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, that consists of a closed three dimensional mesh. The cage can optionally be augmented with additional interior vertices, edges, and faces to more precisely control the interior behavior of the deformation. We show that harmonic coordinates are generalized barycentric coordinates that can be extended to any dimension. Moreover, they are the first system of generalized barycentric coordinates that are non-negative even in strongly concave situations, and their magnitude falls off with distance as measured within the cage.
Additional materials: [HarmonicCoordinates.divx], [SiggraphSlides.pdf]
Available in the proceedings of Siggraph 2007.
Available as Pixar Technical Memo #06-02b
Other versions:
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 require these sort of computations. In this paper, we present Key Point Subspace Acceleration and Soft Caching, a technique for accelerating these types of computations.
Key Point Subspace Acceleration (KPSA) is a statistical acceleration
scheme that uses examples to compute a statistical subspace and a set
of characteristic key points. The full calculation is then computed
only at these key points and these points are used to provide a
subspace based estimate of the entire calculation. The soft caching
process is an extension to the KPSA technique where the key points are
also used to provide a confidence estimate for the KPSA result. In
cases with high anticipated error the calculation will then ``fail
through'' to a full evaluation of all points (a cache miss), while
frames with low error can use the accelerated statistical evaluation
(a cache hit).
Additional materials: [SiggraphSlides.pdf], [softCaching.mov]
Available in the proceedings of Siggraph 2007
Available as Pixar Technical Memo #06-04b
Other versions:
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 small number of sample rays at each sample location. The variation of these noisy solutions over time is then used to create a smooth basis. Finally, the noisy solutions are projected onto the smooth basis to produce the final solution. The resulting animation has greatly reduced spatial and temporal noise, and a computational cost roughly equivalent to the noisy, low sample computation.
Additional materials: [ShotRender.mov]
To appear in SIGGRAPH 2006
Available as Pixar Technical Memo #06-03