CN109285177B - Digital city skyline extraction method - Google Patents
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Abstract
The invention discloses a digital city skyline extraction method, which comprises the following steps: 1) constructing a digital city three-dimensional model; 2) forming a set of contour points for a building; 3) determining a projection cylindrical surface and a projection range of the skyline; 4) from the observation viewpoint, carrying out cylindrical projection transformation on the interpolated building contour points along the observation viewpoint-building-projection column surface to obtain skyline projection contour points of the building; 5) eliminating the skyline projection contour points of the shielded buildings to obtain skyline projection contour points of the rest buildings; 6) and (3) fitting the skyline projection point set by using the skyline projection contour points of the rest buildings obtained in the step 5) to form continuous building group skylines, and finishing the extraction of the digital city skylines.
Description
Technical Field
The invention belongs to the technical field of graphic processing in the field of digital city planning, and relates to a digital city skyline extraction method.
Background
The skyline is an important expression form of a city body outline and also a main component of city landscape resources, although the skyline is a two-dimensional vertical face contour line of a city under a certain visual angle, the skyline is reflected by three-dimensional space level characteristics and is used as one of the elements of city intention, the skyline is the most direct and specific display of the city space landscape and is often the name card and the characteristic identification line of the city image, and the skyline has important significance for enhancing the identifiability of the city and displaying the regional style and features, so that the city planning and design taking the city skyline control as the core can effectively enhance the space order of regional development and improve the overall image of the city. The existing urban skyline is mostly obtained by adopting a manual photographing and drawing method, the method is convenient to use and simple and easy to implement, the manual drawing of the skyline wastes time and cost, and meanwhile, the requirement on the drawing capability of drawing personnel is high, so that an efficient and quick urban skyline automatic extraction method is very necessary.
In the research of two-dimensional city skyline, Wangjianfeng carries out more detailed explanation in the literature 'quantitative analysis research of city space morphology [ D ]. Chongqing university, 2004.', and on the basis of selecting a proper city sightseeing spot as an observation point, an urban building group is photographed from the horizontal direction right opposite to the building by using a small visual angle of a shelter, and after the photograph is analyzed, the skyline can be drawn according to the outer contour of the building group intersected with the sky. However, the city skyline viewpoint extracted through the picture is single and limited by the position of the photographer, and the feeling of people in the real world cannot be expressed in a multi-angle and all-around manner. Cao Yingchun et al in the document "fractal theory-based urban skyline quantitative analysis [ J ]. City problems, 2013(12): 32-36." for skyline photographs shot on the spot and published on the network, the fractal dimensions of skylines of external cities and main cities in China are calculated based on a fractal theory, and the fractal characteristics of the skylines are discussed, but the complex mathematical calculation method of the fractal theory is difficult to be understood by city planners.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a digital city skyline extraction method, which can effectively avoid the problems of single viewpoint and limitation of a photographer station position caused by extracting the city skyline through a photo, and has low calculation complexity.
In order to achieve the purpose, the method for extracting the digital city skyline comprises the following steps:
1) constructing a digital city three-dimensional model;
2) carrying out spatial linear interpolation on the cube corner points of the digital building to form a contour point set of the building;
3) selecting an observation viewpoint from the digital city three-dimensional model, determining an observation distance R of a sight line, a field angle in a horizontal direction and a field angle in a vertical direction according to the visual characteristics of human eyes, and further determining a projection cylindrical surface and a projection range of an interplanetary line;
4) from the observation viewpoint, carrying out cylindrical projection transformation on the interpolated building contour points along the observation viewpoint-building-projection column surface to obtain skyline projection contour points of the building;
5) eliminating the skyline projection contour points of the shielded buildings to obtain skyline projection contour points of the rest buildings;
6) and (5) fitting the skyline projection point set by using the skyline projection contour points of the rest buildings obtained in the step 5) to form continuous building group skylines, and finishing the extraction of the digital city skylines.
