Fabricating Microgeometry for Custom Surface Reflectance

Transcription

1 Fabricating Microgeometry for Custom Surface Reflectance SIGGRAPH 2009 August 4, New Orleans Tim Weyrich 1 Pieter Peers 2 Wojciech Matusik 3 Szymon Rusinkiewicz 3,4 1 University College London 2 University of Southern California, Institute for Creative Technologies 3 Adobe Systems, Inc. 4 Princeton University

2 Acquiring & Fabricating Geometry Wikimedia Common

3 3D Sca n nin g Acquiring & Fabricating Geometry Wikimedia Common

4 3D ting Sca n Prin nin 3D g Acquiring & Fabricating Geometry Wikimedia Common

5 Acquiring & Fabricating Reflectance?

6 Re fle Ac cta qu n isit ce ion Acquiring & Fabricating Reflectance?

7 ??? Re fle Ac cta qu n isit ce ion Acquiring & Fabricating Reflectance?

8 Microfacet Theory Reflectance as a result of microgeometry Surface modelled by tiny mirrors (microfacets) [TORRANCE AND SPARROW 1967]

9 Microfacet Theory Reflectance as a result of microgeometry Surface modelled by tiny mirrors (microfacets) [TORRANCE AND SPARROW 1967] n n v h l

10 Microfacet Theory Reflectance as a result of microgeometry Surface modelled by tiny mirrors (microfacets) [TORRANCE AND SPARROW 1967] Net effect described by microfacet distribution (MFD) 1-D Microfacet Distribution Appearance

11 Microfacet Theory Reflectance as a result of microgeometry Surface modelled by tiny mirrors (microfacets) [TORRANCE AND SPARROW 1967] Net effect described by microfacet distribution (MFD) MFD can be estimated from measured data [NGAN ET AL. 2005] [NGAN ET AL. 2005]

12 Microfacet Theory Reflectance as a result of microgeometry Surface modelled by tiny mirrors (microfacets) [TORRANCE AND SPARROW 1967] Net effect described by microfacet distribution (MFD) MFD can be estimated from measured data [NGAN ET AL. 2005] Our goal: fabricating microgeometry from an MFD

13 Previous Work Material design and editing Aggregate BRDF from arbitrary microgeometry or MFD [WESTIN ET A. 1992; ASHIKHMIN ET AL. 2000] [ASHIKHMIN ET AL. 2000]

14 Previous Work Material design and editing Aggregate BRDF from arbitrary microgeometry [WESTIN ET A. 1992; ASHIKHMIN ET AL. 2000] BRDF design by drawing highlights [COLBERT ET AL. 2006] [COLBERT ET AL. 2006]

15 Previous Work Material design and editing Aggregate BRDF from arbitrary microgeometry [WESTIN ET A. 1992; ASHIKHMIN ET AL. 2000] BRDF design by drawing highlights [COLBERT ET AL. 2006] But no microgeometry from highlights

16 Previous Work Material design and editing Aggregate BRDF from arbitrary microgeometry [WESTIN ET A. 1992; ASHIKHMIN ET AL. 2000] BRDF design by drawing highlights [COLBERT ET AL. 2006] But no microgeometry from highlights Search for mirror geometry with target radiation [PATOW AND PUEYO 2005; PATOW ET AL. 2007] [PATOW AND PUEYO. 2005] Reflector design

17 Previous Work Material design and editing Aggregate BRDF from arbitrary microgeometry [WESTIN ET A. 1992; ASHIKHMIN ET AL. 2000] BRDF design by drawing highlights [COLBERT ET AL. 2006] But no microgeometry from highlights Search for mirror geometry with target radiation [PATOW AND PUEYO 2005; PATOW ET AL. 2007] But fixed light source position and not planar [PATOW AND PUEYO. 2005] Reflector design

18 Previous Work Physical appearance output 3-D printing of artistic geometry [SÉQUIN 2000] [SÉQUIN 2005]

19 Previous Work Physical appearance output 3-D printing of artistic geometry [SÉQUIN 2000] [WEYRICH ET AL. 2007] macroscopic appearance [CIGNONI ET AL. 1997; WEYRICH ET AL. 2007; SONG ET AL. 2007; KERBER ET AL. 2007] [SÉQUIN 2005] Bas-relief sculpture outputs

