Function edge_chords_for 

pub fn edge_chords_for(
    model: &Model,
    shape: &Shape,
    deflection: Deflection,
    tol: Tolerances,
) -> OgeomResult<EdgeChords>

The chords the faces below shape agree to draw their shared edges to.

A face narrower than a few chords draws its edges finer than the caller asked, and so does a face whose boundary crosses itself at that chord; the face across each of those edges must draw it the same or the two meshes disagree along it: a crack in every mesh assembled face by face. triangulate agrees this for itself; a caller meshing face by face (a viewer keeping one mesh per face) asks here once per shape and hands the answer to triangulate_face_with for every face.

The answer costs a draw of every face at the caller’s chord, since a boundary is only known to cross itself once it is triangulated; a caller meshing face by face pays that draw twice over, and one that wants only the welded whole should ask triangulate instead.

Errors

OgeomError::Construction if the deflection is unusable; a face that will not draw asks for nothing rather than failing the shape.