Title: Playing God, Creating Virtual Worlds

Author: Bernie Roehl

Publisher: Waite Group Press

ISBN: 1-878739-62-X

Audience: Generally geared towards C programmers, but accessible to others

Misc: 373 pages, soft cover, $26.95

Synopsis: This book presents a number of tools and techniques for creating

virtual worlds. The basic concepts and terminology of virtual reality are

presented, with an emphasis on some of the technical limitations imposed

by current technology. A general approach to world-building is given, along

with a number of useful guidelines.

The design of virtual objects is explored, and several approaches to

their creation are presented. The use of CAD packages, object generators,

fractals, L-Systems and scripting languages are discussed, all with

practical examples. A chapter is devoted to the layout of objects in

the virtual world.

Examples of programming simple object behaviour are given, and a variety

of different ways of representing behaviour are explored. Finally, a number

of simple virtual worlds are studied, with a chapter devoted to each one.

The book includes several useful pieces of software, including NorthCAD-3D,

VRVIEW, and a number of utilities for creating objects to populate your

virtual worlds. Many of the utilities come with full C source code.

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Table of Contents:

Playing God: Creating Virtual Worlds

Chapter 1: Virtual Reality. . . . . . . . . . . . . . . .1

Chapter 2: What Makes a World Interesting?. . . . . . . 17

Chapter 3: World-Building from the Top Down . . . . . . 35

Chapter 4: World-Building from the Bottom Up. . . . . . 51

Chapter 5: Using VRVIEW . . . . . . . . . . . . . . . . 81

Chapter 6: Creating Objects . . . . . . . . . . . . . . 89

Chapter 7: Using NorthCAD-3D. . . . . . . . . . . . . .157

Chapter 8: Assembling Worlds. . . . . . . . . . . . . .179

Chapter 9: Programming Virtual Worlds . . . . . . . . .211

Chapter 10: The Maze . . . . . . . . . . . . . . . . . .253

Chapter 11: Tag. . . . . . . . . . . . . . . . . . . . .269

Chapter 12: The Museum . . . . . . . . . . . . . . . . .283

Chapter 13: The Haunted Mansion. . . . . . . . . . . . .297

Chapter 14: World Trade Center . . . . . . . . . . . . .309

Afterword: The Future . . . . . . . . . . . . . . . . .323

Appendix A: WLD File Syntax. . . . . . . . . . . . . . .327

Appendix B: CFG File Syntax. . . . . . . . . . . . . . .331

Appendix C: VRLIB Library. . . . . . . . . . . . . . . .333

Appendix D: Format Conversion. . . . . . . . . . . . . .347

Appendix E: NorthCAD-3D Quick Reference. . . . . . . . .350

Appendix F: State Machine Language . . . . . . . . . . .354

Appendix G: Bob Syntax . . . . . . . . . . . . . . . . .356

Appendix H: Stereoscopic Viewing . . . . . . . . . . . .358

Index. . . . . . . . . . . . . . . . . . . .362

Preface xxii

Chapter 1: Virtual Reality . . . . . . . . . . . . . . . . . . .1

History . . . . . . . . . . . . . . . . . . . . . . .2

Technology. . . . . . . . . . . . . . . . . . . . . .3

The Computer . . . . . . . . . . . . . . . . . . .3

Output Devices . . . . . . . . . . . . . . . . . .4

~Window on the World~ Displays. . . . . . . . .4

Projection Systems. . . . . . . . . . . . . . .5

Head-Mounted Displays . . . . . . . . . . . . .5

Sound . . . . . . . . . . . . . . . . . . . . .6

Haptic Feedback . . . . . . . . . . . . . . . .7

Input Devices. . . . . . . . . . . . . . . . . . .8

Bats. . . . . . . . . . . . . . . . . . . . . .8

Forceballs. . . . . . . . . . . . . . . . . . .9

Wands . . . . . . . . . . . . . . . . . . . . .9

Gloves. . . . . . . . . . . . . . . . . . . . .9

Head Trackers . . . . . . . . . . . . . . . . .9

Data Suits. . . . . . . . . . . . . . . . . . 10

2D Devices. . . . . . . . . . . . . . . . . . 10

Speech Input. . . . . . . . . . . . . . . . . 10

Tracking . . . . . . . . . . . . . . . . . . . . 10

Mechanical Tracking . . . . . . . . . . . . . 10

Ultrasonic Tracking . . . . . . . . . . . . . 11

Magnetic Tracking . . . . . . . . . . . . . . 11

Optical Tracking. . . . . . . . . . . . . . . 12

Other Tracking Techniques . . . . . . . . . . 12

Networking . . . . . . . . . . . . . . . . . . . 12

What Is a ~Protocol~? . . . . . . . . . . . . 12

Platform Independence . . . . . . . . . . . . 13

Types of Networks . . . . . . . . . . . . . . 13

A Question of Bandwidth . . . . . . . . . . . 13

What Must Be Sent . . . . . . . . . . . . . . 13

Lag . . . . . . . . . . . . . . . . . . . . . 15

New Networking Technologies . . . . . . . . . 15

Onward... . . . . . . . . . . . . . . . . . . . . . 16

