Hi Jeff,

> I also tried repairing the body after doing the boolean diff, but
> that experience didn't go well.

That was probably the same issue - the thing that looked like a hole was not quite exactly a regular open hole but actually a surface with a messed up trimming boundary. That needs to be removed so you really have a hole there that can then be patched up.

It's a bit of a tricky operation to select a messed up face like that since it doesn't have any of the regular shaded display to it to click on (that's a side effect of having a messed up trimming boundary - messed up trimming means messed up display meshing will happen as well) - instead you have to do a strategic window select around it to select it and then delete it.

- Michael

>You've got to remove the existing bad surfaces first -

Interesting, Michael.
I noticed something strange about those broken segments, a sign of something more off.

>I also tried repairing the body after doing the boolean diff, but that experience didn't go well.

I'm sure it's because the body inherited the existing messed up surfaces.

Also, this issue must also be akin to the instances when I perform a trim of some sort and end up with the random looking naked surface squares.

The easiest way to fix this is to draw a line straight across from a side view level with the top. Then move the smaller block so it sits exactly on top of the bigger one. Boolean union will then work. Then cut the top back to size with a boolean diff using the line you drew first. Delete the top solid.

Hi Mike,

> Also, this issue must also be akin to the instances
> when I perform a trim of some sort and end up with
> the random looking naked surface squares.

Yeah most likely those were also messed up trimming boundaries. Any kind of manglement in the trimming boundary will make for odd display mesh generation like that. That could be stuff like parts of the trimming boundary crossing over itself making a self-intersection.

- Michael

So in this case there appears to be a bug in the boolean handling where it's keeping the wrong surface piece.

This kind of ghost surface piece here:



When you turn on its surface control points, the control points for the actual surface are way up here:



So the trimming boundary is totally off of the surface - the trimming boundary itself is in the right spot for the boolean result but the boolean seems to have decided to keep the wrong surface piece as the underlying surface part of the face.

This is a simple enough case that I may have a good shot at tracking it down and fixing it, I'll give it a try in a bit.

- Michael

I resurfaced the 4 fillet corners of this object and the boolean succeeded. FYI