There are many free resources available online where you can learn GLSL shading language. Some of the best websites for learning GLSL are:
1. The Book of Shaders: This is an interactive introduction to GLSL shaders that guides you through the basics of shader programming. It includes code examples and interactive examples that you can run in your browser.
2. Shader School: This is a free online course that teaches you how to create shaders with GLSL. It includes lessons on lighting, texturing, and working with shaders in WebGL.
3. Shadertoy: This is a website where you can find and share GLSL shaders. You can browse through thousands of user-created shaders, including tutorials and examples, or create your own shaders and share them...