Creating an editable NURBS surface from complex scan data can be a challenging proposition, especially when the original scanned surface is irregular and not smooth in the conventional sense. This White Paper by Simply Rhino shows one workflow that allows an editable surface to be produced whilst maintaining the irregular qualities of the target surface.
Download Simply Rhino White Paper…
Posted Aug 31, 2016 by Delia Robalo on Rhino News, etc.
What advantages does this method have over cleaning up the mesh and running the “Patch” command with the appropriate options? It seems like the author is more or less doing the same thing, just manually.
Thanks for the question.
There are a number of ways of reverse engineering the mesh and using Patch on a simplified mesh would in my opinion be valid but not as controllable as creating the curves first. The curve method allows a surface to be created that is closer to the mesh in some areas or as a whole depending on where the curves are positioned.
The idea in creating the curves in X and Y is to create the U and V parameters of the surface explicitly. Once having gone through the simplification process with the curves (rebuilding) each curve can be compared to the mesh (or original section through the mesh) and adjusted locally if necessary. I would agree that creating and rebuilding the curves is time consuming but once created a number of different surface creation methods can be used and curves omitted or added to create or remove local detail.
In the case of this White Paper example it was a medical application where the requirement was to be close to the mesh at certain areas and be able to modify the surface at a later date by a fixed amount – the use of curves helps to make this a little easier.
I think that once you have the curves there is flexibility to build surfaces in a number of different ways - i.e. just using curves in one direction and lofting, splitting the surface up into a number of smaller surfaces of different densities etc.
Hope this answers your question…
Phil - Simply Rhino UK