Why the "patch" not generated correctly? Bug?

The red curve was generated with the “curve from two views” command.
Subsequently, the “Patch” command fails to correctly generate the surface based on the red curves.
forma a sella.3dm (38.2 KB)

(with the “Loft” command the surface is constructed perfectly, but when a thickness is applied to it, anomalies occur, see last image).

Hi @davide76
Why not just extrudecrv the “parabolic” curve and split with the flat curve? Gives you a much cleaner result! IMHO Patch should only be used if all other options fail! But… I think the complexity of the curve combined with the position of the curve seam is why patch fails in this case. If you use crvseam to move the seam to the center of the “bowtie shape”, the result looks better (but the underlying, untrimmed surface is still really, really complex for such a simple shape!!!).
HTH, Jakob

it’s strange how the patch behaves !!
I tried a lot of things with the patch command, but failed to produce the correct surface,
you have to wait for a mcneel expert to see this patch story

try networksrf, it worked fine with me

Hello - it really seems like you’re looking for the hardest ways to make that surface. Extrude the profile curve and then trim in top with the plan curve.



hi pascal
but why the patch command did not succeed !!!

Hello - without a starting surface, Patch makes its own starting plane from a sampling of points on the geometry - in this case it looks like the starting plane is vertical:


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Another very efficient way to create such a surface:

  1. use “Surface from planar curves” on your base curve in the XY plane
  2. change the degree of your two dimensional surface from 1 to 2 or 3
  3. move the control points to where you want them

The surface in the file below does not match your red curve exactly.
While I don’t know what your goal is, maybe you will have to reconsider your workflow?

And please change the title. It’s no bug… A better title would be:

Why does patch not work in this case?

forma a sella.3dm (66.0 KB)