This chapter discusses the operations that can be applied either to the entire framebuffer or to individual fragments after the execution of the fragment shader in the OpenGL ES 2.0 fragment pipeline. As you’ll recall, the output of the fragment shader is the fragment’s color and depth value. The operations that occur after fragment shader execution and can affect the visibility and final color of a pixel are:
Scissor box testing.
Stencil buffer testing.
Depth buffer testing.
The tests and operations that a fragment goes through on its way to the framebuffer are shown in Figure 11-1.