OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Noise Summary

This section introduced noise, an incredibly useful function for adding irregularity to procedural shaders. After a brief description of the mathematical definition of this function, we used it as the basis for shaders that simulated clouds, turbulent flow, marble, granite, and wood. There is a noise function available as a built-in function in some implementations of GLSL. Portable noise functions can be created with user-defined shader functions or textures. However it is implemented, noise can increase the apparent realism of an image or an animation by adding imperfections, complexity, and an element of apparent randomness.