CN109544683B - Urban building group seismic response dynamic visualization method based on oblique photography data - Google Patents
Urban building group seismic response dynamic visualization method based on oblique photography data Download PDFInfo
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Abstract
The invention provides a dynamic visualization method for earthquake response of an urban building group based on oblique photography data, and belongs to the technical field of civil engineering. Firstly, preparing data, including city geographic information basic data, building group earthquake power reaction course data and oblique photography aerial photography pictures; then, modeling a three-dimensional live-action model, and accelerating the modeling by using various optimization methods of waypoint sparseness, detail level adjustment and computer cluster assistance; then model singleness and post-processing are carried out, including building model singleness, texture compression and environment model flattening; and finally, realizing the dynamic visualization of the reality sense of the earthquake reaction of the building group by using the three-dimensional live-action model, the urban geographic information basic data and the earthquake dynamic reaction history data of the building group. The method can truly display the earthquake displacement process of the building, can be used for virtual emergency drilling in cities, and provides decision reference for earthquake-proof and disaster-reduction planning, emergency plans and the like.
Description
Technical Field
The invention relates to the technical field of civil engineering, in particular to a dynamic visualization method for earthquake response of an urban building group based on oblique photography data.
Background
Earthquakes pose a great threat to urban safety and may cause serious casualties, such as the Wenchuan earthquake and the like. The urban earthquake reaction process visualization can be used for virtual earthquake emergency drilling, and a vivid earthquake scene is provided for personnel, so that the earthquake emergency capacity of the personnel is improved, and casualties are reduced. However, how to show urban seismic processes with high realism is a key challenge.
Oblique photography (Oblique photography) technology provides a highly realistic three-dimensional city model to solve this problem. The oblique photography technology utilizes an unmanned aerial vehicle to load a plurality of cameras, acquires image data from different angles, and then can establish a ground surface three-dimensional model with photo-level reality according to the image data. By the technology, a realistic three-dimensional city model can be established, and the resolution of the model can reach the centimeter level. At present, oblique photography techniques have been applied to digital modeling of urban seismic scenes and assessment of seismic damage. But there are no relevant researches and reports for realizing dynamic visualization of earthquake response of urban building groups based on oblique photography data. The method realizes the highly-realistic dynamic visualization of the earthquake response of the urban building group by utilizing the oblique photography data, provides a reasonable and real scene for the urban virtual earthquake emergency drilling, and better supports earthquake emergency decision.
Disclosure of Invention
The invention aims to provide a dynamic visualization method for urban building group seismic response based on oblique photography data.
The method comprises the following steps:
(1) Preparing data: the data comprises urban geographic information basic data, building group earthquake dynamic response course data and oblique photography aerial pictures;
(2) Modeling a three-dimensional live-action model: establishing a three-dimensional live-action model by utilizing oblique photography aerial pictures, and adopting various optimization methods according to conditions;
(3) Model singulation and post-treatment: the three-dimensional live-action model is subjected to singleization, texture compression is further performed, and the environment model is flattened;
(4) Building group seismic response reality dynamic visualization: and realizing dynamic visualization of the realistic sense of earthquake response of the building group by using the three-dimensional live-action model, the urban geographic information basic data and the building group earthquake dynamic response history data.
Wherein, the basic data of the urban geographic information in the step (1) comprises building numbers, structure types, building heights, building floor numbers, construction times, floor areas and use functions;
the building group earthquake power reaction history data takes the building floors as basic units and corresponds to buildings in the urban geographic information basic data one by one;
the ground resolution of the oblique photography aerial photography picture is between 5cm and 20cm, the overlapping part of continuous images of the oblique photography aerial photography picture exceeds 60 percent, and the division of the same ground object between different shooting points is less than 15 degrees.
The optimization method in the step (2) comprises navigation point sparseness, detail level adjustment and computer cluster assistance;
the sparse waypoints mean that a faster three-dimensional live-action model modeling speed is obtained by deleting part of aerial image groups under the condition of considering both the quality of the model and the overlapping rate of aerial images;
adjusting the detail level means that the resource allocation of object rendering is determined according to the positions and the importance of the nodes of the object model in the display environment, and the number of faces and the detail of non-important objects are reduced, so that the scene rendering efficiency is improved;
the computer cluster assistance means that the three-dimensional real-scene model reconstruction work is divided into a plurality of tiles, a cluster is formed by a plurality of computers in a local area network, and the plurality of tiles are processed at the same time, so that the modeling efficiency is remarkably accelerated.
