Interactive computer graphics a top down approach with sharder based

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INTERACTIVE COMPUTER GRAPHICS
A TOP-DOWN APPROACH WITH SHADER-BASED OPENGL®
6th Edition


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INTERACTIVE COMPUTER GRAPHICS
A TOP-DOWN APPROACH WITH SHADER-BASED OPENGL®
6th Edition

EDWARD ANGEL
University of New Mexico
•

DAVE SHREINER
ARM, Inc.


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Library of Congress Cataloging-in-Publication Data
Angel, Edward.
Interactive computer graphics : a top-down approach with shader-based OpenGL /
Edward Angel, David Shreiner. — 6th ed.

p. cm.
Includes bibliographical references and index.
ISBN-13: 978-0-13-254523-5 (alk. paper)
ISBN-10: 0-13-254523-3 (alk. paper)
1. Computer graphics. 2. OpenGL. I. Shreiner, Dave. II. Title.
T385.A5133 2012
006.6—dc22
2011004742
10 9 8 7 6 5 4 3 2 1—EB—15 14 13 12 11

Addison-Wesley
is an imprint of
ISBN 10: 0-13-254523-3
ISBN 13: 978-0-13-254523-5


To Rose Mary

—E.A.

To Vicki, Bonnie, Bob, and Phantom

—D.S.


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CONTE NTS
Preface

xxi

CHAPTER 1

GRAPHICS SYSTEMS AND MODELS

1

1.1

Applications of Computer Graphics

1.1.1
1.1.2
1.1.3
1.1.4

Display of Information
2
Design
3
Simulation and Animation
User Interfaces
4

2

1.2

A Graphics System

1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
1.2.6
1.2.7

Pixels and the Frame Buffer
The CPU and the GPU
6
Output Devices
7
Input Devices
9
Physical Input Devices
10
Logical Devices
12
Input Modes
13

1.3

Images: Physical and Synthetic

1.3.1
1.3.2

1.3.3

Objects and Viewers
15
Light and Images
16
Imaging Models
18

1.4

Imaging Systems

1.4.1
1.4.2

The Pinhole Camera
20
The Human Visual System

1.5

The Synthetic-Camera Model

23

1.6

The Programmer’s Interface

25

1.6.1
1.6.2
1.6.3
1.6.4

The Pen-Plotter Model
27
Three-Dimensional APIs
28
A Sequence of Images
31
The Modeling–Rendering Paradigm

1.7

Graphics Architectures

1.7.1
1.7.2

Display Processors
34
Pipeline Architectures
34

3

5

5

15

20
22

32

33

vii


viii

Contents

1.7.3
1.7.4
1.7.5
1.7.6
1.7.7

The Graphics Pipeline
35
Vertex Processing
36
Clipping and Primitive Assembly
Rasterization 37

Fragment Processing 37

1.8

Programmable Pipelines

37

1.9

Performance Characteristics

38

Summary and Notes

39

Suggested Readings

40

Exercises
CHAPTER 2

36

41

GRAPHICS PROGRAMMING

43

2.1

The Sierpinski Gasket

43

2.2

Programming Two-Dimensional Applications

46
50

2.3

The OpenGL Application Programming Interface

2.3.1
2.3.2
2.3.3
2.3.4

Graphics Functions
51
The Graphics Pipeline and State Machines
The OpenGL Interface
53

Coordinate Systems 55

2.4

Primitives and Attributes

2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7

Polygon Basics 58
Polygons in OpenGL 59
Approximating a Sphere 60
Triangulation
62
Text
64
Curved Objects
65
Attributes 65

2.5

Color

2.5.1

2.5.2
2.5.3

RGB Color
69
Indexed Color 71
Setting of Color Attributes

2.6

Viewing

2.6.1
2.6.2

The Orthographic View 74
Two-Dimensional Viewing
77

2.7

Control Functions

2.7.1
2.7.2
2.7.3
2.7.4

Interaction with the Window System
78

Aspect Ratio and Viewports
79
The main, display, and init Functions 80
Program Structure 83

53

56

67

72

73

78


Contents

2.8

The Gasket Program

83

2.8.1
2.8.2
2.8.3
2.8.4

2.8.5

Rendering the Points
84
The Vertex Shader
85
The Fragment Shader
86
Combining the Parts
86
86
The initShader Function

