Abstract
Simplification of 3D building models is an important way to improve rendering efficiency. When existing algorithms are directly applied to simplify multi-component models, generally composed of independent components with strong topological dependence, each component is simplified independently. The consequent destruction of topological dependence can cause unreasonable separation of components and even result in inconsistent conclusions of spatial analysis among different levels of details (LODs). To solve these problems, a novel simplification method, which considers the topological dependence among components as constraints, is proposed. The vertices of building models are divided into boundary vertices, hole vertices, and other ordinary vertices. For the boundary vertex, the angle between the edge and component (E–C angle), denoting the degree of component separation, is introduced to derive an error metric to limit the collapse of the edge located at adjacent areas of neighboring components. An improvement to the quadratic error metric (QEM) algorithm was developed for the hole vertex to address the unexpected error caused by the QEM’s defect. A series of experiments confirmed that the proposed method could effectively maintain the overall appearance features of building models. Compared with the traditional method, the consistency of visibility analysis among different LODs is much better.
Highlights
The usage of 3D city scenes is becoming increasingly significant in urban applications because they provide more realistic experiences than 2D maps [1]
They collapse during the simplification process, causing separation between the roof collapse during the simplification process, causing separation between the roof and the wall. To solve this kind of problem, we propose a supplementary rule: when and the wall. To solve this kind of problem, we propose a supplementary rule: when an edge passes through a component and the normal vectors of its two adjacent trian edge passes through a component and the normal vectors of its two adjacent triangles are parallel, the other two vertices of both triangles are regarded as angles are parallel, the other two vertices of both triangles are regarded as gap between components
We show the simplification results derived from different simplification methods
Summary
The usage of 3D city scenes is becoming increasingly significant in urban applications because they provide more realistic experiences than 2D maps [1]. The building model plays a key role in 3D city scenes because its rendering efficiency directly affects the user’s experience during the interactive process. As the demand for detailed expression increases, the data volume of 3D building models has grown rapidly. The performance of computers has substantially improved recently, it is still hard to meet the demand caused by the explosive growth of the data volume, which brings considerable challenges to the real-time rendering of 3D models. In large-scale city scenes, there may be hundreds of building models in the view. LODs can effectively improve the efficiency of spatial analysis, such as visibility analysis in large-scale city scenes [6]
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