The specific operation of the step 1) is as follows:
1a) acquiring all elevation points in the terrain data, constructing a triangular mesh terrain surface from all the elevation points by using a Delaunay triangulation algorithm, and rendering the terrain surface color according to the elevation value to obtain a three-dimensional terrain model;
1b) acquiring space coordinate position information and height information of buildings in a planning map and a topographic map of the urban building, and constructing a digital three-dimensional model of an urban building group by taking a cube as a basic shape;
1c) superposing the three-dimensional terrain model obtained in the step 1a) and the digital three-dimensional model of the urban building group obtained in the step 1b) according to the position coordinates to obtain the digital urban three-dimensional model.
In step 2), performing spatial linear interpolation on the cube corner points of the digital building by using an inverse distance weighting method to form a contour point set of the building, wherein an estimated coordinate value Z of a point to be interpolated is as follows:
wherein z isiIs the actual coordinate value of the ith sample point, diAnd the distance between the ith sample point and the point to be inserted is defined, m is the number of actual sample points participating in calculation, and n is the power exponent.
In step 4), cylindrical projection transformation is carried out on the interpolated building contour points along the observation viewpoint-building-projection cylindrical surface to obtain the skyline projection contour points of the building, wherein the coordinates of the skyline projection points on the perspective projection cylindrical surface are (x)1,y1,z1) Wherein, in the step (A),
y1r, (x, y, z) is the coordinates of any contour point of the building.
The concrete operation of eliminating the skyline projection contour points of the shielded building in the step 5) is as follows:
5a) comprehensively ordering the contour point set of the building in X, Y, Z three coordinate axis directions;
5b) comparing the relative position relationship between the contour point of any building and the contour points of the buildings adjacent to the building, judging whether the contour point of the building is shielded, and deleting the shielded building contour point and the skyline projection point thereof when the contour point of the building is shielded.
And 6), fitting a skyline projection point set according to a cubic B-spline curve by using the skyline projection contour points of the rest buildings obtained in the step 5) to form continuous building group skylines.
The invention has the following beneficial effects:
when the digital city skyline extraction method is specifically operated, a digital city three-dimensional model is constructed first, and then the digital city skyline is extracted on the basis of the digital city three-dimensional model, so that the problems that the viewpoint is single and the position of a photographer is limited due to the fact that the city skyline is extracted through a photo are solved. Specifically, a contour point set of the building is formed, projection cylindrical surfaces and projection ranges of the skylines are determined, then skyline projection contour points of the building are obtained, finally, shielded skyline projection contour points of the building are eliminated, and the skyline projection contour points of the remaining buildings are used for fitting the skyline projection point set to form continuous building group skylines.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a schematic view of a cylindrical projection of the present invention;
FIG. 3 is a schematic view of the building shading relationship of the present invention;
FIG. 4a is a graph of the 3D skyline results extracted in the first embodiment;
FIG. 4b is a front view of the relationship between the 3D skyline and the building extracted in the first embodiment;
FIG. 4c is a top view of the relationship between the 3D skyline and the building extracted in the first embodiment.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 1, 2 and 3, the method for extracting the digital city skyline according to the present invention comprises the following steps:
1) constructing a digital city three-dimensional model;
the specific operation of the step 1) is as follows:
1a) acquiring all elevation points in the terrain data, constructing a triangular mesh terrain surface from all the elevation points by using a Delaunay triangulation algorithm, and rendering the terrain surface color according to the elevation value to obtain a three-dimensional terrain model;
1b) acquiring space coordinate position information and height information of buildings in a planning map and a topographic map of the urban building, and constructing a digital three-dimensional model of an urban building group by taking a cube as a basic shape;
1c) superposing the three-dimensional terrain model obtained in the step 1a) and the digital three-dimensional model of the urban building group obtained in the step 1b) according to the position coordinates to obtain the digital urban three-dimensional model.
