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)

Vertex shader inputs

A vertex shader can have only two different kinds of inputs: vertex attributes and uniform variables.

Vertex attributes

A vertex attribute is simply the information you pass to the shader, in a per-vertex basis, along the plain vertex position in the world. Examples of vertex attributes could be:

  • Texture coordinates

  • Normals

  • Tangents

  • Per-vertex colors

Because of the evolving nature of OpenGL, version after version, details tend to be generalized. OpenGL specification writers try to define the data as uniform as possible. In the early programmable shader's days, there were specific attributes with specific names for texture coordinates, normals, vertex colors, and so on. Now, all attributes are generic and have no special names. They are simply vertex attribute buffers.

In order to show how attributes are bound to the vertex shader, we need to see how to set them up in the OpenGL host application.

First, we have to create and fill a vertex array configured with vertices and texture...