Three-dimensional tile conversion method for component-level digital twin railway tunnel engineering three-dimensional model

Abstract

The invention discloses a component-level digital twin railway tunnel engineering three-dimensional model three-dimensional tile conversion method, which comprises the following steps: opening a tunnel BIM model file, and obtaining external setting parameters, artificial constraint parameters and model information to generate triangular mesh model data; establishing an association relationship between the semantic attribute information and the triangular mesh model, and mapping one by one to obtain LOD4 hierarchical model data; screening and cleaning the semantics, and removing a specified component to obtain LLO3 hierarchical model data; obtaining a maximum outer bounding box fitting elliptic cylinder of the tunnel model, and performing similar block replacement to obtain LOD2 hierarchical model data; the method comprises the following steps: traversing sprayed concrete members according to a line trend sequence to obtain coordinates of geometric center points of bounding boxes of the sprayed concrete members, and forming an ordered point set fitting line as an LOD1 hierarchical model; performing format conversion on the LOD models of different hierarchies, and finally organizing the LOD models into a tree structure to form three-dimensional tile structure data; the method is simple and high in execution efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of geographic space information systems, and in particular to a method for converting a component-level digital twin railway tunnel engineering three-dimensional model into a three-dimensional tile. Background Art

[0002] Railways play an important role in my country's transportation development and economic construction, and strengthening railway construction is of great significance. In the information environment, the development of railway informatization has naturally become the main trend of modern railway development. With the development of science and technology, mechanization, informatization, and intelligence will inevitably be the direction of future railway tunnel development. China's railway tunnel engineering will move from high-speed development to high-quality development. In the current railway informatization construction process, BIM technology and concepts in the construction field can be introduced, and then the information model can be used to uniformly organize and manage the resources, activities and products of the railway project life cycle, so that information sharing can be achieved in all stages of railway construction, saving construction costs and avoiding waste of resources.

[0003] Although in the process of informatization, railway construction can draw on the technology and concepts of BIM in the field of construction, there are significant differences between the two fields of railway and construction: on the one hand, railway engineering shows obvious linear, large span and complex engineering points in the construction process; on the other hand, BIM technology has some obvious deficiencies in the large-scale expression, consistency analysis and management of three-dimensional information models. Therefore, in the informatization construction of railway engineering, GIS technology with three-dimensional visual spatial analysis and spatial database as the core is introduced. From the existing specific analysis, railway construction is closely related to terrain, so all factors can be regarded as research objects related to GIS. Therefore, the use of GIS platform can meet the overall, global and macroscopic expression requirements of railway construction projects.

[0004] The railway tunnel BIM model has the characteristics of large spatial span, high modeling accuracy, large amount of geometric information, and single level of detail of modeling reference standards. When the railway tunnel BIM model is converted into a GIS model, in order to ensure the accuracy of the geometric information description of the GIS model, it is necessary to segment and fit the complex geometric structure of the dense triangulation network. In particular, the data volume surges after the high-precision complex parameter model is converted into a GIS model, which becomes an important factor affecting the organization, rendering and diversified application efficiency of the railway tunnel BIM model in the three-dimensional GIS environment.

[0005] In order to solve the contradiction between image quality and real-time operation of the system, in the real-time dynamic display of the scene, when the viewpoint is very close to an object, a fine model is used for drawing. On the contrary, when the model is far away from the viewpoint, a coarse model is used for representation. This technology is called (LOD) level of detail implementation and simplification technology. This technology selects LOD models of different precisions by dynamically determining the threshold, reducing the complexity of the scene in order to obtain more rational visual effects and computer processing speed. Providing different LOD descriptions for objects is a very effective way to control scene complexity and accelerate graphics drawing speed.

[0006] At present, there are two main types of LOD: 1) Discrete LOD model: It actually saves several copies of the original model, each copy corresponds to a model with different levels of detail, and is stored separately. When the viewpoint is close to the building model, the model with finer details is selected, and vice versa, the model with coarser details is selected to reduce the amount of data drawn. The advantage of this model is that it does not need to generate the model in real time, so it is faster, but because it saves multiple copies of the original model, it occupies more storage space. 2) Continuous LOD model: It only retains a model of a certain resolution at a certain time, and generates a model of another resolution through a certain algorithm according to the needs during operation. This model can ensure the continuity of visual effects, but due to the high requirements for real-time operation, the algorithm design and data structure are relatively complex. Therefore, there is an urgent need for a method that is targeted at the characteristics of tunnel BIM data and three-dimensional tile structure data to solve the problem of tunnel BIM model being difficult to efficiently organize and visualize in a GIS environment. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a lightweight three-dimensional tile conversion method for a component-level digital twin railway tunnel engineering three-dimensional model, which solves the problems mentioned in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a component-level digital twin railway tunnel engineering three-dimensional model three-dimensional tile conversion method, comprising the following steps:

[0009] S1. Open the tunnel BIM model file, obtain the external setting parameters of the BIM model, and set some constraint parameters;

[0010] S2, traverse the BIM model components, obtain the texture information, geometric information, and attribute information of each component one by one, and generate triangular mesh model data based on the above information;

[0011] S3, inputting the attribute information into the railway tunnel engineering entity component table formed by using the semantic description standard of the railway tunnel engineering entity component as a reference and the extended information as a division, so as to form the semantic attribute information of the model component; establishing the association relationship between the semantic attribute information and the triangular mesh model through the identifier UUID, adding the semantic attribute information to the triangular mesh model of each component, and obtaining the LOD4 level model data;

[0012] S4. According to the requirements of different work sections and work points, the semantics that need to be expressed are screened and deleted, and the components corresponding to the semantics are eliminated together, and the remaining components are assembled and reassembled to obtain the LOD3 hierarchical model data containing the components of particular concern;

[0013] S5. For a construction section tunnel in the LOD3 level model data, obtain the coordinates of the center point of the tunnel face plane, the major axis vector, the minor axis vector and the height vector perpendicular to the tunnel face plane, calculate the tunnel face plane ellipse equation and the elliptical cylinder equation perpendicular to the tunnel face plane; draw a tunnel body according to the equation, and then fit multiple construction sections to obtain LOD2 level model data;

[0014] S6. Extract the bounding box information of the component semantics "shotcrete" from the LOD4 level data, calculate the coordinates of the geometric center point of the bounding box, form an ordered point set according to the construction section sequence and fit it into a line, and obtain the LOD1 level model data;

[0015] S7, repeating steps S2-S6 until each component is completely converted into a four-level LOD model;

[0016] S8. Convert the LOD1-4 level models into .b3dm format, organize the models using TileSet.json files, and obtain the three-dimensional tile structure data.

[0017] Preferably, in step S1, the external setting parameters of the BIM model are obtained, including the engineering coordinate system and the model size unit; the setting of some constraint parameters includes the constraint parameters of the triangular mesh model fitting accuracy, the triangular facet form, and the texture normal.

[0018] Preferably, step S4 specifically includes the following:

[0019] Step S41, extracting and organizing the semantic information of the LOD4 level model components, obtaining the semantic information of all model component elements, and matching each component with its semantic information;

[0020] Step S42, constructing a semantic cleaning pool, selecting and screening the expression semantics according to the visual detail level requirements of different engineering sections and work points, and eliminating the components corresponding to the semantics, and only retaining the semantics of interest and their corresponding components; for the LOD3 level to meet the fine recognition requirements such as the real appearance, while maintaining the main contour expression of the shotcrete rail tunnel, the texture information of the actual material is added to meet the basic requirements of appearance recognition, and the initial shotcrete is selected to approximately express the main contour of the tunnel;

[0021] Step S43, in the semantic cleaning pool, remove the semantic components except the initial shotcrete;

[0022] Step S44, assemble and reorganize the initial shotcrete components with the remaining semantics after semantic cleaning to obtain LOD3 hierarchical model data that only meets the requirements of fine recognition of the real appearance.

[0023] Preferably, step S5 specifically includes the following:

[0024] Step S51, a coordinate system is established with the center of gravity of the direction bounding box of the LOD3 level model on the face plane as the coordinate origin, and the directions of the long vector, short vector and high vector of the bounding box are the z-axis, x-axis and y-axis respectively;

[0025] Step S52: Obtain the coordinates of the center point V0 (v x0 ,v y0 ,v z0 ), the long axis vector of the face plane Minor axis vector of the tunnel face plane and the height vector perpendicular to the plane of the tunnel face

[0026] Step S53: Calculate the length of the major semi-axis of the tunnel face ellipse Length of the minor semi-axis of the face ellipse Focal distance to the tunnel face ellipse

[0027] Step S54: The center point coordinate V0 (v x0 ,v y0 ,v z0 ), the height vector perpendicular to the plane of the tunnel face As the normal line, the equation of the ellipse on the tunnel face is obtained: x x+H y y+H z z-(H x v x0 +H y v y0 +H z vz0 )=0. According to the standard equation of an ellipse in three-dimensional space, the coordinate offset is (v x0 ,v y0 ,v z0 ), the scale scaling amount is The coordinates of the two foci are calculated from this