2) Carrying out spatial linear interpolation on the cube corner points of the digital building to form a contour point set of the building;
in step 2), performing spatial linear interpolation on the cube corner points of the digital building by using an inverse distance weighting method to form a contour point set of the building, wherein an estimated coordinate value Z of a point to be interpolated is as follows:
wherein z isiIs the actual coordinate value of the ith sample point, diThe distance between the ith sample point and the to-be-inserted point is defined as m, the number of actual sample points participating in calculation is defined as n, the n is a power exponent, and the n controls the degree of descending of the weight coefficient along with the increase of the distance between the to-be-inserted point and the sample point.
3) Selecting an observation viewpoint from the digital city three-dimensional model, determining an observation distance R of a sight line, a field angle in a horizontal direction and a field angle in a vertical direction according to the visual characteristics of human eyes, and further determining a projection cylindrical surface and a projection range of an interplanetary line;
4) from the observation viewpoint, carrying out cylindrical projection transformation on the interpolated building contour points along the observation viewpoint-building-projection cylindrical surface to obtain the skyline projection contour points of the building, wherein the coordinates of the skyline projection points on the perspective projection cylindrical surface are (x)1,y1,z1) Wherein, in the step (A),
y1r, (x, y, z) is the coordinate of any contour point of the building;
5) eliminating the skyline projection contour points of the shielded buildings to obtain skyline projection contour points of the rest buildings;
the concrete operation of eliminating the skyline projection contour points of the shielded building in the step 5) is as follows:
5a) comprehensively ordering the contour point set of the building in X, Y, Z three coordinate axis directions;
5b) comparing the relative position relationship between the contour point of any building and the contour points of the buildings adjacent to the building, judging whether the contour point of the building is shielded, and deleting the shielded building contour point and the skyline projection point thereof when the contour point of the building is shielded.
6) And (5) fitting the skyline projection point set by using the skyline projection contour points of the rest buildings obtained in the step 5) to form continuous building group skylines, and finishing the extraction of the digital city skylines.
And 6), fitting a skyline projection point set according to a cubic B-spline curve by using the skyline projection contour points of the rest buildings obtained in the step 5) to form continuous building group skylines.
It should be noted that the invention has used Net programming language to complete the development of Active X plug-in, can be loaded directly into Auto CAD for use, can let the planner master the visual form of the skyline in real time while designing the urban planning scheme, expand the software function, and meet the design requirements of digital urban planning.
Example one
Referring to fig. 1, a composite city three-dimensional model of a part of buildings in lonun county and their landforms is established with a city plan 1:2000 in lonun county, Shanxi province, Shandong city, as a data source, and in a coordinate system of the city model, a coordinate point (1908,1126,1100) is taken as an observation viewpoint, and a skyline with the point as the observation viewpoint is extracted and visualized, wherein an observation viewpoint a is selected from the digital city three-dimensional model, an observation distance D is 1000, a horizontal viewing angle is 120 ° and a vertical viewing angle is 70 °, an upward viewing angle is 30 °, a downward viewing angle is 40 °, the extracted 3D skyline result is shown in fig. 4a, a main view of the relationship between the extracted 3D skyline and the buildings is shown in fig. 4b, and a top view of the relationship between the extracted 3D skyline and the buildings is shown in fig. 4 c.
Claims (6)
1. A digital city skyline extraction method is characterized by comprising the following steps:
1) constructing a digital city three-dimensional model;
2) carrying out spatial linear interpolation on the cube corner points of the digital building to form a contour point set of the building;
3) selecting an observation viewpoint from the digital city three-dimensional model, determining an observation distance R of a sight line, a field angle in a horizontal direction and a field angle in a vertical direction according to the visual characteristics of human eyes, and further determining a projection cylindrical surface and a projection range of an interplanetary line;
4) from the observation viewpoint, carrying out cylindrical projection transformation on the interpolated building contour points along the observation viewpoint-building-projection column surface to obtain skyline projection contour points of the building;
5) eliminating the skyline projection contour points of the shielded buildings to obtain skyline projection contour points of the rest buildings;
6) and (5) fitting the skyline projection point set by using the skyline projection contour points of the rest buildings obtained in the step 5) to form continuous building group skylines, and finishing the extraction of the digital city skylines.
