# Isotrim on curved surface not equally distributed?

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)

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.

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?

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…

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

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