Biased path, noise etc...

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Rainydaylover
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Biased path, noise etc...

Post by Rainydaylover »

Hello all there, congratulations for your renderer! Yesterday I experimented with it for the first time in Blender. Its description of the scenes is of a very high quality indeed. The only problem is the noise. Especially, when there are caustics in the scene the problem becomes very heavily felt. Maybe someone has to heighten very much the amount of samples but then there appears the problem of very huge rendering times. What can be done with this problem? What are the best settings for avoiding, as much as possible, it?

Btw, I did see in various discussions about a 'biased path' choice thing... what is it about, does it have any relation to quick, noiseless rendering? And if it is so, where in the Blender's Luxcore setting panels it can be found? I searched for it carefully but I did not find any such setting choice anywhere. Is it there or it is a setting existing only in the older Luxrender's tabs?

Thanks in advance for any help! : - )
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B.Y.O.B.
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Re: Biased path, noise etc...

Post by B.Y.O.B. »

Biased Path was renamed to Tiled Path.
In BlendLuxCore it can be enabled by setting the engine to Path and enabling the "Tiled" checkbox (all in the LuxCore Config panel in the render properties tab).
However its only advantage over Path is that it uses less RAM for storing the film, otherwise the two are mostly the same.

To give good advice about render optimization it would be good if you could upload the scene that is making problems.
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Dade
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Re: Biased path, noise etc...

Post by Dade »

B.Y.O.B. wrote: Sun Apr 22, 2018 3:00 pm To give good advice about render optimization it would be good if you could upload the scene that is making problems.
Or, at least, a rendering.
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batstick
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Re: Biased path, noise etc...

Post by batstick »

My experience with caustics is to use the BiDir CPU engine. CPU isn't going to be as fast as a good GPU. But with GPU Path Tracing the only option is to brute force through the caustics with Metropolis and a lot of samples with a lot of GPUs. Here is an example scene with just a monkey head:
5 minutes on a six-core CPU with BiDir:
bidir 5 mins.png
5 minutes with 5 GPUs with Metropilis + Path Trace:
path 5 mins.png
As you can see even with 5 GPUs it looks extremely noisy.
The only other option is to remove the caustics from the scene by using rougher materials or architectural glass etc. If anyone else has anything better to say please chime in. I am not an expert.
Rainydaylover
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Re: Biased path, noise etc...

Post by Rainydaylover »

Thanks all for the so quick answering! I would never think by myself that 'Biased Path' was renamed to 'Tiled Path'. : - ) Now, as to the information about CPU-GPU and the using of architectural glass, this too is very precious.

I will inspect the whole matter more carefully and send my questions by attaching the related files. Thanks again!
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Dade
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Re: Biased path, noise etc...

Post by Dade »

batstick wrote: Sun Apr 22, 2018 3:07 pm The only other option is to remove the caustics from the scene by using rougher materials or architectural glass etc. If anyone else has anything better to say please chime in. I am not an expert.
Another option is to use a point light so a path tracer will just unable to rendering caustics. You can also use some heavy variance clamping to cut down path tracer caustic noise.
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