Development of a Sophisticated Hull Form CAD System ‘ezhull’ Based on a Non-Manifold Model and ‘X-Topology’

Abstract

The EzHULL system developed in this chapter provides an association based cross fairing and surface generation, using X-topology and nonmanifold data structure. X-topology is the data structure for a wireframe model that supports the association based cross fairing. The association based cross fairing offers designers an effective wireframe fairing by monitoring how adjacent lines are affected when a particular line is changed. Direct conversion from a wireframe model to a surface model enables 3D surface hull form to be visualized even at the earliest design stages. The topological information of the converted surface model helps to resolve the points ordering problem in the wireframe model, and the geometric information is used to shade the wireframe model with a cubic effect. In addition to these features, EzHULL also provides convenient and intuitive wireframe editing system for planar and spatial curves, hull form variations, and various facilities for hull form design. The geometric data of the surface model can be used to display the 3D surface hull form to check the surface fairness at the early design stage of hull form. The topological information can be used to solve the points ordering problem that occurs in the wireframe based design system. An example of a twin skeg hull form showing the effectiveness of the developed system is included.