## Introduction

Tessellation and geometry shaders are relatively new additions to the OpenGL pipeline, and provide programmers with additional ways to modify geometry as it progresses through the shader pipeline. Geometry shaders can be used to add, modify, or delete geometry, and tessellation shaders can be configured to automatically generate geometry at various levels of detail and to facilitate interpolation based on arbitrary input (patches).

In this chapter, we'll look at several examples of geometry and tessellation shaders in various contexts. However, before we get into the recipes, let's investigate how all of this fits together.

### 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...