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

Implementing two-sided shading


When rendering a mesh that is completely closed, the back faces of polygons are hidden. However, if a mesh contains holes, it might be the case that the back faces would become visible. In this case, the polygons may be shaded incorrectly due to the fact that the normal vector is pointing in the wrong direction. To properly shade those back faces, one needs to invert the normal vector and compute the lighting equations based on the inverted normal.

The following screenshot shows a teapot with the lid removed. On the left, the ADS lighting model is used. On the right, the ADS model is augmented with the two-sided rendering technique discussed in this recipe.

In this recipe, we'll look at an example that uses the ADS model discussed in the previous recipes, augmented with the ability to correctly shade back faces.

Getting ready

The vertex position should be provided in attribute location 0 and the vertex normal in attribute location 1. As in previous examples, the...