Spectral rendering and color management questions
Posted: Tue Jul 03, 2018 6:14 am
Hello,
I'm currently playing with LuxCoreRender to render glass and try to do some tests to simulate real world image data(camera data). One of the core features I want to try with Lux is spectral rendering for better rendering of dispersion and some testing with spectra rendering in general. Now I have a few questions:
Greetings,
Ingmar
I'm currently playing with LuxCoreRender to render glass and try to do some tests to simulate real world image data(camera data). One of the core features I want to try with Lux is spectral rendering for better rendering of dispersion and some testing with spectra rendering in general. Now I have a few questions:
- How is spectral rendering activated? Can't find the option for it even in some samples for glass refraction and dispersion from this forum/the sample git I see nothing special. How is the number of spectral bands to use set?
- a) How is the conversion from spectra to RGB done? Integration over CIE-XYZ or LMS and conversion from there I guess?
b) Is it possible, to use another spectral response curve like a measured camera response for experiments? As in general camera color response isn't just a linear combination of the human spectral response and therefore it isn't enough to just do a color conversion afterwards.
c) Can the image be exported in it's wavelength channels as a multichannel exr? Would be nice for simulations where you want to create multispectral image information in a pbr manner but process the spectral data outside of Lux. - How is going from RGB to spectrum done when rendering spectral for material and textures with 3 colors?
I'd guess using something like "Physically Meaningful Rendering using Tristimulus Colours" (Meng et. al. 2015)/"Reproducing Spectral Reflectances From Tristimulus Colours" (Otsu et. al. 2018) - How is the state of color management in Lux? As I found no option and nothing on the luxcorerender.org site hints at it, I guess there is currently the assumption that everything is sRGB? When rendering in a three color model it would work to just color manage outside Lux even if it would preferable to have some options inside. But for spectral rendering it is crucial to have color management as the source color space is a need to know when trying to recover a valid spectral reflectance curve for a color.
Greetings,
Ingmar