2.9
2.10

Polygons and Recursion
The Three-Dimensional Gasket

2.10.1
2.10.2
2.10.3

Use of Three-Dimensional Points
91
Use of Polygons in Three Dimensions
92
Hidden-Surface Removal
96

2.11

Adding Interaction

2.11.1
2.11.2
2.11.3
2.11.4
2.11.5
2.11.6

Using the Pointing Device
98
Window Events
101
Keyboard Events
102
The Idle Callback
103
Double Buffering
105
Window Management
106

2.12

Menus

98

106

Summary and Notes

108

Suggested Readings

109

Exercises
CHAPTER 3

88
91

110

GEOMETRIC OBJECTS AND TRANSFORMATIONS

3.1

Scalars, Points, and Vectors

3.1.1
3.1.2
3.1.3
3.1.4
3.1.5
3.1.6

3.1.7
3.1.8
3.1.9
3.1.10

Geometric Objects
116
Coordinate-Free Geometry
117
The Mathematical View: Vector and Affine Spaces
The Computer Science View
119
Geometric ADTs
119
Lines
120
Affine Sums
121
Convexity
122
Dot and Cross Products
122
Planes
123

3.2
3.3

Three-Dimensional Primitives
Coordinate Systems and Frames

3.3.1
3.3.2
3.3.3

Representations and N-Tuples 128
Change of Coordinate Systems
129
Example Change of Representation
132

115
116

118

125
126

ix


x

Contents

3.3.4
3.3.5
3.3.6

Homogeneous Coordinates
133
Example Change in Frames
136
Working with Representations 137

3.4

Frames in OpenGL

139

3.5

Matrix and Vector Classes

144

3.6

Modeling a Colored Cube

146

3.6.1
3.6.2
3.6.3
3.6.4
3.6.5
3.6.6

Modeling the Faces 146
Inward- and Outward-Pointing Faces 146
Data Structures for Object Representation
147
The Color Cube 148
Interpolation
150
Displaying the Cube
151

3.7

Affine Transformations

152

3.8

Translation, Rotation, and Scaling

155

3.8.1
3.8.2
3.8.3

Translation 155
Rotation
156

Scaling 158

3.9

Transformations in Homogeneous Coordinates

3.9.1
3.9.2
3.9.3
3.9.4

Translation 160
Scaling 161
Rotation
162
Shear 163

3.10

Concatenation of Transformations

3.10.1
3.10.2
3.10.3
3.10.4

Rotation About a Fixed Point 165
General Rotation
167
The Instance Transformation 168

Rotation About an Arbitrary Axis 169

3.11

Transformation Matrices in OpenGL

3.11.1
3.11.2
3.11.3
3.11.4

Current Transformation Matrices
173
Rotation, Translation, and Scaling 174
Rotation About a Fixed Point 175
Order of Transformations
176

3.12

Spinning of the Cube

3.12.1
3.12.2

Updating in the Display Callback
Uniform Variables 178

3.13

Interfaces to Three-Dimensional Applications

3.13.1
3.13.2
3.13.3
3.13.4

Using Areas of the Screen 180
A Virtual Trackball
181
Smooth Rotations
184
Incremental Rotation
185

159

164

172

176
177

180


Contents

3.14

Quaternions

186

3.14.1
3.14.2

Complex Numbers and Quaternions
Quaternions and Rotation
187
Summary and Notes

190

Suggested Readings

190

Exercises
CHAPTER 4

186

191

VIEWING

195

4.1

Classical and Computer Viewing

4.1.1
4.1.2
4.1.3
4.1.4
4.1.5

Classical Viewing
197
Orthographic Projections
197
Axonometric Projections
198
Oblique Projections
200
Perspective Viewing
201

195

4.2

Viewing with a Computer

4.3

Positioning of the Camera

4.3.1
4.3.2
4.3.3
4.3.4

Positioning of the Camera Frame
Two Viewing APIs
209
The Look-At Function
212
Other Viewing APIs
214

4.4

Parallel Projections

4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.4.6

Orthogonal Projections
215
Parallel Viewing with OpenGL
216
Projection Normalization

