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

Creating soft shadow edges with random sampling


The basic shadow mapping algorithm combined with PCF can produce shadows with soft edges. However, if we desire blurred edges that are substantially wide (to approximate true soft shadows) then a large number of samples is required. Additionally, there is a good deal of wasted effort when shading fragments that are in the center of large shadows, or completely outside of the shadow. For those fragments, all of the nearby shadow map texels will evaluate to the same value. Therefore, the work of accessing and averaging those texels is essentially a wasted effort.

The technique presented in this recipe is based on a chapter published in GPU Gems 2, edited by Matt Pharr and Randima Fernando, Addison-Wesley Professional, 2005. (Chapter 17 by Yury Uralsky). It provides an approach that can address both of the preceding issues to create shadows with soft edges of various widths, while avoiding unnecessary texture accesses in areas inside and outside...