Graphics Reference
In-Depth Information
Figure 13.2.
The full shader pipeline showing the place of the tessellation shaders.
Tessellation Shaders or Geometry Shaders?
Both geometry shaders and tessellation shaders are capable of creating new
geometry from existing geometry, and both have uses in giving you level-of-
detail support, so you might be confused about when to use each type. While
their capabilities are in some ways similar, there are distinct differences. A
tessellation shader gives you more geometry, but all the new geometry is of
the same sort as you started with—you can get more segments for a line, more
triangles for a triangular patch, or more isolines or quads for a quad patch, but
you always get the same geometry. You should use a tessellation shader
when
you need to generate many new vertices and one of the tessellation topologies
will suit your needs, or if your required patch input involves many (more than
six
1
) vertices.
On the other hand, a geometry shader gives some different capabilities.
You must use a geometry shader when you need to convert to different geom-
etry topologies, such as presented in the silhouete and hedgehog shaders (tri-
1.
Why six? The input to a geometry shader can have as many as six vertices when you use the
triangles-with-adjacency topology.
