Hi 3image, yeah like Burr mentions it can be a little complicated and may even depend on the source and maybe even on the particular geometry being translated. Each format kind of has its own particular tricky things with it.

STEP format is probably a good bet for the main one to try. The part that's good about STEP is it can transfer the edge joining information so solids come through directly. The area where it can be difficult is that some programs transfer 3D trim curves that can cross over the closing seam of a surface, so when imported into a program like MoI which defines trims with a matching UV and 3D space curves those seam-crossing trims have to be detected and split where they cross the seam. Usually it's not a problem but if the curve kind of wavers around just slightly around the seam it can end up being a difficult calculation.

IGES format doesn't have the seam-crossing difficulty but instead usually only contains a lot of trimmed surfaces without any joining information and so the joining has to be done as another import step and in some situations that can also be a difficult calculation.

SAT is I guess kind of similar to STEP.

Curves are more straightforward in all the formats, any format really should be fine for curves.

I'd say you'd probably normally want to use STEP format, and if you run into a problem where a couple of surfaces are messed up with mangled trim boundaries try a different format for that particular model. If you're working with an ACIS based program like ViaCAD for example it may be good to use SAT as a first choice though especially exporting from MoI because it seems like that involves the least amount of possible mutation and processing when going into ACIS.

- Michael