Function b2MakeOffsetRoundedPolygon 

pub unsafe extern "C" fn b2MakeOffsetRoundedPolygon(
    hull: *const b2Hull,
    position: b2Vec2,
    rotation: b2Rot,
    radius: f32,
) -> b2Polygon

Make an offset convex polygon from a convex hull. This will assert if the hull is not valid. @warning Do not manually fill in the hull data, it must come directly from b2ComputeHull