Chapter 2: What Makes a World Interesting? . . . . . . . . . . 17

Realism . . . . . . . . . . . . . . . . . . . . . . 18

Visual Reality . . . . . . . . . . . . . . . . . 18

Resolution. . . . . . . . . . . . . . . . . . 18

Detail. . . . . . . . . . . . . . . . . . . . 19

Multiple Levels of Detail . . . . . . . . . . 20

Curves and Tessellation . . . . . . . . . . . 20

Texture Mapping . . . . . . . . . . . . . . . 21

Color . . . . . . . . . . . . . . . . . . . . 22

Lights and Shadows. . . . . . . . . . . . . . 24

General Architectural Design. . . . . . . . . 25

Acoustical Reality . . . . . . . . . . . . . . . 25

Music . . . . . . . . . . . . . . . . . . . . 26

Sound Effects . . . . . . . . . . . . . . . . 26

Speech. . . . . . . . . . . . . . . . . . . . 27

Haptic Realism. . . . . . . . . . . . . . . . 27

Animation . . . . . . . . . . . . . . . . . . . . . 27

Repetitive Motion. . . . . . . . . . . . . . . . 27

Newtonian Motion . . . . . . . . . . . . . . . . 27

Algorithmic Motion . . . . . . . . . . . . . . . 28

~Intelligent~ Motion . . . . . . . . . . . . . . 28

Interactivity and Responsiveness. . . . . . . . . . 30

Things to Do. . . . . . . . . . . . . . . . . . . . 31

Puzzles to Solve . . . . . . . . . . . . . . . . 31

Skills to Acquire. . . . . . . . . . . . . . . . 31

Places to Go . . . . . . . . . . . . . . . . . . 32

People to Meet . . . . . . . . . . . . . . . . . 32

Taking Risks . . . . . . . . . . . . . . . . . . 32

Making Discoveries . . . . . . . . . . . . . . . 33

Power. . . . . . . . . . . . . . . . . . . . . . 33

Combinations . . . . . . . . . . . . . . . . . . 34

Conclusions . . . . . . . . . . . . . . . . . . . . 34

Chapter 3: World-Building from the Top Down. . . . . . . . . . 35

Questions to Ask. . . . . . . . . . . . . . . . . . 35

Who Will Use the World?. . . . . . . . . . . . . 35

What Will They Do in the World?. . . . . . . . . 36

How Many Different Locations Are Needed? . . . . 36

Can the Participant Change the World?. . . . . . 36

Are Multiple Participants Allowed? . . . . . . . 37

How Realistic Must the World Be? . . . . . . . . 37

Do Any Tasks Require Assistance? . . . . . . . . 37

What Kinds of Objects Are Needed?. . . . . . . . 38

What Is the Flavor or Atmosphere of the World? . 38

What Is a ~World~ Anyway? . . . . . . . . . . . . . 39

Objects. . . . . . . . . . . . . . . . . . . . . 39

Appearance. . . . . . . . . . . . . . . . . . 39

Location and Orientation. . . . . . . . . . . 40

Attachment to Other Objects . . . . . . . . . 40

Emitted Sounds. . . . . . . . . . . . . . . . 40

Behavior . . . . . . . . . . . . . . . . . . . . 41

Intelligent Behavior. . . . . . . . . . . . . 42

The Mechanical Layer of Behavior. . . . . . . 42

The Activity Layer of Behavior. . . . . . . . 42

The Personality Layer of Behavior . . . . . . 42

Other Attributes . . . . . . . . . . . . . . . . 43

The World Itself. . . . . . . . . . . . . . . . . . 44

Layout . . . . . . . . . . . . . . . . . . . . . 44

Lighting . . . . . . . . . . . . . . . . . . . . 44

Ambient Sounds . . . . . . . . . . . . . . . . . 45

Forces and Other Properties of Space . . . . . . 45

User Interface. . . . . . . . . . . . . . . . . . . 46

Input Devices. . . . . . . . . . . . . . . . . . 46

Functions. . . . . . . . . . . . . . . . . . . . 46

Window-on-the-World, Mouse Only. . . . . . . . . 47

Window-on-the-World, Mouse and Joystick (2D or 3D)48

Immersive, HMD System with Wand. . . . . . . . . 48

Immersive, HMD System with Glove . . . . . . . . 48

General Principles . . . . . . . . . . . . . . . 49

Testing . . . . . . . . . . . . . . . . . . . . . . 49

Summary . . . . . . . . . . . . . . . . . . . . . . 50

Chapter 4: World-Building from the Bottom Up . . . . . . . . . 51

Coordinate Systems. . . . . . . . . . . . . . . . . 51

Left-Handed or Right-Handed? . . . . . . . . . . 52

Translation. . . . . . . . . . . . . . . . . . . 54

Scaling. . . . . . . . . . . . . . . . . . . . . 54

Rotation . . . . . . . . . . . . . . . . . . . . 55

Different Coordinate Systems . . . . . . . . . . 55

The Object Coordinate System. . . . . . . . . 55

The World Coordinate System . . . . . . . . . 57

The View Coordinate System. . . . . . . . . . 57

Objects . . . . . . . . . . . . . . . . . . . . . . 58

Vertices . . . . . . . . . . . . . . . . . . . . 58

Polygons . . . . . . . . . . . . . . . . . . . . 59

Planar. . . . . . . . . . . . . . . . . . . . 59

Convex. . . . . . . . . . . . . . . . . . . . 59

Number of Sides . . . . . . . . . . . . . . . 61

Holes . . . . . . . . . . . . . . . . . . . . 61

Detail Polys. . . . . . . . . . . . . . . . . 62

Double-Sided Polys. . . . . . . . . . . . . . 62

