Quadremesh fails on simple Saddle Surface (Bug)

mac os x 10.15.6 (19G2021), rhino Version 7 (7.2.21012.11002, 2021-01-12)

Preparing a tutorial … I get a lot of strange results for this simple Degree 1, 2x2 Point Saddle Surface.
For me it looks like a bug

quadremeshfail.3dm (59.2 KB)

In some video I heard that the edge layout should be influenced by the principal curvature - is this correct ?
if so - i would have expected a result similar to this - that i only get without Symmetry-Option and with additional guiding curves:

Any simple example - where the quad-typology of a single, simple Surface is completely different from the U-V direction of the input Nurbs-Surface… (my initial intend, why i choose to play with this simple surface)

Is described in command-help

“Multiple axes can be selected. It only makes sense for symmetrical objects and when the correct symmetrical plane is selected.”

Works like a mirror and noting more


Dear @eddi
Thanks for having a look at it. Thanks for the video.
But - the symmetry for the surface is x and y with the rotation in the original post.
see image above:
black / grey -> the surface
violett -> the mirrow-planes
cyan -> the principal curvature at the mid-point of the surface
hope this clarifies my question.

For “symmetry option” I think main edges should be parallel to xy-axis.


symmetry off

symmetry on Y ( as you can see, left side mirrored, right dent not more exist)

main edges diagonal to axis

symmetry on Y (all geometry on reight side cut off)

Even without bringing symmetry into it, it is a little odd, what QuadRemesh does in this case.

I’ll run it by the developer.