BlackBox and Light Leaking

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Dade
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Re: BlackBox and Light Leaking

Post by Dade » Sat Mar 02, 2019 7:58 pm

marcatore wrote:
Sat Mar 02, 2019 4:31 pm
Did you already uploaded it?
I've downloaded the last build now and it crashes again.
It was fixed in this commit: https://github.com/LuxCoreRender/LuxCor ... d1e5a6acce ("PhotonGI can now render black rooms"). It depends if you are using a build from that commit or not.
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marcatore
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Re: BlackBox and Light Leaking

Post by marcatore » Sun Mar 03, 2019 10:00 am

I've used the last build avaiable on the daily build release channel.

Coming back to the thickness I'd like to understand, a bit for my culture and a bit to find a reason to switch my modelling workflow, if that bright pixels in a closed room is a standard behaviour for a path tracer or not.
I will not insist forever about this but I'm quite sure to not be the only one on the CG world that models an interior without thickness, I'm quite sure that when the userbase will grow, this matter will arise again.

Thanks for any further explanation.

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Dade
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Re: BlackBox and Light Leaking

Post by Dade » Sun Mar 03, 2019 10:11 am

marcatore wrote:
Sun Mar 03, 2019 10:00 am
Coming back to the thickness I'd like to understand, a bit for my culture and a bit to find a reason to switch my modelling workflow, if that bright pixels in a closed room is a standard behaviour for a path tracer or not.
It is quite common in any ray tracer. Of the many million of rays traced, some will pass exactly between the 2 edges of adiacente triangles. It is due to numerical error. Floating point numbers have finite and also variable resolution: there is more values near the zero. For instance, moving the same model far from the zero can lead to leaks, changing the scale too.

It is about the same problem of having 2 overlapped triangles: they will fight for who is the nearest and, due to numerical errors, sometime will win one and sometime the other so you will end with a mangled mix of both.
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Re: BlackBox and Light Leaking

Post by marcatore » Sun Mar 03, 2019 10:22 am

Ok, but why , for example, Cycles seems doesn't suffer of this? Comparing the same scene with the same dimensions, position, scale and so on?

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Dade
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Re: BlackBox and Light Leaking

Post by Dade » Sun Mar 03, 2019 10:51 am

marcatore wrote:
Sun Mar 03, 2019 10:22 am
Ok, but why , for example, Cycles seems doesn't suffer of this? Comparing the same scene with the same dimensions, position, scale and so on?
For instance, it depends on default epsilon settings.
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Re: BlackBox and Light Leaking

Post by marcatore » Mon Mar 04, 2019 7:35 am

I've never touched that settings from the defaults.

And as scale I use 1 blender unit as 1 meter for every my Blender.

But that epsilon settings, in Cycles is not changeable or exposed.

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Re: BlackBox and Light Leaking

Post by B.Y.O.B. » Mon Mar 04, 2019 8:01 am

I think Cycles uses epsilon 1e-5 or 1e-4, it's a bit hard to tell:
https://github.com/dfelinto/blender/blo ... bvh.h#L346
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