Vertex Ordering . . . . . . . . . . . . . . . 63

Where Are the Vertices Stored?. . . . . . . . 64

Designing Objects for Portability . . . . . . 64

Surface Specifiers. . . . . . . . . . . . . . . . . 65

Color Resolution . . . . . . . . . . . . . . . . 65

24-Bit Color. . . . . . . . . . . . . . . . . 65

15- or 16-Bit Color . . . . . . . . . . . . . 66

Paletted Systems. . . . . . . . . . . . . . . 66

Color Maps. . . . . . . . . . . . . . . . . . 66

Surface Types. . . . . . . . . . . . . . . . . . 66

Flat Shading. . . . . . . . . . . . . . . . . 66

Gouraud Shading . . . . . . . . . . . . . . . 66

Phong Shading . . . . . . . . . . . . . . . . 67

Transparency. . . . . . . . . . . . . . . . . 67

Special Effects . . . . . . . . . . . . . . . 67

Texture Mapping . . . . . . . . . . . . . . . 68

Lighting. . . . . . . . . . . . . . . . . . . . . . 69

Ambient Lighting . . . . . . . . . . . . . . . . 69

Directional and Point Source Lighting. . . . . . 69

Cameras . . . . . . . . . . . . . . . . . . . . . . 69

Software Organization . . . . . . . . . . . . . . . 71

The Rendering Pipeline . . . . . . . . . . . . . 72

Step 1. Object Culling. . . . . . . . . . . . 72

Step 2. Transformation. . . . . . . . . . . . 73

Step 3. Backface Removal. . . . . . . . . . . 73

Step 4. Lighting. . . . . . . . . . . . . . . 73

Step 5. z-Clipping. . . . . . . . . . . . . . 73

Step 6. Projection and Screen Scaling . . . . 74

Step 7. xy-Clipping . . . . . . . . . . . . . 75

Step 8. Scan Conversion . . . . . . . . . . . 76

Step 9. Page Flipping . . . . . . . . . . . . 76

Step 10. Hidden Surface Removal . . . . . . . 76

A Note on Optimization. . . . . . . . . . . . 76

Hidden Surface Removal . . . . . . . . . . . . . 76

Depth-Sorting Errors. . . . . . . . . . . . . 77

Sound. . . . . . . . . . . . . . . . . . . . . . 78

Digitized Audio . . . . . . . . . . . . . . . 78

FM Synthesis. . . . . . . . . . . . . . . . . 78

Wavetable Synthesis . . . . . . . . . . . . . 79

Summary . . . . . . . . . . . . . . . . . . . . . . 79

Chapter 5: Using VRVIEW. . . . . . . . . . . . . . . . . . . . 81

How to Start VRVIEW . . . . . . . . . . . . . . . . 81

The Position Display . . . . . . . . . . . . . . 82

The Compass Display. . . . . . . . . . . . . . . 82

The Frames/Second Display. . . . . . . . . . . . 82

Moving Around . . . . . . . . . . . . . . . . . . . 82

Moving Using the Keyboard. . . . . . . . . . . . 83

Moving Using the Joystick. . . . . . . . . . . . 84

Moving Using the Mouse . . . . . . . . . . . . . 84

Multiple Virtual Cameras . . . . . . . . . . . . 84

The VRVIEW Menu System. . . . . . . . . . . . . . . 84

Object Selection . . . . . . . . . . . . . . . . 84

The Main Menu. . . . . . . . . . . . . . . . . . 85

The View Menu. . . . . . . . . . . . . . . . . . 85

The Paint Menu . . . . . . . . . . . . . . . . . 86

The Display Menu . . . . . . . . . . . . . . . . 86

The Object Menu. . . . . . . . . . . . . . . . . 87

The Figure Menu. . . . . . . . . . . . . . . . . 87

The Mouse Menu . . . . . . . . . . . . . . . . . 88

The Stereo Menu. . . . . . . . . . . . . . . . . 88

Summary . . . . . . . . . . . . . . . . . . . . . . 88

Chapter 6: Creating Objects. . . . . . . . . . . . . . . . . . 89

Object Formats. . . . . . . . . . . . . . . . . . . 89

DXF. . . . . . . . . . . . . . . . . . . . . . . 90

3D Studio. . . . . . . . . . . . . . . . . . . . 90

RAW Format . . . . . . . . . . . . . . . . . . . 90

OFF. . . . . . . . . . . . . . . . . . . . . . . 91

NFF. . . . . . . . . . . . . . . . . . . . . . . 91

PLG. . . . . . . . . . . . . . . . . . . . . . . 92

PLG File Format . . . . . . . . . . . . . . . . . . 92

Vertices . . . . . . . . . . . . . . . . . . . . 92

Polygons . . . . . . . . . . . . . . . . . . . . 93

Surface Speci_ers. . . . . . . . . . . . . . . . 94

Simple Colors . . . . . . . . . . . . . . . . 95

Flat-Shaded Colors. . . . . . . . . . . . . . 95

Pseudo-Metallic Colors. . . . . . . . . . . . 95

Pseudo-Transparent Colors . . . . . . . . . . 96

Creating PLG Files by Hand. . . . . . . . . . . . . 96

Vertices and Dimensions. . . . . . . . . . . . . 96

Polygons . . . . . . . . . . . . . . . . . . . . 97

A More Complex Example: Creating a Cone. . . . . 97

Algorithmically Generated Objects . . . . . . . . .100

An Algorithmically Generated Cone. . . . . . . .100

An Algorithmic Chessboard. . . . . . . . . . . .104

Using Triangles for Flexibility. . . . . . . . .106

Getting More Adventurous: Modifying the Chessboard107

Making Mountains . . . . . . . . . . . . . . . .109

Star Light, Star Bright_ . . . . . . . . . . . .110

