GPU PRO 3

8 I Geometry Manipulation

Figure 1.2. Fractional transitioning between a tessellation factor 3.0 and a tessellation

factor 5.0 of an edge.

Figure 1.2 shows the tessellation that a fractional tessellation factor of roughly

3.5 would create.

For edges of the tessellated triangles and for interior vertices that need a lower

than maximum fractional tessellation factor, the vertex shader must ensure that

a number of zero-area triangles get created.

This is not the most efficient way of creating a tessellation, especially when

there are big differences between the tessellation factors on the three edges of a

triangle or the four edges of a quad. Nevertheless, ...