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)

The shader environment

Other applications that you might have coded in the past are built to run inside a CPU. This means that you have used a compiler that took your program (programmed in your favorite high-level programming language) and compiled it down into a representation that a CPU could understand. It does not matter if the programming language is compiled or interpreted, because in the end, all programs are translated to something the CPU can deal with.

Shaders are a little different because they are meant only for graphics, so they are closely related to the following two points:

  • First, they need a graphics card, because inside the graphics card lies the processor that will run them. This special kind of processor is called the GPU (Graphics Processing Unit).

  • A piece of software to reach the GPU: the GPU driver.


If you are going to program shaders, the first thing that you have to do is prepare your development environment, and that starts by downloading, and always keeping your graphics card driver updated.

Now suppose you are ready to start and have your first shader finished. You should compile and pass it to the GPU for execution. As GLSL relies on OpenGL, you must use OpenGL to compile and execute the shader. OpenGL has specific API calls for shader compilation: link, execution, and debug. Your OpenGL application now acts as a host application, from where you can manage your shaders and the resources that they might need, like for instance: textures, vertices, normals, framebuffers, or rendering states.