I'm just playing around with smoke simulations. I don't know why, but I can't get the smoke to look smooth (see screenshot or simple hip file at frame 23 or later).
I already tried to - increase the container's resolution - lower the volume step size in mantra's parameters - reduce the whole file to the minimum to isolate the problem
That looks like a filtering issue. H12 changed the default volume filter from a gaussian to a box filter, which will cause the voxels to be more visible than in the past. On the other hand, it's a lot more efficient and produces sharp renders for high voxel count volumes.
To get a smoother result try changing the “Volume Filter” to “Gaussian” and the “Volume Filter Width” to “1.5” on the geometry object.
