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

Discarding Rendered Data

Advanced

As a rule of thumb, you should always clear the framebuffer before you begin rendering a frame. Modern GPUs implement compression and other techniques to improve performance, memory bandwidth requirements, and so on. When you clear a framebuffer, the OpenGL implementation knows that it can discard any rendered data in the framebuffer and return it to a clean, compressed state if possible. However, what happens if you’re sure that you’re about to render over the whole framebuffer? It seems that clearing it would be a waste as you are about to draw all over the cleared area. If you are certain that you are going to completely replace the contents of the framebuffer with new rendering, you can discard it with a ...