How to simulate specific cloud types

Started by chricken, July 29, 2017, 06:46:08 am

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for many years I am occasionally using terragen2, which was good enough for my puposes. But now I want more.
My main focus about terragen is to make clouds/atmosphere as skyboxes for realtime rendering.

TG is fine for cloudy skies and good weather, but I am trying to simulate specific cloud types in a convincing manner.
Especially that wavy pattern in cloud types like cirrocumulus floccus or cirrostratus fibratis ( reference ) make me headaches.

I have been trying to subtract clouds from one another, which seems not to work as expected.
And I simply don't get a clue. Generally I don't get the point, how I can add, multiply or subtract cloud densities from one another.

So I hope, someone has an idea, how to solve this problem or has a link to a tutorial about combining clouds.
I would upgrade to TG4, if it could deliver, what I am looking for. But unfortunately these 'easy clouds' seem much less flexible then the old clouds system.
But maybe I am wrong.

Attachment1: This seems not to work as expected

Attachment2: This works but it doesn't help, because I can't modify position and/or rotation of one of the fractals. Or can I?



You could try using a get postion in texture, x to scalar, divide by a number for size, and sinus function combined with a warp (perhaps by a rotated Z to scalar and sinus, or in a mix with an ordinary PF). Something like that could produce wavy strands of cloud.




Quote from: chricken on July 29, 2017, 06:46:08 am
Attachment2: This works but it doesn't help, because I can't modify position and/or rotation of one of the fractals. Or can I?

You can translate, rotate and scale fractals by using a Transform shader. Add the fractal as the input node for the Transform and then use its output to continue.


I think some users think of clouds very different then terrain.
Actually you can do many things like you do on terrain.


You cannot subtract cloud layers from each other, they do not produce color output, they are for volumetric shading only. You probably need to get a better understanding of what the different colored nodes are. Red are your Shader nodes, they generally output Color and/or Displacement, and can be combined, subtracted, etc. Blue are Function Nodes, they output data specific to their name/category, e.g. "Constant Scalar" outputs scalar data. Blue nodes are atmosphere nodes, they do not output the same kinds of data as other nodes and they only work when plugged-in to the atmosphere input of the planet. Green nodes are Heightfield nodes, they only work when fed into a Heightfield node.

So you need to work on the noise functions (shader and/or function nodes) themselves first, add and subtract, and otherwise manipulate those, then feed them into your cloud layer(s) to volumetrically shade the shapes you have created.

Lots of cloud types are possible. Some examples  are provided in the Terragen Presets Pack 1 (in Free Downloads on our website), as well as by NWDA, Luc Bianco, and others on their respective sites.

Easy Clouds are intended to be just that: easy ways to make the exact cloud type specified. They are not intended to be as versatile, powerful, or flexible as regular cloud nodes. If you want a more powerful cloud node that still uses the new v3 shading model, create a Generic cloud layer.

- Oshyan


Thanks for all your answers.
The transform-shader was, what I was looking for. It takes the shader input for the source shader. Now it works like imagined.
And I just a little burst about using the shader, which I never understood completely ;)

Thanks again