I am begineer user of Vue 8.4 xStream.

• I want make the clouds that disappears gradually near the horizont, and appear just on top of the rendered image with clear horizont, but I don't know how to do this!
  In example I used Spectral2 Clouds> "Stretched Stratus".

• What settings I should tweak to do this?

• I tried to change the Altitude and the Cover settings, but the clouds appears too dense near the far horizont!

• Should I change some filter to set the appearance?

• Should I change the default "Color&Density" function and change some settings relative to the "BasicRepeater" Node?

How I can do?

Many thanks in advance!
Horsepower0171.

Well, ,changing the layer's altitude is all I can think of, really. BUt the results can be unpredictable, because while changing the altitude of the layer, you are also modifying the density function, since this function is evaluated in world coordinate space. Whcich means that each point of the function is evaluated according to its location in world standard space coordinates. This point will then given a density value. When this point is moved in space by changing the layer altitude, the density evaluated for this point now depends on its new location, and can be different from what you had before. This is a problem for what you want to achieve, but it's the magic behind animated clouds.
Another workaround wpuld be to modify the aerial perspective over time, so the cloud layer would fade when AP values get higher. Not sure this would animate (never tried), and not sure it would look realistic either, because it would add a lot of haze to the scene over time.

Bruno, you can animate the Aerial Perspective if I remember correctly. I think I tried it once successfully.

The easiest way that I can think of would be to create a really huge cube or sphere and put it at the height of the cloud layer. You should then hide the object from the render (click on its small icon in your objects list in the world browser) . Next go into the material editor of your cloud material and tick the "Dissolve near objects" box in the "Lighting & Effects" tab. This will make your cloud layer fade away near the huge sphere or cube. You could even animate the fading of the clouds by making the invisible sphere bigger and bigger over time.

Nice trick, Daniel, though he's gonna need a huuuge cube!

I thought so before, too, but in fact it doesn't need to be as big as you might think :-) Even at an AP of 1 the clouds will gradually fade into the haze in the distance, so unless you have a camera focal property of 10mm or less, a big but still managable primitive object will do. The only downside to this is that the clouds fade away in a straight line (they are conforming to the shape of the cube), but you can easily work around this by using more irregularly shaped objects, e.g. a standard vue rock.

I think originally impish published this trick on his Vue blog. He used it at that time to "shape" cloud layers to his liking and to achieve Godrays a lot easier.

 Ehem... Just increase decay in the atmosphere editor.

Quote -  Ehem... Just increase decay in the atmosphere editor.

In the "Sky,Fod and Haze" Tab of AtmosphereEditor, the "Decay amount" and the "Decay mean altitude" options increase the respective "Decay color"!
It doesn't clear the sky from the clouds!
Why you said this?

Quote - I thought so before, too, but in fact it doesn't need to be as big as you might think :-) Even at an AP of 1 the clouds will gradually fade into the haze in the distance, so unless you have a camera focal property of 10mm or less, a big but still managable primitive object will do. The only downside to this is that the clouds fade away in a straight line (they are conforming to the shape of the cube), but you can easily work around this by using more irregularly shaped objects, e.g. a standard vue rock.

I think originally impish published this trick on his Vue blog. He used it at that time to "shape" cloud layers to his liking and to achieve Godrays a lot easier.

That's ingenious.  I would not have thought to do this!

Attached Link: Cloudless Horizon

There is another solution which lets you achieve a cloudless horizon. However it rquires you to be familiar with the function editor to some degree. I have attached a link to an example file. It`s the Stretched Cumulus example. I added some nodes in the FE to achieve a horizon with no clouds. Will make another post with some explanations.

1) This is the Smooth Step Math node. It`s wavelength is set to 0/1/0. The Smoothness parameter is set to 7 or so. It basically determines the smoothness of the transition between clouds and no clouds. Origin is set to 0/-2.5/0. Note: The Origin lets you move the cloud limit. The Origin setting depends on the angle of the camera and some other factors. So you might have to experiment a bit.

1. Rotation. In this example I used 135 degrees z Rotation. With Vue xStream you might need to use a different angle. Leave all parameters except zRotation untouched.

2. Combiner node. Combines the Smooth Step node with the Fractal node.

It may require some experimenting with the parameters of the nodes to get the result you want.

Good luck!

**eonite:** Thanks you very much!

But a little question:

• How can I do to modify the clouds in the manner that resemble a little bit stretched, as "alto stratus Cirrus" instead of puffy cumulus?
• What parameters I should tweak?

I tried to modify the X,Y,Z Wavelenght with 1/2/1, of FractalNode, but unsuccessfully the clouds don't stretch realistically. 

I want made the german "Caspar David Friedrich" painted cloud scene like the above image:
"Il Mare di Ghiaccio".

Please, can you post your .mat file with these modifications, as I can inspect it?
Thanks!
Horsepower0171. 

Your`re welcome :-)

Horsepower0171, can you post a picture with clouds that resemble the ones you want to create?

Quote - Your`re welcome :-)

Horsepower0171, can you post a picture with clouds that resemble the ones you want to create?

I haven't found any picture, but I want make the clouds approximately like in the CasparDavidFriedric's image above:

With clouds centered in the frame, at the top of the image only, little bit stretched that resemble as cirrus, and with clear horizont.
I haven't found any settings to stretch them.

Thanks!
Horsepower0171.

Attached Link: White Stretched

Ok, here is another link.

Started from the same file but replaced the Smooth Step node with a Gaussian Tooth node in order to have clouds restricted to an area.
Also both branches are multiplied now, in order to have distinct boundaries. The map filter nodes serve to remap the values so they are suitable for multiplication and the map filter underneath the multiplication node remaps the values so they start at -1 (If they are too high or too low you may get unintended results, so it`s good to know that the cloud editor expects values between -1 and 1)

Made a couple of changes in the clouds editor, like setting all scale values to 1, as well as decreasing Opacity and Density in order to have bright clouds. The Altitude is set a lot higher.

The fractal node`s wavelength is set to 1/3/1 in order to get stretched clouds. The Multiply node above the fractal nodes serves to scale the clouds.

There have probably been some more changes. It`s best if you try to analyse yourself and then make the changes necessary. But I think this is quite a good approachthat may lead to the result you want.

Hope this helps :-)