OpenGL ES 2.0 Programming Guide

by Aaftab Munshi, Dan Ginsburg, Dave Shreiner

Overview

OpenGL ES 2.0 is the industry’s leading software interface and graphics library for rendering sophisticated 3D graphics on handheld and embedded devices. With OpenGL ES 2.0, the full programmability of shaders is now available on small and portable devices—including cell phones, PDAs, consoles, appliances, and vehicles. However, OpenGL ES differs significantly from OpenGL. Graphics programmers and mobile developers have had very little information about it—until now.

In the OpenGL® ES 2.0 Programming Guide, three leading authorities on the Open GL ES 2.0 interface—including the specification’s editor—provide start-to-finish guidance for maximizing the interface’s value in a wide range of high-performance applications. The authors cover the entire API, including Khronos-ratified extensions. Using detailed C-based code examples, they demonstrate how to set up and program every aspect of the graphics pipeline. You’ll move from introductory techniques all the way to advanced per-pixel lighting, particle systems, and performance optimization. 

Coverage includes:

• Shaders in depth: creating shader objects, compiling shaders, checking for compile errors, attaching shader objects to program objects, and linking final program objects
• The OpenGL ES Shading Language: variables, types, constructors, structures, arrays, attributes, uniforms, varyings, precision qualifiers, and invariance
• Inputting geometry into the graphics pipeline, and assembling geometry into primitives
• Vertex shaders, their special variables, and their use in per-vertex lighting, skinning, and other applications
• Using fragment shaders—including examples of multitexturing, fog, alpha test, and user clip planes
• Fragment operations: scissor test, stencil test, depth test, multisampling, blending, and dithering
• Advanced rendering: per-pixel lighting with normal maps, environment mapping, particle systems, image post-processing, and projective texturing
• Real-world programming challenges: platform diversity, C++ portability, OpenKODE, and platform-specific shader binaries

Product Details

ISBN-13:	9780132701792
Publisher:	Pearson Education
Publication date:	07/24/2008
Series:	OpenGL
Sold by:	Barnes & Noble
Format:	eBook
Pages:	464
File size:	13 MB
Note:	This product may take a few minutes to download.
Age Range:	18 Years

About the Author

Aaftab Munshi is the spec editor for the OpenGL ES 1.1 and 2.0 specifications. Now at Apple, he was formerly senior architect in ATI’s handheld group.

Dan Ginsburg is senior member of technical staff at AMD. At AMD and ATI, he has worked in a variety of roles, including the development of OpenGL drivers, the creation of desktop and handheld 3D demos, and the development of handheld GPU developer tools.

Dave Shreiner is one of the world’s foremost authorities on OpenGL. He is a systems architect at ARM, Inc., and the lead author of the official OpenGL® Programming Guide, Sixth Edition (Addison-Wesley, 2007) and series editor for the Addison-Wesley OpenGL Series.

Read an Excerpt

OpenGL ES 2.0 is a software interface for rendering sophisticated 3D graphics on handheld and embedded devices. OpenGL ES 2.0 is the primary graphics library for handheld and embedded devices with programmable 3D hardware including cell phones, PDAs, consoles, appliances, vehicles, and avionics. With OpenGL ES 2.0, the full programmability of shaders has made its way onto small and portable devices. This book details the entire OpenGL ES 2.0 API and pipeline with detailed examples in order to provide a guide for developing a wide range of high-performance 3D applications for handheld devices.Intended Audience

This book is intended for programmers interested in learning OpenGL ES 2.0. We expect the reader to have a solid grounding in computer graphics. We will explain many of the relevant graphics concepts as they relate to various parts of OpenGL ES 2.0, but we do expect the reader to understand basic 3D concepts. The code examples in the book are all written in C. We assume that the reader is familiar with C or C++ and will only be covering language topics where they are relevant to OpenGL ES 2.0.