217
Orthogonal-Projection Matrices
219
Oblique Projections
220
An Interactive Viewer
224

4.5

Perspective Projections

4.5.1

Simple Perspective Projections

4.6

Perspective Projections with OpenGL

4.6.1

Perspective Functions

4.7

Perspective-Projection Matrices

4.7.1
4.7.2

4.7.3

Perspective Normalization
232
OpenGL Perspective Transformations
Perspective Example
238

4.8

Hidden-Surface Removal

4.8.1

Culling

4.9

Displaying Meshes

4.9.1

Displaying Meshes as a Surface

202
204
204

215

226
226

229

230

232
236

238

241

241
244

xi


xii

Contents

4.9.2
4.9.3

Polygon Offset 246
Walking Through a Scene

4.10

Projections and Shadows
Summary and Notes

253

Suggested Readings

254

Exercises
CHAPTER 5

5.1

247

249

254

LIGHTING AND SHADING

257

Light and Matter

258
261

5.2

Light Sources

5.2.1
5.2.2
5.2.3
5.2.4
5.2.5

Color Sources
262
Ambient Light
262
Point Sources 263
Spotlights
264
Distant Light Sources

5.3

The Phong Reflection Model

5.3.1
5.3.2
5.3.3
5.3.4

Ambient Reflection 267

Diffuse Reflection
267
Specular Reflection 269
The Modified Phong Model

5.4

Computation of Vectors

5.4.1
5.4.2

Normal Vectors 272
Angle of Reflection
274

5.5

Polygonal Shading

5.5.1
5.5.2
5.5.3

Flat Shading 276
Smooth and Gouraud Shading
Phong Shading
279

5.6

Approximation of a Sphere by Recursive Subdivision

280

5.7

Specifying Lighting Parameters

283

5.7.1
5.7.2

Light Sources 283
Materials 284

5.8

Implementing a Lighting Model

5.8.1
5.8.2
5.8.3

Applying the Lighting Model in the Application
Efficiency
289
Lighting in the Vertex Shader
290

5.9

Shading of the Sphere Model

294

5.10

Per-Fragment Lighting

295

5.10.1

Nonphotorealistic Shading

264

265

270

271

275

297

277

286
286


Contents

5.11

Global Illumination

297

Summary and Notes

299

Suggested Readings

300

Exercises
CHAPTER 6

300

FROM VERTICES TO FRAGMENTS

303

6.1

Basic Implementation Strategies

304

6.2

Four Major Tasks

306

6.2.1
6.2.2
6.2.3
6.2.4

Modeling
306
Geometry Processing
Rasterization
308
Fragment Processing

6.3

Clipping

310

6.4

Line-Segment Clipping

310

6.4.1
6.4.2

Cohen-Sutherland Clipping
310
Liang-Barsky Clipping
313

6.5

Polygon Clipping

314

6.6

Clipping of Other Primitives

317

6.6.1
6.6.2
6.6.3

Bounding Boxes and Volumes
318
Curves, Surfaces, and Text
319
Clipping in the Frame Buffer
319

6.7

Clipping in Three Dimensions

319

6.8

Rasterization

323

6.9

Bresenham’s Algorithm

325

6.10

Polygon Rasterization

327

6.10.1
6.10.2
6.10.3
6.10.4
6.10.5

Inside–Outside Testing
327
OpenGL and Concave Polygons
Fill and Sort
329
Flood Fill
330
Singularities
330

6.11

Hidden-Surface Removal

6.11.1
6.11.2
6.11.3
6.11.4
6.11.5
6.11.6
6.11.7

Object-Space and Image-Space Approaches

331
Sorting and Hidden-Surface Removal 332
Scanline Algorithms
333
Back-Face Removal
334
The z-Buffer Algorithm
335
Scan Conversion with the z-Buffer 338
Depth Sort and the Painter’s Algorithm
340

6.12

Antialiasing

307
309

329

331

342

xiii


xiv

Contents

6.13

Display Considerations

6.13.1
6.13.2
6.13.3
6.13.4

Color Systems 345
The Color Matrix
348
Gamma Correction
349
Dithering and Halftoning 349
Summary and Notes

