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