Can't 'Boolean Union" items that touch but do not overlap

Title pretty much says it all. Items that share a common border don’t combine.

Create two rectangles, one wide, one tall. Move bottom left corner of tall rectangle to top left corner of wide rectangle (should be ‘L’ shaped).

Boolean union does nothing, should combine both item one ‘L’ shaped geometry.

CC build 624.

“Just overlap them then”.

I’m using the corner nodes to align things. There’s no way to move things in a way that guarantees that the edges will be aligned afterwards.

Try making the tall rectangle 1 mm taller, set grid to 1 mm, then over lap the top left of the wide rectangle with the bottom left of the tall rectangle by 1 mm using snap to grid. Then select and boolean. Alignment should be retained.

1 Like

Just add another small rectangle (or any shape that will be entirely contained in the new combined part) that slightly overlaps both parts that are just touching. Select all 3 and do a union!


It’s my understanding that detecting this is a hard problem mathematically.

Easiest thing is to just node edit one of the shapes so that they overlap, so starting with:

Node edit the lower one with the shorter segment on the overlap:

so that the Boolean union will be successful:

It really is simpler than node editing, I think… just add a small box across the abutment and union them all (as suggested by @SLabuta above:




This topic was automatically closed after 30 days. New replies are no longer allowed.