Not BadObject becomes "Bad" after Moving

Hi Guys,
I originally thought this was a problem with grasshopper but after repeating the grasshopper process in plain Rhino the same thing happens there:
I have a curve, positioned about 3600 mm from the origin which seems normal: When I run the SelBadObjects command it doesn’t get selected.

Now, after I move the curve a bit in any direction and run the SelBadObjects command, it suddenly became a Bad object:

This ruins the grasshopper definition I made. Is this a bug or what is it causing this?
191008 MoveBad.3dm (26.3 KB)

How did you create this curve? It has two huge arc segments which i assume are the problem here:

Also whenever you move an object via the gumball rhino deletes it and then adds it back to the document with the transform value from the gumball, so it seems your polycurve does not satisfy rhinos inner validity checks there.

Interestingly exploding the polycurve gives arcs with sensible radii. But joining them back up gives a few with huge radii.

Its the “lines” connecting the top and bottom half which are actually huge arcs even when exploding

Replacing those with actual lines gives a polycurve which plays nicely and is within reasonable tolerance


Here is a naive ghpython component which checks arc segments inside polycurves if they are over a specified maximum radius and replace them with straight lines from the arc start to arc end points.

This should fix your gh file (4.3 KB)

Also in my opinion is it good that rhino marks such polycurves is bad objects (although not consistently) since no CNC or LaserCutter will process arcs of such radii and angles.

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Awesome bughunting! Thanks a lot for the help!
The curve was made by a client of mine, possibly using a script.