Rendering with mental ray®

503 Pages·2000·17.546 MB·English

by  Thomas Driemeyer (auth.)

mental ray® Handbooks
Edited by
RolfHerken
VoI. 1
Springer-Verlag Wien GmbH
Th. Driemeyer
Rendering with mental ray®
Springer-V erlag Wien GmbH
Thomas Driemeyer
mental images
Gesellschaft fi.ir Computerfilm und Maschinenintelligenz mbH & Co. KG
FasanenstrafSe 81
D-I0623 Berlin
Copyright © Springer-Verlag Wien 2000
Originally published by Springer-Verlag Wien New York in 2000
AU rights reserved.
This document is protected under copyright law. The contents of this document may not be translated,
copied or duplicated in any form, in whole or in part, without the express written permission of mental
images Springer Fachmedien Wiesbaden GmbH.
The information contained in this document is subiect to change without notice. mental images GmbH
& Co. KG and its employees shaU not be responsible for incidental or consequential damages resulting
from the use of this material or liable for technical or editorial omissions made herein.
mental images®, mental ray®, mental matter™, mental ray Phenomenon™, mental ray Phenomena™,
Phenomenon™, Phenomena™, Phenomenon Creator™, Phenomenon Editor™, Photon MapTM, mental
ray Relay LibraryTM, and Relay LibraryTM are trademarks or, in some countries, registered trademarks of
mental images Springer Fachmedien Wiesbaden GmbH.
AU other product names mentioned in this document may be trademarks or registered trademarks of
their respective companies and are hereby acknowledged.
Printed on acid-free and chlorine-free bleached paper
SPIN: 10747523
CIP data applied for
With numerous (partly coloured) Figures
ISSN 1438-9835
ISBN 978-3-211-83403-9 ISBN 978-3-7091-3697-3 (eBook)
DOI 10.1007/978-3-7091-3697-3
Table of Contents v
Table of Contents
Series Editor's Foreword 1
Introduction 3
Organization of this Book ............................................................. 3
Typesetting Conventions .............................................................. 5
WWW Resources ..................................................................... 5
Acknowledgements ................................................................... 6
1 Overview 7
1.1 Photorealistic Rendering ......................................................... 7
1.2 Scenes and Animations ........................................................... 7
1.2.1 Geometric Objects .......................................................... 8
1.2.2 Materials .................................................................. 10
1.2.3 Light Sources .............................................................. 11
1.2.4 Cameras................................................................... 11
1.3 Shaders ......................................................................... 12
1.4 Phenomena ..................................................................... 14
1.5 Scanline Rendering and Ray Tracing ............................................. 14
1.5.1 Transparency, Refractions, and Reflections .................................. 15
1.5.2 Shadows ................................................................... 17
1.5.3 Motion Blur ............................................................... 17
1.5.4 Lenses .......................... ~ .......................................... 18
1.6 Caustics, Global Illumination, and Photon Maps ................................. 18
1.7 Participating Media ............................................................. 19
1.8 Parallelism ...................................................................... 19
1.9 Stages of Image Generation ...................................................... 20
1.10 mental ray Configurations ..................................................... 21
1.11 mental ray Versions ............................................................ 22
2 Scene Construction 25
2.1 A Simple Scene ................................................................. 26
2.2 Anatomy of a Scene ............................................................. 29
3 Cameras 33
3.1 Pinhole Cameras ................................................................ 33
3.2 Image Resolution ............................................................... 33
3.3 Aspect Ratio .................................................................... 34
3.4 Keystone Distortion ............................................................ 35
vi Table of Contents
3.5 Rendering Subwindows ......................................................... 35
3.6 Orthographic Camera ........................................................... 36
3.7 Clipping Planes ':- ............................................................... 37
3.8 Lenses: Depth of Field .......................................................... 38
3.9 Full Camera Example ........................................................... 40
4 Surface Shading 43
4.1 Color and Illumination .......................................................... 46
4.2 Texture Mapping ................................................................ 51
4.2.1 Texture Projections ........................................................ 52
4.2.1.1 Simple XY Projection ................................................. 53
4.2.1.2 Repeated XY Projection ............................................... 55
4.2.1.3 Other Projections ..................................................... 56
4.2.1.4 Texture Vectors ....................................................... 57
4.2.1.5 Texture Generation from Coordinate Spaces ........................... 62
4.2.2 Local Textures: Avoiding Network Transfers ................................ 63
4.2.3 Memory Mapped Textures: Reducing Memory Usage ....................... 64
4.2.4 Aliasing in Unfiltered Textures ............................................. 66
4.2.5 Simple Filtered Textures: Reducing Texture Aliasing ......................... 69
4.2.6 Elliptic Filtered Textures: Even Better Texture Anti-Aliasing .................. 71
4.2.7 Summary: Selecting Optimal Texturing Methods ............................ 73
4.2.8 3D Textures ............................................................... 74
4.3 Transparency Mapping .......................................................... 77
4.4 Bump Mapping ................................................................. 79
4.5 Displacement Mapping .......................................................... 83
