OpenGL 4.0 Shading Language Cookbook

OpenGL 4.0 Shading Language Cookbook

Overview of this book

The 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 4.0, the language has been further refined to provide programmers with greater flexibility, and additional features have been added such as an entirely new stage called the tessellation shader. The OpenGL Shading Language 4.0 Cookbook provides easy-to-follow examples that first walk you through the theory and background behind each technique then go on to provide and explain the GLSL and OpenGL code needed to implement it. Beginning level through to advanced techniques are presented including topics such as texturing, screen-space techniques, lighting, shading, tessellation shaders, geometry shaders, and shadows. The OpenGL Shading Language 4.0 Cookbook is a practical guide that takes you from the basics of programming with GLSL 4.0 and OpenGL 4.0, through basic lighting and shading techniques, to more advanced techniques and effects. It presents techniques for producing basic lighting and shading effects; 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, shadowing, tessellation and geometry shaders, noise, and animation. The OpenGL Shading Language 4.0 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.

OpenGL 4.0 Shading Language Cookbook

Credits

About the Author

About the Reviewers

www.PacktPub.com

Preface

Free Chapter

Getting Started with GLSL 4.0

Introduction

Using the GLEW Library to access the latest OpenGL functionality

Using the GLM library for mathematics

Determining the GLSL and OpenGL version

Compiling a shader

Linking a shader program

Sending data to a shader using per-vertex attributes and vertex buffer objects

Getting a list of active vertex input attributes and indices

Sending data to a shader using uniform variables

Getting a list of active uniform variables

Using uniform blocks and uniform buffer objects

Building a C++ shader program class

The Basics of GLSL Shaders

Introduction

Implementing diffuse, per-vertex shading with a single point light source

Implementing per-vertex ambient, diffuse, and specular (ADS) shading

Using functions in shaders

Implementing two-sided shading

Implementing flat shading

Using subroutines to select shader functionality

Discarding fragments to create a perforated look

Lighting, Shading Effects, and Optimizations

Introduction

Shading with multiple positional lights

Shading with a directional light source

Using per-fragment shading for improved realism

Using the halfway vector for improved performance

Simulating a spotlight

Creating a cartoon shading effect

Simulating fog

Using Textures

Introduction

Applying a 2D texture

Applying multiple textures

Using alpha maps to discard pixels

Using normal maps

Simulating reflection with cube maps

Simulating refraction with cube maps

Image-based lighting

Applying a projected texture

Rendering to a texture

Image Processing and Screen Space Techniques

Introduction

Applying an edge detection filter

Applying a Gaussian blur filter

Creating a "bloom" effect

Using gamma correction to improve image quality

Using multisample anti-aliasing

Using deferred shading

Using Geometry and Tessellation Shaders

Introduction

Point sprites with the geometry shader

Drawing a wireframe on top of a shaded mesh

Drawing silhouette lines using the geometry shader

Tessellating a curve

Tessellating a 2D quad

Tessellating a 3D surface

Tessellating based on depth

Shadows

Introduction

Rendering shadows with shadow maps

Anti-aliasing shadow edges with PCF

Creating soft shadow edges with random sampling

Improving realism with prebaked ambient occlusion

Using Noise in Shaders

Introduction

Creating a noise texture using libnoise

Creating a seamless noise texture

Creating a cloud-like effect

Creating a wood grain effect

Creating a disintegration effect

Creating a paint-spatter effect

Creating a night-vision effect

Animation and Particles

Introduction

Animating a surface with vertex displacement

Creating a particle fountain

Creating a particle system using transform feedback

Creating a particle system using instanced particles

Simulating fire with particles

Simulating smoke with particles

Index

Customer Reviews

5 star

4 star

3 star

2 star

1 star

Using the GLEW Library to access the latest OpenGL functionality

The OpenGL ABI (application binary interface) is frozen to OpenGL version 1.1 on Windows. Unfortunately for Windows developers, that means that it is not possible to link directly to functions that are provided in newer versions of OpenGL. Instead, one must get access to these functions by acquiring a function pointer at runtime. Getting access to the function pointers requires somewhat tedious work, and has a tendency to clutter your code. Additionally, Windows typically comes with a standard OpenGL header file that conforms to OpenGL 1.1. The OpenGL wiki states that Microsoft has no plans to update the gl.h and opengl32.lib that comes with their compilers. Thankfully, others have provided libraries that manage all of this for us by probing your OpenGL libraries and transparently providing the necessary function pointers, while also exposing the necessary functionality in its header files. One such library is called GLEW (OpenGL Extension Wrangler).

Getting ready

Download the GLEW distribution from http://glew.sourceforge.net. There are binaries available for Windows, but it is also a relatively simple matter to compile GLEW from source (see the instructions on the website: http://glew.sourceforge.net).

Place the header files glew.h and wglew.h from the GLEW distribution into a proper location for your compiler. If you are using Windows, copy the glew32.lib to the appropriate library directory for your compiler, and place the glew32.dll into a system-wide location, or the same directory as your program's executable. Full installation instructions for all operating systems and common compilers are available on the GLEW website.

How to do it...

To start using GLEW in your project, use the following steps:

Make sure that, at the top of your code, you include the glew.h header before you include the OpenGL header files:
```
#include <GL/glew.h>
#include <GL/gl.h>
#include <GL/glu.h>
```
In your program code, somewhere just after the GL context is created (typically in an initialization function), and before any OpenGL functions are called, include the following code:
```
GLenum err = glewInit();
if( GLEW_OK != err )
{
    fprintf(stderr, "Error initializing GLEW: %s\n", 
                     glewGetErrorString(err) );
}
```

That's all there is to it!

How it works...

Including the glew.h header file provides declarations for the OpenGL functions as function pointers, so all function entry points are available at compile time. At run time, the glewInit() function will scan the OpenGL library, and initialize all available function pointers. If a function is not available, the code will compile, but the function pointer will not be initialized.

There's more...

GLEW includes a few additional features and utilities that are quite useful. 

GLEW visualinfo

The command line utility visualinfo can be used to get a list of all available extensions and "visuals" (pixel formats, pbuffer availability, and so on). When executed, it creates a file called visualinfo.txt, which contains a list of all the available OpenGL, WGL, and GLU extensions, including a table of available visuals (pixel formats, pbuffer availability, and the like).

GLEW glewinfo

The command line utility glewinfo lists all available functions supported by your driver. When executed, the results are printed to stdout.

Checking for extension availability at runtime

You can also check for the availability of extensions by checking the status of some GLEW global variables that use a particular naming convention. For example, to check for the availability of ARB_vertex_program, use something like the following:

if ( ! GLEW_ARB_vertex_program )
{
   fprintf(stderr, "ARB_vertex_program is missing!\n");
   ...
}

OpenGL 4.0 Shading Language Cookbook

OpenGL 4.0 Shading Language Cookbook

Overview of this book

Related Content you might be interested in

Current Title:

OpenGL 4.0 Shading Language Cookbook

Using the GLEW Library to access the latest OpenGL functionality

Getting ready

How to do it...

How it works...

There's more...

GLEW visualinfo

GLEW glewinfo

Checking for extension availability at runtime

See also