How to create high altitude clouds? (cirrus and cirrocumulus)

Question

Pretty much all cloud tutorials show how to make Cumulus clouds, or some random blob of a cloud, but I'm looking to create high altitude clouds, which you can see below.

I'm most interested in the cirrus and cirrocumulus clouds, of which you can see some bigger pics below.

Any way to create these as a procedural volume material or as a world shader perhaps? I would prefer a volumetric material though, as I need a transparent background behind the clouds, and lighting in the scene to affect the clouds.

Answer 1

To get the best looking volumetrics you needs to increase the Max Bounces for Volume as well as look at the settings under Volumes a few panes down.

Also worth noting make sure your Principled Volume is set to pure white.

The optimal settings here will depend on the size of your object, for example in my scene a fairly large object renders like this with the above settings.

By decreasing the Step Rate you slow down the ray as it passes through the volume and allow for more accurate detection of the edges of the volume. It's essentially the same as increasing the number of volume slices in Eevee, but for Cycles rays.

Increasing the max steps is maybe not necessary, but... it's an option. Using these settings we produce this image from the same volume.

Fairly detailed, reactive to light, but the downside is render time.

Here's the node group I used to make this:

Wave texture seems particularly suited to making an array of clouds if you spend enough time messing with Detail Scale and Detail Roughness. Be sure to turn Detail up to 4 or higher but beware of performance considerations.

I'm sure with some masking and modifications you can get close to some of these formations. I'm completely lost on how to achieve the swoosh shape right now, but hopefully this gives you a starting point.

Answer 2

This reply might be a bit late, but I figured out a way to at least approximate cirrus clouds using purely volumetric modeling with noise and gradient textures. To begin, I tabbed into Edit mode and scaled the default cube by 4 on X and Y, leaving it at 1 on Z (final dimensions are 8 x 8 x 2, but the scale is still 1 — make sure to apply scale if it isn't 1). Then I applied the material setup pictured below.

If you then add a plane, give it a hair particle system with a low number of particles, choose the cube as the render object, choose a scale of 1, and give it appropriate rotation and rotation randomization. This gives you a field of cirrus clouds. Paired with the Physical Starlight and Atmosphere addon for the sky and sunlight, it looks like this in EEVEE (with best volumetric tile size of 2 px):

Obviously, more work is needed to finesse them and give them some more random variation, but it's at least a start. I'll update with any further improvements I make.