Cloud borders, help needed.

Started by René, March 22, 2020, 04:11:28 am

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René

Does anyone have any idea how I can make tight cloud borders, so without those loose tufts? I've tried all kinds of things, like masking and combinations with the merge shader. Unfortunately, no success.

mhaze

March 22, 2020, 05:26:05 am #1 Last Edit: March 22, 2020, 05:29:58 am by mhaze
Try Making smallest scale in the clouds Density Fractal larger? Reduce Roughness in the colour tab  and octaves in the scale tab.

Dune

Base whispiness also makes small clouds, so reduce that to zero, I'd say.

René

Sounds all plausible. I'll give it a go.

Thanks!

WAS

I have struggled with this too. Getting tight clouds that don't have totally smooth polished borders is tricky.  I think the best option is to use a soft cloud fractal with high small scale as mhaze suggested. You can than create another density fractal masked by your smooth cloud fractal with more normal settings; your detail fractal. Then you an add multiply that detail to the soft clouds, then maybe multiply by the detail clouds or something. Of course you'll still have the challenge of random large blobs wanting to disconnect from the main noise.

Hope that makes sense.

WAS

March 23, 2020, 05:15:01 pm #5 Last Edit: March 23, 2020, 05:33:25 pm by WAS
Here's an example with some border roughness via coverage.

Because of the chaos of the noise shaders, and not being built from a floor up for clouds (not all clouds have a tight base) I'd suggest using simple shape shaders to create meta cloud areas with unique looks, and mix them together. You can cut down on random chaos in a full cloud layer like plumes detached or detaching looking like liquid effects.

It's possible thick coverage in the cloud densities masked by a soft PF could cut the clouds with minimal plume balls without setting up unique seeded meta cloud areas.

René

Quote from: WAS on March 23, 2020, 04:59:45 pmI have struggled with this too. Getting tight clouds that don't have totally smooth polished borders is tricky.  I think the best option is to use a soft cloud fractal with high small scale as mhaze suggested. You can than create another density fractal masked by your smooth cloud fractal with more normal settings; your detail fractal. Then you an add multiply that detail to the soft clouds, then maybe multiply by the detail clouds or something. Of course you'll still have the challenge of random large blobs wanting to disconnect from the main noise.

Hope that makes sense.
Thank you, Jordan.
I have already experimented with combinations of detailed clouds and soft clouds. The idea was to mask the loose tufts and remove them from the contours. That could probably work if the clouds were 2D.
However, I have now turned off 'taper top and base' and adjusted 'Falloff' and 'Value at radius', which makes quite a difference.
Normally all this wouldn't be such a problem, but I'm now trying to create thick clouds with sharp edges, which makes those tufts very annoying.
I wonder why real thick clouds have such tight edges. Is it because they are heavier and thus have more gravity that holds everything together? If so, could this be built into a fractal?

https://upload.wikimedia.org/wikipedia/commons/b/b0/Forest_Fire%2C_Lake_One%2C_Ely%2C_MN_-_panoramio.jpg

Dune

Yeah, building clouds like that is the holy grail in TG. There must be a way, but it should be inside the software, not in working the fractals, I think. Total overhaul.

WAS

Perhaps if you invert your noise and adjust black point / white point and than harden it up (multiply or something) and try to mask the main fractal in a surface layer you may be able to mask those out, since they are softer noise.

I'll do some more tests in the AM. Too tired after dealing with the public panicking. Just trying to get some milk for my kid. Lol

Ideally a "mode" for a PF or something would be better. That would be awesome.

René

I am curious on how you're going to do that. According to my reasoning, the cloud is volumetric and therefore the mask as well. So not only the contours - which are viewdepending - but the whole cloud will be stripped of bulges (tufts). Maybe a 2d projection of the mask from the camera angle could be the solution. :)

René

Quote from: Dune 25-3-2020 12:15:34

    Yeah, building clouds like that is the holy grail in TG. There must be a way, but it should be inside the software, not in working the fractals, I think. Total overhaul.



There is also something else going on: some clouds, like volcanic eruptions for example, are curled inwards. That seems difficult to me with a fractal, that would probably only be achievable with simulation.

Dune

I've also tried starting with a simple cloud and bulging the (smooth) edges out by vdisp or redirect.

WAS

March 26, 2020, 12:46:58 pm #12 Last Edit: March 26, 2020, 01:24:51 pm by WAS
Even in 2D space the masking is the same..we're trying to make out the soft loose stuff you circled, with colour adjusts you can isolate just that while leaving harder shapes alone. It seem difficult though, while you can mask out smaller detail like you circled, it roughs up, and creates more into the harder shapes  Best method really just using large shapes and seeds without much of the issue present.