Multi-scale Material Appearance

128 Pages·2012·4.45 MB·English

Abstract
Multi-scale Material Appearance
HongzhiWu
2012
Modelingandrenderingtheappearanceofmaterialsisimportantforadiverse
range of applications of computer graphics – from automobile design to movies
andculturalheritage. Theappearanceofmaterialsvariesconsiderablyatdifferent
scales, posing significant challenges due to the sheer complexity of the data, as
welltheneedtomaintaininter-scaleconsistencyconstraints.
This thesis presents a series of studies around the modeling, rendering and
editing of multi-scale material appearance. To efficiently render material appear-
ance at multiple scales, we develop an object-space precomputed adaptive sam-
pling method, which precomputes a hierarchy of view-independent points that
preservemulti-levelappearance. Tosupportbi-scalematerialappearancedesign,
we propose a novel reflectance filtering algorithm, which rapidly computes the
large-scale appearance from small-scale details, by exploiting the low-rank struc-
turesofBidirectionalVisibleNormalDistributionFunctionsandpre-rotatedBidi-
rectional Reflectance Distribution Functions in the matrix formulation of the ren-
deringalgorithm. Thisapproachcanguidethephysicalrealizationofappearance,
as well as the modeling of real-world materials using very sparse measurements.
Finally,wepresentabi-scale-inspiredhigh-qualitygeneralrepresentationforma-
terial appearance described by Bidirectional Texture Functions. Our representa-
tionisatoncecompact,easilyeditable,andamenabletoefficientrendering.
Multi-scale Material Appearance
A Dissertation
Presented to the Faculty of the Graduate School
of
Yale University
in Candidacy for the Degree of
Doctor of Philosophy
by
Hongzhi Wu
Dissertation Director: Julie Dorsey
December 2012
Multi-scaleMaterialAppearance
Copyright(cid:13)c 2013byHongzhiWu
Allrightsreserved.
ForLu,myparents&Yixuan
i
Contents
ListofFigures v
ListofTables vii
Glossary viii
Acknowledgments ix
1 Introduction 1
1.1 ThesisOutline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Related Work 5
2.1 MaterialAppearance Modeling&Compression . . . . . . . . . . . 6
2.1.1 BRDF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.2 BTF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 MaterialAppearance Rendering . . . . . . . . . . . . . . . . . . . . 10
2.3 MaterialAppearance Editing . . . . . . . . . . . . . . . . . . . . . . 12
2.4 MaterialAppearance Fabrication . . . . . . . . . . . . . . . . . . . . 13
2.5 RandomizedMatrixSamplingandFactorization . . . . . . . . . . . 14
3 EfficientRenderingofMulti-scale Material Appearance 16
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
ii
3.2 CharacteristicPoints . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2.2 Matrix Formulation of the Filtered Reflectance Distribution
Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2.3 Randomized MatrixColumnSampling . . . . . . . . . . . . 27
3.2.4 VisibleProjected AreaFunction . . . . . . . . . . . . . . . . . 29
3.3 ComputingandUsingCharacteristicPointMaps . . . . . . . . . . . 30
3.3.1 Preprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.3.2 Rendering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.4 ResultsandDiscussions . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4 Bi-scaleMaterialAppearanceDesign 42
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.2 TheRenderingPipeline . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.2.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.2.2 Processing Geometry . . . . . . . . . . . . . . . . . . . . . . . 50
4.2.3 Processing Visibility . . . . . . . . . . . . . . . . . . . . . . . 51
4.2.4 Processing BVNDF . . . . . . . . . . . . . . . . . . . . . . . . 52
4.2.5 Processing Materials . . . . . . . . . . . . . . . . . . . . . . . 54
4.2.6 RenderingtheLarge-scaleAppearance . . . . . . . . . . . . 55
4.2.7 ImplementationDetails . . . . . . . . . . . . . . . . . . . . . 56
4.3 Bi-scaleMaterialEditing . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.3.1 Small-scaleMaterialEditing . . . . . . . . . . . . . . . . . . . 58
4.3.2 Small-scaleGeometryEditing . . . . . . . . . . . . . . . . . . 60
4.4 PhysicalRealizationandModelingofMaterials . . . . . . . . . . . . 65
iii
4.5 ResultsandDiscussions . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5 A Bi-scale-inspired Sparse Parametric Mixture Model for Bidirectional
TextureFunctions 75
