Shaders are often used to create realistic surfaces of natural or artificial material such as wood, marble, granite, metal, stone, etc. without using photographs or pre-rendered images. Here are demonstrations of some basic techniques. All the examples are based on a number of random and noise functions from [Random](http://thebookofshaders.com/10/), [Noise](http://thebookofshaders.com/11/), [Cellular Noise](http://thebookofshaders.com/12/) and [Fractal Brownian Motion](http://thebookofshaders.com/13/) chapters. Once you get the basic ideas, try tweaking and adding more details to make them more realistic, coming up with new textures and optimizing the performance.
Note that the terrain examples at the bottom use normal map and lighting which are techniques not yet introduced in this book. In short, what they do is to generate a map of the directions of the surface and shade the pixels accordingly. We will cover these ideas in future chapters. Stay tuned.
