If you regularly work with 3d scan data, I highly recommend you to buy a program called Atangeo Balancer nPro 2.0. Opt for the “Non-Commercial” license which comes at half the price ($72). That program works super fast with meshes and is capable of reducing large meshes for second. The preview is dynamic, which means that the changes of complexity are immediate, so you can easily decide what percentage of polygon count reduction is good for your purposes. Then you export the optimized model as STL and import it into Rhino.
Another solution may be using a plug-in for reverse engineering called “Mesh2Surface”. You can download a trial version for free which can be used for a limited period of time. It’s fairly easy to use this plug-in and build NURBS surfaces on top of the 3d scan model.
A 3rd option is to use a plug-in called “Sybestrack”. It’s also capable of building NURBS surfaces onto 3d meshes.
A 4th solution is to build a NURBS surface and orient it normal to the 3d mesh, then rebuild the surface to 50x50 control points, then turn the control points on and use either the “Pull” or the “Project” command to project the control points over the 3d mesh. The process is fairly easy. Then select the projected surface and rebuild it to a simpler surface such like 6x6 control points or whatever works best for your shape.
