Function make_blend_curve 

pub fn make_blend_curve(
    model: &mut Model,
    a: (&Shape, End),
    b: (&Shape, End),
    continuity: (Continuity, Continuity),
    tol: Tolerances,
) -> OgeomResult<Built>

Bridge the gap between the ends of two edges with a blend edge.

The blend is a Bézier curve from the end of a to the end of b, joining their vertices. On each side it continues the edge with the continuity asked: Continuity::C0 meets it, Continuity::G1 also leaves along its tangent, Continuity::G2 also with its curvature vector. The tangent’s length on each side is the distance between the two ends.

History: each edge generates the blend edge.

Errors

OgeomError::Construction, by name, where a continuity is Continuity::C1, Continuity::C2 or Continuity::CInfinity; a shape is not an edge, is placed or degenerate, or has no curve; an edge stands still at the end asked, so it has no tangent there; or the two ends are one point.