Been playing around with various profiles and sweeps to form rings, have this 1 ring when I try to Boolean merge out the hole using a curve, it sort of does a Curve Project instead, if I extrude the cure into a solid and try a Boolean Diff, they just get unioned into 1 solid.

I've looked for defects in the solid but can't find them... but I'm not sure what to look for. :)

Hi Steve - that probably means that the solid is confused about which part of the volume is the outside and which part is the inside, it's ending up reversed from what you would usually expect for that shape. Any reversal in the inside/outside region will make things like boolean difference behave like union instead.

The main way for that to happen is if you've got any self intersecting surfaces that sort of squiggle back on top of themselves. It looks like some of your side surfaces have that problem:










That surface kind of hooks back over top of itself and so it is actually folded very tightly back on top of itself in that area there, that's what is likely making for a problem with the solid's structure.

Try to examine the curves that were used to generate that piece and see if the curves used had a little hook type thing at their end. You will probably have to pull some points around (and then undo) to really see it, it can be hard to see things that fold back over themselves with a sudden 180 degree turn like that.

- Michael

I renamed the topic title, since a really long topic name kind of looks weird in the topic list.

- Michael

And basically the way to find that kind of problem in the solid is to use Edit > Separate to break it into individual surfaces and then turn on surface control points and examine them to see if there are any irregularities in the control point structures, mostly it's the tips and end areas that need some close examination to find those types of problems.

It also helps to jiggle the points around a bit if there is a suspicion that there may be some self intersecting areas, when you jiggle a point around you can then see if it was making a kind of zig-zag back tracking type pattern with its neighboring points or not.

The "Area" zoom tool also helps to get your view centered on a particular area at the end of a surface to examine as well.

- Michael

Thanks Michael.,