Graphics Reference
In-Depth Information
12
Geometry Shader
Concepts and Examples
The geometry shader is a new capability in shaders, introduced in late 2006
with the release of Shader Model 4 to take advantage of the ever-growing
capability of high-end graphics cards. It adds to the programmer's graphics
capabilities by providing tools to expand the basic model geometry to include
more or different graphics primitives than were initially defined. Thus, geom-
etry shaders should really be called “geometry creators” or “geometry expand-
ers.” The place of the geometry shader in the graphics pipeline is shown in Fig-
ure 12.1, where “vertex processing” can include a vertex shader, tessellation
control shader, or tessellation evaluation shader.
The geometry expansion that is provided by the geometry shader has
many uses. One is in using the input geometry to create additional geome-
try, such as silhouete edges, shrunk triangles, or hedgehog plots. Another is
in managing
level of detail
(LOD). The LOD, shrunk triangles, and silhouete
edges examples are discussed later in this chapter, and hedgehog plots are
discussed in Chapter 15.
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