Expand description
Which side of a seam a position on it is read from (#263).
A composite curve – a polyline, an arc-length chain, an elevated curve
whose profile is piecewise, a banked curve whose cant law is – is made
of pieces laid end to end. Where two pieces meet, the position is shared
but the tangent, or the roll of a banked section, may jump: the curve
has two frames there. Every evaluator in this workspace that picks a
piece by a distance or a parameter takes the piece that STARTS at the
seam (ElevationLaw::piece_at,
Chain2::piece_at,
CantLaw, a polyline’s spans): that is
SeamSide::Outgoing, the default. SeamSide::Incoming reads the
piece that ENDS there instead, as some authoring rules require (the
previous segment’s tangent governs at a seam).
At the curve’s own start and end only one piece exists, and both sides read it.
Enums§
- Seam
Side - The piece a position exactly on a seam is read from.