Gn filling orbicular N-sided holes using periodic B-spline surfaces

The orbicular N-sided hole filling problem is usually introduced by filleting an end-point of a part with large radius. The existing methods based on quadrilateral partition or constrained-optimization can rarely generate high-order continuous blending surfaces under these circumstances. This paper first reparameterizes the boundary of the specified orbicular N-sided hole to ensure the compatibility of neighboring cross-boundary derivatives on the connecting points, preserving their Gn continuity. Then we compute the control points of the periodic B-spline surface using the sufficient Gn continuity condition on the pole and the algorithm of extending parametric surfaces. This method generates single blending surface, which can be converted into standard Bspline surface by adding knots without introducing errors. It only elevates the degree of the boundary by n. The construction method is simple and efficient, without iteration nor large-scale matrix solving. It achieves Gn continuity under compatible conditions. The blending examples underline its feasibility and practicability.