Flat or Planar areas within a Curved Surface - Rhino 7

Hello Everyone,

I’m trying to make a planar/flat area within in a curved surface, as in a foot path between hills, or, in my case, the flat area around the arch support and grooves of a custom foot orthosis. I thought I might achieve this if I could find a way to move some of the surface control points onto or parallel to the c plane. Currently Cage Edit seems the best way for me to control an organic surface with some precision, but I’m open to Sub D if the perimeter edge can be shaped into an insole.

I’m sure there’s a very obvious way to do this task, but I haven’t yet found the right command.

I’m not terribly technical and I might struggle if the reply is too abbreviated!

Many thanks in advance,

Joanne

SetPt can be used to accurately set the x, y and/or z coordinates of selected control points.

Note that to have a flat section of a degree 3 NURBS curve at least 4 control points have to be on a line. For degree 5 NURBS curves at least 6 control points have to on a line. It is impossible to have a single span / Bezier curve with a flat portion and a curved portion.

A flat section of a degree 3 NURBS surface requires at least a 4 x 4 set of control points to be planar. For a degree 5 NURBS surface it is at least 6 x 6 control points. It is impossible for a portion of a single span surface to be flat and another portion to be curved.

Thank you very much David I will try setpt and see what happens.
Out of curiosity, can we alter the degree of curve in different areas of the same curve by adjusting the control points? . Thank you again. Joanne

The degree of a NURBS curve is the same in the entire curve.

A polycurve is several curves which have been joined. Each curve in a polycurve can have a different degree.

Many thanks for your replies David! I’m closer to what I’m hoping for with your set point suggestion together with simplifying the surface with rebuild. I’m going to try a something different with polycurves with different degrees. Joanne