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)

Render to texture example

The first example will take a texture and will write into it some colors. To illustrate the use of work groups and work items, we will paint each pixel of the image with the index of the work group that processes that pixel. As we will use 16 x 16 work groups, the image will be filled with 16 x 16 solid block colors.

The shader invocation is done with this line: glDispatchCompute(16, 16, 1);.That means that we are going to execute the shader with 16 work groups in the X and Y dimensions and 1 in the Z (1 is the minimum accepted value for a dimension).

#version 430
// Configure how many work items compose the work groups
// Because we are executing the shader with 16 x 16 work groups, we can handle images is 512 x 512 (16*32)
layout(local_size_x = 32,local_size_y = 32, local_size_z = 1) in;
// Declare the uniform variable that holds our image
uniform layout(rgba8) writeonly image2D Image;
void main()
  ivec2 position = ivec2(gl_GlobalInvocationID.xy);
  vec4 color...