This book covers the entire OpenGL ES 2.0 API along with all Khronosratified extensions. The reader will learn about setting up and programming every aspect of the graphics pipeline. The book details how to write vertex and fragment shaders and how to implement advanced rendering techniquessuch as per-pixel lighting and particle systems. In addition, the book provides performance tips and tricks for efficient use of the API and hardware. After finishing the book, the reader will be ready to write OpenGL ES 2.0 applications that fully harness the programmable power of embeddedgraphics hardware.Organization of the Book

This book is organized to cover the API in a sequential fashion, building up your knowledge of OpenGL ES 2.0 as we go.Chapter 1—Introduction to OpenGL ES 2.0

This chapter gives an introduction to OpenGL ES, followed by an overview of the OpenGL ES 2.0 graphics pipeline. We discuss the philosophies and constraints that went into the design of OpenGL ES 2.0. Finally, the chapter covers some general conventions and types used in OpenGL ES 2.0.Chapter 2—Hello Triangle: An OpenGL ES 2.0 Example

This chapter walks through a simple OpenGL ES 2.0 example program that draws a triangle. Our purpose here is to show what an OpenGL ES 2.0 program looks like, introduce the reader to some API concepts, and describe how to build and run an example OpenGL ES 2.0 program.Chapter 3—An Introduction to EGL

This chapter presents EGL, the API for creating surfaces and rendering contexts for OpenGL ES 2.0. We describe how to communicate with the native windowing system, choose a configuration, and create EGL rendering contexts and surfaces. We teach you enough EGL so that you can do everything you will need to do to get up and rendering with OpenGL ES 2.0.Chapter 4—Shaders and Programs

Shader objects and program objects form the most fundamental objects in OpenGL ES 2.0. In this chapter, we describe how to create a shader object, compile a shader, and check for compile errors. The chapter also covers how to create a program object, attach shader objects to it, and link a final program object. We discuss how to query the program object for information and how to load uniforms. In addition, you will learn about the difference between source and binary shaders and how to use each.Chapter 5—OpenGL ES Shading Language

This chapter covers the shading language basics needed for writing shaders. The shading language basics described are variables and types, constructors, structures, arrays, attributes, uniforms, and varyings. This chapter also describes some more nuanced parts of the language such as precision qualifiers and invariance.Chapter 6—Vertex Attributes, Vertex Arrays,and Buffer Objects

Starting with Chapter 6 (and ending with Chapter 11), we begin our walk through the pipeline to teach you how to set up and program each part of the graphics pipeline. This journey begins by covering how geometry is input into the graphics pipeline by discussing vertex attributes, vertex arrays, and buffer objects.Chapter 7—Primitive Assembly and Rasterization

After discussing how geometry is input into the pipeline in the previous chapter, we then cover how that geometry is assembled into primitives. All of the primitive types available in OpenGL ES 2.0, including point sprites, lines, triangles, triangle strips, and triangle fans, are covered. In addition, we describe how coordinate transformations are performed on vertices and introduce the rasterization stage of the OpenGL ES 2.0 pipeline.Chapter 8—Vertex Shaders

The next portion of the pipeline that is covered is the vertex shader. This chapter gives an overview of how vertex shaders fit into the pipeline and the special variables available to vertex shaders in the OpenGL ES Shading Language. Several examples of vertex shaders, including computation of per-vertex lighting and skinning, are covered. We also give examples of how the OpenGL ES 1.0 (and 1.1) fixed-function pipeline can be implemented using vertex shaders.Chapter 9—Texturing

This chapter begins the introduction to the fragment shader by describing all of the texturing functionality available in OpenGL ES 2.0. This chapter covers all the details of how to create textures, how to load them with data, and how to render with them. The chapter details texture wrap modes, texture filtering, and mipmapping. In addition, you will learn about the various functions for compressed texture images as well as how to copy texture data from the color buffer. This chapter also covers the optional texture extensions that add support for 3D textures and depth textures.Chapter 10—Fragment Shaders

Chapter 9 focused on how to use textures in a fragment shader. This chapter covers the rest of what you need to know to write fragment shaders. We give an overview of fragment shaders and all of the special built-in variables available to them. We show how to implement all of the fixed-functiontechniques that were available in OpenGL ES 1.1 using fragment shaders. Examples of multitexturing, fog, alpha test, and user clip planes are all implemented in fragment shaders.Chapter 11—Fragment Operations

This chapter discusses the operations that can be applied either to the entire framebuffer, or to individual fragments after the execution of the fragment shader in the OpenGL ES 2.0 fragment pipeline. These operations include scissor test, stencil test, depth test, multi-sampling, blending, and dithering. This is the final phase in the OpenGL ES 2.0 graphics pipeline.Chapter 12—Framebuffer Objects

