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    OpenGL 4 Shading Language Cookbook: Acquiring the skills of OpenGL Shading Language is so much easier with this cookbook. You'll be creating graphics rather than learning theory, gaining a high level of capability in modern 3D programming along the way.
    OpenGL 4 Shading Language Cookbook: Acquiring the skills of OpenGL Shading Language is so much easier with this cookbook. You'll be creating graphics rather than learning theory, gaining a high level of capability in modern 3D programming along the way.
    OpenGL 4 Shading Language Cookbook: Acquiring the skills of OpenGL Shading Language is so much easier with this cookbook. You'll be creating graphics rather than learning theory, gaining a high level of capability in modern 3D programming along the way.
    Ebook973 pages6 hours

    OpenGL 4 Shading Language Cookbook: Acquiring the skills of OpenGL Shading Language is so much easier with this cookbook. You'll be creating graphics rather than learning theory, gaining a high level of capability in modern 3D programming along the way.

    By David Wolff

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    Read preview

    About this ebook

    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.

    LanguageEnglish
    PublisherPackt Publishing
    Release dateDec 24, 2013
    ISBN9781782167037
    OpenGL 4 Shading Language Cookbook: Acquiring the skills of OpenGL Shading Language is so much easier with this cookbook. You'll be creating graphics rather than learning theory, gaining a high level of capability in modern 3D programming along the way.

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      Book preview

      OpenGL 4 Shading Language Cookbook - David Wolff

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      Table of Contents

      OpenGL 4 Shading Language Cookbook Second Edition

      Credits

      About the Author

      About the Reviewers

      www.PacktPub.com

      Support files, eBooks, discount offers and more

      Why Subscribe?

      Free Access for Packt account holders

      Preface

      What this book covers

      What you need for this book

      Who this book is for

      Conventions

      Reader feedback

      Customer support

      Downloading the example code

      Downloading the color images of this book

      Errata

      Piracy

      Questions

      1. Getting Started with GLSL

      Introduction

      The OpenGL Shading Language

      Profiles – Core vs. Compatibility

      Using a function loader to access the latest OpenGL functionality

      Getting ready

      How to do it...

      How it works...

      There's more...

      Generating a C++ loader

      No-load styles

      Using Extensions

      See also

      Using GLM for mathematics

      Getting ready

      How to do it...

      How it works...

      There's more...

      Using the GLM types as input to OpenGL

      See also

      Determining the GLSL and OpenGL version

      How to do it...

      How it works...

      There's more...

      See also

      Compiling a shader

      Getting ready

      How to do it...

      How it works...

      There's more...

      Deleting a Shader Object

      See also

      Linking a shader program

      Getting ready

      How to do it...

      How it works...

      There's more...

      Deleting a Shader program

      See also

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

      Getting ready

      How to do it...

      How it works...

      There's more...

      Separate attribute format

      Fragment shader output

      Specifying attribute indexes without using layout qualifiers

      Using element arrays

      Interleaved arrays

      Getting a list of active vertex input attributes and locations

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Sending data to a shader using uniform variables

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Getting a list of active uniform variables

      Getting ready

      How to do it…

      How it works...

      There's more...

      See also

      Using uniform blocks and uniform buffer objects

      Getting ready

      How to do it...

      How it works...

      There's more...

      Using an instance name with a uniform block

      Using layout qualifiers with uniform blocks

      See also

      Getting debug messages

      Getting ready

      How to do it...

      How it works...

      There's more...

      Building a C++ shader program class

      Getting ready

      How to do it...

      How it works...

      See also

      2. The Basics of GLSL Shaders

      Introduction

      Vertex and fragment shaders

      Replicating the old fixed functionality

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

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

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

      Getting ready

      How to do it...

      How it works...

      There's more...

      Using a non-local viewer

      Per-vertex versus per-fragment

      Directional lights

      Light attenuation with distance

      See also

      Using functions in shaders

      Getting ready

      How to do it...

      How it works...

      There's more...

      The const qualifier

      Function overloading

      Passing arrays or structures to a function

      See also

      Implementing two-sided shading

      Getting ready

      How to do it...

      How it works...

      There's more...

      Using two-sided rendering for debugging

      See also

      Implementing flat shading

      How to do it...

      How it works...

      See also

      Using subroutines to select shader functionality

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Discarding fragments to create a perforated look

      Getting ready

      How to do it...

      How it works...

      See also

      3. Lighting, Shading, and Optimization

      Introduction

      Shading with multiple positional lights

      Getting ready

      How to do it...

