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)

Drawing a simple geometry sample

In order to have a runnable shader program, we need a vertex shader and a fragment shader. Until now, we have not spoken about fragment shaders, but we still need one to run the samples, so I'll present here a simple fragment shader to use in conjunction with the next vertex shaders. This will be our sample fragment shader, kept as simple as possible for learning purposes:

// Fragment shader
#version 430
#pragma debug(on)
#pragma optimize(off)

uniform vec4 SolidColor;

// Writing to this variable will set the current fragment's color
out vec4 frameBufferColor; 

void main()
  frameBufferColor = SolidColor;

This fragment shader paints the whole triangle surface with a solid color, provided by means of a uniform variable (fragment shaders also have uniform variables).

Coming back to the vertex shaders, let's start with a simple one. The simplest thing we could want to do is show our geometry as it is, on the screen, rendered with a single solid color. So...