2. The digital city skyline extraction method of claim 1, wherein the specific operations of step 1) are as follows:
1a) acquiring all elevation points in the terrain data, constructing a triangular mesh terrain surface from all the elevation points by using a Delaunay triangulation algorithm, and rendering the terrain surface color according to the elevation value to obtain a three-dimensional terrain model;
1b) acquiring space coordinate position information and height information of buildings in a planning map and a topographic map of the urban building, and constructing a digital three-dimensional model of an urban building group by taking a cube as a basic shape;
1c) superposing the three-dimensional terrain model obtained in the step 1a) and the digital three-dimensional model of the urban building group obtained in the step 1b) according to the position coordinates to obtain the digital urban three-dimensional model.
3. The method for extracting digital city skyline as claimed in claim 2, wherein in step 2), an inverse distance weighting method is used to perform spatial linear interpolation on the cube corner points of the digital building to form a contour point set of the building, wherein the estimated coordinate values Z of the points to be interpolated are:
wherein z isiIs the actual coordinate value of the ith sample point, diAnd the distance between the ith sample point and the point to be inserted is defined, m is the number of actual sample points participating in calculation, and n is the power exponent.
4. The digital city skyline extraction method of claim 1, wherein in step 4), the interpolated building contour points are subjected to cylindrical projection transformation along an observation viewpoint-building-projection cylinder to obtain skyline projection contour points of the building, wherein the coordinates of the skyline projection points on the perspective projection cylinder are (x)1,y1,z1) Wherein, in the step (A),
(x, y, z) is the coordinates of any contour point of the building.
5. The digital city skyline extraction method of claim 1, wherein the specific operations of eliminating skyline projected contour points of the occluded building in step 5) are as follows:
5a) comprehensively ordering the contour point set of the building in X, Y, Z three coordinate axis directions;
5b) comparing the relative position relationship between the contour point of any building and the contour points of the buildings adjacent to the building, judging whether the contour point of the building is shielded, and deleting the shielded building contour point and the skyline projection point thereof when the contour point of the building is shielded.
6. The digital city skyline extraction method of claim 1, wherein in step 6), skyline projection point sets are fitted according to a cubic B-spline curve using the skyline projection contour points of the remaining buildings obtained in step 5) to form continuous building group skylines.
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| CN110059699B (en) * | 2019-03-18 | 2021-01-29 | 中南大学 | Automatic detection method for skyline in image based on convolutional neural network |
| CN110033203B (en) * | 2019-04-23 | 2023-05-05 | 重庆市勘测院 | Astronomical line evaluation method based on urban live-action long roll and three-dimensional model projection |
| CN112131324A (en) * | 2019-06-25 | 2020-12-25 | 上海擎感智能科技有限公司 | Map display method and device |
| CN110807787B (en) * | 2019-11-11 | 2022-07-22 | 四川航天神坤科技有限公司 | Skyline extraction method and system |
| CN110926474B (en) * | 2019-11-28 | 2021-09-03 | 南京航空航天大学 | Satellite/vision/laser combined urban canyon environment UAV positioning and navigation method |
| CN112001011B (en) * | 2020-08-10 | 2024-04-02 | 浙大城市学院 | Method for extracting range of esthetic quantization factor of city astronomical line based on wind environment evaluation |
| CN112597905A (en) * | 2020-12-25 | 2021-04-02 | 北京环境特性研究所 | Unmanned aerial vehicle detection method based on skyline segmentation |
| CN113031041B (en) * | 2021-03-11 | 2022-06-10 | 南京航空航天大学 | Urban canyon integrated navigation and positioning method based on skyline matching |
| CN113449363B (en) * | 2021-06-16 | 2023-09-26 | 中国工程物理研究院计算机应用研究所 | Numerical simulation-oriented large-scale city model computable processing method |
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