Computer tools for urban design have been developed for the last few decades. They can be classified into two kinds. One is a semantic simulation tool and the other is a visualization tool. The former is used in examining plans with criteria of urban design. The latter do in providing visual experiences of them. But both have been developed separately and neither of them provides real-time interactivity needed for fast feedback. Therefore an interactive visual simulation system for urban design is required.
This paper introduces a Virtual Reality(VR) system for urban design. VR aims at providing reality and real-time interactivity of virtual environments(VEs). To achieve it, VR mainly uses 3-dimensional visualization based on the rules which are effective to represent VEs. Thus we adopt two concepts - an urban map metaphor for the rules of VEs and Hybrid Scene Graph as a new data structure for simulation and visualization of VEs. The former simplifies a city with some urban elements on the flat ground. It enables the users to create, modify, and interact with the virtual city intuitively. The latter is a composition of two data structures - the hierarchical tree for faster rendering and the relational table for management of complex relationships among urban elements.
