Author Topic: Trying to mask out small random fractals in clouds  (Read 786 times)

Offline eapilot

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Trying to mask out small random fractals in clouds
« on: February 04, 2018, 03:46:14 PM »
I'm working on a 360 sky, as a and template for making skies in general, and I keep getting small wispy fractal bits that I can't mask out effectively.  Does anyone have any tips on how to better control this?  I am using a Cloud Density Fractal with large features and lead-in scale to mask out another density fractal with small features but it does not appear to mask out everything.  Jpg and tgd attached.

Offline eapilot

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Re: Trying to mask out small random fractals in clouds
« Reply #1 on: February 04, 2018, 03:47:06 PM »
here is the image

Offline luvsmuzik

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Re: Trying to mask out small random fractals in clouds
« Reply #2 on: February 04, 2018, 05:00:12 PM »
checking crop area with cirrus disabled  I think a Distance shader would lose too much in this nice setup and do not think it would help the area you are concerned with.

Taper top and base option with such high micro detail and AA may be the culprit.  Too bad there is not some conditional statement for that....or maybe there is.
« Last Edit: February 04, 2018, 06:02:09 PM by luvsmuzik »

Offline luvsmuzik

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Re: Trying to mask out small random fractals in clouds
« Reply #3 on: February 04, 2018, 06:06:51 PM »
Doing small crop now w/o taper top

Offline eapilot

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Re: Trying to mask out small random fractals in clouds
« Reply #4 on: February 04, 2018, 06:10:18 PM »
What do you mean by the taper top?

Offline luvsmuzik

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Re: Trying to mask out small random fractals in clouds
« Reply #5 on: February 04, 2018, 06:21:09 PM »
In cloud layer control box under TWEAKS....I am not sure if this extends the detail to those finger-like wisps or not.

Offline eapilot

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Re: Trying to mask out small random fractals in clouds
« Reply #6 on: February 04, 2018, 06:40:00 PM »
As for render settings, I'm not sure what the impact of microdetail is with clouds and atmosphere renders. As for AA, I would always render a final with the highest AA I can get away with between 6 to 12.  It is the single biggest factor in eradicating noise in a final render.  The AA of 6 is a kind of medium quality test render.  I got rid of other small bits by increasing the small features in the larger Cloud Density Fractal, but not completely.  Here is a snapshot of the macro cloud mask and the detail cloud mask.  In the lower right area of the detail map, there is a small flack of white that appears.  I would assume that this would be masked by the larger shape, unless there is more scalar information in the macro cloud mask that is not visible in the preview. 

Or it could be the taper!  I have never touched those settings.

Offline luvsmuzik

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Re: Trying to mask out small random fractals in clouds
« Reply #7 on: February 04, 2018, 08:46:31 PM »
I'm sure Matt can explain this much better than me. I get it about softening your mask and I use those previews too. These newer clouds if that is what you used are fun to experiment with but render times tend to slow that down. I agree the best resolution w/o excess noise is terrific!

Offline eapilot

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Re: Trying to mask out small random fractals in clouds
« Reply #8 on: February 05, 2018, 04:44:59 AM »
I'm sure Matt can explain this much better than me. I get it about softening your mask and I use those previews too. These newer clouds if that is what you used are fun to experiment with but render times tend to slow that down. I agree the best resolution w/o excess noise is terrific!
the tgd file that I uploaded does not use easy clouds because the render times are slower and I really don't know what the parameters do.  My new approach is focusing on node networks of fractals and simple shapes, not unlike substance designer, and then piping it into a cloud layer v3.  I am still trying to figure out if I can get the control that I want. As a skybox artist, my concern is also thinking about the 360 panorama, so I have to make sure that the noise patterns don't look too funky anywhere.

Online Dune

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Re: Trying to mask out small random fractals in clouds
« Reply #9 on: February 05, 2018, 07:12:50 AM »
Did you try changing the fractal noise variation? With the small preview in sight, you can often adjust the variation and clumping such that smaller stuff disappears. Then there's the gamma correction that might help. Or add a color adjust between fractal and sky and up the black a bit (unclamped). I don't know, but you could try.

Offline Oshyan

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Re: Trying to mask out small random fractals in clouds
« Reply #10 on: February 06, 2018, 02:00:41 AM »
Ooo, so there's lots of room for improvement here. It's going to be hard for anyone else to nail the look you're aiming for without a reference shot. But I think I can help with the smaller bits, and perhaps more importantly, I can give you some better render settings that will allow you to iterate and produce final frames faster so you can dial in the exact look you want much quicker. Assuming, that is, that you were using the "Test render FG Clouds" render node, which I don't know for sure as there are quite a few in here. ;)

I'll start with the render settings first. So first off, I want to note that I'm going to suggest one or two quality settings that will change the look of your clouds a bit. I think this is overall for the better (and you can adjust other things to compensate).

