I wanted to CNC some faces, or gargoyles out of oak, and was trying to find a way to do this in Rhino. But after seeing some tutorials with Rhino 5 and T-Splines, that also used Zbrush to add some fine detail.
This is my test: First I modelled a North Wind style face (quickly in ZBrush) at a high resolution, then modified the export resolution (lower) and output it as a .obj file.
Some detail was lost but this was just a test… I then imported it into Rhino 5 with a T-Splines plugin. It imported the obj file as a Rhino Mesh (but one of all quads) which was accepted by the T-Splines Convert Tool when I made it a T-Splines Surfaces (thing). I then took it back through the T-Splines Convert process and made it a Closed Polysurface Solid.
To which I Split the back and Unioned it to the Poly Rectangle, quickly and without error.
The 3dm file is here: https://www.dropbox.com/sh/duzr7jek8hkdpsg/AACPJidmmJX5SsANEiruGqR2a?dl=0