Image - Based Remapping of Material Appearance A. Sztrajman 1 , J. - - PowerPoint PPT Presentation

▶
image based remapping of material appearance
SMART_READER_LITE
LIVE PREVIEW

Image - Based Remapping of Material Appearance A. Sztrajman 1 , J. - - PowerPoint PPT Presentation

Feb 08, 2024 328 likes •594 views

Image - Based Remapping of Material Appearance A. Sztrajman 1 , J. Kivnek 2 , A. Wilkie 2 , T. Weyrich 1 1 University College London, UK 2 Charles University, Czech Republic Eurographics Workshop on Material Appearance Modeling Helsinki

slide-1
SLIDE 1
  • A. Sztrajman1, J. Křivánek2, A. Wilkie2, T. Weyrich1

1 University College London, UK 2 Charles University, Czech Republic

Image-Based Remapping of Material Appearance

Eurographics Workshop on Material Appearance Modeling – Helsinki 2017

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642841.

slide-2
SLIDE 2

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

Material authoring

SUBSTANCE DESIGNER

1 Unity

[Retrieved from Unity forum]

slide-3
SLIDE 3

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

1. Different BRDF models used by different softwares 1. No clear way to translate between models

Model incompatibility

3. We usually don’t have access to the implementations 4. and they change between renderers

slide-4
SLIDE 4

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

3

BRDF remapping

Reference BRDF model External BRDF model (initial condition) External BRDF model (after remapping)

slide-5
SLIDE 5

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

4

BRDF remapping

Nonlinear

  • ptimization of

BRDF parameters

BRDF model (initial guess) Fitted BRDF

BRDF fitting

Reflectance data

Nonlinear

  • ptimization of

BRDF parameters

External model (initial guess) External model remapped

BRDF remapping

Reference model rendering

slide-6
SLIDE 6

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

5

Appearance comparison

  • Spherical geometry
  • Point light illumination
  • L2 metric for comparison
  • Nonlinear optimization with TRF
slide-7
SLIDE 7

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

6

Results

GGX Ashikhmin-Shirley Beckmann Ward Phong

Conductors Dielectrics

slide-8
SLIDE 8

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

Results: conductors

Ashikhmin-Shirley

  • RGB Reflectivity
  • Roughness

Ward

  • RGB Specular reflectance
  • Roughness

Reference Ashikhmin-Shirley BRDF External Remapped GGX BRDF Error

7

slide-9
SLIDE 9

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

8

Results: remapping of conductors

Ashikhmin-Shirley

  • RGB Reflectivity
  • Roughness

Ward

  • RGB Specular reflectance
  • Roughness

60 conductors from Mitsuba’s DB

slide-10
SLIDE 10

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

9

Results: remapping of conductors

Ashikhmin-Shirley

  • RGB Reflectivity
  • Roughness

Ward

  • RGB Specular reflectance
  • Roughness
slide-11
SLIDE 11

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

10

Ashikhmin-Shirley Ward

Results: remapping of conductors (roundtrip)

Ashikhmin-Shirley

slide-12
SLIDE 12

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

11

Reference Ashikhmin-Shirley BRDF. External Remapped GGX BRDF Error

Results: dielectrics

Ashikhmin-Shirley

  • RGB Diffuse reflectance
  • IOR
  • Roughness

Ward

  • RGB Diffuse reflectance
  • RGB Specular reflectance
  • Roughness
slide-13
SLIDE 13

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

Results: remapping of dielectrics

12

[Ashikhmin-Shirley] [Ward] [Ashikhmin-Shirley] [Ward]

Ashikhmin-Shirley

  • RGB Diffuse reflectance
  • IOR
  • Roughness

Ward

  • RGB Diffuse reflectance
  • RGB Specular reflectance
  • Roughness
slide-14
SLIDE 14

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

Remapping in two stages

13 Remapping of diffuse term

External model (initial guess) External model remapped

Remapping of specular term

External model (initial guess)

Reference Reference (diffuse) Reference (specular)

slide-15
SLIDE 15

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

14

Results: 2-stage remapping of dielectrics

Ashikhmin-Shirley

  • RGB Diffuse reflectance
  • IOR
  • Roughness

Ward

  • RGB Diffuse reflectance
  • RGB Specular reflectance
  • Roughness
slide-16
SLIDE 16

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

Remapping in three stages

15

External model (initial guess)

2-stage remapping Remapping with both terms

External model remapped

slide-17
SLIDE 17

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

16

Results: 3-stage remapping of dielectrics

Ashikhmin-Shirley

  • RGB Diffuse reflectance
  • IOR
  • Roughness

Ward

  • RGB Diffuse reflectance
  • RGB Specular reflectance
  • Roughness
slide-18
SLIDE 18

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

17

Current work: SVBRDF remapping

Diffuse map Glossiness map Specular map

slide-19
SLIDE 19

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

18

Conclusions

  • We presented a scheme for automatic remapping of uniform BRDFs

without access to the BRDF implementations.

  • The remapping procedure has been tested with both dielectric and

conductor materials and with multiple BRDF models. Overall the transformation between models is robust, and in the cases where we find instabilities, these are generally located in a well-defined area of parameter space.

  • When dealing with materials with both diffuse and specular terms,

both need to be remapped independently to avoid instabilities.

slide-20
SLIDE 20

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

Thank you!

19 *We would like to thank Cyrille Damez from allegorithmic

for his contribution to the project.

slide-21
SLIDE 21

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

20

slide-22
SLIDE 22

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

21

slide-23
SLIDE 23

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

22

Results: remapping of conductors

Ashikhmin-Shirley

  • RGB Reflectivity
  • Roughness

Ward

  • RGB Specular reflectance
  • Roughness
slide-24
SLIDE 24

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

23

Results: remapping of conductors

Ashikhmin-Shirley

  • RGB Reflectivity
  • Roughness

Ward

  • RGB Specular reflectance
  • Roughness
slide-25
SLIDE 25

Image-Based Remapping of Material Appearance / A. Sztrajman, J. Krivanek, A. Wilkie, T. Weyrich

Results

Geometry used for remapping Original BRDF Remapped BRDF Error

24