Book Image

OpenGL 4.0 Shading Language Cookbook

Book Image

OpenGL 4.0 Shading Language Cookbook

Overview of this book

The 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 4.0, the language has been further refined to provide programmers with greater flexibility, and additional features have been added such as an entirely new stage called the tessellation shader. The OpenGL Shading Language 4.0 Cookbook provides easy-to-follow examples that first walk you through the theory and background behind each technique then go on to provide and explain the GLSL and OpenGL code needed to implement it. Beginning level through to advanced techniques are presented including topics such as texturing, screen-space techniques, lighting, shading, tessellation shaders, geometry shaders, and shadows. The OpenGL Shading Language 4.0 Cookbook is a practical guide that takes you from the basics of programming with GLSL 4.0 and OpenGL 4.0, through basic lighting and shading techniques, to more advanced techniques and effects. It presents techniques for producing basic lighting and shading effects; 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, shadowing, tessellation and geometry shaders, noise, and animation. The OpenGL Shading Language 4.0 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 (16 chapters)
OpenGL 4.0 Shading Language Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Drawing silhouette lines using the geometry shader


When a cartoon or hand-drawn effect is desired, we often want to draw black outlines around the edges of a model and along ridges or creases (silhouette lines). In this recipe, we'll discuss one technique for doing this using the geometry shader to produce the additional geometry for the silhouette lines. The geometry shader will approximate these lines by generating small, skinny quads aligned with the edges that make up the silhouette of the object.

The following image shows the ogre mesh with black silhouette lines generated by the geometry shader. The lines are made up of small quads that are aligned with certain mesh edges.

The technique shown in this recipe is based on a technique published in a recent blog post by Philip Rideout (prideout.net/blog/?p=54). His implementation uses two passes (base geometry and silhouette), and includes many optimizations such as anti-aliasing and custom depth testing (with g-buffers). To keep things simple...