I just finished a little experiment with realtime cloud rendering, which I wanted to share. Most approaches are either very 2D or very expensive due to raymarching, so I figured I'd try something else. And I'm quite happy with the result. It does look a bit artistic and not 100% photorealistic, but it is fairly cheap and fully 3D. The approach is to make an actual 3D cloud model and then bake the lighting into spherical harmonics. (First 9 components similar to Unity does.) The transparency of the cloud is determined based on the (distance through the) actual 3D model. The lighting is quickly calculated using 3 textures with spherical harmonics mapped on the cloud model. And this is the result (with some other sky layers in the background): Note: Only the front cloud is done this way. The background cloudiness is just a typical 2D technique. Render time for the whole scene is 0.4 ms.