Triangulation using lunchbox on polygonal surface

[AndersDeleuran]

You can use Weaverbird's Loop Subdivision after the coarse triangulation, example here:

Mesh from closed polyline when it fails to make a mesh?

I usually triangulate closed non-planar polylines first, using Polyline.TriangulateClosedPolyline, and then generate a mesh from this. Works pretty well: