How to spread clouds over the surface in a custom shape?

Started by Aleksei, January 08, 2017, 04:08:04 am

Previous topic - Next topic

Aleksei

Hi!
Can you, please, help me and give some keywords for further research.
I'd like to have a full control over the cloud coverage and edit it manually (not just generate). I want to be able define the shape of the cloud coverage spread over the Earth surface. I don't know whether it is possible or not, but ideally, I want to be able to combine alpha textures with hand painting (using graphic tablet).

The look I want to achieve is this:



On top of that, I'd like to know how you, guys, define the shape of vertical development of clouds? For me it was always a mystery. For example, in the reference image we can see very many different types of clouds. Moving from the left hand side of image to the right we see how the clouds change shape from lonely noisy clusters of cumulus clouds to dense stratocumulus. At the same time the blending between the cloud types is very organic and I can't tell that this is just 2 different cloud objects overlapping each other.

Thank you for you knowledge in advance!
Multi-purpose Design Tool: • NORDSKILL •

bobbystahr

Have you tried the Vortex shader between the Density shader and the Cloud in the node view?
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist

Oshyan

That particular image actually uses an image-based mask derived from real-world orbital imagery. You can combine such masks with procedural cloud shapes in Terragen and get results like this. The different "types" of clouds are mostly driven by the actual shapes in the original, real-world imagery, and less due to any fancy Terragen cloud shaping. Such things are possible in TG, but more time consuming and challenging to create vs. just using actual real-world data like this.

Hand-painted masking is possible in Terragen with the Painted Shader, but control is somewhat limited. If you want a really nice painting experience you would need to create the mask in another program then import it.

- Oshyan

Aleksei

I was playing with image mask and the result is not so good yet. The most confusing thing is this (I've marked the most vivid problems):



I assume that this is because I've made my clouds very tall. And in those parts where the clouds were spread in texture like small dots we now have columns of clouds. (maybe I'm wrong). Here is the cloud mask for this region:



Those small clouds in the middle are the same that marked with the shortest arrow in the 1st image.

If that's the problem, is there a way to control the height of the cloud depending on the radius of mask? Maybe I'm asking too much, but maybe there is something like on the image below? Unfortunately, I couldn't find Terragen 4 manual or reference to study from.




And one more thing.
I used PixelPlow render farm to render this 4K image. After the render was finished I noticed patterns (marked on the images below). Looks like different computers in render farm couldn't synchronize their calculations. Is there is something that I can change or should I write to PixelPlow?




Multi-purpose Design Tool: • NORDSKILL •

Oshyan

The brighter and sharper (higher contrast at the edges) the elements of your mask are, the taller they will be. Very small clouds should in general not be so tall and so they need to be less bright (more gray than white). I would suggest decreasing brightness on those smaller shapes to fix the 'column cloud' issue.

As for the tile edge issue you're seeing on renders at PixelPlow, it's a little unclear what is causing it, but there are a few options to try. You can test these locally by just using adjacent crop regions, so you don't have to spend money at PixelPlow for tests.

First, try disabling "Use voxels for shadows". If this fixes the issue, then it's probably due to issues with the sampling of direct lighting (as opposed to GI) which is causing variations between tiles in what shadows are cast. So you can either increase cloud Quality to hopefully reduce the tiling artifacts, or just not use voxels for shadows. Both will increase render times, but one may be better than the other as far as a quality vs. render time balance.

If disabling "Use voxels..." does not help then it is probably a cloud GI issue. You can try increasing Cloud GI quality and see if that helps.

- Oshyan

Dune

I wonder why those tall clouds are on an angle. I'd say it's not near the northpole (0/0/0), and the mask is projected on Y, instead of spherical. Could that be?

Aleksei

Thanks, Ohyan, I'll amke some tests.

Dune, yes exactly. The clouds are somewhere above Nevada (if 0/0/0 is North Pole). The mask is projected on Y, but it is not global. I applied square mask only for this specific region. Do you think if I change it to Spherical it won't cover the entire Earth and will fix the tilted clouds?
Multi-purpose Design Tool: • NORDSKILL •

Dune

No, that wouldn't work, as you'd have to make this part of a complete global mask. If you know how to do that, that would be best.
What you could try is get the angle/slope of the surface near the center of the map (by hovering over the preview or perhaps rightclick (off my head, so I don't know exactly), and try to project the mask on that angle from a camera hovering over that same center. A bit tricky, I admit, and the edges will still have those outwardly angled clouds I suppose, depending on how big the mask is. And you'd have to figure out the height over the terrain to get the right coverage. I don't know if you can tilt the image map (set on Y) shader with a transform shader (filling in the angle variables somehow), if so, that could be an option.

