SVBRDF-Remapping

Code repository for the paper "Image-based remapping of spatially-varying material appearance" (JCGT)

Image-based remapping of spatially-varying material appearance
Alejandro Sztrajman, Jaroslav Krivanek, Alexander Wilkie, Tim Weyrich
Journal of Computer Graphics Techniques (JCGT), 8(4), pp. 1-30, 2019.

Project Page | Paper

hydrant_mitsuward2cyclesggx_svr.mp4

Cross-renderer SVR remapping of hydrant from Mitsuba (Ward) to Cycles (GGX). Left: source material in Mitsuba Ward. Center: remapped in Blender-Cycles (GGX). Right: SSIM difference. Tabac plant environment map rotates from 0 to 360 degrees.

Regression

parametric_remapping.py: Reads uniform remapping data from mitsuba-ward2mitsuba-beck.csv, fits with parametric remapping method and output plots of data and fitting curve (roughness_vs_roughness.jpg and specular_vs_specular.jpg). Also reads specular.exr and roughness.exr textures and outputs remapped versions (roughness_beck_remapped.exr and specular_beck_remapped.exr).

$ python parametric_remapping.py

svr_remapping.py: Reads uniform remapping data from mitsuba-ward2mitsuba-beck.csv, fits with SVR remapping method and uses fitting to remap specular.exr and roughness.exr textures. Fitted SVR models are saved in disk for subsequent runs.

$ python svr_remapping.py

Visualization

For visualisation of the original and remapped SVBRDF assets, install the pbr.cpp plugin in Mitsuba and then run mitsuba on the scene files.

pbr.cpp: Mitsuba PBR BRDF plugin with Schlick's Fresnel term. For usage: copy this file into mitsuba/src/bsdfs and compile Mitsuba. For scons compilation add the following line to mitsuba/src/bsdfs/SConscript:

plugins += env.SharedLibrary('pbr', ['pbr.cpp'])

ward.xml: Mitsuba scene file that uses the Ward BRDF with the original texture maps.

$ mitsuba ward.xml

beck_parametric.xml: Mitsuba scene file that uses the Beckmann BRDF with the parametric remapped texture maps (make sure to run parametric_remapping.py before running this).

$ mitsuba beck_parametric.xml

beck_svr.xml: Mitsuba scene file that uses the Beckmann BRDF with the svr remapped texture maps (make sure to run svr_remapping.py before running this).

$ mitsuba beck_svr.xml

BibTeX

If you find our work useful, please cite:

@article{Sztrajman2019Imagebased,
    author = {Sztrajman, Alejandro and K\v{r}iv\'anek, Jaroslav and Wilkie, Alexander and Weyrich, Tim},
    title = {Image-based Remapping of Spatially-Varying Material Appearance},
    year = 2019,
    month = oct,
    day = 31,
    journal = {Journal of Computer Graphics Techniques (JCGT)},
    volume = 8,
    number = 4,
    pages = {1--30},
    url = {http://jcgt.org/published/0008/04/01/},
    issn = {2331-7418},
    authorurl = {http://reality.cs.ucl.ac.uk/projects/reflectance-remapping/sztrajman2019image-based.html},
}

Contact

If you have any questions, please email Alejandro Sztrajman at a.sztrajman@ucl.ac.uk.