Boolean Split joining cutting object to cut object

So I have this part I designed and I want to trim a bit off the edge. I drew a rectangular cube to use as the cutting surface. When I do Boolean Split, it appears to split, but it also merges the cutting object to the part being cut. boolean issues.3dm (9.2 MB)

I was able to sort it out… apparently a microscopic naked edge was the culprit.

I’ve had this happen numerous times. I think even if there is a problem with the geometry, it should never combine the two elements in this way.

When a Boolean operation produces an unexpected result (as in the inverse of what you expect) it is almost always because one or more of the objects are open and have the normals pointing the wrong way. You may think they are closed but they are not.

Read more about how Boolean operations work here. I always suggest that you go into your shaded display mode and turn on backface coloring and give backfaces (the “insides” of objects) a recognizable color. That way you see what is the “inside” of an object readily. If the object you think is closed is really open and inside-out, you will see it immediately - as in the image of your model below.


I’m not clear on where I find the Backface Color

Never mind. Found it. Thanks - that’s a very useful tool.

I can’t find it on the mac - any ideas?

It’s in each separate display mode.

Preferences > Display Modes > Display mode name > Shading settings > Backface settings



thanks, you’re a star!

having turned this on, it causes a problem with some elements not displaying at all so I have had to revert to the default settings unfortunately.

Hmm, OK… Can you perhaps post an element that doesn’t display when color backfaces is turned on?

Thx, --Mitch

disappearing object.3dm (146.0 KB)

see attached

Hmm, seems to work OK here in both Windows and Mac Rhino (I see one surface). Could be a video card issue on your system, I guess. --Mitch