Noise-aware Metropolis Sampler

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Noise-aware Metropolis Sampler

Postby SATtva » Thu Sep 13, 2012 12:37 pm

Daaaade? Please tell us about the new secret weapon of yours. :)

EDIT:
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Re: Noise-aware Metropolis Sampler

Postby J the Ninja » Thu Sep 13, 2012 12:49 pm

Ah, it's nice to be out of "release mode" again. :)




And yeah, Dade? Tell us about this thing you've been hiding for the past month. :)
-Jason
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Re: Noise-aware Metropolis Sampler

Postby jensverwiebe » Thu Sep 13, 2012 1:55 pm

I added button "Use NoiseAware" to luxblend25, rendersettings/advanced/noiseaware + haltthreshhold for testing.
Default is off atm. Not sure i set the threshhold right atm.

Cheers...Jens
Last edited by jensverwiebe on Thu Sep 13, 2012 4:30 pm, edited 2 times in total.
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Re: Noise-aware Metropolis Sampler

Postby B.Y.O.B. » Thu Sep 13, 2012 2:24 pm

What is this? I'm curious as hell :o
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Re: Noise-aware Metropolis Sampler

Postby jeanphi » Thu Sep 13, 2012 3:38 pm

Hi,

If I'm not mistaken, the new option modifies the acceptance probability of the samples based on pixel variance. So if you have low variance, the samples will be rejected more often so you can expect to sample more often high variance areas.
The sampling scheme however is not modified so if you set the large mutation probability to 1 it will continue to sample the picture uniformly and won't try to generate more samples in high variance areas.
When I saw the first commits of the series, I was really scared, but most of my concerns have been addressed in the following ones. The current implementation looks really interesting.

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Re: Noise-aware Metropolis Sampler

Postby B.Y.O.B. » Fri Sep 14, 2012 2:00 am

jensverwiebe wrote:I added button "Use NoiseAware" to luxblend25

Why not use the old "use variance" button in the Metropolis sampler settings? AFAIK it was never working, jeanphi said something about that once.
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Re: Noise-aware Metropolis Sampler

Postby jeanphi » Fri Sep 14, 2012 2:17 am

Hi,

If the new scheme works well, I think that the old variance stuff can be safely removed.

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Re: Noise-aware Metropolis Sampler

Postby Dade » Fri Sep 14, 2012 2:36 am

SATtva wrote:Daaaade? Please tell us about the new secret weapon of yours. :)


Hehe, yes, I was waiting for the 1.0 release before to push the branch. I'm going to write a long explanation in the weekend. The new branch include 3 new features:

1) A new halt condition (i.e. "haltthreshold"): it will stop the rendering when the human visual system will not be able to tell the difference in adding more samples (when using haltthreshold=0.0). I'm still thinking to name this option HaltWhenCarbonFluxed :lol:

2) Multi-stage noise-aware Metropolis sampler: a noise driven metropolis sampler (instead of luminance driven as usual).

3) User driven sampling: it will possible to paint over the rendering where the zone with more noise are and where the sampler should spend more work. This has probably been one of the most requested feature in the past.

I have a mixed feeling about #2 at the moment but it opens the door to #3 so it is useful anyway.
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Re: Noise-aware Metropolis Sampler

Postby Dade » Fri Sep 14, 2012 2:43 am

jeanphi wrote:When I saw the first commits of the series, I was really scared, but most of my concerns have been addressed in the following ones. The current implementation looks really interesting.


Yup, I have done a lot of tests but the general idea was to obtain 3 new features listed above. They are "coupled" (i.e. noise-aware Metropolis requires haltthreshold condition, etc.) at the moment but I'm going to de-couple them very soon.

BTW, if anyone is interested to work on the LuxRender GUI to support the feature #3, let me know (I'm not very familiar with GUI code). I have exposed #3 via a new Lux API call.
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Re: Noise-aware Metropolis Sampler

Postby SATtva » Fri Sep 14, 2012 3:37 am

Dade wrote:3) User driven sampling: it will possible to paint over the rendering where the zone with more noise are and where the sampler should spend more work. This has probably been one of the most requested feature in the past.

Whoa! It certainly is.
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