Improving Your Creations . . . . . . . . . . . .112

Another Object Generator: SOCCER . . . . . . . .113

Modifying Your Objects with PLGX . . . . . . . .113

Combining Objects with PLGMERGE. . . . . . . . .114

Fractals. . . . . . . . . . . . . . . . . . . . . .116

Making Mountains, Revisited. . . . . . . . . . .118

Step 1: Creating the Input File . . . . . . .118

Step 2: Running the FRGEN Command . . . . . .119

Step 3: Converting to PLG Format. . . . . . .120

Step 4: Cleaning Up and Viewing the PLG File.120

From Mountains to Plains . . . . . . . . . . . .121

Beyond the Mountains . . . . . . . . . . . . . .122

Inside FRGEN . . . . . . . . . . . . . . . . . .123

More Powerful Fractal Generators . . . . . . . .125

Lindenmayer Systems . . . . . . . . . . . . . . . .125

Trained Turtles. . . . . . . . . . . . . . . . .126

L-Systems at Work: Building a Walled City. . . .127

A Complex Plant. . . . . . . . . . . . . . . . .129

The Fibonacci Bush . . . . . . . . . . . . . . .130

A Look Inside the Generator. . . . . . . . . . .130

A Look Inside the Interpreter. . . . . . . . . .131

Roll Your Own. . . . . . . . . . . . . . . . . .133

LPARSER. . . . . . . . . . . . . . . . . . . . .134

Scripting Languages . . . . . . . . . . . . . . . .135

OGRE . . . . . . . . . . . . . . . . . . . . . .135

Object Creation and Deletion . . . . . . . . . .137

File Operations. . . . . . . . . . . . . . . . .137

Control Commands . . . . . . . . . . . . . . . .138

Object Primitives. . . . . . . . . . . . . . . .138

Transformations. . . . . . . . . . . . . . . . .142

Modifying and Combining Objects. . . . . . . . .142

More About Surfaces of Revolution. . . . . . . .142

Some More Examples in OGRE . . . . . . . . . . .142

A House . . . . . . . . . . . . . . . . . . .143

A Fir Tree. . . . . . . . . . . . . . . . . .144

A Chess Piece . . . . . . . . . . . . . . . .145

A Luxo Lamp . . . . . . . . . . . . . . . . .146

An Airplane . . . . . . . . . . . . . . . . .147

A Creepy-Crawly . . . . . . . . . . . . . . .148

A ~Nightmarish~ Creature. . . . . . . . . . .149

Combining Techniques: Algorithmic Script Generation

for OGRE. . . . . . . . . . . . . . . . . . .150

A Pleated Tube. . . . . . . . . . . . . . . .150

A Gnarled Walking Stick . . . . . . . . . . .151

CAD Programs. . . . . . . . . . . . . . . . . . . .153

3D Digitizing . . . . . . . . . . . . . . . . . . .153

Laser Scanners . . . . . . . . . . . . . . . . .153

3D Position Sensors. . . . . . . . . . . . . . .153

Photographic Systems . . . . . . . . . . . . . .154

Limitations of 3D Digitizing . . . . . . . . . .154

Choosing Your Methods . . . . . . . . . . . . . . .154

Summary . . . . . . . . . . . . . . . . . . . . . .155

Chapter 7: Using NorthCAD-3D . . . . . . . . . . . . . . . . .157

NorthCAD Concepts . . . . . . . . . . . . . . . . .157

Entities . . . . . . . . . . . . . . . . . . . .158

Revolutions. . . . . . . . . . . . . . . . . . .159

Extrusions . . . . . . . . . . . . . . . . . . .160

Using NorthCAD-3D . . . . . . . . . . . . . . . . .160

Screen Layout. . . . . . . . . . . . . . . . . .161

Setting Some Options . . . . . . . . . . . . . .162

Setting the Working Object and Pen Color . . . .162

The Coordinate System and Viewing Directions . .163

The Information Display. . . . . . . . . . . . .164

Drawing Planes . . . . . . . . . . . . . . . . .164

Your First NorthCAD-3D Drawing . . . . . . . . .165

Adding Regular Polygons. . . . . . . . . . . . .166

Drawing Arcs . . . . . . . . . . . . . . . . . .166

Moving Around in Your Drawing. . . . . . . . . .167

Using Files. . . . . . . . . . . . . . . . . . .168

Saving Your Con_guration . . . . . . . . . . . .168

Into the Third Dimension . . . . . . . . . . . .168

Fixing the Cube. . . . . . . . . . . . . . . . .169

Creating a Building from the Ground Up . . . . .170

More About Extrusions. . . . . . . . . . . . . .172

You Say You Want a Revolution... . . . . . . . .172

A Glass of Wine. . . . . . . . . . . . . . . . .174

A Heavenly Body. . . . . . . . . . . . . . . . .174

A Lighthouse . . . . . . . . . . . . . . . . . .174

Putting It All Together: A Grove of Trees. . . .175

Summary . . . . . . . . . . . . . . . . . . . . . .176

Chapter 8: Assembling Worlds . . . . . . . . . . . . . . . . .179

Loading, Placing, and Modifying Objects . . . . . .179

Scaling. . . . . . . . . . . . . . . . . . . . .179

Rotation . . . . . . . . . . . . . . . . . . . .180

Translation. . . . . . . . . . . . . . . . . . .181

Surface Mapping. . . . . . . . . . . . . . . . .181

WLD Files. . . . . . . . . . . . . . . . . . . .181

Names for Objects . . . . . . . . . . . . . .181

