Virtual terrain in a parametric 3D based bridge modeling system

An algorithm was developed to quickly generate a virtual terrain in a parametric 3D based bridge modeling system. The terrain’s details was increased by using the fractal theory, a quadtree data structure was used to store triangulation irregular net (TIN) in order to accelerate the retrieval of the triangle containing the given point, the triangle retrieved was subdivided by sparse control points to join bridge models and terrain, the viewpoint range was controlled by a quickly collision detection method between the viewpoint and the terrain. Terrain, sky sphere and bridge models were organized together based on the tree structure, and a node sharing mechanism was designed to reduce the space complexity of the algorithm. In the end, a lifelike scene of bridge was generated. The algorithm has been used in the bridge design software developed by us, which proved the algorithm be efficient.