Ship Line Modeling Based On NURBS

Hull lines design is one of the most important problems in ship design process. After a long term development and study, the method of hull lines design has great progress, but it is not yet the modern design method, what can generate automatically hull lines that are smooth, with optimize hydrodynamic performance, and practical. It is very difficult and complicated to realize this modern hull lines design method. Preliminary research work has been done in the dissertation.From the point of three-dimensional design, a software system using VC"6. 0 and Open GL based on Window' s XP has been developed to reconstruct the hull surface in this dissertation .For the sake of system's agility and practicality, NURBS(Non-Uniform Rational B-Spline)and skinning methods have been used to fit three dimensional hull surface. Three - dimensional geometric design of all kinds of ships and marine structure bodies can be completed using the powerful function of NURBS surface. NURBS is a rapidly developing discipline, which can be applied in many areas. In this paper some key techniques for NURBS ship surface reconstruction such as curve fitting, data segmentation, surface fitting, fairing are studied, and a prototype is develop to verify the algorithms.There are six chapters in this dissertation.In chapter 1, some basic concepts, research contents and significations for ship surface reconstruction are discussed. Some key techniques and difference comparison between ship surface reconstruction and ordinary surface modeling are analyzed.In chapter 2, NURBS conception and the based algorithm are discussed. Formulas, used to describe circular curve in NURBS, are studied deeply.In chapter 3, the methods to calculate NURBS control points of three exponents and combination of separate curve are discussed.; Various ship boundary conditions are given, and then the whole course of hull line formation is presented.In chapter 4, the method to fit hull surface to hull line data is studied. Based on the construction theory and method of NURBS surface, a continuity of several NURBS surface is studied. The problems of fitting ship surface are presented, and then the solutions are given.In chapter 5, fairing of curves and surface are studied. The theorem of energy-based faring is introduced and two methods of ship surface fairing are presented.In chapter 6, systematical summary is given, and some problems need to study in future are suggested.