The aerial image group which can be deleted in the aerial point sparsity comprises: the method comprises the following steps of image blurring, image meaningless, image repetition, lower discrimination between images, image position at the edge of a simulated region, image exceeding of the modeled region and redundancy in a higher region of an image overlapping image.
In the step (3), the monomer is to separate the building model from the environment model in the geometric range according to the basic data of the urban geographic information or other plane geometric information; the model texture compression is specifically one or two of a file format of a converted texture picture and a resolution of a compressed picture; the flattening of the environment model is to replace a complex three-dimensional mesh surface model with a plane model or a simple geometric model.
The specific process of the step (4) is as follows:
utilizing the building number in the urban geographic information basic data to correspond the building unit model to the result of the earthquake power reaction process data of the building group, reading the building floor number data in the urban geographic information basic data and corresponding to the building floor unit in the power reaction process data;
then, expanding the history data taking the floor as a unit to the full height range of the model by using a linear interpolation method;
and finally, rendering a frame in the visualization corresponding to each time step in the process data, and updating the building three-dimensional graph by using the corresponding process data in each frame to continuously update to form the earthquake response dynamic visualization effect of the urban building group.
The technical scheme of the invention has the following beneficial effects:
according to the scheme, the three-dimensional model of the building group can be utilized, and the displacement process calculation result obtained by nonlinear process analysis is combined, so that the response condition of the building group under the earthquake action is truly shown, and the efficiency is high and the sense of reality is strong.
Drawings
FIG. 1 is a flow chart of a dynamic visualization method for earthquake response of urban building groups based on oblique photography data;
FIG. 2 is an example of city geographic information base data according to an embodiment of the present invention;
FIG. 3 is an exemplary city geographic information base data attribute table according to an embodiment of the present invention;
FIG. 4 is a history displacement data file structure employed by the present invention;
FIG. 5 is a waypoint sparseness scheme of an embodiment of the invention;
FIG. 6 is an exemplary scenario of a local city in accordance with an embodiment of the present invention;
FIG. 7 is a flow chart of building singleization according to an embodiment of the present invention;
FIG. 8 is a schematic view of an automatic cutting singulation process according to an embodiment of the present invention;
FIG. 9 is an illustration of a manual cutting singulation example in accordance with an embodiment of the present invention;
FIG. 10 is an example of a three-dimensional live-action model texture image according to an embodiment of the present invention;
FIG. 11 is a flattening illustration of an environmental model in accordance with an embodiment of the present invention;
FIG. 12 is a flow chart of a seismic response dynamics visualization in accordance with an embodiment of the present invention;
FIG. 13 is a linear interpolation method for building seismic deformation using history data according to the present invention;
fig. 14 is an example of dynamic visualization of earthquake reaction of a building according to an embodiment of the present invention, in which (a), (b), (c), and (d) are respectively visualization presentations (displacement magnification of 50 times) of the dynamic visualization of earthquake reaction at times 7 ″ -00, 7 ″ -05, 7 ″ -10, and 7 ″ -13;
fig. 15 is an example of earthquake response dynamic visualization of urban building complex according to an embodiment of the present invention.
Detailed Description
To make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
The invention provides a dynamic visualization method for earthquake response of an urban building group based on oblique photography data.
As shown in fig. 1, the method comprises the steps of:
(1) Preparing data: the data comprises urban geographic information basic data, building group earthquake dynamic response course data and oblique photography aerial pictures;
(2) Modeling a three-dimensional live-action model: establishing a three-dimensional live-action model by utilizing oblique photography aerial pictures, and adopting various optimization methods according to conditions;
(3) Model singulation and post-treatment: the three-dimensional live-action model is subjected to singleness, texture compression is further carried out, and the environment model is flattened;
(4) Building group seismic response reality dynamic visualization: and realizing dynamic visualization of the realistic sense of earthquake response of the building group by using the three-dimensional live-action model, the urban geographic information basic data and the building group earthquake dynamic response history data.
The specific process is as follows:
(1) Data preparation
In the invention, the data preparation comprises city geographic information basic data, building group earthquake dynamic response course data and oblique photography aerial pictures.
