The ones that have "downward pointing" normals were probably created by mirroring other ones, when mirrored the kind of natural local z axis for a circle gets flipped around, that's probably why some happen to be pointing downwards. It's not supposed to make any difference, but these programs that are having problems most likely have a bug in their implementation of the DXF "arbitrary axis algorithm" where they're not generating the coordinate system for downward pointing extrusion vectors properly. The arbitrary axis algorithm needs special case handling when the extrusion direction is colinear in any way with the world z axis, and they're probably only handling the special case when it's in the same direction as world z.

- Michael

Wow, that's a really bizarre and specific kind of problem. I will have to make sure that I keep an eye on that going forward, because I didn't know about that. Fortunately it appears that Corel Draw is smart enough to know how to open the file, so I am saved. However, I will probably try flipping around the parts that are wandering off just to see if I can make a difference.

Thanks again for all the help, I appreciate it!

Paul

Hi Paul,

> However, I will probably try flipping around the parts that are wandering
> off just to see if I can make a difference.

If you copy one of the other circles that is not wandering around in place of the wandering ones it should then work ok with those buggy importers.

- Michael

I've updated MoI's DXF exporter for the next v3 beta release so that for circle and arc entities it will avoid writing an extrusion vector of straight downwards in z and instead flip those to upwards z instead. That should avoid running into the wandering circle bug in those importers with the next v3 beta.

- Michael