STEP or IGES for file import?

 From:  Michael Gibson
3887.3 In reply to 3887.1 
Hi Martin, I'd actually suggest that you request receiving both STEP and IGES formats, because each one can have some particular quirks about it.

Then you would probably want to try importing the STEP format one first, and if there was any problem getting the trimming information calculated from that try IGES instead.

The nice thing about STEP format is that it keeps the joining information intact so it actually holds solids. The not so nice thing is that it doesn't contain any UV trim curve information, so that makes MoI have to create those which can be a somewhat complex process and can be difficult in some particular situations.

IGES format on the other hand usually only contains individual surfaces which then need to be joined together to make it back into a solid, and that joining process can also be a complex process as well, especially if there are little tiny surfaces mixed in with larger pieces. Also you need the result to be joined to get a properly formed mesh result since the mesher takes care to process joined edges to make a shared vertex structure there to avoid cracks between surfaces. If you have just 2 totally separate surfaces sitting side by side but not joined, they can get different vertex structures when meshed and that makes little cracks between them.

So unfortunately it's not quite like one format is automatically better than the other in every single case. But probably more often try STEP first.

Then to go into Modo you want to export to LWO format.

- Michael