Book Image

GLSL Essentials

By : Jacobo Rodriguez
Book Image

GLSL Essentials

By: Jacobo Rodriguez

Overview of this book

Shader programming has been the largest revolution in graphics programming. OpenGL Shading Language (abbreviated: GLSL or GLslang), is a high-level shading language based on the syntax of the C programming language.With GLSL you can execute code on your GPU (aka graphics card). More sophisticated effects can be achieved with this technique.Therefore, knowing how OpenGL works and how each shader type interacts with each other, as well as how they are integrated into the system, is imperative for graphic programmers. This knowledge is crucial in order to be familiar with the mechanisms for rendering 3D objects. GLSL Essentials is the only book on the market that teaches you about shaders from the very beginning. It shows you how graphics programming has evolved, in order to understand why you need each stage in the Graphics Rendering Pipeline, and how to manage it in a simple but concise way. This book explains how shaders work in a step-by-step manner, with an explanation of how they interact with the application assets at each stage. This book will take you through the graphics pipeline and will describe each section in an interactive and clear way. You will learn how the OpenGL state machine works and all its relevant stages. Vertex shaders, fragment shaders, and geometry shaders will be covered, as well some use cases and an introduction to the math needed for lighting algorithms or transforms. Generic GPU programming (GPGPU) will also be covered. After reading GLSL Essentials you will be ready to generate any rendering effect you need.
Table of Contents (13 chapters)

Inputs and outputs

As the rest of the shaders, fragment shaders can receive uniform variables as input. They work exactly as for vertex shaders, so there isn't much to say at this point except if we talk about textures. Textures are represented by an opaque variable type: a sampler (an opaque type is a special type that can only be used with built-in functions and cannot be used in mathematical operations). To make a texture available, you have to declare its uniform variable, using the right sampler type. Depending on the class of the texture you should use one sampler or other. A brief list is:

  • sampler1D (for 1D textures)

  • sampler2D (for 2D textures)

  • sampler3D (for 3D textures)

  • samplerCube (for cubemaps)

  • sampler2DArray (for arrays of 2D textures)

  • sampler2DShadow (for 2D shadow maps)


Samplers are special variable types that can only be used as uniforms. You can't declare a sampler inside a function.

In the host application, when you want to upload a sampler you just have to upload a uniform...