4.5.1 Displacement Approximation " ............................................. 86
4.6 Anisotropic Shading ............................................................ 95
4.7 Environment Mapping .......................................................... 99
4.8 Reflection ..................................................................... 102
4.9 Transparency and Refraction ................................................... 107
4.10 Glossy Reflection ............................................................. 110
4.11 Glossy Transmission (Translucency) ........................................... 112
4.12 Summary of Illumination Models .............................................. 114
5 Light and Shadow 117
5.1 Point, Spot, and Infinite Lights ................................................. 119
5.2 Raytraced Shadows ................................... : ........................ 122
5.2.1 Transparent Shadows with Shadow Shaders ................................ 124
5.2.2 Soft Shadows with Area Light Sources ..................................... 125
5.2.3 Shadow Modes: Regular, Sorted, Segmented ............................... 129
Table of Contents vii
5.3 Fast Shadows with Shadow Maps ............................................... 131
5.4 Internals: How Shadows are Computed :,::. ...................................... 136
5.4.1 Raytraced Shadows ....................................................... 136
5.4.2 Shadow Map Shadows .................................................... 138
5.5 Shadow Summary and Performance 139
6 Volume Rendering 143
6.1 Global Volumes: Atmospheres and Fog ......................................... 144
6.2 Local Volumes: Fur, Fire, Smoke ............................................... 145
6.3 Ray Marching ................................................................. 149
7 Caustics and Globallliumination 155
7.1 Local Illumination vs. Caustics vs. Global Illumination .......................... 156
7.2 Diffuse, Glossy, and Specular Reflection and Transmission ....................... 157
7.3 Classiflcation of Light Paths .................................................... 160
7.4 Caustic and Global Illumination Lights ......................................... 163
7.5 Caustics ....................................................................... 165
7.6 GlobaIIllumination ............................................................ 173
7.6.1 Diffuse Global Illumination (Radiosity) .................................... 173
7.6.2 Glossy Global Illumination ............................................... 176
7.6.3 General Global Illumination .............................................. 178
7.6.4 Final Gathering ........................................................... 181
7.7 Participating Media ............................................................ 184
7.7.1 Volume Caustics .......................................................... 185
7.7.2 Multiple Volume Scattering: Global Illumination in Volumes ............... 190
7.7.3 Global Illumination in Volumes and Surfaces ............................... 193
7.8 Frequently Asked Questions ................................................... 196
7.9 Summary ...................................................................... 199
7.10 Performance .................................................................. 202
8 Motion Blur 205
8.1 Motion Transformations ....................................................... 206
8.2 Motion Vectors ................................................................ 208
8.3 Summary and Performance ..................................................... 210
9 Contours 213
9.1 Outline Contours .............................................................. 214
9.2 PostScript Contours ........................................................... 217
9.3 Edge Contours ................................................................ 218
9.4 Contours on Reflections and Refractions ....................................... 218
9.5 Contours at Color Contrasts ................................................... 219
viii Table of Contents
9.6 Variable-Width Contours ...................................................... 221
9.7 Glowing Contours ............................................................. 222
9.8 Performance ................................................................... 222
10 Shaders and Phenomena 223
10.1 Declarations ................................ '" ........................ " ..... 224
10.2 Definitions ................................................................... 227
10.3 Shader Lists .................................................................. 229
10.4 Shader Graphs ........................................... '" .................. 230
10.5 Phenomena ................................................................... 233
10.5.1 Phenomenon Interface Assignments ...................................... 235
10.5.2 Shader and Phenomenon Options ........................................ 236
10.5.3 Phenomenon Roots ...................................................... 238
10.6 User Data Blocks ............................................................. 240
10.7 Summary and Performance .................................................... 241
11 Postprocessing and Image Output 243
11.1 Image Types .................................................................. 244
11.2 Frame Buffers ................................................................ 246
11.3 Image Formats ............................................................... 247
12 Geometric Objects ** 253
12.1 Vectors and Vertices .......................................................... 256
12.2 Polygonal Geometry .......................................................... 260
12.3 Free-Form Surface Geometry ................................................. 262
12.3.1 Bases .................................................................... 263
12.3.1.1 Bezier .................................. '" ......................... 264
12.3.1.2 B-Spline ............................................................ 264
12.3.1.3 Cardinal ............................................................ 267
12.3.1.4 Basis Matrix ........................................................ 267
12.3.1.5 Taylor .............................................................. 269
