Direct Light Sampling Cache errors

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Sharlybg
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Re: Direct Light Sampling Cache errors

Post by Sharlybg » Wed Nov 07, 2018 8:53 am

Very strange, I will check: it sounds like some kind of normal-related problem (aka taking light from "down" instead of "up").
This remind me of a problem i had recently encountered light passing through et glossy solid object. Will post it.
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Dade
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Re: Direct Light Sampling Cache errors

Post by Dade » Wed Nov 07, 2018 10:26 am

Dade wrote:
Tue Nov 06, 2018 10:22 pm
kintuX wrote:
Tue Nov 06, 2018 8:29 pm
2. It gets more prominent with 'Use Ground Color'.
Very strange, I will check: it sounds like some kind of normal-related problem (aka taking light from "down" instead of "up").
The sky colors were really flipped upside down in sky2 direct light sampling. I have fixed this problem and now the scene renders fine when using matte material:

matte.png

however there is still a problem when using glossy material like in the original test scene:

glossy.png

I'm investing this (different) problem.

A couple of notes about the original scene:

1) the scene is more than 100m large, you can safely use a cache radius of 1m instead of 15cm. The pre-processing will be a LOT faster.

2) Sky, like all environmental light sources, can be very hard to sample so raise the cache warmup samples count to something like 256 (instead of default 12) or you will end with wrong cache entries like shown here:

prob.png
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Asticles
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Re: Direct Light Sampling Cache errors

Post by Asticles » Wed Nov 07, 2018 10:50 am

Thanks for the tips Dade
Salvador Ureña

kintuX
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Re: Direct Light Sampling Cache errors

Post by kintuX » Wed Nov 07, 2018 5:01 pm

Yes, thanks for the fix, tips and tricks ;)

******************************************************************
BTW, i can't produce artifacts/splotches anymore :?
Clear glossy surface, Sun & Sky with White Ground

Tried many different values on DLSC:
1. Entry Radius: 0.15 - 0.60 (15 - 60 cm)
2. Warmup Samples: 12 - 16
3. Max. Depth: 2-3-4
4. Max. Samples: 100000 - 10000000 (1-10 million)
******************************************************************

:!: Aha, artifacts appeared! with Glossy Material Roughness set to Max. (0.8) ;)
As the Roughness is lowered, their appearance diminishes & from the looks, appear to be "gone" once the value goes below 33% (< 0.25).

Glossy Material Roughness comparison:
DLSC MG Rough 025vs080.GIF

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Dade
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Re: Direct Light Sampling Cache errors

Post by Dade » Wed Nov 07, 2018 7:12 pm

kintuX wrote:
Wed Nov 07, 2018 5:01 pm
:!: Aha, artifacts appeared! with Glossy Material Roughness set to Max. (0.8) ;)
Yes, it is what I was observing, I was using 1 in image above, another quite strange problem.
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Asticles
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Re: Direct Light Sampling Cache errors

Post by Asticles » Wed Nov 07, 2018 8:14 pm

Thanks Dave for your support.
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Dade
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Re: Direct Light Sampling Cache errors

Post by Dade » Sun Nov 11, 2018 9:57 am

I give up, I looked in this problem for days. It is related to MIS and Glossy direct light sampling Vs Glossy directly light hitting PDFs but I haven't found anything wrong inside the code. I will list it as a known problem: https://github.com/LuxCoreRender/LuxCore/issues/158
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lacilaci
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Re: Direct Light Sampling Cache errors

Post by lacilaci » Sun Nov 11, 2018 10:39 am

Dade wrote:
Sun Nov 11, 2018 9:57 am
I give up, I looked in this problem for days. It is related to MIS and Glossy direct light sampling Vs Glossy directly light hitting PDFs but I haven't found anything wrong inside the code. I will list it as a known problem: https://github.com/LuxCoreRender/LuxCore/issues/158
is this only sky/env light related issue?

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Re: Direct Light Sampling Cache errors

Post by lacilaci » Sun Nov 11, 2018 10:52 am

btw, visibility map off makes the issue less visible too. But also visibility map is somehow changing the lighting.

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Re: Direct Light Sampling Cache errors

Post by lacilaci » Sun Nov 11, 2018 11:01 am

So I did few quick tests on the scene provided in this thread, I don't get the issue when I use HDRI, I don't get the issue when use sky and disable sun and I don't get the issue with sun&sky if I disable glossy visibility for the sun!

EDIT: nope.. disabling sun glossy didn't fix it.. But at one point the issue was gone.. wtf

EDIT2: Ok so it is actually sky reflection that does this not sun. disabling glossy visibility for sky makes the issue go away

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