Applying Scaling, Rotation, and Translation .181

Depth-Sorting Type. . . . . . . . . . . . . .182

Surface Map . . . . . . . . . . . . . . . . .182

Parent. . . . . . . . . . . . . . . . . . . .182

The Complete Syntax of Object Statements . . . .182

Using a Default Surface Map. . . . . . . . . . .183

Positioning and Rotating Objects . . . . . . . .183

Changing the Depth-Sorting Type. . . . . . . . .183

Attaching and Detaching. . . . . . . . . . . . .183

Two Ways to Do the Same Thing. . . . . . . . . .184

More About Surface Maps. . . . . . . . . . . . .184

The Palette. . . . . . . . . . . . . . . . . . .185

Single-Polygon Objects . . . . . . . . . . . . .185

Multiple Representations . . . . . . . . . . . .185

The Addrep Statement. . . . . . . . . . . . .185

Multiple-Resolution PLG Files . . . . . . . .186

Segmented Figures . . . . . . . . . . . . . . . . .186

The Figure Statement . . . . . . . . . . . . . .186

FIG File Syntax. . . . . . . . . . . . . . . . .187

Lighting. . . . . . . . . . . . . . . . . . . . . .190

Ambient Light. . . . . . . . . . . . . . . . . .190

Directional Light Sources. . . . . . . . . . . .190

Cameras . . . . . . . . . . . . . . . . . . . . . .191

Miscellaneous Statements. . . . . . . . . . . . . .192

The Options Statement. . . . . . . . . . . . . .192

The Screenclear Statement. . . . . . . . . . . .193

The Screencolor Statement. . . . . . . . . . . .193

The Flymode Statement. . . . . . . . . . . . . .193

The Stepsize and Anglestep Statements. . . . . .193

The Worldscale Statement . . . . . . . . . . . .194

The Attachview Statement . . . . . . . . . . . .194

The Include Statement. . . . . . . . . . . . . .194

The Loadpath Statement . . . . . . . . . . . . .194

The Title Statement. . . . . . . . . . . . . . .195

The Window Statement . . . . . . . . . . . . . .195

Statements Related to Splits . . . . . . . . . .195

Other Statements . . . . . . . . . . . . . . . .195

Splitting Planes. . . . . . . . . . . . . . . . . .196

De_ning Planes . . . . . . . . . . . . . . . . .196

The Split Statement . . . . . . . . . . . . .196

The Splitpts Statement. . . . . . . . . . . .197

The Splitting Tree. . . . . . . . . . . . . .197

Advantages and Disadvantages. . . . . . . . .199

Creating a World. . . . . . . . . . . . . . . . . .199

World-Building by Hand. . . . . . . . . . . . . . .199

The Houses . . . . . . . . . . . . . . . . . . .199

The Trees. . . . . . . . . . . . . . . . . . . .200

The Streets. . . . . . . . . . . . . . . . . . .201

Putting It All Together. . . . . . . . . . . . .201

Algorithmic World-Building. . . . . . . . . . . . .203

A Virtual City . . . . . . . . . . . . . . . . .203

Using NorthCAD-3D to Build a World. . . . . . . . .206

The Island Itself. . . . . . . . . . . . . . . .206

Adding the Lighthouse. . . . . . . . . . . . . .207

A Small Boat . . . . . . . . . . . . . . . . . .207

Conversion . . . . . . . . . . . . . . . . . . .207

The Final Product. . . . . . . . . . . . . . . .209

Limitations of NorthCAD for Creating Worlds. . .209

Summary . . . . . . . . . . . . . . . . . . . . . .210

Chapter 9: Programming Virtual Worlds. . . . . . . . . . . . .211

A Brief Survey. . . . . . . . . . . . . . . . . . .212

Superscape . . . . . . . . . . . . . . . . . . .212

Virtual Reality Studio . . . . . . . . . . . . .212

VREAM. . . . . . . . . . . . . . . . . . . . . .212

dVise. . . . . . . . . . . . . . . . . . . . . .213

Sense8 WorldToolKit. . . . . . . . . . . . . . .213

Autodesk Cyberspace Developers Kit . . . . . . .213

VRVIEW . . . . . . . . . . . . . . . . . . . . .213

What ~Behavior~ Really Means. . . . . . . . . . . .214

Modifying the World . . . . . . . . . . . . . . . .214

Objects. . . . . . . . . . . . . . . . . . . . .214

Create and Destroy. . . . . . . . . . . . . .214

Load and Save Object Geometry . . . . . . . .215

Altering Object Visibility and Level-of-Detail215

Obtaining Information About an Object . . . .215

Object Position and Orientation . . . . . . .215

Object Attachment . . . . . . . . . . . . . .215

Light Sources. . . . . . . . . . . . . . . . . .215

Virtual Cameras. . . . . . . . . . . . . . . . .216

Sound Sources. . . . . . . . . . . . . . . . . .216

The Virtual Environment. . . . . . . . . . . . .216

Input Devices. . . . . . . . . . . . . . . . . .216

Display Devices. . . . . . . . . . . . . . . . .217

Other Functions. . . . . . . . . . . . . . . . .217

VR System Structure . . . . . . . . . . . . . . . .217

State Machine Animation . . . . . . . . . . . . . .218

Animations, States, and Statements . . . . . . .218

do and if. . . . . . . . . . . . . . . . . . . .219

