Function chart_crossings 

pub fn chart_crossings(
    model: &Model,
    face: &Shape,
    tol: Tolerances,
) -> OgeomResult<Vec<ChartCrossing>>

Every place where the boundary of face crosses itself in its surface’s chart, as the module documentation describes, in the order of the edges crossing. Nothing where an edge of the face has no pcurve on its surface: what cannot be drawn is not read.

Errors

OgeomError::Dangling if the face or its geometry is not in the model.