Book Image

OpenGL 4 Shading Language Cookbook - Third Edition

By : David Wolff
Book Image

OpenGL 4 Shading Language Cookbook - Third Edition

By: David Wolff

Overview of this book

OpenGL 4 Shading Language Cookbook, Third Edition provides easy-to-follow recipes that first walk you through the theory and background behind each technique, and then proceed to showcase and explain the GLSL and OpenGL code needed to implement them. The book begins by familiarizing you with beginner-level topics such as compiling and linking shader programs, saving and loading shader binaries (including SPIR-V), and using an OpenGL function loader library. We then proceed to cover basic lighting and shading effects. After that, you'll learn to use textures, produce shadows, and use geometry and tessellation shaders. Topics such as particle systems, screen-space ambient occlusion, deferred rendering, depth-based tessellation, and physically based rendering will help you tackle advanced topics. OpenGL 4 Shading Language Cookbook, Third Edition also covers advanced topics such as shadow techniques (including the two of the most common techniques: shadow maps and shadow volumes). You will learn how to use noise in shaders and how to use compute shaders. The book provides examples of modern shading techniques that can be used as a starting point for programmers to expand upon to produce modern, interactive, 3D computer-graphics applications.
Table of Contents (17 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Discarding fragments to create a perforated look


Fragment shaders can make use of the discard keyword to throw away fragments. Use of this keyword causes the fragment shader to stop execution, without writing anything (including depth) to the output buffer. This provides a way to create holes in polygons without using blending. In fact, since fragments are completely discarded, there is no dependence on the order in which objects are drawn, saving us the trouble of doing any depth sorting that might have been necessary if blending was used.

In this recipe, we'll draw a teapot, and use the discard keyword to remove fragments selectively, based on texture coordinates. The result will look like the following image:

Getting ready

The vertex position, normal, and texture coordinates must be provided to the vertex shader from the OpenGL application. The position should be provided at location 0, the normal at location 1, and the texture coordinates at location 2. As in the previous examples, the...