350

Suggested Readings

352

Exercises
CHAPTER 7

344

352

DISCRETE TECHNIQUES

357

7.1

Buffers

357

7.2

Digital Images

359

7.3

Writing into Buffers

362

7.3.1
7.3.2

Writing Modes
363
Writing with XOR 365

7.4

Mapping Methods

366

7.5

Texture Mapping

368

7.5.1

Two-Dimensional Texture Mapping

7.6

Texture Mapping in OpenGL

368

7.6.1
7.6.2
7.6.3
7.6.4
7.6.5
7.6.6
7.6.7

Two-Dimensional Texture Mapping
Texture Objects
375
The Texture Array 376
Texture Coordinates and Samplers
Texture Sampling
382
Working with Texture Coordinates
Multitexturing
386

7.7

Texture Generation

387

7.8

Environment Maps

388

7.9

Reflection Map Example

393

7.10

Bump Mapping

396

7.10.1
7.10.2

Finding Bump Maps
Bump Map Example

7.11

Compositing Techniques

7.11.1
7.11.2
7.11.3
7.11.4
7.11.5
7.11.6

Opacity and Blending 404
Image Compositing 406
Blending and Compositing in OpenGL
406
Antialiasing Revisited 407
Back-to-Front and Front-to-Back Rendering 409
Scene Antialiasing and Multisampling

410

374
375

376
384

397
400

404


Contents

7.11.7
7.11.8

Image Processing
411
Other Multipass Methods

7.12

Sampling and Aliasing

7.12.1
7.12.2
7.12.3

Sampling Theory
413
Reconstruction
418
Quantization
420

412

413

Summary and Notes

421

Suggested Readings

422

Exercises
CHAPTER 8

422

MODELING AND HIERARCHY

425

8.1

Symbols and Instances

426

8.2

Hierarchical Models

427

8.3

A Robot Arm

429

8.4

Trees and Traversal

432

8.4.1

A Stack-Based Traversal

8.5

Use of Tree Data Structures

437

8.6

Animation

441

8.7

Graphical Objects

443

8.7.1
8.7.2
8.7.3
8.7.4
8.7.5

Methods, Attributes, and Messages 443
A Cube Object
445
Implementing the Cube Object
447
Objects and Hierarchy
447
Geometric Objects
448

8.8

Scene Graphs

449

8.9

Open Scene Graph

451

8.10

Graphics and the Internet

453

8.10.1
8.10.2
8.10.3
8.10.4

Hypermedia and HTML
453
Java and Applets
454
Interactive Graphics and the Web
WebGL

455

8.11

Other Tree Structures

8.11.1
8.11.2
8.11.3

CSG Trees
455
BSP Trees
457
Quadtrees and Octrees

434

455

459

Summary and Notes

461

Suggested Readings

461

Exercises

462

454

xv


xvi

Contents

CHAPTER 9

PROCEDURAL METHODS

465

9.1

Algorithmic Models

465

9.2

Physically Based Models and Particle Systems

467

468

9.3

Newtonian Particles

9.3.1
9.3.2
9.3.3

Independent Particles
470
Spring Forces
471
Attractive and Repulsive Forces

9.4

Solving Particle Systems

473

9.5

Constraints

476

9.5.1
9.5.2

Collisions 476
Soft Constraints

9.6

A Simple Particle System

9.6.1
9.6.2
9.6.3
9.6.4
9.6.5

Displaying the Particles 480
Updating Particle Positions
481
Collisions 482
Forces 483
Flocking
483

9.7

Language-Based Models

484

9.8

Recursive Methods and Fractals

487

9.8.1
9.8.2
9.8.3
9.8.4
9.8.5

Rulers and Length 488
Fractal Dimension
489
Midpoint Division and Brownian Motion
Fractal Mountains
492
The Mandelbrot Set
493

9.9

Procedural Noise

479

500

Suggested Readings

501

CHAPTER 10

480

490

496

Summary and Notes
Exercises

472

501

CURVES AND SURFACES

503

10.1

Representation of Curves and Surfaces

10.1.1
10.1.2
10.1.3
10.1.4
10.1.5

Explicit Representation 503
Implicit Representations 505
Parametric Form 506
Parametric Polynomial Curves 507
Parametric Polynomial Surfaces 508

