A Simple Layered RGB BRDF Model - PowerPoint PPT Presentation

1 / 31
About This Presentation
Title:

A Simple Layered RGB BRDF Model

Description:

A Simple Layered. RGB BRDF Model. Xavier Granier - Wolfgang Heidrich ... Convincing and simple model. Not a full simulation. Effect as realistic as possible ... – PowerPoint PPT presentation

Number of Views:43
Avg rating:3.0/5.0
Slides: 32
Provided by: XavierG2
Category:
Tags: brdf | rgb | layered | model | simple

less

Transcript and Presenter's Notes

Title: A Simple Layered RGB BRDF Model


1
A Simple LayeredRGB BRDF Model
2
Motivations
  • Increase the range of possible effects
  • For graphic content creation
  • Work in Color Space RBG - XYZ - LMS
  • Currently limited to linear reflection
  • Convincing and simple model
  • Not a full simulation
  • Effect as realistic as possible

3
Motivations
  • Wavelength effects
  • Interference
  • Colour dispersion
  • Investigation
  • Framework

4
Overview
  • Previous Work
  • General Configuration
  • Glossy Case
  • Diffuse Case
  • Results
  • Conclusion

5
Overview
  • Previous Work
  • General Configuration
  • Glossy Case
  • Diffuse Case
  • Results
  • Conclusion

6
Uniform 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

7
Wavelength effects
  • Diffraction Stam99,Sun00,
  • Interferences
  • Recursive Ray-Tracing Hirayama00-01,
  • Full model Icart99-00,
  • Fine Spectral representation
  • RGB based BRDF
  • Interferences Colour dispersion

8
Overview
  • Previous Work
  • General Configuration
  • Glossy Case
  • Diffuse Case
  • Results
  • Conclusion

9
Approach
  • Semi-transparent layer
  • Interferences effects
  • Local prism configuration
  • One refraction index by colour component
  • Non-parallel layer interfaces
  • Colour dispersion
  • RGB colour space
  • Commonly used in image production

10
Layer configuration
0
Air
1
Layer
2
Support
11
Interference Phase Change
12
Color dispersion Assumption
13
BRDF general expression
  • k?r,g,b
  • R (reflected BRDF)
  • 3 (RGB) lobe-like models
  • T (transmitted BRDF)
  • 3 (RGB) lobe-like models
  • Ex using Phong models

14
Overview
  • Previous Work
  • General Configuration
  • Glossy Case
  • Diffuse Case
  • Results
  • Conclusion

15
Reflected part
  • Phong

16
Transmitted part
  • Assumption
  • No absorption
  • Only one reflection
  • Transmitted term

17
Main 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)

18
Overview
  • Previous Work
  • General Configuration
  • Glossy Case
  • Diffuse Case
  • Results
  • Conclusion

19
Assumptions
  • No colour dispersion
  • Rd ? average reflected energy

20
Diffuse component
  • Final expression

21
Overview
  • Previous Work
  • General Configuration
  • Glossy Case
  • Diffuse Case
  • Results
  • Conclusion

22
Diffuse component
1 - 30 nm
67 - 73 nm
1 - 210 nm
23
Layer Size Change
Constant normal deviation
1-30 nm
79-106 nm
148-200 nm
24
Constant deviation
Parallel Interfaces
Constant deviation
25
Size / Normal correlation
1-10 nm
1-90 nm
rR 1.5 rG 1.7 rB 1.8
26
Overview
  • Previous Work
  • General Configuration
  • Glossy Case
  • Diffuse Case
  • Results
  • Conclusion

27
Conclusion
  • RGB Model
  • Interferences and colour dispersion
  • Continuous along direction
  • Two models
  • Phong - like for specularity
  • Diffuse
  • Validation
  • Such effects are possible in colour space

28
Future Work
  • With current model
  • Hardware acceleration (shader)
  • Try to fit some measured BRDF
  • Investigate other
  • Increase accuracy / More physical
  • Investigate colour spaces
  • Keep simplicity
  • Multi-layer

29
Acknowledgements
  • IMAGER / University of British Columbia
  • Post-doctoral position
  • PIMS Post-doctoral Fellowship
  • Wolfgang Heidrich Lionel Bastard
  • Useful comments and support

30
The End
31
Reflected part
  • Phong reflection
Write a Comment
User Comments (0)
About PowerShow.com