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Real-Time-Shadows.pdf
b11030-1
Contents
Preface
b11030-2
1. Introduction
1.1 Definition
1.2 Importance of Shadows
1.3 Difficulty of Computing Shadows
1.4 Overview
1.5 General Information for the Reader
b11030-3
2. Basic Shadow Techniques
2.1 Projection Shadows
2.2 Shadow Mapping
2.3 Shadow Volumes
2.4 Stencil Shadow Volumes
2.5 Transparency
2.6 Summary
b11030-4
3. Shadow-Map Aliasing
3.1 Shadow Mapping as Signal Reconstruction
3.2 Initial Sampling Error—Undersampling
3.3 Resampling Error
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4. Shadow-Map Sampling
4.1 Fitting
4.2 Warping
4.3 Global Partitioning
4.4 Adaptive Partitioning
4.5 View-Sample Mapping
4.6 Shadow-Map Reconstruction
4.7 Temporal Reprojection
4.8 Cookbook
b11030-6
5. Filtered Hard Shadows
5.1 Filters and Shadow Maps
5.2 Applications of Filtering
5.3 Precomputing Larger Filter Kernels
5.4 Summary
b11030-7
6. Image-Based Soft-Shadow Methods
6.1 Introduction
6.2 Basics
6.3 A Reference Solution
6.4 Augmenting Hard Shadows with Penumbrae
6.5 Blurring Hard-Shadow-Test Results
6.6 Filtering Planar Occluder Images
6.7 Reconstructing and Back-Projecting Occluders
6.8 Using Multiple Depth Maps
6.9 Summary
b11030-8
7. Geometry-Based Soft-Shadow Methods
7.1 Plausible Shadows by Generating Outer Penumbra
7.2 Inner and Outer Penumbra
7.3 Soft Shadow Volumes
7.4 View-Sample Mapping
7.5 Tradeoffs
7.6 Summary of Soft-Shadow Algorithms
b11030-9
8. Image-Based Transparency
8.1 Deep Shadow Maps
8.2 Approximating the Transmittance Function
8.3 Summary
b11030-10
9. Volumetric Shadows
9.1 Real-Time Single Scattering in Homogeneous Participating Media
9.2 Ray Marching a Shadow Map
9.3 Shadow-Volume–Based Approaches
9.4 Summary
b11030-11
10. Advanced Shadow Topics
10.1 Multicolored Light Sources
10.2 Multisample Antialiasing
10.3 Voxels and Shadows
10.4 Ray-Casting Shadows
10.5 Environmental Lighting
10.6 Precomputed Radiance Transfer
b11030-12
11. Conclusion
11.1 Hard Shadows
11.2 Filtered Hard Shadows
11.3 Soft Shadows
11.4 Advanced Methods
11.5 Welcome Tomorrow
b11030-13
A. Down the Graphics Pipeline
A.1 Rendering
A.2 Per-Fragment Processing—Culling and Blending
A.3 The Framebuffer
A.4 Geometry Representation
A.5 Hardware
b11030-14
B. Brief Guide to Graphics APIs
B.1 Transformation Matrices
B.2 State
B.3 Framebuffer and Render Targets
B.4 Texture Sampling
B.5 Shading Languages
b11030-15
C. A Word on Shading
C.1 Analytical Shading Models
C.2 Approximating Incoming Radiance
b11030-16
D. Fast GPU Filtering Techniques
D.1 Mipmap
D.2 N-Buffer and Multiscale Map
D.3 Summed-Area Table
D.4 Summary
b11030-17
E. More For Less: Deferred Shading and Upsampling
E.1 Deferred Shading
E.2 Upsampling
E.3 Summary
b11030-18
F. Symbols
b11030-19
Bibliography
b11030-20
Index
Real-Time Shadows
Real-Time Shadows
Elmar Eisemann
Michael Schwarz
Ulf Assarsson
Michael Wimmer
CRC Press
Taylor & Francis Group
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Boca Raton, FL 33487-2742
© 2012 by Taylor & Francis Group, LLC
CRC Press is an imprint of Taylor & Francis Group, an Informa business
No claim to original U.S. Government works
Printed in the United States of America on acid-free paper
Version Date: 20110526
International Standard Book Number: 978-1-56881-438-4 (Hardback)
This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but
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Library of Congress Cataloging‑in‑Publication Data
Real-time shadows / Elmar Eisemann … [et al.].
p. cm.
Includes bibliographical references and index.
ISBN 978-1-56881-438-4 (alk. paper)
1. Computer animation. 2. Real-time rendering (Computer graphics) 3. Shades and shadows in art. 4. Digital video. I. Eisemann, Elmar.
TR897.7.R396 2011
006.6’96--dc22
2011009331
Visit the Taylor & Francis Web site at
http://www.taylorandfrancis.com
and the CRC Press Web site at
http://www.crcpress.com
K13063_Discl.indd 1
5/26/11 8:16 AM
Dedicated to. . .
. . . my family,
including my uncle, who awakened my scientific curiosity.
E.E.
. . . Ewelina and all the rest of my whole big family.
U.A.
. . . Romana, Sarah, and Laurenz.
M.W.
Contents
Preface
1 Introduction
1.1
1.2
1.3
1.4
1.5
2.1
2.2
2.3
2.4
2.5
2.6
Denition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Importance of Shadows . . . . . . . . . . . . . . . . . . . . . . .
Diculty of Computing Shadows . . . . . . . . . . . . . . . . .
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General Information for the Reader . . . . . . . . . . . . . . . .
2 Basic Shadow Techniques
Projection Shadows . . . . . . . . . . . . . . . . . . . . . . . . .