Aleksei

And is it possible to apply spherical projection for the entire Earth, but limit the degree of the projected texture  to something like 10° ?

On image below I've applied spherical projection, but limited the width of the texture to 9%, which is 32.4°. And the same with height.



For example, in this topic Kyl once suggested me to split one texture into 2 pieces and position them accordingly on the globe. I didn't do that trick yet. But now, when I'm trying to do something similar and cannot find the necessary settings.

What I have now:
1 image: the clouds are tilted along the green arrow (Y).
2 image: I tried to apply the spherical projection and set coordinates the same as cloud object has. And I'm almost there! I just cannot figure out what size of the texture do I need in this case. I was playing with different values between 0 and 1 and it always looked like random part of texture.







Multi-purpose Design Tool: • NORDSKILL •

Mirror

Quote from: Aleksei on January 11, 2017, 04:43:14 am
And is it possible to apply spherical projection for the entire Earth, but limit the degree of the projected texture  to something like 10° ?

On image below I've applied spherical projection, but limited the width of the texture to 9%, which is 32.4°. And the same with height.



For example, in this topic Kyl once suggested me to split one texture into 2 pieces and position them accordingly on the globe. I didn't do that trick yet. But now, when I'm trying to do something similar and cannot find the necessary settings.

What I have now:
1 image: the clouds are tilted along the green arrow (Y).
2 image: I tried to apply the spherical projection and set coordinates the same as cloud object has. And I'm almost there! I just cannot figure out what size of the texture do I need in this case. I was playing with different values between 0 and 1 and it always looked like random part of texture.






Hi,.
    I think you should try terragen global clouds and mask them with spherical texture if you want to render earth from distance.

Dune

That would be easiest indeed.

One more thing I can tell you (I don't have much experience with global clouds) is that you indeed can change the angle of an image map, but you have to do it from 0/0/0 like this. This is way off center, more near equator. Perhaps that would be the best way for you. But I don't know if the clouds will 'stretch' perpendicular to the planet, but I guess the do alright.

Oshyan

What Kyl was probably suggesting is to use a Geog Image Map Shader and manually georeference it so it covers half the planet. You could do the same with your image map for clouds, but it can be tricky to get the right positioning unless you understand Lat/Long position value well.

- Oshyan

Aleksei

Thank you, everybody! I've got answers for the main questions.
And I now have a new one.
Is there an opportunity mo make a Cumulonimbus clouds?



The only one solution I see now is to make 2 clouds: one above the other. Where the upper cloud will have inverted profile:



But I'm afraid that with this approach all clouds will look the same and will have too regular shapes.

Multi-purpose Design Tool: • NORDSKILL •

bobbystahr

Quote from: Aleksei on January 17, 2017, 05:32:35 am
Thank you, everybody! I've got answers for the main questions.
And I now have a new one.
Is there an opportunity mo make a Cumulonimbus clouds?



The only one solution I see now is to make 2 clouds: one above the other. Where the upper cloud will have inverted profile:



But I'm afraid that with this approach all clouds will look the same and will have too regular shapes.




There's a thread where AP is working on thunderheads with that idea...it's current  so do a search...
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist

KyL

Interesting topic :)

I never had the stretched cloud issue like you but it is more than likely due to the Y projection. Regarding the geog image map shader, I was indeed suggesting to use it to map the half or another portion of the planet. But in the case of clouds I always do a projection camera to apply my texture. It is much easier to work with and can be carried easily in other software.

Speaking of the cumulonimbus clouds, I tried a similar approach at some point but had mixed result. This was mainly because the illumination between the cloud layers is not consistent, so the clouds from one layer weren't bouncing on the other layer. This was with Terragen 3 though, but I do not remember Matt saying anything regarding this limitation in TG4, so it might still be the case.

Your best bet is probably to nail your fractals based on the altitude, like what Matt did for this turntable: https://www.youtube.com/watch?v=87TkK1_avO0 (damn that just looks so good)