Non Volumetric procedural clouds are a bit of an obsession of mine at the moment. Unlike sy Bryce or Vue there is no ready out of the box procedural cloud solution like an infinite plane etc.
In Blender procedural clouds have to be slapped onto the world background. But doing this and getting a realistic result is not easy. there are a number of issues;
getting the clouds to scale in the height direction.
getting the clouds to form in bands.
getting the edges of the clouds to be realistic in terms of having a realistic edge which is reasonably sharp in some parts bot not overly so.
getting the clouds to interact with the light of the sky behind them - in particular to try to achieve glwing edges when the clouds are in front of the sun.
Ive made fairly good progress on each of the first four with my degree of success falling as you move through that list.
Setting the clouds for a certain z height is easy as is banding them ( the latter for example can be done through a combination of either a greater than and less than node or two color ramps}
Getting a reasonable edge tpo the clouds has been much harder and ive ended up mixing a greater than/less than band multiplied by noise ( which gives hard edges top and bottom of the band) and multiplying this witha noise band defined by color ramps ( which has a softer top and bottom edge).
The clouds themselves still arent as hard edged as I woudl like within the band but I think I can deal with that.
What stumps me s far is getting the clouds to respond to light so that the edges glow. this is the killer difference for me between real clouds and what Ive been able to do so far. And I am stumped.
I going to put my experiments here and they may be of use to someone else and perhaps someone can crack this.
Here is a typical example of what I can produce so far.
This is harder than it should be!
Anyway after trying some more ideas ive got an approach which gives me better defined cloud shapes and I can control the distribution of the clouds better. Note this wont look impressive - its just one band of clouds at the skyline. But note that this runs along the whole skyline and Im not getting that cut -off look that usually hapens so Ive conquered that bit.
I have a strategy I think for glowing edges.
I need to mask out the middle of the clouds AND the external bit of the clouds and then boost the value for the remaining cloud edges Sounds simple. havent a clue how Im going to do it though.
This is my latest. I just rendered this on a plane with a blue background for now rather than the world.
Still only procedural nodes. Actually similar techniques to the first one but tweaked and this time doing vector blur of the clouds before mixing them with the blue background.
I feel thiis is getting there but there but the light is still not directional. I think I may try to do that by using the vectors from the world to shift the clor of the clouds across the world space. Well see if I can do that.
Anyway heres my latest attempt at a procedural band of clouds - cumulous - the sort you might see sitting at a distance ina band on the horizon.
Transferred the last node group over to the world shader and tweaked it by moving the vector blur to the right part of the node group. This is looking better I think. Ill take a fresh look at this later and think again about what is working and what isnt.
If anyone was interested, I just made a tutorial showing how to create fairly realistic procedural clouds in Blender (non-volumetric). Instead of doing everything in the world node group, I applied the cloud material to a large plane instead.