Builds a path through points; smooth > 1 runs a Catmull-Rom spline with that many samples per segment.
ReadonlyclosedWhether the path loops.
ReadonlydistancesDistance from the start to each vertex.
ReadonlylengthTotal length, metres (closed paths include the closing segment).
Readonlypointsxyz per vertex.
Position and travel direction at distance s from the start (wrapped on closed paths, ping-pong on
open ones, where the tangent flips on the way back).
A polyline with arc-length lookup: rails, flight paths, shipping lanes, roads without a graph. Closed paths loop; open paths are driven back and forth (vehicles turn round at the ends).