For the urban geographic information basic data, the included data should include a building ground contour polygon, a building number (ID), a structure type, a building floor height, a building floor number, a construction age, a floor space, a use function, and the like. It is understood that the data can be obtained through relevant channels such as field research, purchase from mapping institutions, or network navigation maps;
for the dynamic response history data of the building earthquake groups, in order to realize earthquake damage visualization, the invention needs the history data taking the building floors as basic units. The history data of the building beam, column and other elements as basic units or other types of history data need to be formatted into the history data of the building floor as unit. And the calculation result of each building in the history data corresponds to the building number in the basic data of the urban geographic information according to the building number. Further features of the history data will be described in the detailed description;
for oblique photography aerial pictures, the ground resolution of the oblique photography aerial pictures is required according to the requirements of different ruler shooting and picture making, and the ground resolution requirements of the pictures are determined by combining the terrain conditions of the shooting area, the height distance of the mapping and the like, the aerial photography base height ratio, the image application and the like. Generally, the ground resolution of the aerial photo can be selected between 5cm and 20cm according to the time requirement. In addition, the overlapping part between the continuous images should exceed 60%, and the division of the same ground object between different shooting points should be less than 15 degrees, so as to obtain a three-dimensional live-action model with better quality. Further features of the oblique photography aerial photograph will be described in the detailed description.
(2) Three-dimensional live-action model modeling
In the invention, the oblique photography aerial photography picture is used for establishing the three-dimensional live-action model in the aerial photography area. In the invention, in order to accelerate the modeling efficiency of the three-dimensional live-action model, various optimization methods are adopted, including waypoint sparseness, detail level adjustment and computer cluster assistance.
The sparse waypoints mean that a faster three-dimensional live-action model modeling speed is obtained by deleting part of aerial image groups under the condition of considering both the quality of the model and the overlapping rate of aerial images. Generally, the overlapping rate of aerial images obtained by one aerial photographing frame is slightly conservative, so that part of aerial image groups can be deleted. Specifically, in the invention, the following aerial photography image groups can be deleted according to the situation: blurred or meaningless images; repetitive or low inter-image discrimination; the model is positioned at the edge of the simulated region or exceeds the modeled region; the image overlap map is redundant in the higher region;
for adjusting the detail level, the resource allocation of object rendering is determined according to the positions and the importance of the nodes of the object model in the display environment, and the number of faces and the detail of non-important objects are reduced, so that the scene rendering efficiency is improved;
for computer cluster assistance, the invention divides the three-dimensional live-action model reconstruction work into a plurality of tiles (tiles), utilizes a plurality of computers to form a cluster in a local area network, and processes a plurality of tiles at the same time, thereby remarkably accelerating the modeling efficiency.
(3) Model singulation and post-processing
In the invention, the ground contour data of the buildings in the basic data of the urban geographic information is used as a cutter to cut out each building model in the three-dimensional real scene model, and the building numbers in the basic data of the urban geographic information are respectively stored by taking the names of the building numbers so as to correspond to the dynamic response course data of the building seismic group. Due to the fact that flaws such as holes and wrong surfaces can exist in the model in the modeling process. For the model with defects in the part, manual intervention is still needed to assist cutting and singulation.
In the invention, in order to improve the earthquake damage visualization efficiency, the three-dimensional live-action model is further subjected to corresponding post-processing, including model texture compression and environment model flattening. For model texture compression, the format of a model texture image generated in the modeling process is converted, the resolution ratio of the model texture image is compressed, and the memory consumption during loading of the texture image is reduced; the flattening of the environment model means that a part of the three-dimensional real scene model other than the building model is replaced by a simple plane model having a simple map.
(4) Building group seismic response realistic dynamic visualization
In the invention, a building number item in the urban geographic information basic data is utilized to correspond a building unit model to a specific calculation result in the seismic power reaction process data of a building group, and the building floor number data in the urban geographic information basic data is read and corresponds to a building floor unit in the power reaction process data. And then expanding the history data with the floor as the unit to the full height range of the model by utilizing a linear interpolation method. Each time step in the history data corresponds to one rendering frame in the visualization, and each frame updates the building three-dimensional graph by using the corresponding history data and continuously updates to form the dynamic visualization effect of the earthquake response of the city building.
The following description is given with reference to specific examples.
In fig. 1, the method for visualizing earthquake damage of urban building groups comprises the following steps:
in step S1, data preparation is performed. The data comprises city geographic information basic data, building group earthquake dynamic response course data and oblique photography aerial photography pictures.
