How to cover "seams" between cloud layers?

[N-drju]

I try to construct some interesting clouds using the localise option. I use one cloud layer with "tapper top and base" turned off, to get clouds without smoothing effect. Then, I use one more cloud with "TT&B" checked on to create smooth finishing touch to its top (which would otherwise be flat). Both clouds are of the same size and use the same fractal.

While the shape of the cloud made that way is satisfying, there seems to be a problem with clouds' shades that vary unbelievably. The border between the two is evident as you can see...

How can I retain the shape of these clouds and make the color uniform? I cannot check TT&B back in the first layer, because then the cloud will be smoothed-out and loose lots of height. :/

[attach=1]

[Oshyan]

I'm not sure what's happening here is really "incorrect". You would need to make the cloud shapes and area of coverage truly overlap (in the density function, node the localize area). It's hard to say that from the image it is really behaving incorrectly...

- Oshyan

[Hannes]

I vaguely remember Matt writing somewhere that the cloud layers don't "talk to each other" yet, but I'm not sure if he was talking about clouds in general or just specific ones.

[Matt]

I vaguely remember Matt writing somewhere that the cloud layers don't "talk to each other" yet, but I'm not sure if he was talking about clouds in general or just specific ones.

That was true in earlier Alpha versions. In the Beta and final release multiple clouds do transport light to one another. However, it doesn't work with the same spatial resolution as light transport within a single layer and it uses a different algorithm, so this could lead to visible differences.

N-drju, in your render I find it difficult to see whether this is what's happening or whether the cloud densities just aren't blending seamlessly. Do you have any other examples?

Matt

[N-drju]

Hello Matt and other Terragenists.

Sorry for bringing this topic up again after so long but I'm experimenting with clouds again and the problem persists. The differences between the clouds are sickening... This shot was taken with two localised cloud layers. The bottom one, has tapper top & base option unchecked. The top one too + it has invert profile option checked. The camera was placed at the altitude where two cloud layers touch each other. They overlap just slightly (6 meters).

Apart from that those clouds have all values at their defaults!

I attach a picture. As you can see this is a mess from top to bottom... And I mean literally!

[attachimg=1]



I forgot to mention that both cloud layers use exactly the same fractal to make the overall shape seamless.

[Dune]

Ì think it's quite logical that things like this happen because the different settings make different lighting computations, resulting in 'different' clouds. With such a small overlap it will be extra noticable.

[N-drju]

Well, with an overlap of 400 meters this was just the same. See top picture.

All I actually need are tall clouds that fill up to the top of their altitude instead of being cut short, staying in the middle of the localise area, like it always happens when TT&B is on. I don't care how. I just need tall clouds that are not pillow/pancake shaped.

If you have any idea on how to do this, or how to resolve the top cloud casting shadow on the bottom one like in the picture above - don't be shy an please come forward.

[Dune]

So, what if you build from one cloud and use soft simple shapes (central in localized cloud), some pf as mask and altitude settings (distri shader) and perhaps some warp to decrease/change clouds at certain levels? I'd go for that sort of option (for the time being  ).

[N-drju]

Okay, so I tried to restrict "high" areas with SSS and it's getting better in terms of shadows and coloring. Might help, but I'm still not entirely satisfied with it. The problems now include:

1. The area affected by the "smooth stepped" SSS seems to be too sparse compared to the rest of the cloud. This is especially true for higher percentage values.
2. Not really sure how to remove the flat top of the high part of the cloud. How can I make it more cone-like / distorted?

See the pictures...

[attach=1]                                  [attach=2]
SSS smooth step at 15%                                 SSS smooth step at 40%



One more example. Not bad if only I could "wispify" the top part. Also, unchecking the "invert profile" box (which I used for previous images) somehow makes the top part more visible even at high "smooth step" values.


[attach=3]

[Dune]

You could try a warped spherical distance shader and some PF masking to get rid of the top flatness. Just thinking theory. But you'd have to add white to the bottom again or that will be affected by the distance. Camera should be somewhere in the center of the cloud, I think. And what does bevel do instead of smooth step, it might be better.

[N-drju]

Getting better I guess. I used bevel restriction for this picture and as you can see the edges are much smoother now. The problem with this option is that you need quite high values (more than 90%) to actually get this kind of look on the cloud. But it's not that bad. A lot of cloud got cut off unfortunately... But that's probably because I used really high percentage value this time. But I think it looks decent? What do you think?

[attach=1]

Also, I think I won't try this distance shader thing. This can be very time-consuming and would require altitude calculations. Calculations on a part of the cloud, not even the whole layer.

I just don't understand why it has to be so difficult... Joining two cloud layers would have been easier to handle and control.

[Dune]

Looks better indeed, but I would seriously try the distance shader option. It might not be that difficult.

[N-drju]

Unfortunately it is. I am completely lost here. I get how distance shader works but have zero idea whatsoever how to warp it and with what to warp it. None of the warp shaders seems to do anything...

Besides, how am I supposed to mask distance shader with PF when it has no mask input socket...?

[N-drju]

I tried that distance and camera thing but it just won't work. I don't get what and where should be warped. Ughhh...

I start to think that clouds are one of the features of Terragen that are still poorly designed. By default, localised clouds no matter how deep, always stick to the middle of the area and this is the source of all problems if you want to build greater, more diverse clouds. I mean, what's the use of unchecking TT&B option since you end up with unnatural, flat cloud tops that you still need to work on?

I guess that before long I'll be back to using dandelO's metacloud solution. Seriously, for big, complex-shaped clouds this is one of the best and easiest solutions I have seen in a long time... Nothing better was invented since, like, 2007?

[Dune]

I can't tell you much  , but this may work for you. I vaguely remember that I got a distance shader to be warped somehow, but you're right; it's not straightforward. This setup can be warped. In the vector you can set the location, the smooth step makes a soft circle. This can be used as mask.