Here is a new method for approximating Catmull-Clark subdivision surfaces with Gregory patches that is suitable for programmable hardware implementation supporting automatic surface tessellation. This method properly handles serveral kind of surfaces at the same time: triangles, regular and irregular quads. In the video, green patches are triangles, red patches are irregular quads and gray patches are regular quads.
We present a new method for approximating subdivision surfaces with hardware accelerated parametric patches. Our method improves the memory bandwidth requirements for patch control points, translating into superior performance compared to existing methods. Our input is general, allowing for meshes that contain both quadrilateral and triangular faces in the input control mesh, as
well as control meshes with boundary. We present two implementations of our scheme designed to run on Direct3D 11 class hardware equipped with a tessellator unit.
The detail whitepaper is available here: Approximating Subdivision Surfaces with Gregory Patches for Hardware Tessellation.