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

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 two-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...