This chapter discusses the use of framebuffer objects for rendering to offscreen surfaces. There are several uses of framebuffer objects, the most common of which is for rendering to a texture. This chapter provides a complete overview of the framebuffer object portion of the API. Understanding framebuffer objects is critical for implementing many advanced effects such as reflections, shadow maps, and post-processing.Chapter 13—Advanced Programming with OpenGL ES 2.0

This is the capstone chapter, tying together many of the topics presented throughout the book. We have selected a sampling of advanced rendering techniques and show examples that demonstrate how to implement these features. This chapter includes rendering techniques such as per-pixel lighting using normal maps, environment mapping, particle systems, image post-processing, and projective texturing. This chapter attempts to show the reader how to tackle a variety of advanced rendering techniques.Chapter 14—State Queries

There are a large number of state queries available in OpenGL ES 2.0. For just about everything you set, there is a corresponding way to get what the current value is. This chapter is provided as a reference for the various state queries available in OpenGL ES 2.0.Chapter 15—OpenGL ES and EGL on Handheld Platforms

In the final chapter, we divert ourselves a bit from the details of the API to talk about programming with OpenGL ES 2.0 and EGL in the real world. There are a diverse set of handheld platforms in the market that pose some interesting issues and challenges when developing applications for OpenGL ES 2.0. We cover topics including an overview of handheld platforms, C++ portability issues, OpenKODE, and platform-specific shader binaries.Appendix A—GL_HALF_FLOAT_OES

This appendix details the half-float format and provides a reference for how to convert from IEEE floating-point values into half-float (and back).Appendix B—Built-In Functions

This appendix provides a reference for all of the built-in functions available in the OpenGL ES Shading Language.Appendix C—Shading Language Grammar

This appendix provides a reference for OpenGL ES Shading Language grammar.Appendix D—ES Framework API

This appendix provides a reference for the utility framework we developed for the book and describes what each function does.Examples Code and Shaders

This book is filled with example programs and shaders. You can download the examples from the book Web site at www.opengles-book.com. The examples are all targeted to run on Microsoft Windows XP or Vista with a desktop GPU supporting OpenGL 2.0. The example programs are provided in source code form with Microsoft Visual Studio 2005 project solutions. The examples build and run on the AMD OpenGL ES 2.0 Emulator. Several of the advanced shader examples in the book are implemented in RenderMonkey, a shader development tool from AMD. The book Web site provides links on where to download any of the required tools. The OpenGL ES 2.0 Emulator and RenderMonkey are both freely available tools. For readers who do not own Visual Studio, you can use the free Microsoft Visual Studio 2008 Express Edition available for download at www.microsoft.com/express/.Errata

If you find something in the book which you believe is in error, please send us a note at [e-mail]. The list of errata for the book can be found on the book Web site at www.opengles-book.com.

Table of Contents

List of Figures                  xiii
List of Examples                xv
List of Tables                    xix
Foreword                           xxi
Preface                            xxiii
Acknowledgments          xxix
About the Authors          xxxi

Chapter 1. Introduction to OpenGL ES 2.0                       1
What Is OpenGL ES?                     1
OpenGL ES 2.0                              3
Vertex Shader                                 4
Primitive Assembly                       6
Rasterization                                 7
Fragment Shader                             7
Per-Fragment Operations                9
OpenGL ES 2.0 and OpenGL ES 1.x Backward Compatibility           11
EGL                       12
Programming with OpenGL ES 2.0                    13
Further Reading                          18

Chapter 2. Hello Triangle: An OpenGL ES 2.0 Example                    19
Code Framework                      20
Where to Download the Examples                    20
Hello Triangle Example                       21
Building and Running the Examples                       25
Using the OpenGL ES 2.0 Framework                      26
Creating a Simple Vertex and Fragment Shader                    27
Compiling and Loading the Shaders                    29
Creating a Program Object and Linking the Shaders                 30
Setting the Viewport and Clearing the Color Buffer                   32
Loading the Geometry and Drawing a Primitive                   33
Displaying the Back Buffer                   33

