Thank you for the explanation J.

Here is a wireframe view of the two solids sitting next to each other. (There is a wireframe shortcut script.)
Replace the bottom prisms with one larger prism. The bottom prisms can be deleted face by face.
The 2 large circles are to be deleted from the top face of the new prism. Then join everything remaining.

- Brian




I have not tried Michael's methods.

Hi jki, I investigated your model some more by using Edit > Separate on it and moving faces away one by one to look for any weird things and I did run into some little slivery degenerate looking faces here so far:



I think that some stuff similar to these is what's messing up your booleans, but not these specific ones since I removed them and still ran into the same problem. But probably there's more like these.

- Michael

Hi jki - ok so it is those slivery bits that is messing things up. There is a whole chain of them here (and on the other side of the model as well):



I've attached a 3DM file with those slivers removed and this version should now boolean ok with no ShrinkTrimmedSrf used.

I removed those slivers by selecting the larger neighboring faces and using Edit > Separate to break them off the main solid, then use Edit > Hide to hide them temporarily, then it's possible to select the slivers and delete them, then unhide the big faces using Edit > Hide again, then use Edit > Join to glue it back together.

The problem with degenerate faces is that the opposite sides of the trimming boundary touch each other and that makes the outer skin of the model essentially have self-intersecting areas and anything that tries to go over that degenerate surface will lose the proper sense of orientation.

- Michael

Hello Michael,
thank you for explanation, now I understand the problem...
I was confused and I focused on spring, while it was also very tricky to get a solid.
The cage was quite simple construction, so I believed the core of the problem is in spring :-)

I like the "clean" constructions avoiding such mess by principle... therefore I have less experience with fixing such problems...
My next challenge is to re-construct the cage to avoid those slivers...

Just one more question:
if i have 1 solid, then i cut it by boolean diff with a single line to get two solids, then I edit both parts, but not connecting faces...And the if i try to join (bool union them again) - it is not possible, moi does nothing, I still have 2 separate solids... what to search for?

Jozef

Hi Jozef,

> it is not possible, moi does nothing, I still have 2 separate solids... what to search for?

Well, I'd probably just take a general look for problems, like self-intersections, slivers, similar to what I looked for in your other case. See if using ShrinkTrimmedSrf gives different behavior or not.

Can you post the 3DM model file (or send it to me at moi@moi3d.com if you want to keep it private) and I'll take a look and see if anything stands out.

If your objects mate up along the cut line, it should be possible to delete the faces along that line and then with 2 pieces that have common open edges select them and use Edit > Join to glue them together rather than boolean union. Join only tries to glue unattached edges to each other, while boolean union also tries to intersect the objects and see if any pieces need to be removed, so it's a much more complex operation than join.

If your edits were right adjacent to the connecting faces with new pieces partially overlapping it may be difficult for the intersector to figure out how to cleanly divide it into separate chunks.

- Michael