Autodesk, Inc.

Avid Technology Limited

Ian F Stewart

Dominic Laflamme

Jérôme Couture-Gagnon

Daniel Beaudry

Gareth John Morgan

André R Foisy

Luc Bolduc

Eric Cabot

Peter Zion

Alexandre Jean Claude

Ronald Beirouti

Maxime Beaudry

It is desirable for a fragment shader to have access to non-interpolated values for each vertex of the primitive in which the fragment is located. For example, a fragment shader may use the distortion of the primitive with respect to an original state of the primitive as part of the function the fragment shader performs. Due to the specification of fragment shaders and vertex shaders, fragments shaders receive only interpolated values, and thus cannot receive non-interpolated values of, for example, one solution to this problem would be to modify the processing engine for the shader language, and the shader specifications themselves, so that a fragment shader can receive non-interpolated values from the vertices of the primitive on which the fragment is located. Desirable values to receive would be at least the vertex coordinates. Another solution is to specify and use varyings in a manner that pass data to a fragment shader that permit the fragment shader to reconstruct the non-interpolated values. One way to achieve this is to a. allocate varyings and assign them indices, b. assign indices to the vertices and c. have each a shader contribute only to those varyings having the same index as the vertex being processed, and otherwise contribute a null value, such as 0, to the varyings with other indices. In this manner, when the interpolated value for the indexed varying is received by the fragment shader, the indexed varying contains the contribution of only one vertex, scaled by an interpolation parameter. Another indexed varying can be used to pass the interpolation parameter, allowing the original value for the vertex to be computed by the fragment shader.

Exchanging data between vertex shaders and fragment shaders on a graphics processing unit

An operator graph representing three-dimensional animation can be analyzed to identify subgraphs of the operator graph in which operators are not required to operate in a serialized manner. Such a condition may arise, for example, when two operators are not dependent on each other for data. This condition may arise when the operators are operating on different elements in a scene. Such operators may be evaluated in parallel. To identify these operators, a dependency graph is created. The dependency graph indicates which operators have inputs that are dependent on outputs provided by other operators. Using this graph, operators that are independent of each other can be readily identified. These operators can be evaluated in parallel. In an interactive editing system for three-dimensional animation or other rich media, such an analysis of an operator graph would occur when changes are made to the animation. The creation and use of the dependency graph enables faster processing of a scene while changes to the scene are being made.

Efficient processing of operator graphs representing three-dimensional character animation

Wrinkles are produced by computing directional stress, whether compression or stretching, for each pixel within each face of the mesh representing the skin, and then perturbing a surface normal based on the computed stress at each pixel in that face of the mesh. Directional stress at a given frame in an animation is determined, in general, by comparing the current state of the mesh at that frame (called a 'current pose') to the original state of the mesh (called a 'rest pose'). An artist specifies a wrinkle pattern by defining a texture that is mapped to the surface, using conventional techniques. A gradient texture is created from this wrinkle texture by computing the gradient at each pixel in the wrinkle texture. For each location in a face of the surface, the vector from the gradient texture is mapped to the corresponding face of the rest pose skin model and the current pose skin model, to produce two surface vectors. These two vectors are compared to provide an estimate of the surface stress at this location in the face. A wrinkle effect may be implemented using bump mapping, but the surface normal is perturbed differently for each location in the face of the mesh based on the skin stress estimated at that location. Other effects also may be created using the estimated stresses.

Producing wrinkles and other effects for a computer-generated character based on surface stress

To create an arbitrary-degree limit surface from a mesh, the mesh is first linearly subdivided. Additional linear subdivision and smoothing operations are performed on the initially linearly subdivided mesh. The number of sets of linear subdivision and smoothing operations depends on the desired surface-degree and subdivision level. This procedure can be used to create arbitrary-degree limit surfaces without performing a dual operation. During subdivision the topology of the intermediate mesh is independent of the goal limit surface-degree.

Unified subdivision for arbitrary and partial degree surfaces and curves with consistent property propagation

A visual programming interface allows an artist to create real time shaders using a tree of shader nodes. Each shader node represents an operation that can be performed in real time through the real time rendering engine. The visual interface allows the arbitrary combinations of these shader nodes to be made and allows the parameters of the shaders to be manipulated or animated. The visual programming interface may be activated in an interactive animation environment through a designation that a real time shader is to be applied to a surface. By integrating the visual programming interface with an interactive animation environment, an artist can experiment readily with different custom real time shaders. An artist also has the flexibility to create arbitrary real time shader trees and to view them interactively without requiring a programmer to develop or modify a custom shader. Basic operations represented by such shader nodes include drawing to a frame buffer (which may include a blending operation with the contents of the frame buffer), a transform operation and lighting operations. A tree of shader nodes may be processed in multiple passes. Each drawing operation in the tree defines a separate pass. The result of each pass is blended with the results of prior passes according to parameters defined for the drawing operation.

Visual programming interface for a three-dimensional animation system for defining real time shaders using a real-time rendering engine application programming interface

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Ian F Stewart