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

High Performance Atomic Counters

The OpenGL Shading Language also supports a dedicated, high-performance set of atomic counters. However, to motivate their use, we will start with the ones already introduced; that is, the large suite of functions that perform atomic operations on the content of images, as described in “Atomic Operations on Images” on Page 578. These functions are extremely powerful and provide a great deal of flexibility when it comes to dealing with image data. Let’s imagine that we want to count fragments in a shader. This can often be accomplished using an occlusion query. However, an occlusion query blindly counts all fragments that pass the depth and stencil tests and runs after the shader has executed. Look at the example ...