a simple layered rgb brdf model
DESCRIPTION
Xavier Granier - Wolfgang Heidrich IMAGER / University of British Columbia. A Simple Layered RGB BRDF Model. Motivations. Increase the range of possible effects For graphic content creation Work in Color Space RBG - XYZ - LMS Currently limited to linear reflection - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/1.jpg)
A Simple LayeredA Simple LayeredRGB BRDF ModelRGB BRDF Model
Xavier Granier - Wolfgang HeidrichIMAGER / University of British Columbia
![Page 2: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/2.jpg)
2 IMAGER / UBCA Simple layered RGB BRDF
MotivationsMotivations
Increase the range of possible effects For graphic content creation
Work in Color Space RBG - XYZ - LMSCurrently limited to linear reflection
Convincing and simple modelNot a full simulationEffect as realistic as possible
![Page 3: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/3.jpg)
3 IMAGER / UBCA Simple layered RGB BRDF
MotivationsMotivations
Wavelength effectsInterferenceColour dispersion
Investigation Framework
![Page 4: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/4.jpg)
4 IMAGER / UBCA Simple layered RGB BRDF
OverviewOverview
Previous Work General Configuration Glossy Case Diffuse Case Results Conclusion
![Page 5: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/5.jpg)
5 IMAGER / UBCA Simple layered RGB BRDF
OverviewOverview
Previous Work General Configuration Glossy Case Diffuse Case Results Conclusion
![Page 6: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/6.jpg)
6 IMAGER / UBCA Simple layered RGB BRDF
Uniform BRDFUniform BRDF
Phong models [Phong75,Lafortune94-97,…]Most commonly used
Simplified models [Ward92,Schlick94,…]Faster / Better for Global illumination
Micro-facet [Torrance67,Ashikhmin00,…]
Physically based [He91,Hanrahan93,…]
No wavelength dependent effects
![Page 7: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/7.jpg)
7 IMAGER / UBCA Simple layered RGB BRDF
Wavelength effectsWavelength effects
Diffraction [Stam99,Sun00,…]
InterferencesRecursive Ray-Tracing [Hirayama00-01,…]Full model [Icart99-00,…]
Fine Spectral representation RGB based BRDF Interferences + Colour dispersion
![Page 8: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/8.jpg)
8 IMAGER / UBCA Simple layered RGB BRDF
OverviewOverview
Previous Work General Configuration Glossy Case Diffuse Case Results Conclusion
![Page 9: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/9.jpg)
9 IMAGER / UBCA Simple layered RGB BRDF
Approach Approach
Semi-transparent layerInterferences effects
Local prism configurationOne refraction index by colour componentNon-parallel layer interfacesColour dispersion
RGB colour spaceCommonly used in image production
![Page 10: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/10.jpg)
10 IMAGER / UBCA Simple layered RGB BRDF
Layer configurationLayer configuration
0
1
20n
1n
d
i
o
ir
it
tirot
Air
Layer
Support
![Page 11: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/11.jpg)
11 IMAGER / UBCA Simple layered RGB BRDF
Interference : Phase ChangeInterference : Phase Change
0
1 , nttdr
oi
Uncorrelated layers
Resulting energy from interferences trtr IIIII 2cos2
0
1 ,2 ntdr
i
Parallel layers
![Page 12: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/12.jpg)
12 IMAGER / UBCA Simple layered RGB BRDF
Color dispersion : AssumptionColor dispersion : Assumption
i o
o
i
i o
![Page 13: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/13.jpg)
13 IMAGER / UBCA Simple layered RGB BRDF
BRDF BRDF general general expressionexpression
k{r,g,b} R (reflected BRDF)
3 (RGB) lobe-like models T (transmitted BRDF)
3 (RGB) lobe-like models Ex: using Phong models
koiTkoiRkoi
koiTkoiRkoi
,,,,,,2cos2
,,,,,,
![Page 14: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/14.jpg)
14 IMAGER / UBCA Simple layered RGB BRDF
OverviewOverview
Previous Work General Configuration Glossy Case Diffuse Case Results Conclusion
![Page 15: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/15.jpg)
15 IMAGER / UBCA Simple layered RGB BRDF
Reflected partReflected part
