Book Image

OpenGL 4 Shading Language Cookbook - Second Edition

By : David Wolff
Book Image

OpenGL 4 Shading Language Cookbook - Second Edition

By: David Wolff

Overview of this book

OpenGL Shading Language (GLSL) is a programming language used for customizing parts of the OpenGL graphics pipeline that were formerly fixed-function, and are executed directly on the GPU. It provides programmers with unprecedented flexibility for implementing effects and optimizations utilizing the power of modern GPUs. With Version 4, the language has been further refined to provide programmers with greater power and flexibility, with new stages such as tessellation and compute. OpenGL 4 Shading Language Cookbook provides easy-to-follow examples that first walk you through the theory and background behind each technique, and then go on to provide and explain the GLSL and OpenGL code needed to implement it. Beginner level through to advanced techniques are presented including topics such as texturing, screen-space techniques, lighting, shading, tessellation shaders, geometry shaders, compute shaders, and shadows. OpenGL Shading Language 4 Cookbook is a practical guide that takes you from the fundamentals of programming with modern GLSL and OpenGL, through to advanced techniques. The recipes build upon each other and take you quickly from novice to advanced level code. You'll see essential lighting and shading techniques; examples that demonstrate how to make use of textures for a wide variety of effects and as part of other techniques; examples of screen-space techniques including HDR rendering, bloom, and blur; shadowing techniques; tessellation, geometry, and compute shaders; how to use noise effectively; and animation with particle systems. OpenGL Shading Language 4 Cookbook 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)
OpenGL 4 Shading Language Cookbook Second Edition
About the Author
About the Reviewers

Applying a Gaussian blur filter

A blur filter can be useful in many different situations where the goal is to reduce the amount of noise in the image. As mentioned in the previous recipe, applying a blur filter prior to the edge detection pass may improve the results by reducing the amount of high frequency fluctuation across the image. The basic idea of any blur filter is to mix the color of a pixel with that of nearby pixels using a weighted sum. The weights typically decrease with the distance from the pixel (in 2D screen space) so that pixels that are far away contribute less than those closer to the pixel being blurred.

A Gaussian blur uses the 2-dimensional Gaussian function to weight the contributions of the nearby pixels.

The sigma squared term is the variance of the Gaussian, and determines the width of the Gaussian curve. The Gaussian function is maximum at (0,0), which corresponds to the location of the pixel being blurred and its value decreases as x or y increases. The following...