Targets, Commands, and Assignment Instructions .220

Changing State . . . . . . . . . . . . . . . . .220

Conditional Assignments. . . . . . . . . . . . .221

The State Animation Commands . . . . . . . . . .221

A Simple Example: The Wall Clock . . . . . . . .222

A More Complex Example: Suburban Transit . . . .224

BOB . . . . . . . . . . . . . . . . . . . . . . . .226

BOB Syntax . . . . . . . . . . . . . . . . . . .226

Functions . . . . . . . . . . . . . . . . . .227

Classes . . . . . . . . . . . . . . . . . . .227

Flow Control . . . . . . . . . . . . . . . . . .229

Global Variables . . . . . . . . . . . . . . . .229

Expressions. . . . . . . . . . . . . . . . . . .229

BOB Built-in Variables and Functions . . . . . .230

A Short BOB Program. . . . . . . . . . . . . . .231

Interfacing Between BOB and VRVIEW . . . . . . .232

After Initialization. . . . . . . . . . . . .233

At Simulation Time. . . . . . . . . . . . . .233

After Rendering . . . . . . . . . . . . . . .233

At Shutdown Time. . . . . . . . . . . . . . .233

When a Key Is Pressed . . . . . . . . . . . .233

BOB Development with VRVIEW . . . . . . . . . . . .233

An Example: The Wall Clock, Revisited. . . . . .234

A More Complex Example: A Bunch of Things. . . .235

Programming Behavior Using C and C++. . . . . . . .240

Program Structure. . . . . . . . . . . . . . . .241

How the vr_system Functions Work . . . . . . . .242

vr_systemStartup(). . . . . . . . . . . . . .242

vr_systemCommandLine(). . . . . . . . . . . .242

vr_systemRun(). . . . . . . . . . . . . . . .243

Default Routines. . . . . . . . . . . . . . .243

Tasks. . . . . . . . . . . . . . . . . . . . . .244

A Typical Example in C . . . . . . . . . . . . .244

Choosing a Language . . . . . . . . . . . . . . . .251

Summary . . . . . . . . . . . . . . . . . . . . . .252

Chapter 10: The Maze. . . . . . . . . . . . . . . . . . . . . .253

Planning Ahead. . . . . . . . . . . . . . . . . . .253

Creating Geometry . . . . . . . . . . . . . . . . .254

Level 1. . . . . . . . . . . . . . . . . . . . .254

Level 2. . . . . . . . . . . . . . . . . . . . .255

Taking Apart and Putting Together. . . . . . . .256

Collision Detection . . . . . . . . . . . . . . . .257

Extracting the Data. . . . . . . . . . . . . . .257

The Algorithm. . . . . . . . . . . . . . . . . .260

The Ramp, Stairs, and Elevator . . . . . . . . .262

Outside or On the Stairs. . . . . . . . . . .263

First Floor and the Ramp. . . . . . . . . . .264

Second Floor and Elevator . . . . . . . . . .264

The Roof. . . . . . . . . . . . . . . . . . .264

Adjusting Height Using the Ramp and the Elevator265

The Elevator . . . . . . . . . . . . . . . . . .265

Dressing the Set. . . . . . . . . . . . . . . . . .268

Summary . . . . . . . . . . . . . . . . . . . . . .268

Chapter 11: Tag . . . . . . . . . . . . . . . . . . . . . . . .269

The Game of Tag . . . . . . . . . . . . . . . . . .269

The Playing Field . . . . . . . . . . . . . . . . .270

Generating the Vertices. . . . . . . . . . . . .271

Generating the Lines and Polygons. . . . . . . .271

The Runners . . . . . . . . . . . . . . . . . . . .272

The Obstacles . . . . . . . . . . . . . . . . . . .272

Choosing a Language . . . . . . . . . . . . . . . .273

Data Structures . . . . . . . . . . . . . . . . . .273

Obstacles. . . . . . . . . . . . . . . . . . . .273

Runners. . . . . . . . . . . . . . . . . . . . .275

Initialization and the Simulation Loop. . . . . . .276

The Algorithm . . . . . . . . . . . . . . . . . . .277

The Strategy When You~re ~It~. . . . . . . . . .277

The Strategy When You~re Not ~It~. . . . . . . .279

Collision Detection. . . . . . . . . . . . . . .280

A Final Complication . . . . . . . . . . . . . .281

Summary . . . . . . . . . . . . . . . . . . . . . .282

Chapter 12: The Museum. . . . . . . . . . . . . . . . . . . . .283

Overall Approach. . . . . . . . . . . . . . . . . .283

Creating the Museum Itself. . . . . . . . . . . . .284

The Program . . . . . . . . . . . . . . . . . . . .284

The Coil Spring . . . . . . . . . . . . . . . . . .286

The Coil . . . . . . . . . . . . . . . . . . . .286

The Base . . . . . . . . . . . . . . . . . . . .286

The Algorithm. . . . . . . . . . . . . . . . . .286

The Globe . . . . . . . . . . . . . . . . . . . . .287

The Globe and Its Pedestal . . . . . . . . . . .287

The Algorithm. . . . . . . . . . . . . . . . . .287

The Wheel of Chance . . . . . . . . . . . . . . . .288

The Wheel. . . . . . . . . . . . . . . . . . . .288

The Base . . . . . . . . . . . . . . . . . . . .288

The Algorithm. . . . . . . . . . . . . . . . . .289

