Hi Petr,

> Is it a side-effect of improving offset handling an edges?

Not directly, just as I was testing the edge offset it happened to remind me that I should tune up join to allow edges as well.


> MoI writes "inch-flag" into IGES file

I just discussed this with the guy that makes the IGES library that I'm using, and I also looked through the IGES spec a bit.

There isn't really an offical way to mark an IGES file as having "no units". And the IGES spec says that the default value for units should be value "1" which is inches.

So that's why that happens.

A units flag of "0" is not officially listed in the spec as a valid value. I suppose it is possible that some system could interpret this to mean no units, but I think it is probably not a good idea to put something in here that is not officially supported, it is difficult to guess what might happen to other systems when reading it.

There is a flag of "3" which is some kind of custom unit support, but it is not commonly used and according to the spec it is supposed to be accompanied with a label that matches a particular IEEE unit naming convention. It is tempting to just write "None" for the label there, but it does not seem to be officially supported so it would again be producing something outside of the strict spec.

Do you have any other software that has a "no unit system" setting and also writes IGES files? If so, I would be curious what they do to handle this situation. If I knew that there was some kind of existing practice of using a flag of "0" or "3 + None" for handling this, it would make me more confident to do the same.

- Michael