[0028] Step S55: Based on the ellipse equation of the face plane in step S54: H x x+H y y+H z z-(H x v x0 +H y v y0 +H z v z0 )=0, and the mathematical constraint condition is that the distance from any point on the ellipse to the two foci is less than or equal to twice the length of the major semi-axis, resulting in the constraint inequality: Combining the equations with the inequalities, we get the equation of the complete plane ellipse of the tunnel face:

[0029]

[0030] Step S56, calculate the length of the perpendicular line from point P (x, y, z) on the surface of the elliptical cylinder to the base ellipse of the elliptical cylinder. This L direction is The direction of the constraint is: is the generatrix of the elliptical cylinder surface, and the ellipse on the face plane is the directrix of the elliptical cylinder surface. c ,y c ,z c ), the generatrix equation passing through this point is: Combining the above constraints with the equation, we get an equation for the tunnel body in the construction section:

[0031]

[0032] Step S57, draw the tunnel bodies of each construction section one by one according to the equation in step S56, and then fit and splice the tunnel bodies of multiple construction sections together to obtain LOD2 level model data.

[0033] The beneficial effects of the present invention are as follows: the present invention establishes the association between semantic attribute information and triangular mesh models through identifiers (UUIDs), and obtains the most refined LOD4 hierarchical model data through a one-to-one mapping method; by constructing a semantic cleaning pool, the LOD4 hierarchical model is semantically cleaned to obtain LOD3 hierarchical model data containing components of outstanding concern; by similar block replacement and centerline extraction methods, simplified LOD2 hierarchical models and LOD1 hierarchical model data are obtained; by format conversion and TileSet.json files, three-dimensional tile structure data that organizes the above models is obtained. The lightweight three-dimensional tile conversion method of the component-level digital twin railway tunnel engineering three-dimensional model proposed by the present invention has the advantages of simple method and high execution efficiency, and effectively solves the problem that the BIM model of a long tunnel is difficult to efficiently organize and visualize in a GIS environment, and is suitable for lightweight conversion of various tunnel BIM models into three-dimensional tile structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the overall flow chart of the present invention;

[0035] Figure 2 A flow chart for generating a LOD4 hierarchical model in an embodiment of the present invention;

[0036] Figure 3 A flow chart for generating a LOD3 hierarchical model in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of elliptical cylinder fitting in the embodiment;

[0038] Figure 5 This is a structure diagram of the LOD model data organization structure in the embodiment. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] See also Figure 1-Figure 5 The present invention provides a technical solution: a lightweight three-dimensional tile conversion method for a component-level digital twin railway tunnel engineering three-dimensional model, the process is as follows Figure 1As shown in the figure, the main idea is to convert the tunnel BIM model into the most refined LOD4 level model, and then gradually simplify it to obtain the LOD3~LOD1 level model, and finally convert the LOD models of different levels into formats, and finally organize them into a tree structure to form three-dimensional tile structure data. The implementation process is automated by computer, and the method specifically includes the following steps:

[0041] Step 1: Open the tunnel BIM model file and obtain external setting parameters such as the engineering coordinate system and model size unit as constraint parameters for conversion to the GIS model. Then manually set constraint parameters such as triangular mesh model fitting accuracy, triangular facet form, texture normal, etc. The triangular mesh model fitting accuracy determines the fineness of the converted model by setting the angle between adjacent facets, and the texture normal constraint parameter determines whether the texture and normal are output.

[0042] Step 2: traverse the BIM model components and obtain the texture information, geometry information, and attribute information of each component one by one. The geometry information and texture information can meet the needs of triangular mesh model construction and visual rendering, and the triangular mesh model data is generated based on the above information.

[0043] Step 3: After extracting the attribute information from the model component, input the attribute information into the railway tunnel engineering entity component table formed by using the railway tunnel engineering entity component semantic description standard as a reference and the extended information as a division to form the semantic attribute information of the model component. Finally, the association between the semantic attribute information and the triangular mesh model is established through the identifier (UUID), and the semantic attribute information is added to the triangular mesh model of each model component. The BIM model components are mapped one by one to obtain the LOD4 hierarchical model data. The process is as follows: Figure 2 As shown;

[0044] Step 4: According to the requirements of different work sections and work points, the semantics that need to be expressed are screened and deleted, and the components corresponding to the semantics are eliminated. The remaining components are assembled and reassembled to obtain the LOD3 hierarchical model data containing the components of particular concern. The flow chart is as follows: Figure 3 As shown, the specific steps are as follows:

[0045] Step 4.1, extract and organize the semantic information of the LOD4 level model components, obtain the semantic information of all model component elements, and correspond each component to its semantic information;

[0046] Step 4.2, construct a semantic cleaning pool, select and filter the expression semantics according to the visual detail level requirements of different engineering sections and work points, and remove the components corresponding to the semantics, and only retain the semantics of interest and their corresponding components. In order to meet the fine recognition requirements such as the real appearance at the LOD3 level, the texture information of the actual material is added while maintaining the main outline expression of the shotcrete rail tunnel to meet the basic requirements of appearance recognition. The initial shotcrete can be selected to approximate the main outline of the tunnel.