The Traf_c Light. . . . . . . . . . . . . . . . . .289

The Lights . . . . . . . . . . . . . . . . . . .289

The Box and Stand. . . . . . . . . . . . . . . .290

The Algorithm. . . . . . . . . . . . . . . . . .290

The Marquee . . . . . . . . . . . . . . . . . . . .292

Creating the Marquee . . . . . . . . . . . . . .292

Color Table Animation. . . . . . . . . . . . . .293

Summary . . . . . . . . . . . . . . . . . . . . . .295

Chapter 13: The Haunted Mansion . . . . . . . . . . . . . . . .297

Building the House. . . . . . . . . . . . . . . . .297

The First Floor. . . . . . . . . . . . . . . . .297

The Ouija Board. . . . . . . . . . . . . . . . .298

The Second Floor . . . . . . . . . . . . . . . .299

The Pentagram. . . . . . . . . . . . . . . . . .299

Miscellaneous Objects. . . . . . . . . . . . . .300

Adding a Coat of Paint. . . . . . . . . . . . . . .300

Object Behavior . . . . . . . . . . . . . . . . . .301

Lightning. . . . . . . . . . . . . . . . . . . .302

Rain . . . . . . . . . . . . . . . . . . . . . .303

The Gate . . . . . . . . . . . . . . . . . . . .303

The Doors. . . . . . . . . . . . . . . . . . . .304

The Keys . . . . . . . . . . . . . . . . . . . .306

Summary . . . . . . . . . . . . . . . . . . . . . .307

Chapter 14: World Trade Center. . . . . . . . . . . . . . . . .309

The Scenario. . . . . . . . . . . . . . . . . . . .309

Object Creation . . . . . . . . . . . . . . . . . .310

The Fire Engine. . . . . . . . . . . . . . . . .310

The Axe and the Saw. . . . . . . . . . . . . . .311

The Moveable Light . . . . . . . . . . . . . . .311

The Cars . . . . . . . . . . . . . . . . . . . .312

The Simple Buildings and Roads . . . . . . . . .312

The Fire Station . . . . . . . . . . . . . . . .312

The Vista Hotel. . . . . . . . . . . . . . . . .314

The Parking Garage . . . . . . . . . . . . . . .315

Smoke. . . . . . . . . . . . . . . . . . . . . .316

The Animation . . . . . . . . . . . . . . . . . . .317

The Opening Sequence . . . . . . . . . . . . . .317

The Explosion. . . . . . . . . . . . . . . . . .319

Sawing the Door. . . . . . . . . . . . . . . . .320

The Saw . . . . . . . . . . . . . . . . . . .320

Opening the Door. . . . . . . . . . . . . . .320

The Cutting Operation . . . . . . . . . . . .321

The Smoke. . . . . . . . . . . . . . . . . . . .321

Summary . . . . . . . . . . . . . . . . . . . . . .322

Afterword: The Future. . . . . . . . . . . . . . . . . . . . .323

About REND386, VR-386, and AVRIL. . . . . . . . . .323

Other Information Sources . . . . . . . . . . . . .324

Electronic Newsgroups and Mailing Lists. . . . .324

DIASPAR. . . . . . . . . . . . . . . . . . . . .324

Printed Magazines, Books, and User Groups. . . .325

Other Books. . . . . . . . . . . . . . . . . . .325

Conferences. . . . . . . . . . . . . . . . . . .325

Appendix A: WLD File Syntax . . . . . . . . . . . . . . . . . .327

Appendix B: CFG File Syntax . . . . . . . . . . . . . . . . . .331

Appendix C: VRLIB Library . . . . . . . . . . . . . . . . . . .333

Data Types. . . . . . . . . . . . . . . . . . . . .333

Object Altering Functions . . . . . . . . . . . . .334

Vertex Functions. . . . . . . . . . . . . . . . . .336

Facet Functions . . . . . . . . . . . . . . . . . .337

Light Source Functions. . . . . . . . . . . . . . .337

Virtual Camera Functions. . . . . . . . . . . . . .338

Environmental Functions . . . . . . . . . . . . . .339

Rendering Functions . . . . . . . . . . . . . . . .339

Stereoscopic Viewing System Functions . . . . . . .340

Video Display System Functions. . . . . . . . . . .341

Input Device Functions. . . . . . . . . . . . . . .343

User-Interface Functions. . . . . . . . . . . . . .343

File Reading Functions. . . . . . . . . . . . . . .344

Tasking Functions . . . . . . . . . . . . . . . . .345

Timer-Related Functions . . . . . . . . . . . . . .345

State Machine Functions . . . . . . . . . . . . . .345

BOB Interpreter/Compiler Functions. . . . . . . . .346

BOB Routines. . . . . . . . . . . . . . . . . . . .346

Appendix D: Format Conversion . . . . . . . . . . . . . . . . .347

3DS2PLG . . . . . . . . . . . . . . . . . . . . . .347

DXF2PLG . . . . . . . . . . . . . . . . . . . . . .347

RAW2PLG . . . . . . . . . . . . . . . . . . . . . .347

OFF2PLG . . . . . . . . . . . . . . . . . . . . . .348

The .AOF File. . . . . . . . . . . . . . . . . .348

Color Handling . . . . . . . . . . . . . . . . .348

PLGFILT . . . . . . . . . . . . . . . . . . . . . .349

Appendix E: NorthCAD-3D Quick Reference . . . . . . . . . . . .350

Special Keys. . . . . . . . . . . . . . . . . . . .350

The Menus . . . . . . . . . . . . . . . . . . . . .350