In particular you are using a very, very low Ray-Marching Quality value in one of your cloud layers, 0.075 I believe. That's going to really cause the renderer to undersample that cloud layer, especially relative to the other one which actually has a rather high value of 1.3 or so, so you're going to get an odd mismatch in quality, and will have to crank up AA to get low noise in your cloud layer with very low ray-marching quality. Instead I'd suggest a value of 0.5 or so for both, and use AA and the global Voxel Scattering Quality (GI in Clouds tab of Renderer) to get quality up where you want it overall.

Now increasing the Ray-marching quality is what's going to change the look of your clouds. It will make one of your layers look more dense, at least it did in my tests. You can compensate for this by reducing the offset in the density function if you want, or adjusting cloud noise function Coverage Gamma (Tweaks tab), or other methods.

AA of 6 should be fine for a cloudscape like this. One of your renderers had AA12, hopefully you're not using that. You also don't need more than 0.25 or at most 0.5 for Micropoly Detail since you have no terrain and you're rendering the atmo with Defer, which doesn't use the Micropoly at all. That being said reducing it won't save you much, if any, render time. Likewise you can turn off GI Surface Details in the GI settings since it only applies to *surfaces*, and again while it won't save a lot of time, it does avoid a post processing pass and possibly reduce memory when disabled.

Finally, I'd suggest you consider increasing Voxel Scattering Quality to 100 *if* you have noise issues at AA6. But the default of 50 may be fine depending. I just don't think you need to go above AA to get noise-free clouds here.

Now on to tweaking the wispy bits. It's a bit unclear to me which parts you are concerned with, so I tried to address issues in two areas and you can choose which settings to adjust accordingly.

For the dark gray wisps that seem to appear randomly *below* the main cloud layer, that's coming from a secondary layer, and if you just enable Clamp Low in the Density tab on the "Density fractal Cumulus cloud01_1" noise function, you get rid of those. There are probably other ways, and this may make other changes you don't like, but from what I saw in the crop render area it pretty much just got rid of those wisps alone.

Now for the patchy bits of the *other* cloud layer, there are a couple of things you can do, depending on how significant the issue is for your need. First, reducing Roughness is always a good thing to try when you have too many small bits. It will of course have an overall effect, but it does tend to especially produce those little "flyaway" bits. Another thing to consider early on is the minimum scale of your noise functions. 5 meters may not seem too small, but if your cloud layers are quite far away it could add some very fine, wispy detail like you see here, so increasing that minimum value to for example 20 will get rid of some of the finer scale detail. Now admittedly this removes some detail from other areas of your clouds too, but if that's not desirable then perhaps focus on Roughness and noise type.

Consider also adjusting Noise Variation, though this will change the coverage of the cloud layer, which you can compensate for if desired by changing the Coverage Adjust. I recommend changing it in the noise function(s) rather than in the Cloud Layer.

I've attached a TGD showing the effects of some of these settings changes, along with a couple of images. The image file name that corresponds to the .tgd shows how that one in particular looks, of course.

- Oshyan

Offline eapilot

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Re: Trying to mask out small random fractals in clouds
« Reply #11 on: February 06, 2018, 02:07:55 PM »
Now increasing the Ray-marching quality is what's going to change the look of your clouds. It will make one of your layers look more dense, at least it did in my tests. You can compensate for this by reducing the offset in the density function if you want, or adjusting cloud noise function Coverage Gamma (Tweaks tab), or other methods.

Thanks Oshyan.  This is all very helpful and there is a lot to unpack. I looked at your file and compared it to mine.  As for the offset in the density function, I am not sure what you mean by that.  Is it Cloud Density in the Cloud layer v3 node, or is it a Density Parameter in the Cloud Density Fractal Tab? 

I found out shortly after the email that reducing the roughness from 1.3 to 1 got rid of a lot of the wispy parts in the "Macro Cloud Shape" Cloud density Fractal.

Offline zaxxon

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Re: Trying to mask out small random fractals in clouds
« Reply #12 on: February 06, 2018, 02:11:54 PM »
An excellent explanation and much appreciated Oshyan. Good thread eapilot!

Offline luvsmuzik

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Re: Trying to mask out small random fractals in clouds
« Reply #13 on: February 06, 2018, 02:35:32 PM »
I also wondered about using soft shadows in a scene and if this effects the shadows in the clouds? I have been cranking up my soft shadows so I can see the forest for the trees....I was just curious since most cloud control boxes also have shadow function options.

Offline Oshyan

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Re: Trying to mask out small random fractals in clouds
« Reply #14 on: February 08, 2018, 12:13:19 AM »
The Density Function is the noise function (node/shader) that you are feeding into the Density Shader input of the Cloud Layer node. By default it is a modified Power Fractal (you've added some extra nodes but do still have the Cloud Density Shader in there with everything plugged-in to it). So in *that* node (the density shader that's similar to a Power Fractal), on the Density tab there is a Coverage Adjust. There is *also* a Coverage Adjust in the cloud node's settings, but that one affects all data coming into the Density Shader input, and does so in a different way that I feel is less optimal in many cases (you can test the difference yourself, you should see what I mean at higher values of each).

- Oshyan

 

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