While the Walkthrough Project relies on the tracking and graphics hardware groups for advances in those areas, most of our research involves software efforts to make advances on four fronts: prettier models, faster display, real application and model building, and handier interfaces. Current efforts in these areas include:
Faster Display. Hierarchical view frustum culling processes only those portions of a model that are in the user's field of view. Fidelity-based level of detail creates lower complexity representations of objects and renders these simpler versions when the user can not discern the difference. Our most recent work in this area has been in the use of Hierarchical Levels of Detail (HLODs). Distant geometry is replaced by images for gauranteed frame rates. Potentially visible sets break a model into rooms and holes in walls between rooms, called "portals," thus making it possible to render only the current room and those rooms which are visible from the current room through a string of one or more portals. Other occlusion culling techniques have been developed for more general models that may not be appropriate for the use of portals. Texture mapped radiosity represents the high geometric complexity of a meshed primitive resulting from radiosity as a photo-texture on a single polygon.
Interaction. Collision detection and proximity queries with large models are used for evaluation of maintenace and operaton requirements. We have developed techniques for performing these operations that are both fast enough for interactivity, and use a small enough memory footprint to be of use with models of large size (millions of primitives).
Prettier Models. Radiosity, a physically-based lighting model which simulates diffuse illumination in a model, generates realistic gradients and shadows on model primitives. Photo- and procedural textures convey visually complex patterns, such as brick and woodgrain. A sound server generates a 3D audio environment for the user. Mirrors and glass windows display reflections of primitives in models. Superposition Rendering allows for interactive rendering while accomidating sophisticated reflectance and transmission functions (BRDF/BTDF), such as glossy reflections.
Real Application and Model Building. A model of the Brooks House has been used in walkthroughs by the client, architect, and interior designer to evaluate remodeling options. The model is now used for model validation and future planning. Models of real or proposed structures worked on by the Walkthrough Project team include: Henderson County (NC) Courthouse, Orange Methodist Church (Chapel Hill, NC), Sitterson Hall (UNC Dept. of Computer Science building), Brooks House I and II, Frank Lloyd Wright's Fallingwater (model courtesy of Cornell University), the torpedo room of a notional submarine (model courtesy of the Electric Boat Division of General Dynamics), the auxilliary machine room of a notional submarine (also courtesy of the Electric Boat Division of General Dynamics), Yuan Ming Yuan garden (courtesy of Xing Xing Computer Graphics Inc), a coal-fired electric power plant, and a double-hull tanker ship. The torpedo room, auxilliary machine room, power plant, and tanker models are used to help determine the value of virtual-environment systems as tools for simulation-based design in order to avoid the cost and time required to build and revise physical models.
Handier Interface. Wide-area optical ceiling tracking allows users to navigate through and interact with a model in a natural fashion. High-resolution and wide field-of-view HMDs help the user better understand and view the models during walkthroughs. Object-to-object constraints and hand-tracked interaction with objects allow the user to manipulate the model naturally. We are investigating how people navigate and perform spatial problem solving in virtual environments. We are also exploring more effective ways to create models while immersed in a virtual environment.
Last updated: 2-17-01