Feature request: Polyline/Curve representation about manifold

[elalish]

I have this: https://elalish.github.io/manifold/classmanifold_1_1_manifold.html#a8631da9e82e21ccf91a53e016aa18c30

Polygons are just a vector of vectors; it could use more methods of its own for sure.

[bhouston]

Polygon implies it is a closed loop (whatever the 2D equivalent of a manifold is.) I think that requiring that on Curves/Polylines to always be closed isn't accurate. I think you often want to create them as not closed and then you may connect a few together to create one or more polygons as a result.

I think that a 2D drawing is fundamentally a collection of lines, many of which are connected and then from that set of connected lines you can extract a set of closed regions, e.g. polygons. But the mapping of lines to polygons it not 1:1.

[bhouston]

The lines are absolutely fundamental because these are usually the primitives in the CAD tool upon which the constraints act. Thus keeping these in a proper representation matters a lot.

Basically everything in CAD is derived from the line set, both polygons and trimeshes in your case. Thus you need to have these as a first class representation.