how would I go about doing something like this using NURBS in Rhino:
I’m basically trying to teach myself on how to design guitars in Rhino, and the surfacing stuff is doing my head in.
(almost on the verge on giving up and learning SubD 
).
_VariableChamferSrf
if you need other ratios then 1:1 (45degree chamfer)
in case of your guitar, you can scale (_scale1d or _scaleNU) the model in Z
do the Chamfer, scale back.
or - of course a self made surface:
draw a curve (the upper shape/edge of the chamfer)
_offset (loose)
move curve in z
_loft
_trim _join
maybe post a file, and also a sketch so it s easier to give a feedback to the design you re after.
kind regards -tom
So he mentions split lines to break those surfaces. Presumably he’s still creating those split lines by hand ie sketching them? You can do something similar in rhino - sketch those lines then loft between them to create the chamfer.
I tried lofting a few times, and the resulting surfaces would come out somewhat wonky - plus I couldn’t use the lofted surface to trim to main solid - so I figured I was doing something seriously wrong.
turns out, I just needed to ease out the curves for the loft, and instead of trimming the solid I could just split the solid along the sketched lines and then join it up with the lofted surface.
(gonna tweak it a lot more tho)
thanks a lot though, to both you and Tom_P! finally gained some much needed confidence to design surfaces like this.
I think it s important to notice, that a loft between two curves that have the same start/endpoint might cause problems in later steps - for example Filleting.
Nurbs surfaces always have 4 edges - in this case (screenshot at the right) 2 edges have length zero. - and are degenerated - therefor the normals in the corners are not defined.
left is showing the workflow I recommend in the post above:
draw the initial curve on the planar top.
do an offset with option loose and a vertical move.
(the surface used to split the body at the left is the same as the surface in the middle)
this will give a perfect pair of curves with the same nurbs structure / setup - resulting in a very pure loft surface.
this loft is used to _booleanSplit or _trim/_join the initial body / part.