20 Previous Work Physical appearance output 3-D printing of artistic geometry [SÉQUIN 2000] But no user-defined reflectance output [WEYRICH ET AL. 2007] macroscopic appearance [CIGNONI ET AL. 1997; WEYRICH ET AL. 2007; SONG ET AL. 2007; KERBER ET AL. 2007] [SÉQUIN 2005] Bas-relief sculpture outputs

21 Problem Definition BRDF specification by microfacet distribution (MFD) Find microgeometry that has normals that satisfy MFD is a height field is tileable (for efficiency)

22 Problem Definition BRDF specification by microfacet distribution (MFD) Find microgeometry that has normals that satisfy MFD is a height field is tileable (for efficiency) In a sense, MFD integration problem

23 Problem Definition BRDF specification by microfacet distribution (MFD) Find microgeometry that has normals that satisfy MFD is a height field is tileable (for efficiency) In a sense, MFD integration problem Related to Poisson problem except that gradient locations not known

24 Approach Desired Highlight Shape (MFG)

25 Approach Low-Discrepancy Sampling Desired Highlight Shape (MFG) Sampled MF Orientations

26 Approach Low-Discrepancy Sampling Simulated Annealing / Poisson Equation Desired Highlight Shape (MFG) Sampled MF Orientations Continuous Height Field

27 Approach Low-Discrepancy Sampling Simulated Annealing / Poisson Equation Computer-Controlled Milling Desired Highlight Shape (MFG) Sampled MF Orientations Continuous Height Field Milled Surface

28 Reflectance Specification Target BRDF assumptions Spatially homogeneous Purely specular (describable by MFD) Hemispherical MFD Defined by highlight under frontal illumination 2-D representation in parabolic mapping

29 Reflectance Specification Target BRDF assumptions Spatially homogeneous Purely specular (describable by MFD) Hemispherical MFD Defined by highlight under frontal illumination 2-D representation in parabolic mapping

30 Reflectance of Base Material Substrate exhibits its own, base BRDF

31 Reflectance of Base Material Substrate exhibits its own, base BRDF Altered reflectance by shaped microgeometry

32 Reflectance of Base Material Substrate exhibits its own, base BRDF Altered reflectance by shaped microgeometry Net BRDF is convolution of MFD by base BRDF

33 Reflectance of Base Material Substrate exhibits its own, base BRDF Altered reflectance by shaped microgeometry Net BRDF is convolution of MFD by base BRDF Goal: Shaping base material to exhibit aggregate target BRDF

34 Accounting For Base BRDF Deconvolving Target MFD by Base BRDF Lucy-Richardson deconvolution algorithm Target MFD

35 Accounting For Base BRDF Deconvolving Target MFD by Base BRDF Lucy-Richardson deconvolution algorithm Base MFD Target MFD

36 Accounting For Base BRDF Deconvolving Target MFD by Base BRDF Lucy-Richardson deconvolution algorithm Target MFD Deconvolved by base MFD

37 Accounting For Base BRDF

38 Sampling the MFD Microfacets cannot control brightness of a reflection

39 Sampling the MFD Microfacets cannot control brightness of a reflection Stippling instead: drawing discrete facets from MFD 0

40 Sampling the MFD Low-discrepancy sampling required Target MFD Random Sampling

41 Sampling the MFD Low-discrepancy sampling required We use centroidal Voronoi tesselation [SECORD 2002] Target MFD Random Sampling Low-discrepancy Sampling

42 Result of MF Sampling

43 Result of MF Sampling Should exhibit desired aggregate reflectance...

44 Result of MF Sampling Should exhibit desired aggregate reflectance but: Discontinuities hard to manufacture Interreflection at verticals

45 Height Field Optimization Maximize continuity and integrability

46 Height Field Optimization Maximize continuity and integrability Two-stage procedure 1. Arrangement

47 Height Field Optimization Maximize continuity and integrability Two-stage procedure 1. Arrangement 2. Vertical displacement

48 Arrangement Optimization Shuffling facets to optimize: Shuffling

49 Arrangement Optimization Shuffling facets to optimize: Compatibility of neighboring slopes Shuffling

50 Arrangement Optimization Shuffling facets to optimize: Compatibility of neighboring slopes Mean-free rows and columns Shuffling

51 Arrangement Optimization Shuffling facets to optimize: Compatibility of neighboring slopes Mean-free rows and columns Minimize valleys in end result (physical process causes horizontal flats at concavities) Shuffling

