Hell and Halos, a Random Walk
I’ve spent a lot of time trying to come up with simple cloud systems to use with Blender. This is the result of one test, in which I used the Python scripting interface to create a model using a random walk.
In a random walk you start at the origin and select a random direction to move one space. Repeat. After many thousands of repetitions I was left with a cloud of vertices. I applied a red halo material to the cloud model and rendered.
The very first render produced a very pleasant result. As a still image. Right away I tried to animate this scene, as a single frame renders very quickly. Unfortunately, since all the vertices are placed at regular intervals, once the image moves, artificial structure becomes very easy to see.
I may have to try this again with a random jump between steps in the random walk. Another challenge for making this a good cloud material is to figure out a way to animate the structure of the cloud itself.