Abstract: One embodiment of the present invention sets forth technique for watertight tessellation in a displaced subdivision surface. A subdivision surface is represented as a novel parametric quad patch that is continuous with respect to position (C0) and partial derivatives (C1) along boundaries as well as interior regions. The novel parametric quad patch is referred to herein as a Hermite Gregory patch and comprises a Hermite patch augmented to include a pair of twist vector parameters per vertex. Each pair of twist vectors is combined into one twist vector during evaluation, according to weights based on proximity to parametric boundaries. Evaluation yields an approximation mesh comprising a position for each vertex and a corresponding normal vector for the vertex. Displacement is performed based on the approximation mesh and a displacement map to generate a displaced approximation mesh that is reflective of the displaced subdivision surface.

Abstract: One embodiment of the present invention sets forth technique for watertight tessellation in a displaced subdivision surface. A subdivision surface is represented as a novel parametric quad patch that is continuous with respect to position (C0) and partial derivatives (C1) along boundaries as well as interior regions. The novel parametric quad patch is referred to herein as a Hermite Gregory patch and comprises a Hermite patch augmented to include a pair of twist vector parameters per vertex. Each pair of twist vectors is combined into one twist vector during evaluation, according to weights based on proximity to parametric boundaries. Evaluation yields an approximation mesh comprising a position for each vertex and a corresponding normal vector for the vertex. Displacement is performed based on the approximation mesh and a displacement map to generate a displaced approximation mesh that is reflective of the displaced subdivision surface.