There are a couple of ways to do it: One is to make skirts and base for the mesh, stitch the mesh, skirts and base into a solid, which can be bent and/or twisted. Another is to convert the mesh to nurbs, extrude the nurbs face and again, the solid result can be bent or twisted. These aren't universal solutions because they depend on the picture resolution, what powerpack version etc. I'm a windows user, there are a couple of external apps that I've used to do some of this. or to do it differently: ZSurf4 is a heightfield producer that has its own limitations, like 300 x 300 resolution, picture's gotta be greyscale (easy enough, even Paint does it), and it produces an IGES nurbs surface, but good, and simple. Marcus Bole's PolyCAD, polycad.co.uk converts mesh to nurbs or nurbs surface to mesh. Both are free, Marcus requires registration for polycad.
Did you mean that the slicer software gives poor resolution, or did you mean relief, the relative scale of the picture's z axis? Once the picture's been made into a heightfield, you can exaggerate the relief with z scale, mesh or nurbs.

Edited by user Sunday, November 12, 2017 6:21:19 PM(UTC)  | Reason: Not specified