Book Image

OpenGL 4 Shading Language Cookbook - Third Edition

By : David Wolff
Book Image

OpenGL 4 Shading Language Cookbook - Third Edition

By: David Wolff

Overview of this book

OpenGL 4 Shading Language Cookbook, Third Edition provides easy-to-follow recipes that first walk you through the theory and background behind each technique, and then proceed to showcase and explain the GLSL and OpenGL code needed to implement them. The book begins by familiarizing you with beginner-level topics such as compiling and linking shader programs, saving and loading shader binaries (including SPIR-V), and using an OpenGL function loader library. We then proceed to cover basic lighting and shading effects. After that, you'll learn to use textures, produce shadows, and use geometry and tessellation shaders. Topics such as particle systems, screen-space ambient occlusion, deferred rendering, depth-based tessellation, and physically based rendering will help you tackle advanced topics. OpenGL 4 Shading Language Cookbook, Third Edition also covers advanced topics such as shadow techniques (including the two of the most common techniques: shadow maps and shadow volumes). You will learn how to use noise in shaders and how to use compute shaders. The book provides examples of modern shading techniques that can be used as a starting point for programmers to expand upon to produce modern, interactive, 3D computer-graphics applications.
Table of Contents (17 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Configuring the depth test


GLSL 4 provides the ability to configure how the depth test is performed. This gives us additional control over how and when fragments are tested against the depth buffer.

Many OpenGL implementations automatically provide an optimization known as the early depth test or early fragment test. With this optimization, the depth test is performed before the fragment shader is executed. Since fragments that fail the depth test will not appear on the screen (or the framebuffer), there is no point in executing the fragment shader at all for those fragments and we can save some time by avoiding the execution.

 

 

The OpenGL specification, however, states that the depth test must appear to be performed after the fragment shader. This means that if an implementation wishes to use the early depth test optimization, it must be careful. The implementation must make sure that if anything within the fragment shader might change the results of the depth test, then it should avoid using...