A Walk Through the Planned CS Building

Using the architectural plan views of our future CS building as test objects, we have completed the first stage of a Building walkthrough system. The inputs to our system are AutoCAD files. An AutoCAD converter translates the geometrical information in these files into a format suitable for 3D rendering. Major model errors, such as incorrect polygon intersections and random face orientations, are detected and fixed automatically. Interactive viewing and editing tools are provided to view the results, to modify and clean the model and to change surface attributes. Our display system provides a simple-to-use user interface for interactive exploration of buildings. Using only the mouse buttons, the user can move inside and outside the building and change floors. Several viewing and rendering options are provided, such as restricting the viewing frustum, avoiding wall collisions, and selecting different rendering algorithms. A plan view of the current floor, with the position of the eye point and viewing direction on it, is displayed at all times. The scene illumination can be manipulated, by interactively controlling intensity values for 5 light sources. We have improved the rendering speed of our system by subdividing the model into cells and reducing the fraction of the building that is sent to the rendering pipeline at display time. Each floor is divided into approximately room-sized cells, each with a precomputed cell-to-cell visibility list. During display, the cell containing the viewpoint is identified, and the contents of the potentially visible cells are retrieved from storage. This set is further reduced by culling it against the observers view frustum. The contents of the remaining cells are then sent to the graphics pipeline.