Interactive CAD Of The Hull Surface Based On NURBS

As one of the important components of the CAGD and the best numerical method in the curve and surface modeling technology, Non-Uniform Rational B-Spline (NURBS for short) has been designated as the unique mathematical method for defining the shape of industrial products by ISO. Its specialities of united expressing cubic B-spline, conic section and straight line make it fit the hull surface design, so bringing NURBS in the hull surface design and practice is the common ideal of ship designers.Based on NURBS algorithm, this thesis researches into the hull surface modeling technology, progressively approaches how to apply NURBS to the molded line and hull surface design both in theory and practice, and detailed introduces the specific process that develops a proprietary software with interactive design concept.This thesis starts with the basic algorithms, discusses the property of curve and surface, the general process of calculation and anti-calculation, and studies the important parameter of the curve. After the interface is designed with the MFC and OpenGL, especially in the visual transformation, such as the building of physical coordinates, the model translation, rotation and zoom function, multi-directional projection, and including the response to the keyboard and mouse and so on. On this basis, from the perspective of information management, functions are expanded. The software establishes a tree data structure and concentrate curve informations on the control node, which has the functions to select, activate, modify, output the value and display curvature characteristics. Ultimately the thesis selects a real ship model as an example to introduce how to use the software, in particular, pointed out the problems of the stem and stern.Overall, the software has the functions of multi-angle observations, drawing curves and surfaces according to the offsets, displaying the curves by types, parameterization of the visual body, managing messages by tree data structure, modifying points by pick-up and checking fairing by"curvature stick"and so on. It also has the advantages of friendly interactivity, simple operation, clear logic and good stereoscopic perception. These are all effective explorations in applying NURBS to ship engineering practice.