With the new CopperCube 3d game engine editor Hadoken Fog Designer extension you can easily create,  design & animate many types of fake volumetric billboard fog, mist & clouds. 

The extension comes with a mandatory set of fog cloud asset/prefab, the designer plugin to customize the asset/prefab in the editor, a special behavior for animation &  appearance control at runtime plus 20 unique fog textures in over hundred color & opacity variations.

https://hadoken-records.itch.io/coppercube-fog-designer