      How it works...

      See also

      Shading with a directional light source

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Using per-fragment shading for improved realism

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Using the halfway vector for improved performance

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Simulating a spotlight

      Getting ready

      How to do it...

      How it works...

      See also

      Creating a cartoon shading effect

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Simulating fog

      Getting ready

      How to do it...

      How it works...

      There's more...

      Computing distance from the eye

      See also

      Configuring the depth test

      How to do it...

      How it works...

      See also

      4. Using Textures

      Introduction

      Applying a 2D texture

      Getting ready

      How to do it...

      How it works...

      There's more...

      Specifying the sampler binding within GLSL

      See also

      Applying multiple textures

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Using alpha maps to discard pixels

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Using normal maps

      Getting ready

      How to do it...

      How it works...

      See also

      Simulating reflection with cube maps

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Simulating refraction with cube maps

      Getting ready

      How to do it...

      How it works...

      There's more...

      The Fresnel equations

      Chromatic aberration

      Refracting through both sides of the object

      See also

      Applying a projected texture

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Rendering to a texture

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Using sampler objects

      Getting ready

      How to do it...

      How it works...

      See also

      5. Image Processing and Screen Space Techniques

      Introduction

      Applying an edge detection filter

      Getting ready

      How to do it...

      How it works...

      There's more...

      Optimization techniques

      See also

      Applying a Gaussian blur filter

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Implementing HDR lighting with tone mapping

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a bloom effect

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Using gamma correction to improve image quality

      How to do it...

      How it works...

      There's more...

      Using multisample anti-aliasing

      Getting ready

      How to do it...

      How it works...

      There's more...

      Using deferred shading

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Implementing order-independent transparency

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      6. Using Geometry and Tessellation Shaders

      Introduction

      The shader pipeline extended

      The geometry shader

      The tessellation shaders

      Point sprites with the geometry shader

      Getting ready

      How to do it...

      How it works...

      There's more...

      Drawing a wireframe on top of a shaded mesh

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also…

      Drawing silhouette lines using the geometry shader

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Tessellating a curve

      Getting ready

      How to do it...

      How it works...

      There's more...

      Tessellating a 2D quad

      Getting ready

      How to do it...

      How it works...

      See also

      Tessellating a 3D surface

      Getting ready

      How to do it...

      How it works...

      See also

      Tessellating based on depth

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      7. Shadows

      Introduction

      Rendering shadows with shadow maps

      Getting ready

      How to do it...

      How it works...

      There's more...

      Aliasing

      Rendering back faces only for the shadow map

      See also

      Anti-aliasing shadow edges with PCF

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating soft shadow edges with random sampling

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating shadows using shadow volumes and the geometry shader

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      8. Using Noise in Shaders

      Introduction

      See Also…

      Creating a noise texture using GLM

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a seamless noise texture

      Getting ready

      How to do it...

      How it works...

      See also

      Creating a cloud-like effect

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a wood-grain effect

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a disintegration effect

      Getting ready

      How to do it...

      How it works...

      See also

      Creating a paint-spatter effect

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a night-vision effect

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      9. Particle Systems and Animation

      Introduction

      Animating a surface with vertex displacement

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a particle fountain

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a particle system using transform feedback

      Getting ready

      How to do it...

      How it works...

      There's more...

      Using layout qualifiers

      Querying transform feedback results

      Recycling particles

      See also

      Creating a particle system using instanced particles

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Simulating fire with particles

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Simulating smoke with particles

      Getting ready

      How to do it...

      How it works...

      See also

      10. Using Compute Shaders

      Introduction

      Compute space and work groups

      Executing the Compute Shader

      Implementing a particle simulation with the compute shader

      Getting ready

      How to do it...

      How it works...

      See also

      Using the compute shader for cloth simulation

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Implementing an edge detection filter with the compute shader

      Getting ready

      How to do it...

      How it works...

      There's more...

      See also

      Creating a fractal texture using the compute shader

      Getting ready

      How to do it...

      How it works...

      There's more...

      Index

      OpenGL 4 Shading Language Cookbook Second Edition

      OpenGL 4 Shading Language Cookbook Second Edition

      Copyright © 2013 Packt Publishing

      All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

      Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

      Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

      First published: July 2011

      Second edition: December 2013

      Production Reference: 1171213

      Published by Packt Publishing Ltd.

      Livery Place

      35 Livery Street

      Birmingham B3 2PB, UK.

