Isotrim on curved surface not equally distributed?

Grasshopper
#1

I’m trying to subdivide a surface, more specifically just a simple cylindrical surface.
So we already know the surface has constant curvature, nothing irregular or special.

Apparently, the subsurfaces do not have the same area.
I wonder why, because I actually expect them to be approximately equal, at least with far less deviations as I’m experiencing.
No problem with a simple plane surface though.

Does anyone have a clue why this is actually the case, and more importantly how to solve this issue and actually divide a curved surface into equal subsurfaces?

P.S.: I’ve tried to do a subdivision with paneling tools inside grasshopper, but this not really efficient, although the cells seem to be far more equal.

unequal subsurfaces.gh (14.2 KB)

#2

This is indeed disconcerting! I rebuilt the circle with 100 points and the results are much better, but then, its no longer a circle. I’ve noticed some other strange things involving circles over time, like how they sometimes don’t behave well in surface splits. Again, rebuilding solved the problem.

#3

Confirmed your erratic results using R5. However, when I replace the extruded circle with a Cylinder, all SubSrf have identical Area and Length, as expected. But U and V counts are reversed?

cylinder

#4

Oh man, that’s an elegant solution indeed. And it definitely works, although, as you stated, the U and V orientation is switched compared to the circles.

But now I really wonder how the extruded circle example is so different from the cylinder…

#5

And I wonder about other extrusions, like an ellipse? Or what about two circles lofted? Unable to test these myself at the moment…

#6

Well, that’s how I originally did it, loft between 2 circles. Same result.