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
About the Author
About the Reviewers

Creating a paint-spatter effect

Using high-frequency noise, it is easy to create the effect of random spatters of paint on the surface of an object. The following image shows an example:

We use the noise texture to vary the color of the object, with a sharp transition between the base color and the paint color. We'll use either the base color or paint color as the diffuse reflectivity of the shading model. If the noise value is above a certain threshold, we'll use the paint color; otherwise, we'll use the base color of the object.

Getting ready

Start with a basic setup for rendering using the Phong shading model (or whatever model you prefer). Include texture coordinates and pass them along to the fragment shader.

There are a couple of uniform variables that define the parameters of the paint spatters:

  • PaintColor : The color of the paint spatters

  • Threshold : The minimum noise value where a spatter will appear

Create a noise texture with high frequency noise (see Creating a seamless noise texture...