Hi Otterman,

re:
> I then tried to diff that shape out of the main hull, but the hull
> vaporized instead (see second and third pictures).

It's a little hard to see without increasing the display mesh density to be tighter, but that small piece has edges that are just barely grazing along the surface of the main piece:



Often times what is actually happening there is that the edges are in some places just a micro amount underneath that main object's surface and in other places just a micro amount above it. Sometimes this leads to confusion in the booleans where it has problems with this "skipping in and out" type of intersection.

It is possible for me to make some adjustment to how tolerances are handled so that these kinds of things sort of glom together better. But unfortunately that then causes problems in other situations where things glom together where you don't really want them to.

It's a pretty tough problem to solve without causing other bad side effects, at least currently. I think the current setup where it is tuned for "less glomming" helps in more situations overall, but it actually hurts in this one.

At the moment the easiest workaround is to move the cutting piece up just very slightly so that its edges are not hugging right along that other main object's outer surface.

- Michael