503

10.2

Design Criteria

509

10.3

Parametric Cubic Polynomial Curves

510


Contents

10.4

Interpolation

511

10.4.1

10.4.2

Blending Functions
513
The Cubic Interpolating Patch

10.5

Hermite Curves and Surfaces

10.5.1
10.5.2

The Hermite Form
517
Geometric and Parametric Continuity

10.6

´
Bezier
Curves and Surfaces

10.6.1
10.6.2

´
Bezier
Curves
521

´
Bezier
Surface Patches

10.7

Cubic B-Splines

10.7.1
10.7.2
10.7.3

The Cubic B-Spline Curve
B-Splines and Basis
528
Spline Surfaces
528

10.8

General B-Splines

10.8.1
10.8.2
10.8.3
10.8.4
10.8.5

Recursively Defined B-Splines
Uniform Splines

532
Nonuniform B-Splines
532
NURBS
532
Catmull-Rom Splines
534

10.9

Rendering Curves and Surfaces

10.9.1
10.9.2
10.9.3
10.9.4

Polynomial Evaluation Methods
536
´
Recursive Subdivision of Bezier
Polynomials 537
Rendering Other Polynomial Curves by Subdivision
´
Subdivision of Bezier
Surfaces
541

515

517
519

520

523

524
525

529
530

535

540

10.10 The Utah Teapot

542

10.11 Algebraic Surfaces

545

10.11.1 Quadrics
545
10.11.2 Rendering of Surfaces by Ray Casting

10.12 Subdivision Curves and Surfaces

10.12.1 Mesh Subdivision

10.13.1 Height Fields Revisited
10.13.2 Delaunay Triangulation
10.13.3 Point Clouds
555

551
551

Summary and Notes

556

Suggested Readings

556

557

546

547

10.13 Mesh Generation from Data

Exercises

546

550

xvii


xviii

Contents

CHAPTER 11

ADVANCED RENDERING

559

11.1

Going Beyond Pipeline Rendering

559

11.2

Ray Tracing

560
564

11.3

Building a Simple Ray Tracer

11.3.1
11.3.2
11.3.3

Recursive Ray Tracing 564
Calculating Intersections 566
Ray-Tracing Variations
568