[0047] Step 4.3, in the semantic cleaning pool, remove all semantic components except the primary shotcrete.

[0048] In step 4.4, the semantics remaining after semantic cleaning are assembled and reorganized for the primary shotcrete components to obtain LOD3 hierarchical model data that only meets the fine recognition requirements such as real appearance.

[0049] Step 5: For a construction section tunnel in the LOD3 hierarchical model data, obtain the coordinates of the center point of the face plane, the major axis vector, the minor axis vector and the height vector perpendicular to the face plane, calculate the ellipse equation of the face plane and the elliptical cylinder equation perpendicular to the face plane, draw a tunnel body according to the equation, and then fit multiple construction sections to obtain the LOD2 hierarchical model data. The specific steps are as follows:

[0050] Step 5.1, take the center of gravity of the direction bounding box of the LOD3 model on the face plane as the coordinate origin, and establish a coordinate system with the long vector, short vector and high vector directions of the bounding box as the z-axis, x-axis and y-axis respectively;

[0051] Step 5.2: Obtain the coordinates of the center point V0 (v x0 ,v y0 ,v z0 ), the long axis vector of the face plane Minor axis vector of the tunnel face plane and the height vector perpendicular to the plane of the tunnel face

[0052] Step 5.3: Calculate the length of the major semi-axis of the tunnel face ellipse Length of the minor semi-axis of the face ellipse Focal distance to the tunnel face ellipse

[0053] Step 5.4: Use the coordinates of the center point V0 (v x0 ,v y0 ,v z0 ), the height vector perpendicular to the plane of the tunnel face As the normal line, the equation of the ellipse on the tunnel face is obtained:x x+H y y+H z z-(H x v x0 +H y v y0 +H z v z0 )=0. According to the standard equation of an ellipse in three-dimensional space, the coordinate offset is (v x0 ,v y0 ,v z0 ), the scale scaling amount is The coordinates of the two foci are calculated from this

[0054] Step 5.5: Based on the ellipse equation of the face plane in step 5.4: H x x+H y y+H z z-(H x v x0 +H y v y0 +H z v z0 )=0, and the mathematical constraint condition is that the distance from any point on the ellipse to the two foci is less than or equal to twice the length of the major semi-axis, resulting in the constraint inequality: Combining the equations with the inequalities, we get the equation of the complete plane ellipse of the tunnel face:

[0055]

[0056] Step 5.6: Calculate the length of the perpendicular line from point P (x, y, z) on the surface of the elliptical cylinder to the base ellipse of the elliptical cylinder. This L direction is The direction of the constraint is: is the generatrix of the elliptical cylinder surface, and the ellipse on the face plane is the directrix of the elliptical cylinder surface. c ,y c ,z c ), the generatrix equation passing through this point is: Combining the above constraints with the equation, we get an equation for the tunnel body in the construction section:

[0057]

[0058] Step 5.7, draw the tunnel bodies of each construction section according to the equation in step 5.6, and then fit and splice the tunnel bodies of multiple construction sections to obtain LOD2 hierarchical model data;

[0059] Step 6: From the LOD4 level data, extract each component with the semantics of "shotcrete" in order according to the direction of the tunnel line, calculate its bounding box information, and obtain the three-dimensional coordinates of the geometric center point of the component bounding box. Then, store the point data stored in multiple construction sections in order to form a point set. Use the "point set fit to line" function in the rendering engine to fit the ordered point set to a line symbol to obtain the LOD1 level model data.

[0060] Step 7, repeat steps 2-6 until each component is converted into a four-level LOD model;

[0061] Steps 2-7 belong to the process of building a LOD multi-level detail model, and step 8 belongs to the process of organizing the three-dimensional tile structure.

[0062] Step 8: Convert the LOD1-4 models into .b3dm format and organize the models at different levels into a tree structure. Figure 5 As shown, the model is organized using the TileSet.json file to obtain the three-dimensional tile structure data.

