Hi Val - re: terminology - usually a "polyline" means a series of line segments, so that's not a smooth curve unlike a "spline". It sounds like you don't mean that things are getting converted into just a set of angular lines like I had previously thought you meant.


So what happens in both of these cases for doing 3dmcurves2dxf as well as SAT format exports is that arcs and circles end up being translated as a general purpose NURBS spline curve which has the exact shape of a circle but it is apparently not recognized as a circle since it was not set up as an actual specialized "circle" type entity.

Some programs are able to analyze the shapes of NURBS spline curves that are imported and recognize them as circles and arcs but it seems like those programs are not doing that.

One thing you might try is to edit your moi.ini file and set:

[NURBS Export]
WriteAnalyticCurves=y

Then try exporting using IGES format after that - that should then make special arc and circle type entities in the IGES file instead of just general spline curve entities. And I guess if you've got your arcs joined with other curves into long connected pieces you will probably need to use Edit > Separate on them so that they are just individual pieces before they would get exported as an analytic.

I'm not sure if analytics works with SAT format or not - the translation library that I use for doing SAT export does not deal with analytic surfaces for SAT format (like spheres and cylinders), but I'm not sure if it does analytic curves or not. I think that analytic curves will work for IGES and STEP formats though.

But anyway try setting WriteAnalyticCurves=y and see if that helps any.

- Michael