Mike Bailey & Steve Cunningham 
Graphics Shaders [PDF ebook] 
Theory and Practice, Second Edition

This book uses examples in Open GL and Open GL Shading Language to present the theory and application of shader programming. It explains how to program graphics shaders effectively for use in art, animation, gaming, and visualization. Along with improved graphics and new examples and exercises, this edition includes a new chapter on converting a fixed-function Open GL program to a shader-based Open GL program. It also explains how best to use tessellation shaders, illustrates the importance of the invariant qualifier for multipass rendering, and presents new applications, including terrain bump-mapping and LIDAR data.