Only the volume drawing part is really finished and exposed to the user. Hair plugs into the existing hair rendering code and is fairly straightforward. The pointcloud drawing is a hack using overlays rather than Eevee and workbench. The most tricky part for volume rendering is the case where each volume grid has a different transform, which requires an additional matrix in the shader and non-trivial logic in Eevee volume drawing. In the common case were all the transforms match we don't use the additional per-grid matrix in the shader. Ref T73201, T68981 Differential Revision: https://developer.blender.org/D6955