I did some cloud shaders for the announce cinematic that were basically raytraced heightfield materials that traced towards the light. Since they were still basically cards, the number of traces didn’t have to be that high to look good. I even got them receiving distance field shadows.
For use ingame we were actually taking those and using in editor merge tool to bake them down to simply unlit shaders with lighting baked in the textures.
For that last step, we had to briefly change the cloud materials from emissive to regular lit, and had to hook the Emissve to the BaseColor and the Opacity to the Specular so that the merge tool would capture it (doesn’t support translucency properly yet). Then of course we had to reverse that step and convert the merged material back to translucency.
One part of it that DID work out quite well though, is that even though the clouds were individual blueprints per cloud, the merge tool still worked to combine the selected ones into a single draw call just fine.
And I will add that the work I started doing for the sky in the actual level was very early and I have been working on other projects the last few months. Some other env artists have done work in there so I am not 100% sure what they are using currently to be honest. I heard it was a mix of the raytrace clouds and some simple cards. And of course a mix of photosource and hand painted tweaking for the actual HDRI behind the translucent clouds.