Book Image

OpenGL 4 Shading Language Cookbook - Third Edition

By : David Wolff
Book Image

OpenGL 4 Shading Language Cookbook - Third Edition

By: David Wolff

Overview of this book

OpenGL 4 Shading Language Cookbook, Third Edition provides easy-to-follow recipes that first walk you through the theory and background behind each technique, and then proceed to showcase and explain the GLSL and OpenGL code needed to implement them. The book begins by familiarizing you with beginner-level topics such as compiling and linking shader programs, saving and loading shader binaries (including SPIR-V), and using an OpenGL function loader library. We then proceed to cover basic lighting and shading effects. After that, you'll learn to use textures, produce shadows, and use geometry and tessellation shaders. Topics such as particle systems, screen-space ambient occlusion, deferred rendering, depth-based tessellation, and physically based rendering will help you tackle advanced topics. OpenGL 4 Shading Language Cookbook, Third Edition also covers advanced topics such as shadow techniques (including the two of the most common techniques: shadow maps and shadow volumes). You will learn how to use noise in shaders and how to use compute shaders. The book 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)
Title Page
Packt Upsell
Contributors
Preface
Index

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 NoiseTex uniform sampler variable.

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