Importance

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Abstract

A system and method for efficiently specifying vertex information for a three-dimensional graphical object which includes a plurality of geometric primitives. The method comprises organizing a first subset of the object's vertices into a strip of geometric primitives (typically triangles). The method next includes representing vertices of the strip by encoding a plurality of commands into a data stream. These commands are usable, during decompression, to reassemble the strip of primitives from a list of vertices. Selected commands specify that attributes of a particular vertex (position, color, normal value, etc.) are to be stored into a mesh buffer for use in forming subsequent primitives. The mesh buffer includes a fixed maximum number of memory locations which are accessible during the decompression process. In one embodiment, vertex parameters are 'pushed' on to the mesh buffer, which is organized as a stack. Commands subsequent to mesh buffer push commands may reference a vertex's parameter values by providing an offset into the stack. In this manner, parameter values may be re-specified without having to encode them two or more times in the geometry data stream. The use of mesh buffer push and reference instructions in combination with generalized triangle strip commands advantageously avoid having to re-specify data when the original instance and the re-use of a vertex are separated by one or more intervening primitives which do not include the vertex. This contend format is referred to herein as 'generalized triangle mesh format'.

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First Claim