OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Geometry Shader Best Practices

The following are some tips for using geometry shaders wisely. This will help you obtain the best possible performance from a program using geometry shaders. These aren’t hard-and-fast rules, but if followed should allow you to use geometry shaders effectively in your programs.

Do Work in the Right Place

If you have work that is to be done per-vertex, do it in the vertex shader (or tessellation evaluation shader, if present). When rendering triangle strips or fans, each triangle is presented individually to the geometry shader. Performing per-vertex work in the geometry shader will result in it being done multiple times per vertex. Likewise, if you have work that is to be done per-face (such as calculating the values ...