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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Introduction

The OpenGL Shading Language (GLSL) Version 4 brings unprecedented power and flexibility to programmers interested in creating modern, interactive, and graphical programs. It allows us to harness the power of modern Graphics Processing Units (GPUs) in a straightforward way by providing a simple yet powerful language and API. Of course, the first step toward using GLSL is to create a program that utilizes the OpenGL API. GLSL programs don't stand on their own; they must be a part of a larger OpenGL program. In this chapter, we will provide some tips and techniques for getting started. We'll cover how to load, compile, link, and export a GLSL shader program. First, let's start with some background.

GLSL

The GLSL is a fundamental and integral part of the OpenGL API. Every program written using the OpenGL API will internally utilize one or several GLSL programs. These "mini-programs" are referred to as shader programs. A shader program usually consists of several components called shaders. Each shader executes within a different stage of the OpenGL pipeline. Each shader runs on the GPU, and as the name implies, they (typically) implement the algorithms related to lighting and shading effects. However, shaders are capable of doing much more than just shading. They can perform animation, generate additional geometry, tessellate geometry, or even perform generalized computation.

Note

The field of study called General Purpose Computing on Graphics Processing Units (GPGPU) is concerned with the utilization of GPUs (often using specialized APIs such as CUDA or OpenCL) to perform general-purpose computations such as fluid dynamics, molecular dynamics, and cryptography. With compute shaders, introduced in OpenGL 4.3, we can now do GPGPU within OpenGL. See Chapter 11, Using Compute Shaders, for details about using compute shaders.

Shader programs are designed for direct execution on the GPU and are executed in parallel. For example, a fragment shader might be executed once for every pixel, with each execution running simultaneously. The number of processors on the graphics card determines how many can be executed at one time. This makes shader programs incredibly efficient, and provides the programmer with a simple API for implementing highly-parallel computation.

Shader programs form essential parts of the OpenGL pipeline. Prior to OpenGL Version 2.0, the shading algorithm was hardcoded into the pipeline and had only limited configurability. When we wanted to implement custom effects, we used various tricks to force the fixed-function pipeline into being more flexible than it really was. With the advent of GLSL, we now have the ability to replace this hardcoded functionality with our own programs written in GLSL, thus giving us a great deal of additional flexibility and power. For more details on this programmable pipeline, see the introduction to Chapter 3, The Basics of GLSL Shaders.

In fact, OpenGL Version 3.2 and above not only provide this capability, but they require shader programs as part of every OpenGL program. The old fixed-function pipeline has been deprecated in favor of a new programmable pipeline, a key part of which is the shader program written in GLSL.

Profiles – core versus compatibility

OpenGL Version 3.0 introduced a deprecation model, which allowed for the gradual removal of functions from the OpenGL specification. Functions or features can be marked as deprecated, meaning that they are expected to be removed from a future version of OpenGL. For example, immediate mode-rendering using glBegin/glEnd was marked as deprecated in version 3.0 and removed in version 3.1.

In order to maintain backwards compatibility, compatibility profiles were introduced with OpenGL 3.2. A programmer that is writing code for a particular version of OpenGL (with older features removed) would use the core profile. Those who wanted to maintain compatibility with older functionality could use the compatibility profile.

Note

It may be somewhat confusing that there is also the concept of a forward-compatible context, which is distinguished slightly from the concept of a core/compatibility profile. A context that is considered forward-compatible basically indicates that all deprecated functionality has been removed. In other words, if a context is forward-compatible, it only includes functions that are in the core, but not those that were marked as deprecated. Some Windows APIs provide the ability to select a forward-compatible status along with the profile.

The steps for selecting a core or compatibility profile depend on the Windows system's API. For example, with GLFW, one can select a forward-compatible, 4.6 core profile using the following code:

glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); 
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6); 
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); 
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); 
 
GLFWwindow *window = glfwCreateWindow(800, 600, "Title", nullptr, nullptr);

All programs in this book are designed to be compatible with a forward-compatible OpenGL 4.6 core profile. However, many of them can be used with older versions or even compatibility profiles.

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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OpenGL 4 Shading Language Cookbook - Third Edition

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Introduction

GLSL

Note

Profiles – core versus compatibility

Note