Geometry shaders

Definition:
Geometry shaders add and remove vertices from a mesh. Geometry shaders can be used to generate geometry procedurally or to add volumetric detail to existing meshes that would be too costly to process on the CPU.


Software support:
Microsoft's Direct 3D 10 and Silicon Graphic's OpenGL 3.2 supports geometry shaders.


Description:
Geometry shader programs are executed after vertex shaders. They take as input a whole primitive, possibly with adjacency information. For example, when operating on rectangles, the four vertices are the geometry shader's input.


Uses in graphic system:
Typical uses of a geometry shader include point sprite generation, geometry tessellation, shadow volume extrusion, and single pass rendering to a cube map.
A geometry shader can generate new graphics primitives, such as points, lines, and triangles, from those primitives that were sent to the beginning of the graphics pipeline.