52 Arrangement Optimization Shuffle using simulated annealing optimization Shuffling

53 Arrangement Optimization Shuffle using simulated annealing optimization Global penalty function Pair-wise facet swaps Logarithmic annealing schedule Shuffling

54 Arrangement Optimization

55 Displacement Optimization Vertical displacement to minimize discontinuities Vertical Displacement

56 Displacement Optimization Vertical displacement to minimize discontinuities Maps to Poisson problem Facets determine local gradients Cyclic connectivity for tileability Vertical Displacement

57 Displacement Optimization

58 Effect of Valley Optimization Halves horizontal areas Preserves continuity Unoptimized: 918 Concave Edges 418 Concave Edges

59 Fabricating Microgeometry Requires shaping glossy materials

60 Fabricating Microgeometry Requires shaping glossy materials Many processes exist Milling Etching Cutting Minting...

61 Our Prototype Process Prototype fabrication Base material: aluminum Computer-controlled mill

62 Our Prototype Process Prototype fabrication Base material: aluminum Computer-controlled mill Practical challenges Drill bit tip has finite extent Milling creates grooves Milling speed

63 Our Prototype Process Process Details Milling at inch resolution Milling x- and y-scanlines

64 Our Prototype Process Process Details Milling at inch resolution Milling x- and y-scanlines Sample size -height field ca. 1mm 2 facets Overall milling time: 5.5 hours

65 Highlight Observation Distant light source + distant observer Mirror reflection where facet orientations match No visible highlight Light Direction Observer

66 Highlight Observation Distant light source + local observer Multiple off-specular observations Visible highlight formation Light Direction Observer

67 Highlight Observation Distant light source + local observer Multiple off-specular observations Visible highlight formation Requires tiled material Light Direction Observer

68 Evaluation Imaging reflectance lobe

69 Evaluation Imaging reflectance lobe Experimental setup:

70 Evaluation Imaging reflectance lobe Experimental setup:

71 Evaluation Imaging reflectance lobe Experimental setup:

72 Results

73 Results

74 Results

75 Results

76 Results

77 Results

78 Results

79 Results

80 Results

81 Results

82 Results

83 Results

84 Results

85 Results

86 Results

87 Results

88 Results

89 Results

90 Curved Surfaces Curved surface + general observer Multiple off-specular observations Visible highlight formation Observer Light Direction

91 Curved Surfaces Curved surface + general observer Multiple off-specular observations Visible highlight formation (Simulation)

92 Curved Surfaces Curved surface + general observer Multiple off-specular observations Visible highlight formation (Simulation)

93 Constraints Only integrable MFDs

94 Constraints Only integrable MFDs Barycenter along surface normal

95 Constraints Only integrable MFDs Barycenter along surface normal What goes up has to go down

96 Constraints Only integrable MFDs Barycenter along surface normal What goes up has to go down Purely specular reflectance

97 Constraints Only integrable MFDs Barycenter along surface normal What goes up has to go down Purely specular reflectance Shadowing term implicit

98 Practical Scenarios Various application scenarios exist Architectural decorations Courtesy by Panormaio

99 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Courtesy by Vicky Shaw

100 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Lighting control (interior design) With permission Studio Make Light

101 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Lighting control (interior design) Camouflage ( stealth materials) Wikimedia Commons

102 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Lighting control (interior design) Camouflage ( stealth materials) Security markers Courtesy by Kent Quirk

103 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Lighting control (interior design) Camouflage ( stealth materials) Security markers Logos, product design, etc.

104 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Lighting control (interior design) Camouflage ( stealth materials) Security markers Logos, product design, etc.

105 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Lighting control (interior design) Camouflage ( stealth materials) Security markers Logos, product design, etc. Manufacturing methods are application-dependent

106 Practical Scenarios Various application scenarios exist Architectural decorations Material design (not selection) Lighting control (interior design) Camouflage ( stealth materials) Security markers Logos, product design, etc. Manufacturing methods are application-dependent Microgeometry computation remains general

107 Acknowledgments Saskia Mardijck, Bruce Lamond, Monica Nichelson, Paul Debevec, Bill Swartout, Randy Hill, Randolph Hall NSF grants CCF and CCF U.S. Army Research, Development, and Engineering Command (RDECOM) University of Southern California Office of the Provost The content of the information does not necessarily reflect the position or the policy of the US Government, and no official endorsement should be inferred.