OpenGL 4 Shading Language Cookbook - Third Edition

The shader pipeline extended

The following diagram shows a simplified view of the shader pipeline, when the shader program includes geometry and tessellation shaders:

The tessellation portion of the shader pipeline includes two stages: the Tessellation Control Shader (TCS) and the Tessellation Evaluation Shader (TES). The geometry shader follows the tessellation stages and precedes the fragment shader. The tessellation shader and geometry shader are optional; however, when a shader program includes a tessellation or geometry shader, a vertex shader must be included.

All shaders except the vertex shader are optional. When using a geometry shader, ...