Join a collection of curves into one or more longer curves when possible.

Input parameters:

1. Cr → Curve to join.
2. Mt → Joining method to use.
   • 0 → Standard
   • 1 → First (Position)
   • 2 → First (Tangent)
   • 3 → First (Curvature)
3. Rd → Retain the original direction of curves.
   •  True → Retain
   • False → Ignore

Output parameters:

1. Cr → Joined curves.