Author Topic: Noise limit's limitation?  (Read 5724 times)

2016-05-19, 10:47:44

romullus

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Now, that adaptivity is enabled by default, we are supposed to use noise limit to get equal quality over range of images. Usually it works great, but i just ran into situation, where i can't get acceptable results using noise limit. Moreover, i can't achieve that neither with pass nor time limit when adaptivity is enabled.

Here's my situation: i want to render very simple animation, where bunch of objects gradually fills blank white background. At first few frames, where empty background predominates image space, noise limit (5%) is achieved very fast, and adaptivity has no chance to kick in. Obviously few objects that gets rendered at that time, becomes very noisy. At some point, where more objects fills in image space, adaptivity finally gets chance to do its job before noise limit is reached and at that point, jump in quality between two neighbour frames, is very drastical (see attached gif). I could try to fiddle with noise limit, but i can never acvieve fine balance between acceptable noise and acceptable render time in this particular situation. Pass and time limits won't work here too.

Eventually, i choose to turn adaptivity OFF and used pass limit to render animation with all frames being equall in quality. But if i'm not mistaken, Ondra wants to remove non adaptivity and/or pass limits at some time, so i think situations like these should be taken into consideration before removing old features.
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2016-05-19, 11:04:22
Reply #1

Lucutus

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in your example the two neigbouring frames one is rendered with 5 the next one with 10 passes.
The noise level is updated every 5 passes. i guess this would get much better if the noise level would be updated every pass.

What happens when you set your noise level to 2? in this case i guess there could be enough passes to avoid the big jump you have.

Greetz

Lucutus

2016-05-19, 11:30:44
Reply #2

romullus

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If i set noise limit to 2, render time at latter frames, where there are more lemons in frame, would be unacceptably high.

As for adaptivity recalculation rate, i didn't test it in this scene, but from my previous experience, setting it to low values have negative impact on render time as well as adaptivity quality. But i'll give it a try this time and will see if that helps.
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2016-05-19, 11:49:32
Reply #3

Lucutus

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i guess this is a special case. if your noise Level would be reached after 50 passes or something i guess nobody would recongnize the difference.
Please inform us about your results.

Greetz

Lucutus

2016-05-19, 17:13:38
Reply #4

maru

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How about setting noise + time limit? So if noise limit X is reached before time Y - stop render. If time Y is reached before noise limit X - stop render. Does it make sense?
You could also try lowering adaptivity recalculation interval.
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2016-05-19, 17:19:40
Reply #5

romullus

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I don't think that pairing noise limit with time limit, makes much sense in this situation, because a. it would lead to unequal quality of frames and b. that could require too much time to find best configuration of those limits.

As for adaptivity recalculation, i will do some tests later and will let you know if i'll manage to get satisfying results.
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2016-05-19, 17:31:19
Reply #6

pokoy

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Interesting example. I have limited experience with adaptivity in production and need to test it more but from brief tests on production scenes I can tell that it behaves strangely in some cases. I get super long render times for the same amount of passes or visually more prominent noise for the same render time, there's no benefit at all. Not to derail the thread but just to confirm and support the notion that adaptivity needs to be optional and not hidden from the UI.

2016-05-19, 18:21:27
Reply #7

romullus

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I was about to start my tests with adaptivity recalculations, when i realised that it won't help in this particular situation - thing is that first few frames gets finished before adaptivity can even begin its job, so fiddling with recalculation rate won't change a thing here. Lowering noise level limit is not an option, because 5% limit gives acceptable quality for me and lowering it, would rise render times way too much. Combining noise, pass and/or time limits wouldn't help either, because that way i couldn't achieve equal quality. Seams like the only option is to turn adaptivity OFF. That's where noise limit without adaptivity could make sense ;] https://forum.corona-renderer.com/index.php/topic,11823.0.html

Not to derail the thread but just to confirm and support the notion that adaptivity needs to be optional and not hidden from the UI.

Don't worry, i started this topic because i want to find the best way to control image quality when rendering animations in tricky conditions. So everyones experience is more than welcome.
I'm not Corona Team member. Everything i say, is my personal opinion only.
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