Dispersion example (0-1 in 50 frames):
Roughness example (0.01-1 in 50 frames):
To me it simply feels as too dark and I think (IIRC) that glass had much better behavior in previous LuxRender 1.7 (classic&core) version, at least it wasn't loosing so much energy. Any ground truth examples around?
Glass is getting too dark...
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Please upload a testscene that allows developers to reproduce the problem, and attach some images.
Please upload a testscene that allows developers to reproduce the problem, and attach some images.
Glass is getting too dark...
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Re: Glass is getting too dark...
I changed material in your example file a bit...
Re: Glass is getting too dark...
Please correct me if I'm wrong, but I think this is why glass needs multiscatter ggx.
https://blender.stackexchange.com/quest ... catter-ggx
https://blender.stackexchange.com/quest ... catter-ggx
Re: Glass is getting too dark...
Also the issue with clear glass might just be the values that you are using. The tool tip for dispersion says:
"Realistic values range from 0.00354 to 0.01342"
"Realistic values range from 0.00354 to 0.01342"
Re: Glass is getting too dark...
Yes, you go out of visible spectrum out of an healthy range.
Re: Glass is getting too dark...
See https://en.wikipedia.org/wiki/Cauchy%27s_equation (upper right image) for values on visible spectrum.
Re: Glass is getting too dark...
Yes, i know.
The scene shared is set as i left it, after few more experiments to brighten the glass... but got tired and also ran out of time (am slowly recovering from an accident).
Thanks, all that got me thinking again...Dade wrote: ↑Thu Aug 16, 2018 9:08 am See https://en.wikipedia.org/wiki/Cauchy%27s_equation (upper right image) for values on visible spectrum.
Roughness (0-1 in 50 frames) with Cycles 'MultiscatterGGX' Glass Using "Multiple-Scattering Microfacet BSDFs with the Smith Model" in Cycles is pleasant, comfortable, feels very natural & got me really spoiled
So, especially in cases of physically accurate light transport, IMHO, this much darkening shouldn't happen. M-GGX is clear proof of that and I also believe similar would apply for dispersion - even when using extreme values, light transport within medium should go without such strong loss of energy (Diamond is also very nice example). Here's where artists add to scientific & technical limits.
Anyways, if anyone knows how this kind of result can be accomplished with LuxCore2 would be really grateful. Also, since there's no additive material layering it's really hard to get nice frosted glass, milky glass, snow, gems & precious stones...
Experimenting & exploring further.
And Thank you all again for your help and explanations
Re: Glass is getting too dark...
We were talking of the first image, of dispersion and Cauchy's equation: how can be Cycles used as reference if it doesn't support dispersion at allkintuX wrote: ↑Thu Aug 16, 2018 1:52 pmThanks, all that got me thinking again...Dade wrote: ↑Thu Aug 16, 2018 9:08 am See https://en.wikipedia.org/wiki/Cauchy%27s_equation (upper right image) for values on visible spectrum.
Roughness (0-1 in 50 frames) with Cycles 'MultiscatterGGX' Glass
CyclesMGGX_GlassRoughness.gif
P.S. Cycles is also not rendering any caustic at all in your image.
Re: Glass is getting too dark...
Can simulate dispersion in Cycles with shader nodes, separating RGB chanels using different IORs and adding, summing it back.
& Here are examples with Cauchy @ 1 using Classic Lux BiDir.
Clear Glass Rough Glass (U-R=0.01) it become an emitter
I know engine is spectral & values unreal, i am ignorant in detailed science and math behind, but from observing matter/medium in nature, this results still feel more likely to be realistic than results with present engine. As for Cycles matter, i'm also able to accomplish similar results easier and faster, while differences are almost never noticeable to observer's eye.
Had disabled caustics (both/ reflective & refractive) for the sake of clearer image, since second example is mainly about roughness and multi-scattering. With caustics on, i assume, rough glass would just be a fraction brighter since all rays get scattered thus caustic effect can't even be produced.