Bad Boolean Union

Problem Union (977.4 KB)

In the attached I have two closed polysrfs. The don’t show bad surfaces or non-manifold edges. If I intersect them I get two closed curves. Yet booleanunion fails.

Hello- there is a near- zero width surface here -



Actually 2 near zero width surfaces (shown in yellow here).

Text dots show the length of the edges at these locations.


They great mystery is why Rhino was creating those zero-width surfaces in a loft in the first place.

Please post the curves used for the loft and maybe we can solve the mystery.

You have an unusual tolerance setting:

Has the model or any of its parts been imported from another system? Have you changed the units from something else to inches?

Problem (32.3 KB)

Here are the curves. I just lofted them. For the example, I probably left off the last 2 curves at the end.

Everything was done in Rhino from the start in Inches.

The odd tolerance is “1/128”.

I haven’t been able to reproduce the micro-surfaces by lofting your curves. Did you use any of the seam adjustment options?

If not, what release of Rhino are you using? (I’m on 7.27.23009.13001, 2023-01-09)

I just did a loft in Rhino

Version 7 (7.26.23009.07002, 2023-01-09)

Problem (44.0 KB)

Here is the same loft frames as a before but with the vertical lines removed to create open curves.

For me these always create the “microsurfaces”.

When the loft was closed, I would get them sometimes. If I rebooted (not just restart Rhino), they could go away then come back again.

2 of your curves have near-zero length segments


Thanks very much. I am surprised that does not generate some kind of bad object warning. No idea how those even got created