Hi Peter, unfortunately a system like that which only takes parallel slices will only really work well with certain kinds of shapes.

Anything that has protrusions in it can lead to this kind of a problem:





Notice there how the protrusions caused a kind of bifurcation or branching in the profiles, at one point there is one large profile and then the next one up suddenly has 2 small islands. That kind of thing is not good to try and do with Loft.


If you want to convert Sub-d to NURBS, probably the best way to do it currently is to use T-Splines, which can convert the Sub-d control cage into a set of NURBS surfaces.

Otherwise, if you have frozen smoothed polygons or something like the result of a digitizer or scanner, there are various specialized programs that are focused on this kind of reverse engineering task of fitting surfaces to polygon data. Often times they work by doing some steps to trace out different curves on the mesh data, then those curves form a kind of network topology and boundary lines for fitted NURBS surfaces. That kind of method allows for more general purpose shapes to be handled than planar slicing.


Some of the programs you could check out for this:

Raindrop Geomagic: http://www.geomagic.com/en/
Rapidform: http://www.rapidform.com/
headus CySlice: http://www.headus.com.au/

A few different ones for Rhino are listed here: http://www.rhino3d.com/resources/?category=13


It can be a kind of specialized and finicky area of stuff though... it tends to involve quite a lot of work to make software that does a good job at this, so it is probably not going to be very feasible for me to do it built into MoI directly anytime soon.

- Michael