OpenGL 4 Shading Language Cookbook

OpenGL 4 Shading Language Cookbook - Third Edition

By : David Wolff

Buy this Book

OpenGL 4 Shading Language Cookbook - Third Edition

By: David Wolff

Buy this Book

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.

Title Page

Packt Upsell

Contributors

Preface

Free Chapter

Getting Started with GLSL

Introduction

Using a loading library to access the latest OpenGL functionality

Using GLM for mathematics

Determining the GLSL and OpenGL version

Compiling a shader

Linking a shader program

Saving and loading a shader binary

Loading a SPIR-V shader program

Working with GLSL Programs

Introduction

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

Getting a list of active vertex input attributes and locations

Sending data to a shader using uniform variables

Getting a list of active uniform variables

Using uniform blocks and uniform buffer objects

Using program pipelines

Getting debug messages

Building a C++ shader program class

The Basics of GLSL Shaders

Introduction

Diffuse and per-vertex shading with a single point light source

Implementing the Phong reflection model

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 and Shading

Introduction

Shading with multiple positional lights

Shading with a directional light source

Using per-fragment shading for improved realism

The Blinn-Phong reflection model

Simulating a spotlight

Creating a cartoon shading effect

Simulating fog

A physically-based reflection model

Using Textures

Introduction

Applying a 2D texture

Applying multiple textures

Using alpha maps to discard pixels

Using normal maps

Parallax mapping

Steep parallax mapping with self shadowing

Simulating reflection with cube maps

Simulating refraction with cube maps

Applying a projected texture

Rendering to a texture

Using sampler objects

Diffuse image-based lighting

Image Processing and Screen Space Techniques

Introduction

Applying an edge detection filter

Applying a Gaussian blur filter

Implementing HDR lighting with tone mapping

Creating a bloom effect

Using gamma correction to improve image quality

Using multisample anti-aliasing

Using deferred shading

Screen space ambient occlusion

Configuring the depth test

Implementing order-independent transparency

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

Creating shadows using shadow volumes and the geometry shader

Using Noise in Shaders

Introduction

Creating a noise texture using GLM

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 rusted metal effect

Creating a night-vision effect

Particle Systems and Animation

Introduction

Animating a surface with vertex displacement

Creating a particle fountain

Creating a particle system using transform feedback

Creating a particle system using instanced meshes

Simulating fire with particles

Simulating smoke with particles

Using Compute Shaders

Introduction

Implementing a particle simulation with the compute shader

Creating a fractal texture using the compute shader

Using the compute shader for cloth simulation

Implementing an edge detection filter with the compute shader

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Using a loading library to access the latest OpenGL functionality

The OpenGL application binary interface (ABI) 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 gain access to the OpenGL functions by acquiring a function pointer at runtime. Getting access to the function pointers is not difficult, but requires somewhat tedious work, and has a tendency to clutter code. Additionally, Windows typically comes with a standard OpenGL gl.h file that also conforms to OpenGL 1.1.

The OpenGL wiki states that Microsoft has no plans to ever update the gl.h and opengl32.lib that come with their compilers. Thankfully, others have provided libraries that manage all of this for us by transparently providing the needed function pointers, while also exposing the needed functionality in header files. Such a library is called an OpenGL Loading Library (or OpenGL function loader), and there are several such libraries available. One of the oldest is OpenGL Extension Wrangler (GLEW). However, there are a few issues with GLEW. First, it provides one large header file that includes everything from all versions of OpenGL. It might be preferable to have a more streamlined header file that only includes functions that we might use. Second, GLEW is distributed as a library that needs to be compiled separately and linked into our project. I find it preferable to have a loader that can be included into a project simply by adding the source files and compiling them directly into our executable, avoiding the need to support another link-time dependency.

In this recipe, we'll use a loader generator named GLAD, available from https://github.com/Dav1dde/glad. This very flexible and efficient library can generate a header that includes only the needed functionality, and also generates just a few files (a source file and a few headers) that we can add directly into our project.

Getting ready

To use GLAD, you can either download and install it using pip (or from https://github.com/Dav1dde/glad ),or you canuse the web service available here: http://glad.dav1d.de/. If you choose to install it, you'll need Python. The install is simple and described in detail on the GitHub page.

How to do it...

The first step is to generate the header and source files for the OpenGL version and profile of your choice. For this example, we'll generate files for an OpenGL 4.6 core profile. We can then copy the files into our project and compile them directly alongside our code:

To generate the header and source files, run the following command:

glad --generator=c --out-path=GL --profile=core --api=gl=4.6

The previous step will generate its output into a directory named GL. There will be two directories: GL/include and GL/src. You can move the GL directory into your project as is, or move the individual files into appropriate locations. Include GL/src/glad.c in your build, and put GL/include into your include path. Within your program code, include glad/glad.h whenever you need access to the OpenGL functions. Note that this fully replaces gl.h, so there is no need to include that.
In order to initialize the function pointers, you need to make sure to call a function that does so. The needed function is gladLoadGL(). Somewhere just after the GL context is created (typically in an initialization function), and before any OpenGL functions are called, use the following code:

if(!gladLoadGL()) {
  std::cerr << "Unable to load OpenGL functions!" << std::endl;
  exit(EXIT_FAILURE);
}

That's all there is to it!

How it works...

The command in step 1 generates a few header files and a source file. The header provides prototypes for all of the selected OpenGL functions, redefines them as function pointers, and defines all of the OpenGL constants as well. The source file provides initialization code for the function pointers as well as some other utility functions. We can include the glad/glad.h header file wherever we need prototypes for OpenGL functions, so all function entry points are available at compile time. At runtime, the gladLoadGL() call will initialize all available function pointers.

Note

Some function pointers may not be successfully initialized. This might happen if your driver does not support the requested OpenGL version. If that happens, calling the functions will fail.

The command-line arguments available to GLAD are fully documented on the GitHub site and are available via glad -h. One can select any OpenGL version, select core/compatibility profiles, include desired extensions, and/or create debug callbacks.

There's more...

GLAD provides a web service at http://glad.dav1d.de/ that makes it easy to generate the loader source and header files without installing GLAD. Simply visit the URL, select the desired configuration, and the loader files will be generated and downloaded.

OpenGL 4 Shading Language Cookbook - Third Edition

By : David Wolff

OpenGL 4 Shading Language Cookbook - Third Edition

By: David Wolff

Overview of this book

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