Research On Extraction Method Of The Skyline And Visible Area In Digital City

Traditional urban planning has been more mature in the visualization and analysis of two-dimensional information,but it is still insufficient to meet the needs of the visualization and utilization of spatial information.It is an inevitable trend to build a city planning and analysis platform with 3D visualization technology and to study related technologies and visualization methods,which can provide spatial analysis and decision-making methods for urban planning and design.The skyline is a special visual form that people perceive the urban space landscape,and it is also an significant indicator of urban planning.Aiming at the problem that the current urban planning mainly extracts skyline by taking pictures,which leads to the planning scheme is unintuitive.Designing the visualized extraction and visualization methods under the 3D urban model,and constructing the visible area visualization models in the building group can be used for the analysis of buildings' spatial relationships.The main work of the paper is as follows.In order to achieve the purpose of extraction and three dimensional visualization for the digital city skyline and visible area,the three-dimensional model of terrain and ground are constructed by the triangular network and the entity model,which provided the basis for spatial information analysis and extraction in urban planning and design.On the constructed three-dimensional urban model,designed a three-dimensional skyline extraction method by constructing a visual line analysis model between the observation point and the building group.The new method was based on the relative position of observation points,buildings and projections,using the cylindrical projection transformation to obtain the boundary between the building group and the visual space,so as to realize the visualization of the skyline.Starting from the nature of the visible area,transformed the problem of visible area visualization into the visible surface visualization by dividing the area to be analyzed.Then based on the point-to-point visibility analysis principle,constructed a visible area visualization modelm,and finally proposed a new method for three-dimensional visualization of the visible area.