Generation of discrete G1 continuous B-spline ship hullform surfaces from given curve network using virtual iso-parametric curves

摘要

Ship hullform is usually designed with a curve network, and smooth hullform surfaces are supposed to be generated by filling in (or interpolating) the curve network with appropriate surface patches. Tensor-product surfaces such as B-spline and Bezier patches are typical representations to this interpolating problem. However, they have difficulties in representing the surfaces of irregular topological type which are frequently appeared in the fore- and after-body of ship hullform curve network. In this paper, we proposed a method that can automatically generate discrete G1 continuous B-spline surfaces interpolating given curve network of ship hullform. This method consists of three steps. In the first step, given curve network is reorganized to be of two types: boundary curves and reference curves of surface patches. Especially, the boundary curves are specified for their surface patches to be rectangular or triangular topological type that can be represented with tensor-product (or degenerate) B-spline surface patches. In the second step, surface fitting points and cross boundary derivatives are estimated by constructing virtual isoparametric curves at discrete parameters. In the last step, discrete G1 continuous B-spline surfaces are generated by surface fitting algorithm. Finally, several examples of resulting smooth ship hullform surfaces generated from the curve network data of actual ship hullform are included to demonstrate the quality of the proposed method.