11.4

The Rendering Equation

569

11.5

Radiosity

571

11.5.1
11.5.2
11.5.3
11.5.4

The Radiosity Equation 572
Solving the Radiosity Equation 574

Computing Form Factors
575
Carrying Out Radiosity 577

11.6

RenderMan

578

11.7

Parallel Rendering

579

11.7.1
11.7.2
11.7.3

Sort-Middle Rendering
581
Sort-Last Rendering 583
Sort-First Rendering
586

11.8

Volume Rendering

11.8.1
11.8.2

Volumetric Data Sets 588
Visualization of Implicit Functions

11.9

Isosurfaces and Marching Cubes

588
589

591

11.10 Mesh Simplification

594

11.11 Direct Volume Rendering

595

11.11.1
11.11.2
11.11.3
11.11.4

Assignment of Color and Opacity
596

Splatting
596
Volume Ray Tracing
598
Texture Mapping of Volumes
599

11.12 Image-Based Rendering
11.12.1 A Simple Example
Summary and Notes

602

Suggested Readings

603

Exercises
APPENDIX A

600

600

604

SAMPLE PROGRAMS

A.1

Shader Initialization Function

A.1.1

Application Code

608

607
608


Contents

A.2

Sierpinski Gasket Program

A.2.1
A.2.2
A.2.3

Application Code
610
Vertex Shader
612
Fragment Shader
612

A.3

Recursive Generation of Sierpinski Gasket

A.3.1
A.3.2
A.3.3

Application Code
613
Vertex Shader
615
Fragment Shader
615

A.4

Rotating Cube with Rotation in Shader

A.4.1
A.4.2
A.4.3

Application Code
615
Vertex Shader
620
Fragment Shader
620

A.5

Perspective Projection

A.5.1
A.5.2
A.5.3

Application Code
621
Vertex Shader
625
Fragment Shader
626

A.6

Rotating Shaded Cube

A.6.1
A.6.2
A.6.3

Application Code
626
Vertex Shader
631
Fragment Shader
632

A.7

Per-Fragment Lighting of Sphere Model

A.7.1
A.7.2
A.7.3

Application Code
632
Vertex Shader
637
Fragment Shader
638

A.8

Rotating Cube with Texture

A.8.1
A.8.2
A.8.3

Application Code
638
Vertex Shader
644
Fragment Shader
645

A.9

Figure with Tree Traversal

A.9.1
A.9.2
A.9.3

Application Code
646
Vertex Shader
659
Fragment Shader
659

A.10

Teapot Renderer

A.10.1
A.10.2
A.10.3

Application Code
659
Vertex Shader
664
Fragment Shader
664

APPENDIX B

SPACES

610

613

615

621

626

632

638

646

659

665

B.1

Scalars

665

B.2

Vector Spaces

666

xix


xx

Contents

B.3
B.4
B.5
B.6

Affine Spaces
Euclidean Spaces
Projections
Gram-Schmidt Orthogonalization
Suggested Readings
Exercises

APPENDIX C

668
669
670
671

672

672

MATRICES

675

C.1
C.2

Definitions
Matrix Operations

675
676

C.3

Row and Column Matrices

677

C.4
C.5
C.6
C.7

Rank

Change of Representation
The Cross Product
Eigenvalues and Eigenvectors

678
679
681
682

C.8

Vector and Matrix Classes

683

Suggested Readings
Exercises
APPENDIX D

684

684

SYNOPSIS OF OPENGL FUNCTIONS

687

D.1
D.2

Initialization and Window Functions
Vertex Buffer Objects

687
689

D.3
D.4
D.5
D.6

Interaction
Setting Attributes and Enabling Features
Texture and Image Functions
State and Buffer Manipulation

690
692
693
694

D.7
D.8

Query Functions
GLSL Functions

694
695

References

699

OpenGL Function Index
Subject Index

711

709


P RE FACE
NEW TO THE SIXTH EDITION
Use of modern Shader-Based OpenGL throughout
No use of OpenGL functions deprecated with OpenGL 3.1
Increased detail on implementing transformations and viewing in both application code and shaders
Consistency with OpenGL ES 2.0 and WebGL
Use of C++ instead of C
Addition of vector and matrix classes to create application code compatible
with the OpenGL Shading Language (GLSL)
Discussion of per-vertex and per-fragment lighting
Addition of polygon and Delaunay triangularization
Introduction to volume rendering
All code examples redone to be compatible with OpenGL 3.1
New co-author, Dave Shreiner, author of the OpenGL Programming Guide

T

his book is an introduction to computer graphics, with an emphasis on applications programming. The first edition, which was published in 1997, was somewhat revolutionary in using a standard graphics library and a top-down approach.

Over the succeeding 13 years and five editions, this approach has been adopted by
most introductory classes in computer graphics and by virtually all the competing
textbooks.
The major changes in graphics hardware over the past few years have led to major
changes in graphics software. For its first fifteen years, new OpenGL versions were
released with new versions always guaranteeing backward compatibility. The ability
to reuse code as the underlying software was upgraded was an important virtue, both
for developers of applications and for instructors of graphics classes. OpenGL 3.0
announced major changes, one of the key ones being that, starting with OpenGL 3.1,
many of the most common functions would be deprecated. This radical departure
from previous versions reflects changes needed to make use of the capabilities of the

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xxii

Preface

latest programmable graphics units (GPUs). These changes are also part of OpenGL
ES 2.0, which is being used to develop applications on mobile devices such as cell
phones and tablets, and WebGL, which is supported on most of the latest browsers.
As the authors of the previous five editions of this textbook (EA) and of the
OpenGL Programming Guide and OpenGL ES 2.0 Programming Guide (DS), we were
confronted with a dilemma as to how to react to these changes. We had been writing books and teaching introductory OpenGL courses at SIGGRAPH for many years.
We found that almost no one in the academic community, or application programmers outside the high-end game world, knew about these changes, and those of our
colleagues who did know about them did not think we could teach these concepts
at the beginning level. That was a challenge we couldn’t resist. We started by teaching a half-day short course at SIGGRAPH, which convinced us that we could teach
someone without previous graphics programming experience how to write a nontrivial shader-based OpenGL application program with just a little more work than
with earlier versions of OpenGL.