      ISBN 978-1-78216-702-0

      www.packtpub.com

      Cover Image by Aniket Sawant (<[email protected]>)

      Credits

      Author

      David Wolff

      Reviewers

      Bartłomiej Filipek

      Thomas Le Guerroué-Drévillon

      Muhammad Mobeen Movania

      Dario Scarpa

      Javed Rabbani Shah

      Acquisition Editors

      Gregory Wild

      Edward Gordon

      Usha Iyer

      Lead Technical Editor

      Neeshma Ramakrishnan

      Technical Editors

      Kunal Anil Gaikwad

      Jinesh Kampani

      Aman Preet Singh

      Project Coordinator

      Shiksha Chaturvedi

      Proofreaders

      Elinor Perry-Smith

      Chris Smith

      Indexer

      Mariammal Chettiyar

      Graphics

      Sheetal Aute

      Ronak Dhruv

      Production Coordinator

      Nilesh R. Mohite

      Cover Work

      Nilesh R. Mohite

      About the Author

      David Wolff is an associate professor in the Computer Science and Computer Engineering Department at Pacific Lutheran University (PLU). He received a PhD in Physics and an MS in Computer Science from Oregon State University. He has been teaching computer graphics to undergraduates at PLU for over 10 years, using OpenGL.

      About the Reviewers

      Bartłomiej Filipek is an experienced software developer with a passion for teaching. He has been leading OpenGL and graphics programming courses at Jagiellonian University in Cracow for around five years now. Additionally he gives lectures and workshops about modern C++ techniques at local universities.

      His professional experience focuses mostly on native application development including rendering systems, large-scale software development, game engines, multimedia applications, user interfaces, GPU computing, and even biofeedback.

      He shares his programming stories at his blog: http://www.bfilipek.com/.

      Thomas Le Guerroué-Drévillon is a freshly graduated software engineer. Having a profound interest in mathematics and drawing, it came easily to him to mix together these two passions in one field: computer graphics.

      Originally French, he used up all the opportunities given by his university to study and work all around the world. It allowed him to enjoy his first international experience in Estonia, the second in the prestigious KAIST in South Korea, and finally ending up now in Canada.

      Even though his university provided the mathematical background, he got his experience with OpenGL and GLSL on his own. He believes that the link between the well documented API and the shader samples is missing. Thus he naturally accepted to review this cookbook, which for him is the material he would have loved to get a hand on when he started developing interests in OpenGL/GLSL.

      Dr. Muhammad Mobeen Movania received his PhD degree in Advance Computer Graphics and Visualization from Nanyang Technological University, Singapore. After finishing his PhD, he joined Institute for Infocomm Research, A-Star, Singapore to work on Augmented Reality based Virtual Tryon and Cloth Simulation systems using GPU and OpenGL. Before joining NTU, he was a junior graphics programmer at Data Communication and Control (DCC) Pvt. Ltd., Karachi, Pakistan. He worked on DirectX and OpenGL API for producing real-time interactive tactical simulators and dynamic integrated training simulators. His research interests include GPU-based volumetric rendering techniques, GPU technologies, real-time soft body physics, real-time dynamic shadows, real-time collision detection and response, and hierarchical geometric data structures. He is also the author of the OpenCloth project (http://code.google.com/p/opencloth), which implements various cloth simulation algorithms in OpenGL. His blog (http://mmmovania.blogspot.com) lists a lot of useful graphics tips and tricks. When not involved with computer graphics, he composes music and is an avid squash player.

      Dr. Mobeen has published several conference and journal papers on real-time computer graphics and visualization. Recently, he authored a book on OpenGL (OpenGL Development Cookbook by Packt Publishing, published in 2013) which details several applied recipes using modern OpenGL. He has also authored a book chapter in another book (OpenGL Insights by AK Peters/CRC Press, published in 2012).

      Dr. Mobeen is currently an Assistant Professor at DHA Suffa University, Karachi, Pakistan where he is busy nurturing young minds to become outstanding programmers and researchers of tomorrow.

      I would like to thank almighty ALLAH for bestowing his countless blessings on me and my family. After that, I would like to extend my gratitude towards my family, my parents (Mr. and Mrs. Abdul Aziz Movania), my wife (Tanveer Taji), my sisters (Mrs. Azra Saleem and Mrs. Sajida Shakir), my brothers (Mr. Khalid Movania and Mr. Abdul Majid Movania), all my nephews/nieces and my daughter (Muntaha Movania).

