Research On Parametric Sketch Method In Three Dimensional Feature Modeling

Research on parametric sketch method in three dimensional feature modeling has developed prototype system, which achieves drawing graph, display and modification based on two dimensional plane, and realizes parametric graphs by adding constraints to graph elements and changing its characteristic parameters. The system is designed under the developing environment of VC++ and Windows 98 and it is software model that is suitable for Windows system.In the system, parametric method based on the graph is used, while users select a graph element, the system can search for adjacent list beginning the selected one, and establish relative constraint equations according to constraint conditions. Relative parameters of the selected graph element can be displayed, while users modify these parameters, it will be used for relative constraint equations. Sketch system can seek and judge roots of constraint equations, the roots of equations are new characteristic parameters of the graph element in the adjacent list. At last, the system redraws the graphs in the adjacent list with the new characteristic parameters and realizes parametric graph.The parametric sketch system mainly has the following functions:1. Friendly graphical user interface. In the system, menus, toolbar, status bar, dialogs and the like are designed, input of text and parametric graph are completed in the dialog, all operations are very simple and available.2. Basic drawing graph and display function. In parametric system, user can draw basic graph elements, such as point, line, continuous line, circle, arc, ellipse, rectangle, text and dimension and so on, these graph elements can be displayed on the screen of computer, and come into being a basic drawing.3. View management. The parametric sketch system strengthens view management by functions of graph redrawing, graphs zoom-out, screen move, all graphs display on the screen and view scroll and the like.4. Saving and opening files. The parametric sketch system can save graph file and open existed file to edit by serial operations.5. Adding constraints and parametric graph. In the system, users can add constraints to graph elements, such as horizon, upright, conjunct point, parallel, perpendicularity and tangent and so on, in the same time, users can modify parameters of graphics in the parametric dialog and realize parametric graphics.