As we developed this edition, we discovered some other reasons that convinced
us that this approach is not only possible but even better for students learning computer graphics. Only a short while ago, we touted the advantages OpenGL gave us
by being available for Windows, Linux, and Mac OS X so we could teach a course in
which students could work in the environment they preferred. With OpenGL ES and
WebGL they can now develop applications for their cell phones or Web browsers. We
believe that this will excite both students and instructors about computer graphics
and open up many new educational and commercial opportunities.
We feel that of even greater importance to the learning experience is the removal
of most defaults and the fixed function pipeline in these new versions of OpenGL. At
first glance, this removal may seem like it would make teaching a first course much
harder. Maybe a little harder; but we contend much better. The tendency of most
students was to rely on these functions and not pay too much attention to what the
textbook and instructor were trying to teach them. Why bother when they could use
built-in functions that did perspective viewing or lighting? Now that those functions
are gone and students have to write their own shaders to do these jobs, they have to
start by understanding the underlying principles and mathematics.

A Top-Down Approach
These recent advances and the success of the first five editions continue to reinforce
our belief in a top-down, programming-oriented approach to introductory computer
graphics. Although many computer science and engineering departments now support more than one course in computer graphics, most students will take only a single
course. Such a course is placed in the curriculum after students have already studied
programming, data structures, algorithms, software engineering, and basic mathematics. A class in computer graphics allows the instructor to build on these topics
in a way that can be both informative and fun. We want these students to be programming three-dimensional applications as soon as possible. Low-level algorithms,


Preface

such as those that draw lines or fill polygons, can be dealt with later, after students are
creating graphics.

John Kemeny, a pioneer in computer education, used a familiar automobile
analogy: You don’t have to know what’s under the hood to be literate, but unless
you know how to program, you’ll be sitting in the back seat instead of driving. That
same analogy applies to the way we teach computer graphics. One approach—the
algorithmic approach—is to teach everything about what makes a car function: the
engine, the transmission, the combustion process. A second approach—the survey
approach—is to hire a chauffeur, sit back, and see the world as a spectator. The third
approach—the programming approach that we have adopted here—is to teach you
how to drive and how to take yourself wherever you want to go. As the old auto-rental
commercial used to say, “Let us put you in the driver’s seat.”

Programming with OpenGL and C++
When Ed began teaching computer graphics over 25 years ago, the greatest impediment to implementing a programming-oriented course, and to writing a textbook
for that course, was the lack of a widely accepted graphics library or application programmer’s interface (API). Difficulties included high cost, limited availability, lack of
generality, and high complexity. The development of OpenGL resolved most of the
difficulties many of us had experienced with other APIs (such as GKS and PHIGS)
and with the alternative of using home-brewed software. OpenGL today is supported
on all platforms. It is bundled with Microsoft Windows and Mac OS X. Drivers are
available for virtually all graphics cards. There is also an OpenGL API called Mesa
that is included with most Linux distributions.
A graphics class teaches far more than the use of a particular API, but a good API
makes it easier to teach key graphics topics, including three-dimensional graphics,
lighting and shading, client–server graphics, modeling, and implementation algorithms. We believe that OpenGL’s extensive capabilities and well-defined architecture
lead to a stronger foundation for teaching both theoretical and practical aspects of
the field and for teaching advanced concepts, including texture mapping, compositing, and programmable shaders.
Ed switched his classes to OpenGL about 15 years ago, and the results astounded
him. By the middle of the semester, every student was able to write a moderately complex three-dimensional program that required understanding of three-dimensional
viewing and event-driven input. In previous years of teaching computer graphics, he
had never come even close to this result. That class led to the first edition of this book.
This book is a textbook on computer graphics; it is not an OpenGL manual.

Consequently, it does not cover all aspects of the OpenGL API but rather explains
only what is necessary for mastering this book’s contents. It presents OpenGL at a
level that should permit users of other APIs to have little difficulty with the material.
Unlike previous editions, this one uses C++ rather than C as the dominant
programming language. The reason has to do with the OpenGL Shading Language
(GLSL) used to write shaders, the programs that control the GPU. GLSL is a C-like
language with atomic data types that include vectors and matrices, and overloaded

xxiii