Hi Felix - most likely the piece that looks weird was actually damaged in the original file as well, when you save a file MoI actually has to translate its internal object structures into the OpenNURBS structures which is what actually goes into the 3DM file.

Normally that doesn't really involve making any changes to the data, but it can in the case of objects with damaged or invalid trim curves on them - the 3DM file container will attempt to correct things but if the trim curve structure is really messed up it can potentially look a little different after you save the file and reload it.

Again, this appears to be caused by the base object in your boolean being made up of a self-intersecting surface that folds back over top of itself.

Having any additional object will not fix this - the surface that you see here is not going to work to use in a boolean:



Doing a boolean on that has created an object that is damaged and has a messed up trim curve structure, it will behave weird in several different ways - having it look like things are leaking out of it, and it can be possible for it to look a little different after saving and reloading.

Again, the main problem is that you can't really do booleans with objects that are made up of surfaces that fold back through themselves - surfaces that fold back through themselves will confuse the surface intersector and you'll get weird objects from that.

- Michael

Michael,

as usual, your tips are very useful. To get a pseuso render real quit like that is a great idea, thanks.

I suppose I can shrink (scale down) my second profile such that it doesn't fold on itself like it does now but this will also affect other aspect of the model that I'd prefer not modify if possible. I did this to create the red model kind of thing in the last image I posted. For this first attempt I used an open profile curve to generate the sweep, I was just fooling around and then decide it would be nice to use 2 of these objects and join them with a nice flowing shape to connect them. I realised I needed a symmetric profile curve such that it would be possible to use these profile as well for the connecting part.

Personnaly, I have 2 problems with this models, the first is obviously the self intercecting part and the second is that a real object like this wouldn't have empty space like it's clearly visible in your image (felix_self_intersection3.jpg). I guess my question would be, is how can we design such object without self intersecting part and with no voids? Any suggestion will be helpful, I have no doubt about that.

Thanks,
Felix

Michael,

thanks for the explanation about internal data and saved data. I guess we must avoid self intersecting part at all cost if we don't want to get into trouble.

Thanks,
Felix

Hi Felix, you can actually make a self-intersecting object if you only want to make a render mesh for it, but yeah they need to be avoided if you want to do things that will involve surface/surface intersection calculations with the object such as booleans.

This is certainly a tricky shape to try and make without self-intersection though.

I think you'll have to stop the main sweep something around here:



And then make the rest of it with just the outside half portion of the profile, something like this:




Or maybe you could try only doing a half profile (the outer half) along the entire sweep length and then an inner profile that stops before it folds in on itself, and then do a blend between them to connect them up.

- Michael