In one embodiment of the present invention, the city geographic information base data includes the name of a building, a building number (ID), a building floor outline polygon, a structure type, a building story height, a building story number, a construction year, a floor area, and a use function, as shown in fig. 2. It is understood that the building data may be obtained through related channels such as research in the field, purchase from mapping agencies, or web-navigation maps. These data are stored in the form of geographic information data shown in fig. 2, and an attribute table of the geographic information data is derived as needed for earthquake damage visualization, as shown in fig. 3.
In one embodiment of the invention, the displacement history data portion of the building group power history data is used with building floor as a base unit. Before earthquake damage visualization is carried out, the displacement history data needs to be formatted according to a file structure as shown in fig. 4, and the purpose of the formatting is to enable an earthquake damage visualization program to read and process the displacement history data more quickly.
Next, the file structure of this file will be explained. And setting n buildings for earthquake damage calculation in the region, wherein the time step number in the process analysis calculation is m. Then in the file, the first data is the total number n of buildings in the building group; the subsequent n groups of data are the history calculation results of n buildings in the building group; setting a building to have k layers in total, wherein m calculation results are contained in a data group corresponding to the building and correspond to m time steps in the process calculation results; each calculation result contains k data, which represent the displacement response of each floor of the building at the corresponding time step and have the unit of meter (m).
For oblique photography aerial photography pictures, recommending that the ground resolution of the reference surface of each photography partition is required to be aerial photography pictures according to different scale scales, combining the terrain conditions of the partitions, the height distances of mapping and the like, the aerial photography base height ratio, the image purposes and the like, and on the premise of ensuring the picture forming accuracy, selecting the ground resolution of the aerial photography pictures according to the time requirements between 5cm and 20 cm. According to experience, the overlapping part between the continuous images should exceed 60%, and the segmentation of the same ground object between different shooting points should be less than 15 degrees, so that a good modeling effect can be obtained.
In step S2, a three-dimensional live-action model is established.
In one embodiment of the invention, the modeling work of the three-dimensional live-action model of the town area is completed by using the current and universal oblique photography modeling software. In order to accelerate the modeling efficiency, the invention adopts an optimization method of sparse waypoints, adjustment of detail levels and computer cluster assistance.
The sparse waypoints mean that a faster three-dimensional live-action model modeling speed is obtained by deleting part of aerial image groups under the condition of considering both the quality of the model and the overlapping rate of aerial images. Generally, the overlapping rate of aerial images obtained from one aerial photographing frame is slightly conservative, so that part of aerial image groups can be deleted. Specifically, in the invention, the following aerial image groups can be deleted according to the situation: blurred or meaningless images; repetitive or low inter-image discrimination; the model is positioned at the edge of the simulated region or exceeds the modeled region; the image overlay is redundant in the higher regions. In one embodiment of the present invention, as shown in fig. 5, in the case of considering both the overlap ratio and the model accuracy, the aerial image group in the periphery of the aerial region is deleted, and the image group in the central area of the aerial region is thinned to 50% of the original image group. Through processing, the original 2860 image groups are reduced to 599 image groups, and the modeling efficiency is greatly improved.
For adjusting the detail level, in one embodiment of the present invention, a "single level detail level" is used to generate three-dimensional live-action models of different detail level levels, respectively. Taking the scenario shown in fig. 6 as an example, the generated model includes 8 detail levels from detail level 14 to detail level 21, and statistics of the number of vertices and the number of polygon faces of the model at each detail level are shown in table 1. Compared with the model with the highest quality, the model with the medium level of detail effectively balances the geometric precision and the texture quality, the visual effect is similar to that of the model with the highest quality, but the resource occupation is less than that of the model with the highest quality, and the smoother visualization effect can be realized. For the city scale, the present invention recommends levels of detail 17-20.
TABLE 1 Effect of level of detail on number of vertices and number of polygon faces
For computer cluster assistance, the invention divides the three-dimensional real scene model reconstruction work into a plurality of tiles (tiles), wherein the tiles are basic units for oblique photography model generation and can be distributed to different computers for parallel planning. The invention uses a plurality of computers to form a cluster in the local area network, and processes a plurality of tiles at the same time, thereby remarkably accelerating the modeling efficiency.
Determining the number of computers in a cluster is a key issue. In the cluster, the network bandwidth is NTR, the host hard disk reading rate is IO, the data volume required to be transmitted by a single task is D, and the data volume transmitted back by the computing node is D passback The data processing rate of the computing node is v process At a transmission rate v transport The variable units are Mbps.