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.2 ASparseParametricMixtureModel . . . . . . . . . . . . . . . . . . 77
5.2.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.2.2 TheFittingMethod . . . . . . . . . . . . . . . . . . . . . . . . 81
5.3 BTFCompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.3.1 TheAlgorithm . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.3.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
5.4 BTFEditing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.4.1 AdjustingtheWeights . . . . . . . . . . . . . . . . . . . . . . 88
5.4.2 AdjustingtheModelParameters . . . . . . . . . . . . . . . . 91
5.4.3 AdjustingtheNormalDistribution . . . . . . . . . . . . . . . 92
5.4.4 UserInterface . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.5 BTFRendering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
6 ConclusionsandFutureWork 100
Bibliography 103
iv
List of Figures
1.1 Examplesofmaterialappearance: chalk,metalandvelvet. . . . . . 2
1.2 Multi-scalematerialappearance variation . . . . . . . . . . . . . . . 3
2.1 Differentcomponentsofdigitalmaterialappearance . . . . . . . . . 6
2.2 AdiagramshowingvectorsthatdefineaBRDF . . . . . . . . . . . . 7
2.3 AtypicalBTFacquisitionsetup. . . . . . . . . . . . . . . . . . . . . . 9
2.4 RectifiedphotographstakenatanearlystageformthefinalBTF. . . 10
3.1 Bolts with complex geometry and materials rendered at different
scales. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2 Renderingsofacylinderusingdifferentmethods. . . . . . . . . . . 18
3.3 AnillustrationofourCPMrepresentation. . . . . . . . . . . . . . . 19
3.4 An illustration of the filtered reflectance distribution function for-
mulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.5 Aconceptualdiagramforcomputingcharacteristicpointsandweights. 24
3.6 Filteredreflectancereconstructionbyrenderingatcharacteristicpoints. 33
3.7 Comparisonofrenderingresultsusingvariousmethods. . . . . . . 36
3.8 RenderingofCloisonne´ gargoyles. . . . . . . . . . . . . . . . . . . . 36
3.9 Characteristicpointdensityvisualization. . . . . . . . . . . . . . . . 39
3.10 CPMmiplevelvisualization. . . . . . . . . . . . . . . . . . . . . . . 40
v
4.1 Bi-scalematerialdesign . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2 Therenderingpipeline . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.3 Small-scalematerialediting. . . . . . . . . . . . . . . . . . . . . . . . 59
4.4 Editinganisotropicmetallicappearance. . . . . . . . . . . . . . . . . 61
4.5 Velvet-likeappearance usingsmall-scalerodsandameasured BRDF. 62
4.6 Cloth-likeappearanceusingasmall-scalewovenstructure. . . . . . 63
4.7 Usingheight-fieldsasthesmall-scalegeometry. . . . . . . . . . . . 64
4.8 Physicalrealizationofappearance. . . . . . . . . . . . . . . . . . . . 66
4.9 Modelingofreal-worldmaterialsusingbi-scaleconstraints. . . . . 68
4.10 Theeffect ofSVDapproximationforN. . . . . . . . . . . . . . . . . 71
4.11 Comparisonswithpathtracingresults . . . . . . . . . . . . . . . . . 73
5.1 AdiagramofourpipelineforusingSPMM. . . . . . . . . . . . . . . 78
5.2 ABTFslicerepresented usinganSPMM. . . . . . . . . . . . . . . . 81
5.3 Renderingcomparisons. . . . . . . . . . . . . . . . . . . . . . . . . . 86
5.4 Changingthehue/saturation. . . . . . . . . . . . . . . . . . . . . . . 91
5.5 Increasingspecularintensityandchangingspecularhue. . . . . . . 92
5.6 Narrowingspecularlobes. . . . . . . . . . . . . . . . . . . . . . . . . 93
5.7 Changingthenormaldistribution. . . . . . . . . . . . . . . . . . . . 94
5.8 TheuserinterfaceofourinteractiveeditingsystemforSPMM. . . . 95
5.9 Aseriesofeditingoperationsareappliedtoawoolblouse . . . . . 96
5.10 SPMM-basedimportancesampling. . . . . . . . . . . . . . . . . . . 99
vi
List of Tables
3.1 SummaryofthenotationusedinChapter3. . . . . . . . . . . . . . . 21
3.2 Pseudo-codeofrandomizedmatrixcolumnsampling . . . . . . . . 27
3.3 Timingresultsandvariousstatisticsfromourexperiments. . . . . . 35
4.1 SummaryofthenotationusedinChapter4. . . . . . . . . . . . . . . 45
4.2 Pseudo-codeofrandom-projectionacceleratedSVD. . . . . . . . . . 54
4.3 Variousstatisticsfromprecomputationofdifferentmaterials. . . . . 70
4.4 Comparisons between a ground-truth approach and our approxi-
mation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5.1 SummaryofthenotationusedinChapter5. . . . . . . . . . . . . . . 79
5.2 Pseudo-codeofourstagewise-Lasso-based fittingalgorithm. . . . . 84
5.3 Variousstatisticsfromourexperiments. . . . . . . . . . . . . . . . . 89
vii