Book Image

OpenGL Development Cookbook

By : Muhammad Mobeen Movania
Book Image

OpenGL Development Cookbook

By: Muhammad Mobeen Movania

Overview of this book

OpenGL is the leading cross-language, multi-platform API used by masses of modern games and applications in a vast array of different sectors. Developing graphics with OpenGL lets you harness the increasing power of GPUs and really take your visuals to the next level. OpenGL Development Cookbook is your guide to graphical programming techniques to implement 3D mesh formats and skeletal animation to learn and understand OpenGL. OpenGL Development Cookbook introduces you to the modern OpenGL. Beginning with vertex-based deformations, common mesh formats, and skeletal animation with GPU skinning, and going on to demonstrate different shader stages in the graphics pipeline. OpenGL Development Cookbook focuses on providing you with practical examples on complex topics, such as variance shadow mapping, GPU-based paths, and ray tracing. By the end you will be familiar with the latest advanced GPU-based volume rendering techniques.
Table of Contents (15 chapters)
OpenGL Development Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Preface

This book is based on modern OpenGL v3.3 and above. It covers a myriad of topics of interest ranging from basic camera models and view frustum culling to advanced topics, such as dual quaternion skinning and GPU based simulation techniques. The book follows the cookbook format whereby a number of steps are detailed showing how to accomplish a specific task and are later dissected to show how the whole technique works.

The book starts with a gentle introduction to modern OpenGL. It then elaborates how to set up a basic shader application. Following this discussion, all shader stages are introduced using practical examples so that readers may understand how the different stages of the modern GPU pipeline work. Following the introductory chapter, a vector-based camera viewing model is presented with two camera types: target and free camera. In addition, we also detail how to carry out picking in modern OpenGL using depth buffer, color buffer, and scene intersection queries.

In simulation applications and games in particular, skybox is a very useful object. We will detail its implementation in a simple manner. For reflective objects, such as mirrors and dynamic reflections, render-to-texture functionality using FBO and dynamic cube mapping are detailed. In addition to graphics, image processing techniques are also presented to implement digital convolution filters using the fragment shader, and basic transformation, such as twirl is also detailed. Moreover, effects such as glow are also covered to enable rendering of glowing geometry.

Seldom do we find a graphics application without light. Lights play an important role in portraying the mood of a scene. We will cover point, directional, and spot lights with attenuation and both per-vertex and per-fragment approaches. In addition, shadow mapping techniques are also covered including support of percentage closer filtering (PCF) and variance shadow mapping.

In typical applications, more complex mesh models are used which are stored in external model files modeled in a 3D modeling package. We elaborate two techniques for loading such models by using separate and interleaved buffer objects. Concrete examples are given by parsing 3DS and OBJ model formats. These model loaders provide support for most attributes, including materials. Skeletal characters are introduced by a new skeletal animation format (the EZMesh format). We will see how to load such models with animation using both matrix palette skinning and dual quaternion skinning. Wherever possible, the recipes also detail pointers to external libraries and web addresses for more information. Fuzzy objects, such as smoke are often used to add special effects. Such objects are typically handled using a particle system. We introduce a stateless and a state-preserving particle system in detail.

When a scene with a high depth complexity is presented, normal alpha blending techniques fail miserably. Hence, approaches such as depth peeling are used to render the geometry in the correct depth order with correct blending. We will take a look at the implementation of both the conventional front-to-back depth peeling as well as the more recent dual depth peeling approach. All steps needed in the process are detailed.

With computer graphics, we are always pushing the limits of hardware to get a true life-like rendering. Lighting is one thing that can convincingly represent such a depiction. Unfortunately however, normal everyday lighting is impossible to simulate in real-time. The computer graphics community has developed various approximation methods for modeling of such lighting. These are grouped under global illumination techniques. The recipes elaborate two common approaches, spherical harmonics and screen space ambient occlusion, on the modern GPU. Finally, we present two additional methods for rendering scenes, namely, ray tracing and path tracing. Both of these methods have been detailed and implemented on the modern GPU.

Computer graphics have influenced several different fields ranging from visual effects in movies to biomedical and engineering simulations. In the latter domain in particular, computer graphics and visualization methods have been widely adopted. Modern GPUs have tremendous horsepower, which can be utilized for advanced visualization methods, and volume rendering is one of them. We will take a look at several algorithms for volume rendering, namely view-aligned 3D texture slicing, single-pass GPU ray casting, pseudo-isosurface rendering, splatting, polygonal isosurface extraction using the Marching Tetrahedra algorithm, and half-angle slicing method for volumetric lighting.

Physically-based simulations are an important class of algorithms that enable us to predict the motion of objects through approximations of the physical models. We harness the new transform feedback mechanism to carry out two physically-based simulations entirely on the GPU. We first present a model for cloth simulation (with collision detection and response) and then a model for particle system simulation on the modern GPU.

