The Number One Educational Resource for the Game Industry
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Overview:
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Collision detection and occlusion culling can be sped up considerably by reducing the complexity of the used triangle meshes. A popular method for decimating a mesh is the Garland-Heckbert algorithm. This approach uses edge contractions to reduce the number of triangles. The maximum error of the decimated mesh is bounded by a so-called quadric error metric (QEM). In this talk, properties of QEMs are discussed. We show what causes issues when using QEMs to find positions for newly created vertices and how to improve mesh quality. We show how to choose the new vertex positions conservatively, i.e. such that the decimated mesh either completely encapsulates the original mesh for the purpose of collision detection, or is completely encapsulated by the original mesh for the purpose of occlusion culling. Performance tweaks and termination criteria are addressed, and trade-offs are discussed.
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