12.3.2 Surfaces ................................................................. 269
12.3.3 Rational Surfaces and NURBS ........................................... 273
12.3.4 Trimming and Holes ..................................................... 275
12.3.5 Special Points and Curves ................................................ 279
12.3.6 Texture Surfaces ......................................................... 281
12.3.7 Surface Derivatives ...................................................... 283
12.3.8 Approximations ......................................................... 284
12.3.9 Triangle Count and Performance ......................................... 292
12.3.10 Connections ........................................................... 294
12.3.11 Adjacency Detection and Edge Merging ................................. 294
Table of Contents ix
12.4 Procedural Geometry ......................................................... 295
13 Instancing and Grouping 299
13.1 Instances ..................................................................... 299
13.2 Instance Groups .............................................................. 301
13.3 Multiple Instancing ........................................................... 301
13.4 Coordinate Spaces ............................................................ 304
14 Inheritance 307
14.1 MateriaIInheritance .......................................................... 307
14.2 Tagged Material Inheritance ................................................... 312
14.3 Parameter Inheritance ......................................................... 315
14.4 Object Flag Inheritance ....................................................... 317
15 Incremental Changes and Animations 321
16 Using and Creating Shader Libraries ** 327
17 Parallelism 333
17.1 Thread Parallelism ............................................................ 333
17.2 Network Parallelism .......................................................... 334
17.3 Parallelism Efficiency ......................................................... 335
17.4 Balancing Network Rendering ................................................ 337
17.5 Rendering Animations ........................................................ 338
17.6 Filename Rewriting ........................................................... 339
18 The Options Block 345
18.1 Feature Flags ................................................................. 345
18.2 Rendering Quality and Performance ........................................... 347
18.3 Shadows ..................................................................... 349
18.4 Ray Tracing Control .......................................................... 350
18.5 Global Illumination and Caustics .............................................. 352
18.6 Scene Modeling ............................................................... 353
18.7 Diagnostic Modes ............................................................ 355
19 Quality and Performance Tuning 357
19.1 Reading the Message Log 'r .................................................... 357
19.2 Image Sampling Quality ...................................................... 360
19.3 Ray Tracing vs. Scanline Rendering 'r .......................•.................. 364
19.4 OpenGL Hardware Acceleration 'r .............•.............................. 366
19.5 Tuning BSP Ray Tracing Parameters 'r ......•......•.......................•... 367
19.6 Optimizing Memory Usage 'r ................................................. 369
x Table of Contents
19.7 Address Space Limitations ':. .................................................. 374
19.8 Summary: Quality and Performance Checklist ................................. 375
19.8.1 Sampling ................................................................ 375
19.8.2 Texture Mapping ........................................................ 375
19.8.3 Light and Shadow ....................................................... 376
19.8,4 Caustics and Global Illumination ......................................... 376
19.8.5 Geometry Modeling ..................................................... 377
19.8.6 Shaders and Phenomena .................................................. 377
19.8.7 Networking and Multithreading .......................................... 377
20 Troubleshooting * 379
20.1 Sampling ..................................................................... 379
20.2 Shading...................................................................... 380
20.3 Caustics and Global Illumination .............................................. 380
20,4 Geometry .................................................................... 381
20.5 System ....................................................................... 382
Color Plates 385
A Command Line Options 403
A.1 mental ray .................................................................... 403
A.2 Inventor mental ray ........................................................... 413
A.3 Environment Variables ':. ...................................................... 414
A,4 Image Display: imLdisp ....................................................... 415
A.5 Image Copy: imLcopy ........................................................ 417
A.6 Image Information: imLinfo ................................................... 418
A.7 Image Comparison: imLdiff ................................................... 418
A.8 Create Shader Skeletons: mkmishader ':.,:. ....................................... 419
A.9 Convert Scenes to C: mitoapi ':"f ............................................... 420
B The 5phere and Utah Teapot Models 421
B.1 NURBS Sphere ............................................................... 421
B.2 Utah Teapot ................................................................... 423
C Base 5haders * 429
C.1 Overview ..................................................................... 429
C.2 Texture Space Mapping ........................................................ 431
C.3 Environments ................................................................. 436
C,4 Textures ...................................................................... 438
C.5 Sample Compositing .......................................................... 442
C.6 Illumination.................................................................. 446