In summary, this book contains a wealth of information from a wide array of topics. I had a lot of fun writing this book and I learned a lot of techniques on the way. I do hope that this book serves as a useful resource for others in the years to come.

What this book covers

Chapter 1, Introduction to Modern OpenGL, details how to set up a modern OpenGL v3.3 core profile application on Visual Studio 2010 professional version.

Chapter 2, 3D Viewing and Object Picking, discusses how to implement a vector-based camera model for a viewing system. Two camera types are explained along with view frustum culling. Finally, object picking methods are also detailed.

Chapter 3, Offscreen Rendering and Environment Mapping, explains how to use the framebuffer object (FBO) for offscreen rendering. Mirror and dynamic cube mapping are implemented. In addition, image processing using digital convolution and environment mapping using static cube mapping are also elaborated.

Chapter 4, Lights and Shadows, discusses how to implement point, spot, and directional lights with attenuation. Moreover, methods of rendering dynamic shadows, such as shadow mapping, percentage close filtered (PCF) shadow maps, and variance shadow mapping are also covered in detail.

Chapter 5, Mesh Model Formats and Particle Systems, shows how to parse standard model formats, such as 3DS and OBJ models using separate and interleaved buffer object formats. Skeletal animation format using the EZMesh model format is also detailed along with the simple particle system.

Chapter 6, GPU-based Alpha Blending and Global Illumination, explains how to implement order-independent transparency with front-to-back and dual depth peeling. It also covers screen space ambient occlusion (SSAO) and the spherical harmonics method for image-based lighting and global illumination. Finally, alternate methods to render geometry, that is, GPU ray tracing and GPU path tracing are presented.

Chapter 7, GPU-based Volume Rendering Techniques, discusses how to implement several volume rendering algorithms in modern OpenGL including view-aligned 3D texture slicing, single-pass GPU ray casting, splatting, pseudo-isosurface as well as polygonal isosurface rendering using Marching Tetrahedra algorithm. Volume classification and volume lighting using the half-angle slicing technique are also detailed.

Chapter 8, Skeletal and Physically-based Simulation on the GPU, describes how to implement skeletal animation using matrix palette skinning and dual quaternion skinning on the modern GPU. In addition, it details how to use the transform feedback mode of the modern GPU for implementing a cloth simulation system with collision detection and response as well as particle systems entirely on the GPU.

What you need for this book

The book assumes that the reader has basic knowledge of using the OpenGL API. The example code distributed with this book contains Visual Studio 2010 Professional version project files. In order to build the source code, you will need freeglut, GLEW, GLM, and SOIL libraries. The code has been tested on a Windows 7 platform with an NVIDIA graphics card and the following versions of libraries:

  • freeglut v2.8.0 (latest version available from: http://freeglut.sourceforge.net)

  • GLEW v1.9.0 (latest version available from: http://glew.sourceforge.net)

  • GLM v0.9.4.0 (latest version available from: http://glm.g-truc.net)

  • SOIL (latest version available from: http://www.lonesock.net/soil.html)

We recommend using the latest version of these libraries. The code should compile and build fine with the latest libraries.

Who this book is for

This book is for intermediate graphics programmers who have working experience of any graphics API, but experience of OpenGL will be a definite plus. Introductory knowledge of GPU and graphics shaders will be an added advantage. The book and the accompanying code have been written with simplicity in mind. We have tried to keep it simple to understand. A wide array of topics are covered and step-by-step instructions are given on how to implement each technique. Detailed explanations are given that helps in comprehending the content of the book.

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 are shown as follows: "The maximum number of color attachments supported on any GPU can be queried using the GL_MAX_COLOR_ATTACHMENTS field."

A block of code is set as follows:

for(int i=0;i<16;i++) {
  float indexA = (random(vec4(gl_FragCoord.xyx, i))*0.25);
  float indexB = (random(vec4(gl_FragCoord.yxy, i))*0.25);
  sum += textureProj(shadowMap, vShadowCoords + 
         vec4(indexA, indexB, 0, 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()
{
  vEyeSpacePosition = (MV*vec4(vVertex,1)).xyz;
  vEyeSpaceNormal   = N*vNormal;
  vShadowCoords     = S*(M*vec4(vVertex,1));
  gl_Position       = MVP*vec4(vVertex,1);
}

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "by going to the Properties menu item in the Project menu".

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 , 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.

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/5046OT_ColoredImages.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.

Piracy

Piracy of copyright material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works, in any form, on the Internet, please provide us with the location address or website name immediately so that we can pursue a remedy.

Please contact us at with a link to the suspected pirated material.

We appreciate your help in protecting our authors, and our ability to bring you valuable content.

Questions

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