Add Procedural Textures to the gallery

proceduralTexture/SUMMARY.md

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 *[kynd](http://www.kynd.info) Nov 20, 2016*
 
-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. For the sake of simplicity, all the examples are based on the same random and noise functions so that you can focus on the main part of the algorithms. Once you get the ideas, try replacing these functions with with others from [Random](http://thebookofshaders.com/10/) and [Noise](http://thebookofshaders.com/11/) chapters, making them more realistic, and optimizing the performance. [Cellular Noise](http://thebookofshaders.com/12/) is very useful for making various textures like animal skin, plant, rock surface, etc. Try it out too.
+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 anumber 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.
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+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.

proceduralTexture/featured_examples.php

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