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

Using subroutines to select shader functionality


In GLSL, a subroutine is a mechanism for binding a function call to one of a set of possible function definitions based on the value of a variable. In many ways, it is similar to function pointers in C. A uniform variable serves as the pointer and is used to invoke the function. The value of this variable can be set from the OpenGL side, thereby binding it to one of a few possible definitions. The subroutine's function definitions need not have the same name, but must have the same number and type of parameters and the same return type.

Subroutines therefore provide a way to select alternative implementations at runtime without swapping shader programs and/or recompiling, or using the if statements along with a uniform variable. For example, a single shader could be written to provide several shading algorithms intended for use on different objects within the scene. When rendering the scene, rather than swapping shader programs or using a conditional...