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Glass Rendering-Compasrison

Posted: Tue Jan 16, 2018 6:49 am
by arzaquna
Hi everyone,

Recently I have done a test to render a couple of glasses and I found the result of Luxcorerender v.2 looks too dark at the edges, which in my opinion is a bit strange. Then I did a test using classic Luxrender ( Linux Version 1.7-dev Build) as a comparison with the same scene and the result is really different. I believe the result from luxrender is more acceptable.
glass_rendering_comparison_a.jpg
then i tried to compare with some other renderer like mitsuba and tungsten and the results are similar to Classic Luxrender. All the images were rendered using path tracer.
glass_rendering_comparison_b.jpg
when I render using bidir + metropolis the result is even more strange. it's kind of glowing
glass_rendering_comparison_c.jpg

Re: Glass Rendering-Compasrison

Posted: Tue Jan 16, 2018 9:34 am
by Dade
Can you post the test scene ?

There are many factors that could influence the outcome (like the Russian Roulette settings, etc.). It is hard to say looking only to the rendering. Anyway the BiDir result looks wrong.

Re: Glass Rendering-Compasrison

Posted: Tue Jan 16, 2018 9:56 am
by arzaquna
Thanks for your reply,
Here's the test scene
GELAS_luxcorev2.blend
(1.09 MiB) Downloaded 92 times

Re: Glass Rendering-Compasrison

Posted: Tue Jan 16, 2018 10:02 am
by B.Y.O.B.
Here it is as LuxCore scene.

Re: Glass Rendering-Compasrison

Posted: Tue Jan 16, 2018 12:53 pm
by Dade
I'm looking into the problem but a first side note: you are using a sphere made of 960 triangles as light source, it obliterates the rendering performance.

Are you using a "true" (i.e. analytical) spherical lights source in classic LuxRender (and probably in Mitsuba too) ? It doesn't explain why the end result is different but it may be a very good hint of where the source of the problem is.

Re: Glass Rendering-Comparison

Posted: Tue Jan 16, 2018 2:45 pm
by arzaquna
well, I'm just an inexperienced artist who put the default uv sphere and use it as a light source :lol: .But yes, I was using the same scene for classic luxrender as well as mitsuba

Re: Glass Rendering-Compasrison

Posted: Wed Jan 17, 2018 11:03 am
by Dade
I should have fixed the problem. It wasn't really a bug but a (bad) sampling problem. I have highly improved the way glass is now sampled.

I have slightly modified the scene to have shorter rendering times and to compare "oranges" to "oranges" (1 point light source instead of 960, removed the black body from the classic Lux scene, etc.).

This is a LuxCore rendering with the old glass code:
old.png
and this with the new one:
new.png
A quite spectacular difference in term of noise and quality :D

This is LuxCore Vs. classic LuxRender:
cmp.png
I can reproduce the BiDir problem with this scene:
bidir.png
But I'm quite sure it is a problem related to the 960 light sources and not the glass material. Going to check what is going wrong in that case.

Re: Glass Rendering-Compasrison

Posted: Wed Jan 17, 2018 11:04 am
by Dade
Dade wrote:
Wed Jan 17, 2018 11:03 am
I can reproduce the BiDir problem with this scene:
Typo: "I can't"

Re: Glass Rendering-Compasrison

Posted: Wed Jan 17, 2018 11:23 am
by Sharlybg
A quite spectacular difference in term of noise and quality :D
like comparing gazoil to EV cars ! OMG ve-----ry spectacular. are you sure it is in the same rendering time ?
Dade wrote:
Wed Jan 17, 2018 11:04 am
Dade wrote:
Wed Jan 17, 2018 11:03 am
I can reproduce the BiDir problem with this scene:
Typo: "I can't"
But do you now know what is going on ?

Re: Glass Rendering-Compasrison

Posted: Wed Jan 17, 2018 3:50 pm
by Dade
Applied the same solution to the architectural glass.

Old version:
oldarch.png
New version:
newarch.png
LuxCore Vs. classic Lux:
cmparch.png