Research On Key Technologies Of Computer Aided Sketching Design For Conceptual Expression

Conceptual design is the initial stages of product development which is characterized by inadequate and vague design information. However, current CAD systems need to input precise dimensional and geometric constraints information in the process of product modeling. At the same time, the use of WIMP-based user interface makes the process of modeling very cumbersome, tedious and time-consuming. These reasons make current CAD systems mainly be suited for the detailed design and not the conceptual design. In the conceptual design stage, designers usually use pencil and paper to rapidly record their creative ideas. Only when the configuration of the product is determined fully, the digital model will be constructed by using the computer aided design technologies. Because the design and the modeling process are separate, some important information will be lost during information conveyance. Combining the flexibility and ease of use of paper and pencil with the processing power of the computer, Computer Aided Sketching Design (CASD) technology specially suits for conceptual design and can help designer write down design ideas rapidly. For many years it has been one of key issues which many specialists and scholars research. The present situation of CASD is introduced firstly. And then some key technologies of CASD, that is pen-based user interface design, sketch recognition and beautification, gesture-based sketch editing, 3D sketching modeling, are analyzed. The main research contents and achievements are articulated as follows:(1) Some basic theories and algorithms on sketching design and sketch recognition have been researched, such as sketch preprocessing, feature points detection, strokes fragment, primitives recognition, shape reconstruction, and primitives beautification, etc. The aim is integrating users' sketching styles and the abilities of recognizing sketch with the technologies of CAD in order to develop new intelligent CAD systems.(2) The gesture is an important interactive way to realize a certain operation for sketch editing. In order to realize online conceptual sketch editing, some kinds of gestures have been designed and defined, such as delete gestures, move gestures, copy gestures, rotate gestures, etc. These gestures have been recognized by using a trainablegesture recognizer. In order to improve the recognition efficiency and the user adaptation of gestures, several recognition algorithms have been used. Finally, A series of algorithms for sketch editing based on pen gestures are presented.(3) A simple, rapid, efficient approach to construct 3D conceptual solid models on sketch-based user interface is presented. It emulates the traditional sketching design approach with paper and pencil metaphor to sketch strokes on the calligraphic interface, and then applies the feature-based modeling method to construct different sweep feature-based primitives according to the shape and location relationship of feature strokes. In order to construct complex solid models, the feature joining and cutting mechanism based on intention capturing is introduced. Additionally, a gesture-based model editing method is presented briefly. We illustrate the implementation of the algorithm and experiments show that our algorithm is efficient and well suited for real time on-line 3D conceptual model creation.(4) The Sketch2D system, a sketching design system for engineering sketch design and editing, and the Sketch3D system, a sketch-based modeling system for conceptual expression of products, have been developed by using the object-oriented design method and the technologies of current CAD. Some basic frame structures and functions of the systems have been presented. Some experimental examples have been provided to verify the efficiency of the recognition and modeling algorithms. Finally, some capabilities of the SketchXD system (the abbreviation of the Sketch2D system and the Sketch3D system) have been compared with the current CAD systems such as AUTOCAD, Pro/Engineer, etc., and some classical sketching design systems such as SILK, SKETCH, etc.