Building Modeling Oriented Graphical Software Support System

According to the analysis on the architecture of traditional CAD systems, the dissertation builds an object-oriented CAD development environment. Based on the studying of the building-oriented polyhedral modeling system, some primitive algorithms are implemented and some are improved. The displaying speed and real-rendering quality of geometics get better, because some particular OpenGL techniques are used. A lot of interactive tools are discussed and implemented. An undo/redo mechanism for object-oriented system is built, according to the research on the traditional mechanism. The main work is summarized as follows:1)using object-oriented method to build a framework for building modeling; based on the framework, building an object-oriented graphical development environment; the environment can be used widely, can efficiently utilize the memory of computer, and so on.2)implementing the sweep-line intersection algorithm for line segments with a higher speed than the common intersection algorithm; raising a new triangulation method for concave polygon face in which holes exist; raising a new method for the face loop calculation, that replaces part of geometric computing by type-flags'deduction, and so the efficiency of face loop calculation rises; by giving the definition of feature points, proposing an offset algorithm that can overcome the shortcoming like bumping and divided-lines that would occur in the region-cutting algorithm;3)based on the method of saving and restoring the color and Z buffer, speeding up the method of interactive dynamic displaying that is widely used in the support system; using such OpenGL techniques as full-screen antialias, texture compression to increase the speed and quality of real-rendering.4)proposing the concept of base-face location; building a 3D-type dynamic user coordinate that can automatically treat any visible face as a 2D working plane according to the cursor's position on the screen;5)under the enlighten of OpenGL select mode, building up a select culling method that links together the pixel on the screen and the corresponding geometric vector graphics, and implementing a rapid selecting mode in the 2-dimensional part of the support system.6)building a undo/redo mechanism for object-oriented system; the undo/redo mechanism enable single one object or a group of objects to undo one operation or multi-operations in one time.