Is this a bug in .iges file from MoI or not??

 From:  Michael Gibson
658.2 In reply to 658.1 
Hi Boatstalker, it seems to be a bug in Prosurf. Can you please send the .iges file to their technical support for them to confirm?

I can't seem to find anything wrong with the IGES file itself - it loads into both MoI and Rhino fine and Rhino is able to make a proper DXF from it.

It appears that Prosurf is ignoring the trimming information.

When you do any cutting operation on a surface (for example booleans), what happens is the same surface actually remains "underneath" and there are new "trimming curves" that are calculated. Trimming curves are curves that live on the surface and mark regions of the surface that are supposed to be inactive. There is some other explanation of this here:

It appears that ProSurf is ignoring the trimming information and only using the underlying surface when generating DXF polygon data. I'm not sure if it ignores all trims or if there is some reason that it is ignoring them for just this particular case. To test you could draw a plane and cut a circular hole in the middle of it - if ProSurf ignores the circular hole when making a DXF, then it would seem that they don't support trims in the polygon generation.

Another way to get your DXF would be to export to either OBJ (probably use quads & triangles option), 3DS or STL formats out of MoI and then use a polygon format converter, such as 3DWin ( to convert it into DXF format.

- Michael