I get this buggy behavior with the fillet command (shown in video). To my understanding, the fillet command should not 'move' the original line work, either connect them, or create an error if they are not co-planar. I'm working with curves that are created in a large complex file (low resource error?), and / or are referenced off of surfaces, or curves that are created from surfaces (iso / edges / intersections / etc.). I get similar behavior when using the CurveBoolean command with similar linework, where the original linework is modified (sometimes dramatically) when working with curves that are created from surfaces.
The typical workflow that I'm using when I encounter this bug is as follows - I'm using a plane to create intersection curves through a bunch of complex geometry (hull and hull structure).
Trouble shooting measures that I've taken:
1. I draw lines over top of these lines and they fillet correctly, but I can't find any discernible difference to the two lines. The original lines were drawing using surfaces as reference. They were the projected to the CPLANE in the right view.
2. I started up in safe mode, in rhino 4, and rhino 4 safe mode... filleting these curves all has the same behavior.
This is at least partially due to your file tolerances - you are working at a tolerance of .01 (meters), and if you're trying to place fillets and or do curve intersection operations like CurveBoolean with details around that size, you will have trouble. Try tightening your file tolerances to .001, the fillets seem to work fine even at .01 and CurveBoolean is also better.
There is a bug in CB though, doesn't look like it's gotten fixed for SR2, some areas refuse to respond immediately to clicking in them, you have to search around for he right pick point.
Actually, if you tighten the file tolerances even more, to .0001, CB also works very well in your example, no problem with clicking in regions and not getting them to highlight.
great, thanks a bunch. one of those items i didn't realize was related. Much happier drafting from here on out.