In the context of a Building Walkthrough Program, we investigate methods for interactively placing and rearranging furniture within the building model while in an interactive real-time Walkthrough session. We have created a simple 3D editor that allows the user to move objects, while observing some object-dependent constraints. Different objects may have different alignment properties. For example, desks and chairs would be given the property that they will remain aligned with the floor polygons, while pictures and white boards might be confined to be coplanar with the vertical walls of the building. When objects with such alignment properties are placed or moved in the model, the program searches for a nearby suitable face, and if an object comes within a certain distance of such a face, the object is snapped to that face. These alignment properties can be used by our interactive editor as well as by programs that populate the interior of a building model procedurally.
Of course, within the given alignment constraints, the user is allowed to rotate, scale, and duplicate objects (operations will-known from 2D graphics editors). A good graphical user interface with iconic handles makes such operations easy and unambiguous in a 3D model with only the 2D mouse pad as an input device. This editor should make it much easier for the developers and users of a building model to place furniture and other objects into natural positions without the need to change views or to zoom into the space between an object and its supporting surface. By reducing the tedium of placing thousands of objects inside a large and complicated building model, we will be able to populate such models to a degree that makes them look realistic and that makes for exciting Walkthrough experiences.