For the commonly used ten-million and hundred-million bandwidth networks, the transmission rate is much lower than the read rate of the hard disk, so that all the networks have IO>NTR, then data transmission rate v transport = NTR. The total time for a single tile to process may be defined as the data out time T tramsport A processing time T process And a return time T passback The sum of the three parts is as follows:
wherein, D is passback Can be represented by D, i.e.:
1.D passbak λ D, λ is data compression coefficient
The optimal number of compute nodes in the cluster is then:
the above calculation method helps the skilled person to determine the size of the computer cluster. For example, when a hundred million network is used, it is generally preferable that the number of computers does not exceed 4 by calculation.
In one embodiment of the invention, two high performance computers (the configuration information of which is shown in table 2) are used to form a cluster within a local area network.
TABLE 2 computer hardware configuration
In step S3, the three-dimensional live-action model is subjected to singulation and other post-processing. In the invention, the three-dimensional live-action model is singly and automatically completed through Boolean operation, and manual intervention is needed for a few parts with defects. And post-processing the three-dimensional live-action model, including model texture compression and environment model flattening. Post-processing may or may not be required for seismic hazard visualization.
For a three-dimensional model obtained by oblique photogrammetry, the model is actually a continuous triangular mesh model, since there is no human intervention in the modeling process. For such an integrated three-dimensional model, it is impossible to individually process a certain building model. Therefore, the oblique photogrammetry model needs to be processed in a single body. The "singleization" in the present invention means that a building model is separated from an integral three-dimensional model by a certain method or device to form a model independent of the whole. After the processing, the visualization work can be performed for a single building. The invention is based on the thought of cutting and unitizing, directly modifies the three-dimensional model, and physically separates the polygon surface related to the building from the integral model through a certain method, thereby enabling the polygon surface to be an independent model. Therefore, the oblique photography measurement model is divided into a plurality of building single body models and an environment model.
In one embodiment of the present invention, the building unitization method proposed by the present invention is shown in fig. 7: firstly, loading building bottom surface outline polygons and oblique photography model data in urban geographic information basic data, and finishing alignment to ensure the correspondence of building graphs and outline polygons; vertically stretching the outline polygon into a cylindrical body by utilizing the outline polygon of the bottom surface of the building in the urban geographic information basic data, and overlapping the cylindrical body with the three-dimensional real scene model; and performing Boolean operation on the three-dimensional live-action model and the bottom surface contour columnar body, thereby taking out a three-dimensional model part overlapped with the bottom surface contour columnar body, wherein the part is the required building monomer model. In one embodiment of the invention, the three-dimensional model may have defects such as holes, overlapping, isolated faces and the like. For the three-dimensional model part with flaws, all polygons of the response building need to be manually selected and separated; and finally, independently storing the separated buildings into files, renaming the files, and calling the files in a visual mode for earthquake damage. The results of building model singleness are shown in fig. 8 and 9.
In one embodiment of the present invention, when constructing the oblique photogrammetry model, the modeling software automatically generates a JPG format texture picture with extremely high quality, and the resolution can reach 8192 pixels by 8192 pixels, as shown in fig. 10. When loading such textures, a considerable amount of computer memory resources are consumed.
To address the problem of excessive texture, in one embodiment of the invention, all texture files are converted to TGA format. After the compression conversion processing, although the volume of the generated TGA picture file is slightly larger than that of the previous JPG file, the TGA format file has a smaller compression ratio than that of the JPG format file, so that the TGA format file occupies less memory space after being loaded. Taking the monolithic model shown in fig. 10 as an example, before texture conversion is performed, 303.8MB of memory is required to be occupied for loading the model; and the memory usage during loading is reduced to 125.1MB using the translated texture. When the models to be loaded have a certain scale, the method can save considerable memory resources of the computer.
In one embodiment of the invention, the individualized environmental model portion with the building portion removed from the model is replaced with a simple planar model with a specific mapping, as shown in FIG. 11. The simple plane model has the same size as the original environment model, and the map of the simple plane model is a rendering image of the top view of the original environment model. The original environment model has a similar visual effect as a simple planar model with a specific map when viewed at a non-specific angle (e.g., head-up or less than 45 deg. head-up). Compared with the original environment model which is complex, has millions of vertexes and a great number of maps, the simple plane model with the specific map only has four vertexes and one specific map. Therefore, the load of the visualization device can be obviously reduced, and the earthquake damage visualization effect is smoother and more natural without distorting the reality.
