Hi mir4ea,

> And I also include in this project another example. Thanx.

The "X" one in your second attachment is a different problem - that's a problem in the surface/surface intersector in handling singular "crown point" intersections. It's probably the biggest remaining surface/surface intersection bug that's in the geometry library.

You get the result you see there because all the intersections are not being generated, if you select the pieces and use Construct > Curve > Isect you'll see it only finds 3 of the intersections and is missing one.

I'm hoping at some point to get this fixed in the geometry library, it's a delicate area to mess around with though.

- Michael