Create class for intrinsic triangulation without correspondence?

[keenancrane]

There are situations where one wants to work with intrinsic triangulations that do not correspond to an extrinsic mesh, and hence where no correspondence data structure is needed.

Currently, one option is to use an EdgeLengthGeometry, but (if I understand correctly) this class does not support flipping. So, one possibility is to add edge flip methods to this class, though this would break with parallel structure of other geometry classes (e.g., VertexPositionGeometry also does not support edge flips). Alternatively, we could add methods to this class that allow one to query (i) whether an edge is flippable, and (ii) the flipped edge length, without actually performing the flip.

Another option, which I currently adopt, is to re-implement flip(Edge) locally in my project, i.e., a method that mutates the surface mesh associated with an EdgeLengthGeometry, using this geometry to do convexity checks, etc. The drawback here is that I duplicate a bunch of code (diamond layout, convexity checks, flipping logic) locally in my project by copy-pasting it from within the GC implementation.

A third option would be to extend the mutation manager to support mutations of edge-based quantities, and provide some mutators suitable for intrinsic triangulation options.

@MarkGillespie has talked through this with me a bit, but may have additional thoughts…