      Dario Scarpa has been coding for fun and profit for the last 15 years, and has no intention to stop. Jumping around among IT jobs as developer/sysadmin, amateur video game programming, and CS exams at the University of Salerno (Italy), he also managed to work with Adventure Productions in building Zodiac, a digital delivery platform focused on adventure games. At the time of reviewing this book, he's about to get his Master's degree, with a thesis on computer graphics that got him working intensively with—guess what—OpenGL.

      Javed Rabbani Shah received his degree in Electrical Engineering from the University of Engineering and Technology, Lahore, Pakistan in 2004. He started his professional career by joining Delta Indus Systems (now Vision Master Inc.), where he worked with solder paste inspection systems for statistical process control involving technologies such as Image Processing, 3D Machine Vision, and FPGAs. He then joined the Embedded Systems Division of Mentor Graphics in 2007 and got the opportunity to work with the Nucleus+ real-time operating system, USB 2.0 middleware, WebKit, and OpenGL ES 2.0. He spearheaded the effort to integrate OpenGL ES 2.0 features in Mentor's cross-platform Inflexion 3D user interface engine.

      He is currently working at Saffron Digital in central London, where he is involved in work related to cross-platform secure video playback, DRM, and UltraViolet technologies.

      In his spare time, he likes to learn emerging technologies like OpenGL ES 3.0 and OpenCL.

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      Preface

      The OpenGL Shading Language (GLSL) is now a fundamental and critical part of programming with OpenGL. It provides us with unprecedented flexibility and power by making the formerly fixed-function graphics pipeline programmable. With GLSL, we can leverage the Graphics Processing Unit (GPU) to implement advanced and sophisticated rendering techniques and even do arbitrary computation. With GLSL 4.x, programmers can do more with the GPU than ever before thanks to new shader stages such as tessellation shaders and compute shaders.

      In this book, we cover the full spectrum of GLSL programming. Starting with the basics of shading with the vertex and fragment shaders, we take you from simple to advanced techniques. From textures, shadows, and image processing, to noise and particle systems, we cover practical examples to give you the tools you need to leverage GLSL in your projects. We also cover how to use geometry shaders, tessellation shaders, and the very recent addition to GLSL: compute shaders. With these, you can make use of the GPU for a variety of tasks that go beyond just shading. With geometry and tessellation shaders, we can create additional geometry or modify geometry, and with compute shaders we can do arbitrary computation on the GPU.

      For those new to GLSL, it's best to read this book in order, starting with Chapter 1. The recipes will walk you through from basic through to advanced techniques. For someone who is more experienced with GLSL, you might find it better to pick out specific recipes and jump directly there. Most recipes are self-contained, but some may refer to other recipes. The introduction to each chapter provides important general information about the topic, so you might want to read through that as well.

      GLSL 4.x makes programming with OpenGL even more rewarding and fun. I sincerely hope that you find this book to be useful and that you use these recipes as a starting point in your own projects. I hope that you find programming in OpenGL and GLSL as enjoyable as I do, and that these techniques inspire you to create beautiful graphics.

      What this book covers

      Chapter 1, Getting Started with GLSL, explains the steps needed to compile, link, and use GLSL shaders within an OpenGL program. It also covers how to send data to shaders using attributes and uniform variables, and the use of the GLM library for mathematics support. Every modern OpenGL program today requires a function loader. In this chapter, we also cover the use of GLLoadGen, a relatively new and easy-to-use OpenGL loader generator.

      Chapter 2, The Basics of GLSL Shaders, introduces you to the basics of GLSL programming with per-vertex shading. In this chapter, you see examples of basic shading techniques such as the ADS (ambient, diffuse, and specular) shading algorithm, two-sided shading, and flat shading. It also covers examples of basic GLSL concepts such as functions and subroutines.

      Chapter 3, Lighting, Shading, and Optimization, presents more advanced shading techniques, with a focus on the fragment shader. It introduces you to techniques such as spotlights, per-fragment shading, toon shading, fog, and others. We also discuss several simple optimizations to make your shaders run faster.

      Chapter 4, Using Textures, provides a general introduction to using textures in GLSL shaders. Textures can be used for a variety of purposes besides simply pasting an image onto a surface. In this chapter, we cover the basic application of one or more 2D textures, as well as a variety of other techniques including alpha maps, normal maps, cube maps, projected textures, and rendering to a texture. We also cover sampler objects, a relatively new feature that decouples sampling parameters from the texture object itself.

