Boolean union failure

 From:  Michael Gibson
4287.2 In reply to 4287.1 
Hi eric, actually the Boolean union will work in this case if you do it in a couple of stages, like select just these 2 pieces here:

Then with just those 2 pieces selected, run Boolean union and it will successfully merge those together, then you can select that result and also the last piece and run Boolean union again to get the whole thing together.

Boolean Union internally works on pairs of objects at a time, and when you select all 3 pieces all at once, it happens in this case that it tries to do these 2 objects together at first:

And that's causing it to get confused because those pieces don't actually touch each other at all. Something in the boolean processing can tend to get confused in this situation. I think it should be possible in the future to try and fix this up so that it would work when selecting all 3 objects like you initially did - that is actually theoretically supposed to work and this is a pretty simple example so it may help me when I get a chance to dig into it to try and make an improvement.

Anyway, I hope that explanation of how when selecting 3 objects it is first trying to combine those outer 2 that don't touch each other that was running into the difficult area, and that you can work around this problem by selecting just 2 pieces at a time that touch each other it can help to avoid this problem for now.

- Michael