The simplification of 3D building models to effectively reduce model complexity and improve rendering efficiency is an important component of 3D GIS. To reduce the data volume while preserving the model appearance, this article proposes a novel simplification method for complex 3D building models. Texture discontinuities are addressed by developing a new data model that records the mapping relation between the texture coordinates of each vertex and its neighboring triangles. The surface mesh of the building model is then segmented into regions, guided by topology and appearance. Finally, the mesh segmentation information is used to derive an improved error metric that considers both geometric and texture errors, and the texture coordinates are adjusted after each simplification operation. A series of comparative experiments alongside traditional methods demonstrates that our approach achieves a good balance between geometric fidelity and texture preservation, and produces simplified 3D building models with better visual quality.
A multiple criteria decision analysis (MCDA) problem is studied in this paper, for which the evaluation results obey a particular distribution. First, when solving a multiple criteria decision analysis (MCDA) problem, a grey target decision analysis framework is proposed to determine uncertain parameters and criteria weights. A measurement for comprehensive off-target distance is defined, which includes the undetermined parameters. Second, to satisfy the requirements of a specific distribution (such as a normal distribution) in the assessment results, an optimization model that incorporates the off-target distance constraints is proposed by considering the skewness and kurtosis test method. Third, a particle swarm optimization (PSO) algorithm is extended to solve the proposed model by seeking the appropriate parameters and weights. Fourth, a numerical example is applied to demonstrate the feasibility and application of the proposed method. In the end, the proposed model is extended to other distribution requirements.
How to qualitatively and quantitatively evaluate the ability of the whole subway system to maintain the maximum normal operation has become a noteworthy topic. In this study, the hypergraph space structure of Nanjing subway network is used for research. This study uses the method of time-space evolution mechanism to dynamically and quantitatively analyze the gradual change characteristics of Nanjing subway system vulnerability under the influence of time and space. In addition, this study also makes static and dynamic comparative analysis on the vulnerability of a subway system by using connectivity rate and trip efficiency index, which provides new analysis methods and ideas for the study of a subway system network. The results show that although the overall structure of Nanjing’s subway network shows a loose trend, as Nanjing’s subway is still in a rapid development stage, it can be seen from the long-term planning of Nanjing’s subway that the construction of Nanjing’s subway ring line will be strengthened after the completion of the connection between the main city and the suburbs. Therefore, the vulnerability of the subway system should be reduced and the reliability will be improved.
Empirical evidences on how urban road accessibility affects air pollution is scarce for the specific Yangtze River Delta (YRD) region that is characterised by high density in economic activities and rapid urban expansion. Using novel Digital Elevation Model (DEM), road network and points-of-interest (POI) datasets to measure road accessibility, moderating and mediating effect models then were conducted to explore direct and indirect effects of road accessibility on environmental externality expressed by air pollution through urban connection and urban agglomeration. When exploiting exogenous variable in urban populations, the result of moderating effect model shows that road accessibility decreases air quality-to-connection elasticity by around -5.2% which indicates that road accessibility increases air pollution through internal connection. However, the finding of mediating effect model indicates that road accessibility slightly improves air quality through decreasing urban agglomeration. The findings of this paper suggest that high levels of road accessibility may have negative consequence for live-ability of YRD cities because of current urban internal connection and urban decision makers should consider the improvement of urban connection for obtaining better air quality.
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