Chapter 3. An Introduction to EGL                         35
Communicating with the Windowing System               36
Checking for Errors                   37
Initializing EGL                   37
Determining the Available Surface Configurations                 38
Querying EGLConfig Attributes                    39
Letting EGL Choose the Config                     39
Creating an On-Screen Rendering Area: The EGL Window                43
Creating an Off-Screen Rendering Area: EGL Pbuffers                  46
Creating a Rendering Context                     50
Making an EGLContext Current                        52
Putting All Our EGL Knowledge Together                       52
Synchronizing Rendering                       54

Chapter 4. Shaders and Programs                     57
Shaders and Programs                      57
Uniforms and Attributes                    67
Shader Compiler and Shader Binaries                     72

Chapter 5. OpenGL ES Shading Language                   77
OpenGL ES Shading Language Basics                     78
Variables and Variable Types                    78
Variable Constructors                   79
Vector and Matrix Components                  81
Constants                   82
Structures                     82
Arrays                    83
Operators                     84
Functions                        85
Built-In Functions                      86
Control Flow Statements                 87
Uniforms                    88
Attributes                89
Varyings                    90
Preprocessor and Directives                 92
Uniform and Varying Packing                 94
Precision Qualifiers                     96
Invariance                     97

Chapter 6. Vertex Attributes, Vertex Arrays, and Buffer Objects                101
Specifying Vertex Attribute Data                  102
Declaring Vertex Attribute Variables in a Vertex Shader               110
Vertex Buffer Objects                 115
Mapping Buffer Objects                   124

Chapter 7. Primitive Assembly and Rasterization                 127
Primitives                     127
Drawing Primitives                  131
Primitive Assembly                   136
Rasterization                 141

Chapter 8. Vertex Shaders                   147
Vertex Shader Overview                 148
Vertex Shader Examples                 159
Generating Texture Coordinates                167
Vertex Skinning             168
OpenGL ES 1.1 Vertex Pipeline as an ES 2.0 Vertex Shader            173

Chapter 9. Texturing                 181
Texturing Basics                181
Compressed Textures            201
Texture Subimage Specification               202
Copying Texture Data from the Color Buffer               204
Optional Extensions               207

Chapter 10. Fragment Shaders              215
Fixed Function Fragment Shaders              216
Fragment Shader Overview                218
Implementing Fixed Function Techniques Using Shaders            222

Chapter 11. Fragment Operations                233
Buffers                234
Fragment Tests and Operations                238
Blending                246
Dithering               249
Multisampled Antialiasing                249
Reading and Writing Pixels to the Framebuffer                  250

Chapter 12. Framebuffer Objects                   253
Why Framebuffer Objects                   253
Framebuffer and Renderbuffer Objects                 255
Creating Framebuffer and Renderbuffer Objects               258
Using Renderbuffer Objects                   259
Using Framebuffer Objects                     262
Deleting Framebuffer and Renderbuffer Objects               269
Examples                    271
Performance Tips and Tricks                 277

Chapter 13. Advanced Programming with OpenGL ES 2.0                279
Per-Fragment Lighting                279
Environment Mapping                  286
Particle System with Point Sprites               290
Image Postprocessing                  296
Projective Texturing                   300
Noise Using a 3D Texture              307
Procedural Texturing                 315

Chapter 14. State Queries                 323
OpenGL ES 2.0 Implementation String Queries              323
Querying Implementation-Dependent Limits                 324
Querying OpenGL ES State             327
Hints               330
Entity Name Queries             331
Nonprogrammable Operations Control and Queries               332
Shader and Program State Queries               333
Vertex Attribute Queries               335
Texture State Queries              336
Vertex Buffer Queries                337
Renderbuffer and Framebuffer State Queries              337

Chapter 15. OpenGL ES and EGL on Handheld Platforms              339
Handheld Platforms Overview              339
C++ Portability                341
OpenKODE                  343
Platform-Specific Shader Binaries                 350
Targeting Extensions                  351

Appendix A. GL_HALF_FLOAT_OES                    353
16-Bit Floating-Point Number                     354
Converting Float to Half-Float                   355

Appendix B. Built-In Functions                    357
Angle and Trigonometry Functions                358
Exponential Functions                     360
Common Functions                     361
Geometric Functions                      364
Matrix Functions                     366
Vector Relational Functions                 367
Texture Lookup Functions                 369
Derivative Functions                 371

Appendix C. Shading Language Grammar                 375

Appendix D. ES Framework API                     385
Framework Core Functions                   385
Transformation Functions                     390

Index                       395