Editing Shader (section)

==== Geometry shaders ====
Geometry shaders were introduced in Direct3D 10 and OpenGL 3.2; formerly available in OpenGL 2.0+ with the use of extensions.<ref>[http://www.opengl.org/wiki/Geometry_Shader Geometry Shader - OpenGL]. Retrieved on December 21, 2011.</ref> This type of shader can generate new graphics [[primitive (geometry)|primitive]]s, such as points, lines, and triangles, from those primitives that were sent to the beginning of the [[graphics pipeline]].<ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/bb205123(VS.85).aspx|title=Pipeline Stages (Direct3D 10) (Windows)|website=msdn.microsoft.com|date=January 6, 2021 }}</ref>

Geometry shader programs are executed after vertex shaders. They take as input a whole primitive, possibly with adjacency information. For example, when operating on triangles, the three vertices are the geometry shader's input. The shader can then emit zero or more primitives, which are rasterized and their fragments ultimately passed to a [[pixel shader]].

Typical uses of a geometry shader include point sprite generation, geometry [[Tessellation (computer graphics)|tessellation]], [[shadow volume]] extrusion, and single pass rendering to a [[cube map]]. A typical real-world example of the benefits of geometry shaders would be automatic mesh complexity modification. A series of line strips representing control points for a curve are passed to the geometry shader and depending on the complexity required the shader can automatically generate extra lines each of which provides a better approximation of a curve.