In the attached file, I cannot boolean union the two solids. From the intersection, it looks to me like Rhino is getting faked out on the tangents.
I can split the two object and join them together. However, (1) splitting produces a bad surface that gets discarded. (2) the splitting creates separate surfaces but they remain joined (they have to be exploded or extractsrf to remove); and (3) I have to do a second split to get all the way through.
Problem Union.3dm (5.4 MB)
So here I have split purple with red (which causes no visible problems). Now I have split red with purple. Notice the spit lines but the surfaces remain joined.
And I can extractsrf or explode them out.
Notice the surface at the top of the opening was not split. But a second Split command does split it.
If I split Red with Purple I get a clean cut of the bottom but I have to do extractsrf on the two surface above because they split but remain joined.
Then I have to do a second split to open the surface above. Then I can split purple with red and join to form a closed polysrf.
In the alternative, I can
- Split red with purple and delete the bottom surface that is not joined.
- Do a second split of red with purple which unjoins that split but joined surfaces and the surface that was not split.
- Split purple with red and joint to create a closed polysrf.
This behavior just seemed odd enough to report.