I've been reading through http://www.opengl.org/registry/specs...ion_shader.txt today because I wanted to know how exactly triangles are tessellated when using a tessellation shader.

However, there's a part I found strange - maybe I don't understand if fully (math/vocabulary wise). In "Section 2.X.2.1, Triangle Tessellation" there is a part about how the vertices for inner triangles are created. Specifically:

If I understand this right, it works like illustrated in this picture (assuming an inner tessellation level of 4): http://stud4.tuwien.ac.at/~e0725517/images/tri_tess.pngOriginally Posted byGL_ARB_tessellation_shader text

However, if this was correct, it would be flawed, in that for obtuse triangles it would be possible that the inner vertices are placed outside the original triangle.

I've tested it on an NVidia card, where the tessellation clearly results in correct concentric triangles.

Thanks in advance.