ABSTRACT
A tessellation operator increases the number of nodes in a mesh and can be understood as an upsampling method for polygonal surfaces. Using real-time tessellation allows the application developer to specify a coarse mesh at the application level, but dynamically add vertices as needed at GPU level. Phong tessellation can be implemented on today's GPU using either uniform or adaptive instanced tessellation, or on the geometry shader for low tessellation rates. Upcoming graphics hardware and APIs such as Microsoft Direct3D will feature a standard tessellator unit with two new programmable stages: the Hull Shader, which defines the control network of the polygon to tessellate and the Domain Shader, which evaluates the curved geometry. Triangle and quad Phong tessellation reproduce the same geometry on polygon edges, as only edge vertices are involved on this parameter domain. Therefore we obtain a crack-free tessellation scheme for triangle, tri-quad, and quad meshes.
