We just wrapped up production on a project which required us to create all the major cloud types inside of Unity. It was a challenging task with limited budget required as they have to perform well in real time. Our initial approach of using mesh and particles around the edges to soften didn't work so well. We then moved on to a pure particle approach. While it looked fine, it had proven to be too costly in the engine.
After some more experimentation, we were able to come up with a particle card facing hybrid that not only looked very volumetric, but also z-sorted well. We used this technique on most of the cloud systems with the exception of the Cumulonimbus, in which we used a mesh to define the base shape and emit particles along its surface.
Nimbostratus rain cloud
We found while creating the different cloud particles, the two important elements in creating convincing clouds involved their subtle movement and the edge softness. You can create really convincing clouds if you can nail those two things.
Check out the screen captured footage of the Cumulus cloud. In the second half of the video, the camera was hand rotated, you will notice the cloud holds up from both up-close and from afar. Since the movement on the clouds are subtle, expand the video full screen for best viewing.
Music- Uncle Albert- Saving Mr. Banks
*These clouds can be heavy on overdraw but since this is not done on mobile, we can afford to put a bit more bells and whistles into them.
I'm busy working on my blog posts. Watch this space!