Main Menu. . . . . . . . . . . . . . . . . . . .350

Model Menu . . . . . . . . . . . . . . . . . . .351

Move Menu . . . . . . . . . . . . . . . . . . .351

Scale Menu . . . . . . . . . . . . . . . . . . .351

Rotate Menu . . . . . . . . . . . . . . . . . .351

Extrude Menu . . . . . . . . . . . . . . . . . .352

Revolve Menu . . . . . . . . . . . . . . . . . .352

Copy Menu . . . . . . . . . . . . . . . . . . .352

Files Menu . . . . . . . . . . . . . . . . . . .352

Objects Menu . . . . . . . . . . . . . . . . . .353

Group Menu . . . . . . . . . . . . . . . . . . .353

Settings Menu . . . . . . . . . . . . . . . . .353

Edit Menu. . . . . . . . . . . . . . . . . . . .353

Draw Menu. . . . . . . . . . . . . . . . . . . .353

Appendix F: State Machine Language. . . . . . . . . . . . . . .354

Appendix G: Bob Syntax. . . . . . . . . . . . . . . . . . . . .356

Program Structure . . . . . . . . . . . . . . . . .356

Member De_nitions. . . . . . . . . . . . . . . .356

Statements . . . . . . . . . . . . . . . . . . .356

Expressions. . . . . . . . . . . . . . . . . . .357

Appendix H: Stereoscopic Viewing. . . . . . . . . . . . . . . .358

Stereoscopic Viewing Parameters . . . . . . . . . .358

Convergence and Focusing. . . . . . . . . . . . . .359

Field Of View . . . . . . . . . . . . . . . . . . .360

Lens Distortion . . . . . . . . . . . . . . . . . .360

Summary . . . . . . . . . . . . . . . . . . . . . .361

Index . . . . . . . . . . . . . . . . . . . . . . .362

============================================================================

---------------------------------------------------------------------------

Some notes:

1. I did not create the table of contents; the publisher did.

2. The notes on the cover of the book can be *very* misleading; just

for the record, I did not write any of the text on the cover, nor

was I given a chance to look at the cover before it went to print.

Caveat Emptor. Trust this document, not the book cover.

============================================================================

Errata:

I wasn't given a chance to proofread the final draft of the

book, so several of the figures in it contain errors.

Figure 4-9: The illustration shows the origin of the chesspiece as being

at one edge; it should be in the center of the base of the piece.

Figure 4-12: The pyramid looks like it's four sides plus a base; it should

be three sides plus the base (which is why there are 4 vertices, not

5).

Figure 4-14: The two cubes look identical in the figure; one of them, the

one on the right, is supposed to have each square face made up of two

triangles.

Figure 4-31b: This figure is just plain confusing. Ignore it.

Figure 4-32: It should be clearer that the the triangle in the upper left

is entirely visible, the one in the lower left is not visible (i.e.

it's completely Z-clipped) and the middle triangle is partially

Z-clipped.

Figure 4-33: The equation is set wrong. It should be:

Y' Y DY

--- = --- so Y' = ---

D Z Z

Figure 4-36: The artist tooks some liberties with the relative sizes of

the objects; the idea was to have been that the left- and right-hand

edges of Object B (the wall) extend past the bounds of objects A and

C (which is why there's a depth-sorting problem).

Figure 6-2: Showing a color palette in black and white doesn't make much

sense; it would be nice if the book had color plates, but it doesn't.

Figure 6-21: Not sure what's happening there at all.

Figure 7-19: Caption should read "Revolving a) A bracket shape to form

b) A cylinder shape".

Figure 7-27: Caption should read "The grove as seen in VRVIEW".

Figure 8-1: All three circular arrows are going in the wrong direction.

Figure 8-8: The caption should read "The splitting tree for Figure 8-7".

Figure 8-14: The a) and b) figures are swapped; the one on the left is

the right way, the one on the right is the wrong way (not the other

way around).

Figure 9-1: The words on the ellipsoids are "ALPHA", "BETA", and "GAMMA".

Figure 9-8: The left part of the equation should of course have a horizontal

line separating the numerator from the denominator.

Page 325: PCVR magazine is no longer being published; however, check out

Virtual Reality World (published by the Meckler organization described

under "Conferences".

Figure H-1: The diagram came out looking a little strange, and again the

line between the numerator and denominator on each side of the equation

has gone missing.

If you notice any other errors in the book, please send me email; my

address is broehl@uwaterloo.ca, and I check my mail fairly often (though

it sometimes takes me a long time to respond).