And in the step S4, realizing the real sense dynamic visualization of the earthquake response of the building group. The method realizes the visualization of earthquake damage of the building group based on city geographic information basic data, a three-dimensional live-action model subjected to monomer and post-processing according to conditions and earthquake dynamic response history data of the building group.
The invention realizes dynamic visual display of earthquake damage of building groups based on an Open Source Graphic (OSG) platform. One embodiment of the invention adopts a Callback mechanism (Callback) to complete the work required to be completed by the program before each frame of rendering, such as vertex coordinate transformation, camera motion and the like. By utilizing the mechanism, the invention reads the displacement process calculation result in the building group time process analysis calculation result obtained in the previous step, updates the vertex coordinates of the building three-dimensional model in each frame, and thus realizes the dynamic earthquake damage visualization process. A flowchart for earthquake damage visualization based on an update callback mechanism is shown in fig. 12.
(1) Loading visually relevant essential files
In the invention, to realize the visual display of earthquake damage of the building group, various necessary files are loaded into a memory so as to be convenient for program calling, accessing or modifying. In one embodiment of the invention, the model files to be loaded include a single building model and an environment model. It should be noted that although a method of reducing the load of the visualization system by replacing the environment model with a simple plane model with a specific map is mentioned in step S3, if the earthquake damage visualization scene is small, the original environment model may still be adopted as the environment model has a small influence on the load of the visualization system. Besides the three-dimensional model, a building information attribute table derived from the city geographic information basic data and seismic dynamic response course data of a building group are read.
(2) Create updater and initialization thereof
In order to implement the operation of updating the coordinates of the vertices of the building model, an updater (updater) needs to be created. In one embodiment of the invention, updater needs to inherit the update callback base class (UpdateCallback) to achieve full control of the callback process.
In the creation stage of the updater, the building three-dimensional model and the environment model need to be loaded into a scene for rendering. In the initialization stage of updater, the displacement time history data of the building group needs to be loaded so as to be used for updating the coordinates of the building vertex model.
(3) Execution updater
In the process of program execution updating and callback, each time step in the displacement time history data of the building group corresponds to one rendering frame in the earthquake damage visualization display. In the rendering frame, the program dynamically updates the coordinates of each vertex in each building model in the building group according to the data of the corresponding time step in the displacement time history data. And continuously modifying the coordinates of each vertex in the building model through updating a callback mechanism, and finishing earthquake damage visualization through continuous change of the positions of the vertices of the model.
In one embodiment of the invention, the calculation results of corresponding buildings in the building unit model, the city geographic information basic data and the dynamic response course data are unified based on the building number (ID) data in the city geographic information basic data.
In the present invention, the power reaction history data is used in units of floors. While for the building model in the seismic hazard visualization scenario, its vertical coordinates are continuous. Obviously, the displacement of all vertices in the building cannot be simply replaced with the displacement at each building floor. Therefore, the invention is based on a linear interpolation method to determine the displacement data of the vertex at any height of the model. The linear interpolation method employed in the present invention will be explained in detail below.
As shown in FIG. 13, a building with a model number (ID) of k has n floors, and the ith floor is as high as
The vertical coordinate of the lowest point of the three-dimensional model of the building is
The vertical coordinate of the highest point is
The total height of the building model
Comprises the following steps:
by using
Indicates that the kth building is at the ith time step (i.e., t = t) 0 Time + i × Δ t, Δ t is time step of time interval analysis), the model is located at the mth layer and the height
The displacement response value of the vertex is determined,
represents the displacement response value of the kth building at the jth layer of the ith time step, and is shown in FIG. 10
Can be expressed as:
in the formula (I), the compound is shown in the specification,
height of the vertex in the layer:
in the above calculation, attribute information about the building, such as the ID, floor number, and floor height data of the building, can be read from the urban GIS data. When the building layers are the same in height
Can be simplified as follows:
for bidirectional displacement, updating of model y-direction coordinates should be considered, and corresponding coordinate increment Δ y i The calculation principle of (1) and Δ x i The same, and therefore, will not be described in detail. The visualization effect of earthquake damage of the building in response to earthquake realized by the method is shown in fig. 14.