Shadow Mapping . . . . . . . . . . . . . . . . . . . . . . . . . .
Shadow Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stencil Shadow Volumes
. . . . . . . . . . . . . . . . . . . . . .
Transparency . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Shadow-Map Aliasing
3.1
3.2
3.3
Shadow Mapping as Signal Reconstruction . . . . . . . . . . .
Initial Sampling Error—Undersampling . . . . . . . . . . . . .
Resampling Error . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Shadow-Map Sampling
4.1
Fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Warping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Global Partitioning . . . . . . . . . . . . . . . . . . . . . . . . .
4.3
4.4
Adaptive Partitioning . . . . . . . . . . . . . . . . . . . . . . . .
vii
xi
1
3
12
15
19
20
21
22
31
44
48
72
73
75
75
81
87
89
89
93
110
123
viii
Contents
4.5
4.6
4.7
4.8
View-Sample Mapping . . . . . . . . . . . . . . . . . . . . . . .
Shadow-Map Reconstruction . . . . . . . . . . . . . . . . . . .
Temporal Reprojection . . . . . . . . . . . . . . . . . . . . . . .
Cookbook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Filtered Hard Shadows
5.1
5.2
5.3
5.4
Filters and Shadow Maps . . . . . . . . . . . . . . . . . . . . . .
Applications of Filtering . . . . . . . . . . . . . . . . . . . . . .
Precomputing Larger Filter Kernels . . . . . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 Image-Based Soft-Shadow Methods
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Reference Solution . . . . . . . . . . . . . . . . . . . . . . . .
Augmenting Hard Shadows with Penumbrae . . . . . . . . . .
Blurring Hard-Shadow-Test Results . . . . . . . . . . . . . . . .
Filtering Planar Occluder Images . . . . . . . . . . . . . . . . .
Reconstructing and Back-Projecting Occluders . . . . . . . . .
Using Multiple Depth Maps
. . . . . . . . . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7 Geometry-Based Soft-Shadow Methods
7.1
7.2
7.3
7.4
7.5
7.6
Plausible Shadows by Generating Outer Penumbra . . . . . . .
Inner and Outer Penumbra . . . . . . . . . . . . . . . . . . . . .
So Shadow Volumes . . . . . . . . . . . . . . . . . . . . . . . .
View-Sample Mapping . . . . . . . . . . . . . . . . . . . . . . .
Tradeos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Summary of So-Shadow Algorithms
. . . . . . . . . . . . . .
8 Image-Based Transparency
8.1
8.2
8.3
Deep Shadow Maps . . . . . . . . . . . . . . . . . . . . . . . . .
Approximating the Transmittance Function . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9 Volumetric Shadows
9.1
9.2
9.3
9.4
Real-Time Single Scattering in Homogeneous Participating
Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ray Marching a Shadow Map . . . . . . . . . . . . . . . . . . .
Shadow-Volume–Based Approaches
. . . . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
131
134
136
137
139
140
144
147
160
161
161
166
172
174
178
187
191
204
206
209
209
215
217
225
234
236
239
240
243
258
259
259
261
265
268
Contents
ix
10 Advanced Shadow Topics
10.1 Multicolored Light Sources . . . . . . . . . . . . . . . . . . . . .
10.2 Multisample Antialiasing . . . . . . . . . . . . . . . . . . . . . .
10.3 Voxels and Shadows . . . . . . . . . . . . . . . . . . . . . . . . .
Ray-Casting Shadows . . . . . . . . . . . . . . . . . . . . . . . .
10.4
Environmental Lighting . . . . . . . . . . . . . . . . . . . . . .
10.5
10.6
Precomputed Radiance Transfer . . . . . . . . . . . . . . . . . .
11 Conclusion
11.1 Hard Shadows . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2
. . . . . . . . . . . . . . . . . . . . . . .
Filtered Hard Shadows
11.3
So Shadows . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.4 Advanced Methods . . . . . . . . . . . . . . . . . . . . . . . . .
11.5 Welcome Tomorrow . . . . . . . . . . . . . . . . . . . . . . . . .
A Down the Graphics Pipeline
Rendering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.1
A.2
Per-Fragment Processing—Culling and Blending . . . . . . . .
A.3 e Framebuer . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.4
Geometry Representation . . . . . . . . . . . . . . . . . . . . .
Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.5
B Brief Guide to Graphics APIs
Transformation Matrices . . . . . . . . . . . . . . . . . . . . . .
State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Framebuer and Render Targets . . . . . . . . . . . . . . . . . .
Texture Sampling . . . . . . . . . . . . . . . . . . . . . . . . . .
Shading Languages
. . . . . . . . . . . . . . . . . . . . . . . . .
B.1
B.2
B.3
B.4
B.5
C.1
C.2
C A Word on Shading
Analytical Shading Models . . . . . . . . . . . . . . . . . . . . .
Approximating Incoming Radiance . . . . . . . . . . . . . . . .
D Fast GPU Filtering Techniques
D.1 Mipmap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
N-Buer and Multiscale Map . . . . . . . . . . . . . . . . . . .
D.2
D.3
Summed-Area Table . . . . . . . . . . . . . . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D.4
E More For Less: Deferred Shading and Upsampling
E.1
E.2
E.3
Deferred Shading . . . . . . . . . . . . . . . . . . . . . . . . . .
Upsampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
269
269
274
275
283
285
294
297
297
299
299
300
301
303
303
306
307
308
309
311
312
316
319
320
321
323
323
327
329
329
332
336
340
341
341
343
349
x
F
Symbols
Bibliography
Index
Contents
351
353
377
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