chrisb wrote: ↑Sun Jan 23, 2022 5:03 pm
I have increased the cube to avoid all so called coplanar problems. To no avail. Then I swapped the sequence of subtractions and now it works without geometry errors.
I noticed this too, by now. Unfortunatly, swapping the subtractions is not an option, as I need the object with the drill hole, but the backside
not cut away, in another context too (as a clone).
I also noticed another way of avoiding the problem, which may be applicable in my full model. If the base cylinder is rotated by 180° about it's axis, the problem goes away. For this there is no need to disassemble the tree, you just select the base cylinder and enter 180° under Properties/Placement/Angle. For the model proper, this is a no-op, as the cylinder is rotated about it's symmetry axis. However, Open Cascade's cylindrical surfaces always have a "seam" along the side, and this seam gets rotated to the other side, where in the model I posted it gets cut away.
Cheers Peter
PS.: Originally, I thought the seams exist because every surface in OpenCascade needs to be a
simply connected manifold, but I realised that that does not explain the seams on spheres. Does anybody know more about the seams? Seems it'd be beneficial to understand them better.