Well, since the angle is 90 degrees, the crease angle must be above that to keep it smooth.

However, Poser doesn't smooth 90 degree angles perfectly. It only really works for angles less than 90 degrees.

Both boxes have 1-inch displacement. The second one is welded with crease=100.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)