Book Image

OpenGL 4 Shading Language Cookbook - Second Edition

By : David Wolff
Book Image

OpenGL 4 Shading Language Cookbook - Second Edition

By: David Wolff

Overview of this book

OpenGL Shading Language (GLSL) is a programming language used for customizing parts of the OpenGL graphics pipeline that were formerly fixed-function, and are executed directly on the GPU. It provides programmers with unprecedented flexibility for implementing effects and optimizations utilizing the power of modern GPUs. With Version 4, the language has been further refined to provide programmers with greater power and flexibility, with new stages such as tessellation and compute. OpenGL 4 Shading Language Cookbook provides easy-to-follow examples that first walk you through the theory and background behind each technique, and then go on to provide and explain the GLSL and OpenGL code needed to implement it. Beginner level through to advanced techniques are presented including topics such as texturing, screen-space techniques, lighting, shading, tessellation shaders, geometry shaders, compute shaders, and shadows. OpenGL Shading Language 4 Cookbook is a practical guide that takes you from the fundamentals of programming with modern GLSL and OpenGL, through to advanced techniques. The recipes build upon each other and take you quickly from novice to advanced level code. You'll see essential lighting and shading techniques; examples that demonstrate how to make use of textures for a wide variety of effects and as part of other techniques; examples of screen-space techniques including HDR rendering, bloom, and blur; shadowing techniques; tessellation, geometry, and compute shaders; how to use noise effectively; and animation with particle systems. OpenGL Shading Language 4 Cookbook 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)
OpenGL 4 Shading Language Cookbook Second Edition
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Using deferred shading


Deferred shading is a technique that involves postponing (or "deferring") the lighting/shading step to a second pass. We do this (among other reasons) in order to avoid shading a pixel more than once. The basic idea is as follows:

  1. In the first pass, we render the scene, but instead of evaluating the reflection model to determine a fragment color, we simply store all of the geometry information (position, normal, texture coordinate, reflectivity, and so on) in an intermediate set of buffers, collectively called the g-buffer (g for geometry).

  2. In the second pass, we simply read from the g-buffer, evaluate the reflection model, and produce a final color for each pixel.

When deferred shading is used, we avoid evaluating the reflection model for a fragment that will not end up being visible. For example, consider a pixel located in an area where two polygons overlap. The fragment shader may be executed once for each polygon that covers that pixel; however, the resulting color...