Function edge_crosses_face 

pub fn edge_crosses_face(
    params: &ValidationParameters,
    model: &Model,
    edge_id: EdgeId,
    face_id: FaceId,
) -> GeopResult<Option<Vector3>>

Where the edge edge_id crosses the trimmed region of the face face_id, away from every vertex, if it does — never for an edge that bounds the face (see [check_edges_and_faces_consistent]).