Normals, texture coordinates, and other data can be computed similarly. The TES's job would be to take the abstract patch coordinate and use bicubic Bezier interpolation to interpolate the 16 positions on the patch to that particular location in the abstract patch. For example, if you're creating a Bezier patch, you would have 16 patch vertices.
TESSELLATION TRIANGLE OPENGL TUTORIAL HOW TO
The job of the TES is to decide how to use the abstract patch coordinate and the real patch vertex data to generate the actual per-vertex data to be used by the rendering pipeline. The TES will be called that many times (at least it can be called multiple times for the same vertex), and it will be told where within the abstract patch that particular vertex is. Available in DirectX for a few versions now, it's finally come to OpenGL and offers up some great new features for automatic tessellation and geometry processing. So, if you tessellate a quad, and your outer levels are (4, 4, 4, 4) and the inner levels are (4, 4), that will generate 25 vertices. If you've been keeping up with OpenGL 4.x, then you've no doubt heard of the new Tessellation features they've added. It's once per-vertex of the tessellated primitive. But not per vertex in the GL_PATCHES primitive. The TES is a bit like a vertex shader it gets called once per vertex. How many patch vertices you have is completely irrelevant to this process. If your TES specifies that the abstract patch is a quad, then the tessellator will perform tessellation on a unit quad. Also demonstrates the use of pipeline derivatives. The tessellation unit, the part of the pipeline that actually generates triangles (or lines), operates on an abstract patch. Using pipeline state objects (pso) that bake state information (rasterization states, culling modes, etc.) along with the shaders into a single object, making it easy for an implementation to optimize usage (compared to OpenGLs dynamic state machine). The actual tessellation hardware doesn't actually use your patch data.
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