      Chapter 5, Image Processing and Screen Space Techniques, explains common techniques for the post-processing of rendered images and some other screen-space techniques. Image post-processing is becoming a crucially important part of modern game engines and other rendering pipelines. This chapter discusses how to implement some of the more common post-processing techniques such as tone mapping, bloom, blur, gamma correction, and edge detection. We also cover some screen-space rendering techniques such as deferred shading, multisample antialiasing, and order-independent transparency.

      Chapter 6, Using Geometry and Tessellation Shaders, covers techniques that demonstrate how to use these new and powerful shader stages. After reading this chapter, you should be comfortable with their basic functionality and understand how to use them. We cover techniques such as geometry-shader-generated point sprites, silhouette lines, depth-based tessellation, Bezier surfaces, and more.

      Chapter 7, Shadows, introduces basic techniques for producing real-time shadows. This chapter includes recipes for the two most common shadow techniques: shadow maps and shadow volumes. We cover common techniques for antialiasing shadow maps, as well as how to use the geometry shader to help produce shadow volumes.

      Chapter 8, Using Noise in Shaders, covers the use of Perlin noise for creating various effects. The first recipe shows you how to create a wide variety of textures containing noise data using GLM (a powerful mathematics library). Then we move on to recipes that use noise textures for creating a number of effects such as wood grain, clouds, disintegration, paint, and static.

      Chapter 9, Particle Systems and Animation, focuses on techniques for creating particle systems. We see how to create a particle system to simulate fire, smoke, and water. We also make use of the OpenGL feature called transform feedback, in order to gain additional efficiency by moving the particle updates onto the GPU.

      Chapter 10, Using Compute Shaders, introduces you to several techniques that make use of one of the newest features in OpenGL, the compute shader. The compute shader provides us with the ability to do general computation on the GPU within OpenGL. In this chapter, we discuss how to use the compute shader for particle simulations, cloth simulation, edge detection, and the generation of a procedural fractal texture. After reading this chapter, the reader should have a good feel for how to use the compute shader for arbitrary computational tasks.

      What you need for this book

      The recipes in this book use some of the latest and greatest features in OpenGL 4.x. Therefore, in order to implement them, you'll need graphics hardware (graphics card or onboard GPU) and drivers that support at least OpenGL 4.3. If you're unsure about what version of OpenGL your setup can support, there are a number of utilities available for determining this information. One option is GLview from Realtech VR, available at: http://www.realtech-vr.com/glview/. If you're running Windows or Linux, drivers are readily available for most modern hardware. However, if you're using MacOS X, unfortunately, you may need to wait. As of this writing, the latest version of MacOS X (10.9 Mavericks) only supports OpenGL 4.1.

      Once you've verified that you have the required OpenGL drivers, you'll also need the following:

      A C++ compiler. On Linux, the GNU Compiler Collection (gcc, g++, and so on) may already be available, and if not, it should be available through your distribution's package manager. On Windows, Microsoft Visual Studio will work fine, but if you don't have a copy, then the MinGW compiler (available from http://mingw.org/) is a good option.

      The GLFW library Version 3.0 or later, available from http://www.glfw.org/. This library provides OpenGL context creation, window support, and support for user input events.

      The GLM library Version 0.9.4 or later, available from http://glm.g-truc.net/. This provides mathematics support with classes for matrices, vectors, common transformations, noise functions, and much more.

      Who this book is for

      The primary focus of this book is the OpenGL Shading Language (GLSL). Therefore, we don't spend any time discussing the basics of programming with OpenGL. In this book I assume that the reader has some experience with programming in OpenGL, and understands basic 3D rendering concepts such as model coordinates, view coordinates, clip coordinates, perspective transforms, and the other associated transformations. There's no assumption of any experience with shader programming, however, so if you're new to GLSL, this is a great place to start.

      If you're an OpenGL programmer looking to learn about GLSL programming, then this book is for you. Even if you have some shader programming experience, you will very likely find the recipes in this book to be valuable. We cover a range of simple to advanced techniques, using some of the newest features of OpenGL (such as compute shaders and tessellation shaders). So even experienced GLSL programmers, who are looking to learn how to use these new features, may also find this book to be useful.

      In short, this book is for programmers who understand the basics of 3D graphics in OpenGL, and are interested in either learning GLSL, or taking advantage of some of the newest features in modern GLSL 4.x.

      Conventions

      In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

      Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: The number of work groups are determined by the parameters to glDispatchCompute.

