Cirrus clouds?

[Elegy]

Does anyone have any tips on how to make cirrus clouds? Cirrus clouds from what I can tell seem to be characterised by thin fibrous strings but I'm at a loss at how to create such fibres procedurally. Ideally, I'd like to create clouds like this:

http://www.freewebs.com/thomp730/Cirrus%20clouds-Horz.jpg
http://upload.wikimedia.org/wikipedia/commons/d/d9/Cirrus-clouds-warsaw-may-22-2005.jpg
http://outdoors.webshots.com/photo/2988600270057907249vjmFSN (I think these clouds are cirrocumulus)

I've tried warping a Perlin Ridges cloud layer using a redirected Alpine Fractal with some reasonable results but I still can't seem to create the fibres.

[CCC]

The first image of cirrus i have yet to see done in terragen 2 or any software for that matter. I think it is really a matter of coming up with a new particular noise type that kind of resembles long feathery inverted erosive flows.

The second image looks more achievable as i have seen somewhat similar clouds done in terragen 2.   

The link is dead for your third image.


As far as tips i have not gotten to this area yet (Experimental Cirrus) but no doubt there are others here that can assist you. 

[Elegy]

Oops. I've fixed the last link now.

Recently I had an idea of making large features using Perlin Ridges or one of the Perlin Mixes (~1500m) and warping them very heavily to form the basic shape of the cirrus, then merging the result with medium regular Perlin/Perlin Mix features (~300m) which are also warped, and then merging that result with small Ridged features (~40m).

The merging of Ridged-Mix-Ridged or Ridged-Original Perlin-Mix should in theory give some variation and make the result look somewhat like the second picture but unfortunately, so far that's only been in theory. In practice, my results look obviously merged or warped.

[inkydigit]

you could try 'stretched' fractals with a warp shader(s) to blend??...I have dreamt of these(mares tails) clouds in 1 and 2, and have often tried to think of a way to do these, but have not tried myself (yet!!)

[Henry Blewer]

I mostly use alto-cumulus clouds for this. Change the height to about 12,000. Make the noise type ridged. Change the lead in scale to 80,000. Make the scale 1500. 1 works well for detail. I change the edge sharpness to 0.4 to 0.8. Set the cloud height to 45 to 65. Increase the coverage to 50 to 70 percent. Make the clouds very wispy and add some softness. They can be noise stretched as well. Huge noise stretching makes good ring clouds for a planet. I'll attach a clip file, might be easier to see it.
Can't save the node as a clip file. Using free edition.

[Elegy]

Inkydigit - I've tried stretched fractals with unconvincing results.

Njeneb - Thank you, I'll try that and see where it goes.

[Henry Blewer]

In the image sharing threads, I posted a link and a tgd file. Check out the tgd. It uses my cirrus layer clouds. The thread is Towers.

[Matt]

Can't save the node as a clip file. Using free edition.

That is not a restricted feature

Matt

[Elegy]

I've just had a few ideas for how to create altocumulus clouds with promising results. Once I've seen this through, I'll be sure to download your file and get back to the cirrus. Thanks again.

[dandelO]

Njeneb:
You must highlight all the nodes you want to save or the 'save nodes as clipfile' option will be greyed-out in the context menu.

[Henry Blewer]

That's what happened. I just clicked on the one node, the density shader. I've been working long shifts lately, with little sleep. It's making it hard to concentrate.
I've been experimenting using a voroni noise merged with a power fractal then pumped into the blending input of the density shader. I am trying to get the bumpy look cirrus clouds sometimes have.