Zbrush has had an excellent quad remesher for years, but with their newest release they have once again improved it considerably. With previous versions of their mesher one could already create good SubD-Cages from Nurbs input. Now their ZRemesher even respects existing groups of polygons (polygroups) found in the input mesh. As Zbrush can identify UVs in Nurbs-derived meshes, one can therefore force the Mesher to create a SubD control mesh which inherits the surface-layout of the Nurbs model.
This addition could turn out immediately useful for those who want the cleanest possible meshes from Nurbs geometry for rendering and at the same time want to use existing UV’s for material assignment.
The most interesting aspect, I think is something else: Retaining Nurbs surface-borders in control cages, as demonstrated by Pixologic might serve as a foundation for a repeated conversion back and forth between Nurbs and SubD.
Right now conversion from Catmull Clark mesh to Nurbs is a one-way street, as automatic, unguided surface creation from SubD leads to very heavy, no more human-editable polysurfaces. Output which makes surfacing specialists shudder and question the whole point (also of Limit-Surface based) SubD: ‘Why at all bother, if one needs to remodel the whole thing anyway (before I can modify it) ?’
Typical Auto-Surfacing result (Autodesk Fusion here). Output isn’t suitable for further (meaningful) Surfacing operations. But even assuming that would only want to punch a precise round hole into this auto-surfaced body – one at that point cleary could no more reconvert this ugly thing back to SubD.
If one could convert polysurfaces to Catmull-Clark meshes which retain the surface logic of the Nurbs model one could turn every Nurbs model to clay. Even without adding or removing faces one could freely reshape the geometry (in a Cage-Edit on steroids fashion) and convert the result back to Nurbs. It was even ok if the converter failed creating high quality surfaces / surface matching in very challenging areas – but one would at least end up with human editable geometry, that may get further refined.
Users however, who convert a polysurface to a surface layout retaining cage and go further by adding and removing geometry could help the Nurbs converter, by assigning polygon groups to modified model sections – Zbrush even creates these automatically (but one may freely change the assignment later).
Face addition to the control cage, marked by polygon-groups.
These groups might aid a Nurbs converter create human editable Nurbs also from altered portions in the SubD-model.