      A block of code is set as follows:

      void main()

      {

          Color = VertexColor;

          gl_Position = RotationMatrix * vec4(VertexPosition,1.0);

      }

      When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

      void main()

      {

          Color = VertexColor;

          gl_Position = RotationMatrix * vec4(VertexPosition,1.0);

       

      }

      Any command-line input or output is written as follows:

      Active attributes: 1    VertexColor (vec3) 0    VertexPosition (vec3)

      New terms and important words are shown in bold.

      Note

      Warnings or important notes appear in a box like this.

      Tip

      Tips and tricks appear like this.

      Reader feedback

      Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or may have disliked. Reader feedback is important for us to develop titles that you really get the most out of.

      To send us general feedback, simply send an e-mail to <[email protected]>, and mention the book title via the subject of your message.

      If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide on www.packtpub.com/authors.

      Customer support

      Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.

      Downloading the example code

      You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

      Full source code for all of the recipes in this text is available on GitHub at: https://github.com/daw42/glslcookbook.

      Downloading the color images of this book

      We also provide you a PDF file that has color images of the screenshots/diagrams used in this book. The color images will help you better understand the changes in the output. You can download this file from: http://www.packtpub.com/sites/default/files/downloads/7020OS_Colorimages.pdf

      Errata

      Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in the text or the code—we would be grateful if you would report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this book. If you find any errata, please report them by visiting http://www.packtpub.com/submit-errata, selecting your book, clicking on the errata submission form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded on our website, or added to any list of existing errata, under the Errata section of that title. Any existing errata can be viewed by selecting your title from http://www.packtpub.com/support.

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      Questions

      You can contact us at <[email protected]> if you are having a problem with any aspect of the book, and we will do our best to address it.

      Chapter 1. Getting Started with GLSL

      In this chapter, we will cover the following recipes:

      Using a function loader to access the latest OpenGL functionality

      Using GLM for mathematics

      Determining the GLSL and OpenGL version

      Compiling a shader

      Linking a shader program

      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

      Getting debug messages

      Building a C++ shader program class

      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 towards using GLSL is to create a program that utilizes the latest version of 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 a basic program up and running. First, let's start with some background.

      The OpenGL Shading Language

      The GLSL is now a fundamental and integral part of the OpenGL API. Going forward, every program written using the OpenGL API will internally utilize one or several GLSL programs. These mini-programs are often referred to as shader programs. A shader program usually consists of several components called shaders. Each shader executes within a different section of the OpenGL pipeline. Each shader runs on the GPU, and as the name implies, (typically) implement the algorithms related to the lighting and shading effects of an image. However, shaders are capable of doing much more than just implementing a shading algorithm. They are also capable of performing animation, tessellation, or even generalized computation.

      Note

      The field of study dubbed GPGPU (General Purpose Computing on Graphics Processing Units) is concerned with utilization of GPUs (often using specialized APIs such as CUDA or OpenCL) to perform general purpose computations such as fluid dynamics, molecular dynamics, cryptography, and so on. With compute shaders, introduced in OpenGL 4.3, we can now do GPGPU within OpenGL.

      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 on a separate GPU thread. 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.

      The computing power available in modern graphics cards is impressive. The following table shows the number of shader processors available for several models in the NVIDIA GeForce series cards (source: http://en.wikipedia.org/wiki/Comparison_of_Nvidia_graphics_processing_units).

      Shader programs are intended to replace parts of the OpenGL architecture referred to as the fixed-function pipeline. Prior to OpenGL Version 2.0, the shading algorithm was hard-coded into the pipeline and had only limited configurability. This default lighting/shading algorithm was a core part of the fixed-function pipeline. When we, as programmers, wanted to implement more advanced or realistic effects, we used various tricks to force the fixed-function pipeline into being more flexible than it really was. The advent of GLSL will help by providing us with the ability to replace this hard-coded functionality with our own programs written in GLSL, thus giving us a great deal of additional flexibility and power. For more details on the programmable pipeline, see the introduction to Chapter 2, The Basics of GLSL Shaders.

      In fact, recent (core) versions of OpenGL 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 vs. 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 deprecated in version 3.0 and removed in version 3.1.

      In order to maintain backwards compatibility, the concept of compatibility profiles was introduced with OpenGL 3.2. A programmer that is writing code intended to be used with a particular version of OpenGL (with older features removed) would use the so-called core profile. Someone who also 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 window APIs provide the ability to select forward

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