Dynamic Tessellation - Practical Rendering and Computation with Direct3D 11 - page 463

Figure 9.47. Results of using back-face culling.
Given that this optimization has no impact on the final image (unless transparency or
similar complex blending operations are being used) it results in a non-trivial reduction in
the work that the GPU has to perform.
9.2.2 Conclusion
As previously demonstrated, it is straightforward to implement the original Direct3D-8-era
algorithm using Direct3D 11. Given that tessellation is a basic requirement of the specifica-
tion, this also eliminates the original problem with ATI's TruForm implementation, which
only worked on a limited set of hardware. Now, all Direct3D 11 generation hardware sup-
ports this algorithm.
The added expressiveness of the Direct3D 11 pipeline allows further extensions to
the original algorithm. The main extension to be considered is to break the uniform tes-
sellation across the entire surface of the mesh. As shown in previous images, triangles
are generated and distributed evenly across the surface, even where there are only low-
frequency variations.
By utilizing mathematics similar to that shown in the back-face culling section, one
can dynamically alter the tessellation factors output by the hull shader and weight them to
be higher near the edge of the mesh, and in areas of high-frequency variation. However,
this requires modification of the input data, since adjacency becomes necessary to avoid
cracks between neighboring tiles.
Without any of these changes, the Curved Point Normal Triangles algorithm is a good
demonstration of Direct3D 11 's new functionality, as well as being a convenient technique
to enhance existing triangle-based meshes.