(4) Reset updating device
And when the earthquake damage visualization display reaches the maximum time step number in the earthquake response time process calculation of the building group, resetting the updater after a period of time, and repeatedly displaying the earthquake reaction process until the user terminates the program.
Through the process, the dynamic visual display of the earthquake response of the urban building group is realized, as shown in fig. 15.
While the foregoing is directed to the preferred embodiment of the present invention, it will be appreciated by those skilled in the art that various changes and modifications may be made therein without departing from the principles of the invention as set forth in the appended claims.
Claims (6)
1. A dynamic visualization method for earthquake response of urban building groups based on oblique photography data is characterized in that: the method comprises the following steps:
(1) Preparing data: the data comprises urban geographic information basic data, building group earthquake dynamic response course data and oblique photography aerial pictures;
(2) Modeling a three-dimensional live-action model: establishing a three-dimensional live-action model by utilizing oblique photography aerial pictures, and adopting various optimization methods according to conditions;
(3) Model singulation and post-treatment: the three-dimensional live-action model is subjected to singleization, texture compression is further performed, and the environment model is flattened;
(4) Building group seismic response reality dynamic visualization: the three-dimensional live-action model, urban geographic information basic data and building group seismic dynamic response history data are used for realizing the dynamic visualization of the building group seismic response reality;
the specific process of the step (4) is as follows:
utilizing the building number in the city geographic information basic data to correspond the building unit model to the result of the earthquake power reaction process data of the building group, reading the building floor number data in the city geographic information basic data and corresponding to the building floor unit in the power reaction process data;
then, expanding the history data taking the floor as a unit to the full height range of the model by using a linear interpolation method;
and finally, rendering a frame in the visualization corresponding to each time step in the process data, and updating the building three-dimensional graph by using the corresponding process data in each frame to continuously update to form the earthquake response dynamic visualization effect of the urban building group.
2. The method for dynamically visualizing earthquake response of urban building complex based on oblique photography data as claimed in claim 1, wherein: the basic data of the urban geographic information in the step (1) comprise building numbers, structure types, building heights, building floor numbers, construction times, floor areas and use functions;
building groups earthquake power reaction course data take building floors as basic units and correspond to buildings in the city geographic information basic data one by one;
the oblique photography aerial photography picture meets the ground resolution and overlapping degree requirements required by the establishment of the model.
3. The method for dynamically visualizing earthquake response of urban building complex based on oblique photography data as claimed in claim 2, wherein: the ground resolution of the oblique photography aerial photography picture is between 5cm and 20cm, the overlapping part of continuous images of the oblique photography aerial photography picture exceeds 60 percent, and the division of the same ground object between different shooting points is less than 15 degrees.
4. The method for dynamically visualizing earthquake response of urban building complex based on oblique photography data as claimed in claim 1, wherein: the optimization method in the step (2) comprises navigation point sparseness, detail level adjustment and computer cluster assistance;
the method comprises the following steps that (1) waypoint sparseness refers to that a faster three-dimensional live-action model modeling speed is obtained by deleting part of aerial image groups under the condition that model quality and aerial image overlapping rate are both considered;
adjusting the detail level, namely determining the resource allocation of object rendering according to the position and the importance of the node of the object model in the display environment, and reducing the number of faces and the detail of non-important objects so as to improve the scene rendering efficiency;
the computer cluster assistance means that the three-dimensional real-scene model reconstruction work is divided into a plurality of tiles, a cluster is formed by a plurality of computers in a local area network, and the plurality of tiles are processed at the same time, so that the modeling efficiency is remarkably accelerated.
5. The method for dynamically visualizing earthquake response of urban building groups based on oblique photography data as recited in claim 4, wherein: the aerial photography image group which can be deleted in the aerial spot sparsity comprises: the method comprises the following steps of image blurring, image meaningless, image repetition, lower discrimination between images, image position at the edge of a simulated region, image exceeding of the modeled region and redundancy in a higher region of an image overlapping image.
6. The method for dynamically visualizing earthquake response of urban building groups based on oblique photography data as recited in claim 1, wherein: in the step (3), the monomer is to separate the building model from the environment model in the geometric range according to the basic data of the urban geographic information or other plane geometric information; the model texture compression specifically comprises one or two of conversion texture picture file format and compression picture resolution; the flattening of the environment model is to replace a complex three-dimensional mesh surface model with a plane model or a simple geometric model.
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