Function march_blend_sided 

pub fn march_blend_sided(
    first: &SurfaceGeometry,
    second: &SurfaceGeometry,
    radius: f64,
    guide: &Curve,
    sides: Sides,
    options: Marching,
    tol: Tolerances,
) -> OgeomResult<MarchedBlend>

As march_blend, with the ball’s sides named by the caller.

The four seatings are four different balls (a fillet’s rides the material’s own side of each support, a carving ball the opposite) and a caller that knows its seat should say so rather than take whichever converges first.

Errors

As march_blend.