Strange banding in Clouds

Started by cyphyr, December 17, 2011, 11:22:55 am

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Tangled-Universe

December 27, 2011, 04:38:09 pm #30 Last Edit: December 27, 2011, 04:51:56 pm by Tangled-Universe
I'll show you another example...it's a crop from my Dutch Landscape WIP you know about...I will render it now using 32 atmo samples and 32 cloud samples (det 0.82) with AA8 and detail 0.8 and GI 1/2/6 in the renderer. I'll compare it with RTA @ AA8 with 1 atmo sample and 4 cloud samples.

In my previous test AA4 allowed for a 2-fold reduction of cloud samples and since AA8 is 4 times "better" than AA4 ((8x8)/(4x4)=2) I estimate an 8-fold reduction of cloud samples should be ok.

Tangled-Universe

Here it is...
Notice the slight slight slightly more noisy atmosphere, but especially notice the quite different looking clouds!
Rendering it now with RTA and 2 atmo samples + 8 cloud samples...see what it takes to make it look as good as RTA OFF :)

When it comes to practical examples I think it can't get any closer than this.
It's a difficult lighting situation, requiring good sample settings and it has objects which justify using high AA levels and thus even more carefully chosen sample levels for atmosphere/clouds. As this test shows AA8 doesn't offer extreme reduction in samples as it is already slower and inferior in regards of cloud-rendering.

This fits with the previous example which showed atmosphere rendering comes cheap and clouds don't...

Tangled-Universe

Getting closer with 2 atmo samples and 8 cloud samples...took exactly 18 minutes:

Tangled-Universe

Last one...now with 12 cloud samples and still 2 atmo samples...
It turns out I have been lucky with the 1 and 2 atmo samples, since this "seed" shows I was short on atmo samples.
Clouds are nearly the same, but rendertime was 32m37s.

Logically I won't push this further...I think/hope the examples are clear enough.

Cheers,
Martin

Oshyan

I guess I'll have to wait until my own re-tests are finished to comment with anything useful. All I know is in the past my findings have been different than what you show, so it's very surprising to me. Definitely worth more investigation.

- Oshyan

Tangled-Universe

Well, I'm a bit surprised too since I too remember we tested some stuff together "in the beginning"...at least we discussed in detail how this would be benificial and how the approach should be, for hours even :)
Nonetheless it turns out that it somehow doesn't hold, but frankly I don't understand why this happens now.
Not that I think it has to do with changes in TG2, but the only reason I can think of is that we tested it too artificial and not enough in practical situations. Perhaps.