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
About the Author
About the Reviewers

Creating a cloud-like effect

To create a texture that resembles a sky with clouds, we can use the noise values as a blending factor between the sky color and the cloud color. As clouds usually have large scale structure, it makes sense to use low octave noise. However, the large scale structure often has higher frequency variations, so some contribution from higher octave noise may be desired.

The following image shows an example of clouds generated by the technique in this recipe:

To create this effect, we take the cosine of the noise value and use the result as the blending factor between the cloud color.

Getting ready

Set up your program to generate a seamless noise texture and make it available to the shaders through the uniform sampler variable NoiseTex.

There are two uniforms in the fragment shader that can be assigned from the OpenGL program:

  • SkyColor: The background sky color

  • CloudColor: The color of the clouds

How to do it...

To create a shader program that uses a noise texture to create...