Bug: Extend/ExtendDynamic arc with Natural and Merge creates line segment

8.13.24317.13001, 2024-11-12

Extend the red arc using the green line in
Extend_Natural_Merge_arc_creates_line_segment.3dm (46.4 KB)
_Extend _Type=Natural _Join=Merge
or using a small enough extension length, up to about 0.07 in this case,
results in a 2-segment polycurve consisting of the original arc and a line.

Doing the same in V7.37, which doesn’t have the Join option, lengthens the arc just as I expect.

When a boundary object is being used, a workaround is to use _Type=Smooth .

The above also occurs in V8.13 with
_ExtendDynamic _ToBoundary _Type=Natural _Join=Merge

The other _Join settings work as I expect:
Join=No results in an additional arc
Join=Yes results in a polycurve consisting of 2 arcs.