SKETCHPAD+ ARCHITECTURAL MODELING THROUGH PERSPECTIVE SKETCHING ON A PEN-BASED DISPLAY

Design is a subjective and iterative process. Through drawings, models and other artifacts, designers define physical form that satisfies both their functional and artistic objectives. Of all modalities, freehand sketching is used by most designers as their primary means of generating and visualizing conceptual design solutions. To date, computers have served designers primarily in accelerating engineering and presentation tasks. Software programs for precise twodimensional drafting and three-dimensional modeling produce construction documents, photo-realistic images and interactive visualizations of a finalized design solution. Unfortunately, few applications exist that truly support the more creative endeavor of early conceptual design. In this thesis, we introduce a new paradigm for computer-based conceptual design. We have developed a system that allows a designer to freely draw on the surface of a large design table that is both a pen-based digitizer and computer display. These freehand strokes, drawn directly onto the computer display, are projected into the application’s virtual space to become the primary elements of a sketch-model – a three-dimensional drawing. Traditionally, a designer draws several drawings in order to view an object from various perspectives. In our system, however, a user need only draw a single three-dimensional freehand model. By using the pen-digitizer combination, we have been able to avoid the monitor-mouse paradigm so inconvenient to architectural designers. Simultaneously, we are also able to offer valuable real estate necessary for the portrayal of complex building design. More importantly, by using the tabletop projection surface, we have provided a means for the architect to sketch directly into a realistically simulated three-dimensional virtual environment. This capability spans the preliminary and final design stages, providing immediate visual feedback for design modifications and decisions. Our system thus simultaneously provides the means for loose and ambiguous freehand drawing and precise and robustly defined representation. The latter, based on the ACIS solid modeling kernel, provides a large variety of modeling capabilities including free-form NURBS surfaces, primitive elements, and all of the necessary Boolean operations. Currently, means for combining the sketching, solid modeling, and rendering modules are done by file transfer, but in the future they should be integrated into one consistent system. Lastly, our system provides a framework in which several designers can converse verbally as well as graphically while working in a shared virtual model space from geographically remote locations. This thesis presents a new approach to geometric modeling. We believe that for conceptual design, precision is less important than artistic freedom. Therefore, software tools should allow designers to create geometric form from loose gestures rather than precise dimensions. We have developed a system that supports this notion by utilizing freehand drawing as a primary input mechanism. Through powerful modeling functionality and sensitive interface design, we have provided a tool that is appropriate to the creative endeavors of conceptual designers.