Phong 0,,,,e
i orkifkoiR
0n
1n
i o
ir
![Page 16: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/16.jpg)
16 IMAGER / UBCA Simple layered RGB BRDF
Transmitted partTransmitted part
Assumption No absorption Only one reflection
1,,,,,e
otio trkttkitkoiT
Transmitted term
d
i
it
tirot
kvfkvt ,1,
i
ot
![Page 17: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/17.jpg)
17 IMAGER / UBCA Simple layered RGB BRDF
Main ParametersMain Parameters
Normally r0(k) 1 (air/vacuum) Local geometric configuration : layer-normal Material properties : exponents - indices Fully determined by 4-12 parameters
2-6 Exponents (control transition smoothness)1-3 RGB refraction indices (rB rG rR)1 Layer size 0-2 Normal variation (colour dispersion)
![Page 18: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/18.jpg)
18 IMAGER / UBCA Simple layered RGB BRDF
OverviewOverview
Previous Work General Configuration Glossy Case Diffuse Case Results Conclusion
![Page 19: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/19.jpg)
19 IMAGER / UBCA Simple layered RGB BRDF
AssumptionsAssumptions
kTkRkkTkRk dddddd 2cos2
Similar expression
kRTkTkRk 2cos2
Diffuse case Average along direction
Rd average reflected energy
No colour dispersion
![Page 20: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/20.jpg)
20 IMAGER / UBCA Simple layered RGB BRDF
Diffuse componentDiffuse component
kTkTk
dkrk ddd
1
)(4cos21 1
Phase change for orthogonal incidence
)(4 1
k
dkr
Final expression
No absorption at the interface kRkT dd 1
![Page 21: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/21.jpg)
21 IMAGER / UBCA Simple layered RGB BRDF
OverviewOverview
Previous Work General Configuration Glossy Case Diffuse Case Results Conclusion
![Page 22: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/22.jpg)
22 IMAGER / UBCA Simple layered RGB BRDF
Diffuse componentDiffuse component
1 - 30 nm67 - 73 nm 1 - 210 nm
![Page 23: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/23.jpg)
23 IMAGER / UBCA Simple layered RGB BRDF
Layer Size ChangeLayer Size Change
1-30 nm 79-106 nm 148-200 nm
Constant normal deviation
![Page 24: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/24.jpg)
24 IMAGER / UBCA Simple layered RGB BRDF
Constant deviationConstant deviation
Parallel Interfaces Constant deviation
![Page 25: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/25.jpg)
25 IMAGER / UBCA Simple layered RGB BRDF
Size / Normal correlationSize / Normal correlation
1-10 nm 1-90 nmrR = 1.5 rG = 1.7 rB = 1.8
![Page 26: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/26.jpg)
26 IMAGER / UBCA Simple layered RGB BRDF
OverviewOverview
Previous Work General Configuration Glossy Case Diffuse Case Results Conclusion
![Page 27: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/27.jpg)
27 IMAGER / UBCA Simple layered RGB BRDF
ConclusionConclusion
RGB ModelInterferences and colour dispersionContinuous along direction
Two modelsPhong - like for specularityDiffuse
ValidationSuch effects are possible in colour space
![Page 28: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/28.jpg)
28 IMAGER / UBCA Simple layered RGB BRDF
Future WorkFuture Work
With current modelHardware acceleration (shader)Try to fit some measured BRDF
Investigate otherIncrease accuracy / More physicalInvestigate colour spacesKeep simplicity
Multi-layer
![Page 29: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/29.jpg)
29 IMAGER / UBCA Simple layered RGB BRDF
AcknowledgementsAcknowledgements
IMAGER / University of British ColumbiaPost-doctoral position
PIMS Post-doctoral Fellowship
Wolfgang Heidrich & Lionel BastardUseful comments and support
![Page 30: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/30.jpg)
30 IMAGER / UBCA Simple layered RGB BRDF
The EndThe End
![Page 31: A Simple Layered RGB BRDF Model](https://reader035.vdocuments.site/reader035/viewer/2022081517/5681584e550346895dc5a843/html5/thumbnails/31.jpg)
31 IMAGER / UBCA Simple layered RGB BRDF
Reflected partReflected part
Phong reflection
0,,,,e
i orkifkoiR
2
10
10
5
0,11,
krr
krrkF
nvkFFkvf Fresnel term (Schlick approximation)