaries. Here we introduce an approximate depth-of-field computation that is good enough for film preview, yet ... more

Paper (PDF)

Additional materials: [movie.avi]

Available as Pixar Technical Memo #06-01

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

Lpics: a Hybrid Hardware-Accelerated Relighting Engine for Computer Cinematography

Fabio Pellacini, Kiril Vidimce, Aaron Lefohn, Alex Mohr, Mark Leone, John Warren
August 2005

In computer cinematography, the process of lighting design involves placing and configuring lights to define the visual appearance of environments and to enhance story elements. This process is labor intensive and time consuming, primarily because ... more

Paper (PDF)

Additional materials: [lpics_siggraph.mp4]

Available in the Proceedings of SIGGRAPH 2005

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

Volumetric Methods for Simulation and Rendering of Hair

Lena Petrovic, Mark Henne, John Anderson
January 2005

Hair is one of the crucial elements in representing believable digital humans. It is one of the most challenging elements, too, due to the large number of hairs on a human head, their length, and their complex interactions. Hair appearance, in rendering and simulation, is ... more

Paper (PDF)

Additional materials: [clip1.mp4], [clip4.mp4], [clip2.mp4], [clip5.mp4], [clip6.mp4], [clip3.mp4]

Available as Pixar Technical Memo #06-08

Mio: Fast Multipass Partitioning via Priority-Based Instruction Scheduling

Andrew Riffel, Aaron Lefohn, Kiril Vidimce, Mark Leone, John Owens
August 2004

Real-time graphics hardware continues to offer improved resources for programmable vertex and fragment shaders. However, shader programmers continue to write shaders that require more resources than are available in the hardware. One way to virtualize the resources necessary to run complex shaders is to partition the ... more

Paper (PDF)

Available in the Proceedings of Graphics Hardware 2004

An Irradiance Atlas for Global Illumination in Complex Production Scenes

Per H. Christensen, Dana Batali
June 2004

We introduce a tiled 3D MIP map representation of global illumination data. The representation is an adaptive sparse octree with a "brick" at each octree node; each brick consists of 8 cubed voxels with sparse irradiance values. The representation is designed to enable efficient caching. Combined with ... more

Paper (PDF)

Published as pp. 133-141 in the Proceedings of the Eurographics Symposium on Rendering 2004, Eurographics/ACM, June 2004.

Ray Differentials and Multiresolution Geometry Caching for Distribution Ray Tracing in Complex Scenes

Per H. Christensen, David M. Laur, Julian Fong, Wayne L. Wooten, Dana Batali
September 2003

When rendering only directly visible objects, ray tracing a few levels of specular reflection from large, low curvatures surfaces, and ray tracing shadows from point-like light sources, the accessed geometry is coherent and a geometry cache performs well. But in many other cases, ... more

Paper (PDF)

Published as pp. pp. 543-552 in Computer Graphics Forum (Eurographics 2003 Conference Proceedings), Blackwell Publishers, September 2003.

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

RenderMan, Theory and Practice

Dana Batali, Byron Bashforth, Chris Bernardi, Per H. Christensen, David Laur, Christophe Hery, Guido Quaroni, Erin Tomson, Thomas Jordan, Wayne Wooten
July 2003

Siggraph 2003 course notes.

Paper (PDF)

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.

Advanced Issues in Level of Detail

Martin Reddy
August 2002

Siggraph 2002 course slides. See the abstracts in the additional materials below for more details.

Paper (PDF)

Additional materials: [4-terrain.pdf], [3-terrain-abstract.txt], [2-perception.pdf], [1-perception-abstract.txt]

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.

Subdivision Surfaces in Character Animation

Tony DeRose, Michael Kass, Tien Truong
August 1998

The creation of believable and endearing characters in computer graphics presents a number of technical challenges, including the modeling, animation and rendering of complex shapes such as heads, hands, and clothing. Traditionally, these shapes have been modeled ... more

Paper (PDF)

Available in the Proceedings of SIGGRAPH 1998.

Dinosaur Input Device

Brian Knep, Craig Hayes, Rick Sayre, Tom Williams
June 1995

We present a system for animating an articulate figure using a physical skeleton, or armature, connected to a workstation. The skeleton is covered with sensors that monitor the orientations of the joints and send this information to the computer via custom-built hardware. ... more

Paper (PDF)

Appeared in the Proceedings of SIGCHI 1995

Efficient, Fair Interpolation using Catmull-Clark Surfaces

Mark Halstead, Michael Kass, Tony DeRose
July 1993

We describe an efficient method for constructing a smooth surface that interpolates the vertices of a mesh of arbitrary topological type. Normal vectors can also be interpolated at an arbitrary subset of the vertices. The method improves on existing interpolation techniques in that it is fast, robust and general.

Paper (PDF)

Appeared in SIGGRAPH 1993.

Surface Reconstruction from Unorganized Points

Hugues Hoppe, Tony DeRose, Tom Duchamp, John McDonald, Werner Stuetzle
July 1992

We describe and demonstrate an algorithm that takes as input an unorganized set of points x1,...,xn in R3 on or near an unknown manifold M, and produces as output a simplicial surface that approximates M. Neither the topology, the presence of boundaries, nor the geometry of M are assumed to be known in advance ... more

Paper (PDF)

Published in SIGGRAPH 1992.

Texture On Demand

Darwyn Peachey

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

Rendering Antialiased Shadows with Depth Maps

William T. Reeves, David H. Salesin, Robert L. Cook
July 1987

We present a solution to the aliasing problem for shadow algorithms that use depth maps. The solution is based on a new filtering technique called percentage closer filtering. In addition to antialiasing, the improved algorithm provides soft shadow boundaries that resemble penumbrae. We describe ... more

Paper (PDF)

Available in the Proceedings of SIGGRAPH 1987.

The Reyes Rendering Architecture

Robert L. Cook, Loren Carpenter, Edwin Catmull
July 1987

An architecture is presented for fast high-quality rendering of complex images. All objects are reduced to common world-space geometric entities called micropolygons, and all of the shading and visibility calculations operate on these micropolygons. Each type of calculation is performed in a coordinate system that is ... more

Paper (PDF)

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.

Distributed Ray Tracing

Robert L. Cook, Thomas Porter, Loren Carpenter
July 1984

Ray tracing is one of the most elegant techniques in computer graphics. Many phenomena that are difficult or impossible with other techniques are simple with ray tracing, including shadows, reflections, and refracted light. Ray directions, however, have been determined precisely, and this had limited the capabilities of ray tracing. By ... more

Paper (PDF)

Available in the Proceedings of SIGGRAPH 1984

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.

Shade Trees

Robert L. Cook
July 1984

Shading is an important part of computer imagery, but shaders have been based on fixed models to which all surfaces must conform. As computer imagery becomes more sophisticated, surfaces have more complex shading characteristics and thus require a less rigid shading model. This paper presents a flexible tree-structured shading model ... more

Paper (PDF)

Available in the Proceedings of SIGGRAPH 1984.

A Reflectance Model for Computer Graphics

Robert L. Cook, Kenneth E. Torrance
January 1982

A new reflectance model for rendering computer sythesized images is presented. The model accounts for the relative brightness of different materials and light sources in the same scene. It describes the directional distribution of the reflected light and a color shift that occurs as ... more

Paper (PDF)

Published in Transactions on Graphics, Vol. 1, No. 1, January 1982.

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