[0063] The component-level digital twin railway tunnel engineering 3D model lightweight 3D tile conversion method proposed in the present invention has the advantages of simple method and high execution efficiency. It effectively solves the problem that long tunnel BIM models are difficult to efficiently organize and visualize in a GIS environment. It is suitable for lightweight conversion of various tunnel BIM models into 3D tile structures.

[0064] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A component-level digital twin railway tunnel engineering 3D model 3D tile conversion method, characterized in that: The steps include: S1. Open the tunnel BIM model file, obtain the external setting parameters of the BIM model, and set some constraint parameters; S2, traverse the BIM model components, obtain the texture information, geometric information, and attribute information of each component one by one, and generate triangular mesh model data based on the above information; S3, inputting the attribute information into a railway tunnel engineering entity component table formed by dividing the entity component semantic description standard of the railway tunnel engineering as a reference and the extended information as a reference, to form semantic attribute information of the model component; The association relationship between the semantic attribute information and the triangular mesh model is established through the identifier UUID, and the semantic attribute information is added to the triangular mesh model of each component to obtain the LOD4 level model data; S4. According to the requirements of different work sections and work points, the semantics that need to be expressed are screened and deleted, and the components corresponding to the semantics are eliminated together, and the remaining components are assembled and reassembled to obtain the LOD3 hierarchical model data containing the components of particular concern; S5. For a construction section tunnel in the LOD3 level model data, obtain the coordinates of the center point of the tunnel face plane, the major axis vector, the minor axis vector and the height vector perpendicular to the tunnel face plane, calculate the tunnel face plane ellipse equation and the elliptical cylinder equation perpendicular to the tunnel face plane; draw a tunnel body according to the equation, and then fit multiple construction sections to obtain LOD2 level model data; S6. Extract the bounding box information of the component semantics "shotcrete" from the LOD4 level data, calculate the coordinates of the geometric center point of the bounding box, form an ordered point set according to the construction section sequence and fit it into a line, and obtain the LOD1 level model data; S7, repeating steps S2-S6 until each component is completely converted into a four-level LOD model; S8. Convert the LOD1-4 level models into .b3dm format, organize the models using TileSet.json files, and obtain the three-dimensional tile structure data.

2. The component-level digital twin railway tunnel engineering 3D model 3D tile conversion method according to claim 1 is characterized by: In step S1, the external setting parameters of the BIM model are obtained, including the engineering coordinate system and the model size unit; the setting of some constraint parameters includes the constraint parameters of the triangular mesh model fitting accuracy, the triangular facet form, and the texture normal.

3. The component-level digital twin railway tunnel engineering 3D model 3D tile conversion method according to claim 1 is characterized by: Step S4 specifically includes the following: Step S41, extracting and organizing the semantic information of the LOD4 level model components, obtaining the semantic information of all model component elements, and matching each component with its semantic information; Step S42: construct a semantic cleaning pool, select and filter the expression semantics according to the visual detail level requirements of different engineering sections and work points, and remove the components corresponding to the semantics, and only retain the semantics of interest and their corresponding components; In order to meet the requirements of fine recognition such as real appearance at LOD3 level, the texture information of actual materials is added to meet the basic requirements of appearance recognition while maintaining the main outline of the shotcrete rail tunnel. The initial shotcrete is selected to approximate the main outline of the tunnel. Step S43, in the semantic cleaning pool, remove the semantic components except the initial shotcrete; Step S44, assemble and reorganize the initial shotcrete components with the remaining semantics after semantic cleaning to obtain LOD3 hierarchical model data that only meets the requirements of fine recognition of the real appearance.

4. The component-level digital twin railway tunnel engineering 3D model 3D tile conversion method according to claim 1 is characterized by: Step S5 specifically includes the following: Step S51, a coordinate system is established with the center of gravity of the direction bounding box of the LOD3 level model on the face plane as the coordinate origin, and the directions of the long vector, short vector and high vector of the bounding box are the z-axis, x-axis and y-axis respectively; Step S52: Obtain the coordinates of the center point V0 (v x0 ,v y0 ,v z0 ), the long axis vector of the face plane Minor axis vector of the tunnel face plane and the height vector perpendicular to the plane of the tunnel face Step S53: Calculate the length of the major semi-axis of the tunnel face ellipse Length of the minor semi-axis of the face ellipse Focal distance to the tunnel face ellipse Step S54: The center point coordinate V0 (v x0 ,v y0 ,v z0 ), the height vector perpendicular to the plane of the tunnel face As the normal line, the equation of the ellipse on the tunnel face is obtained: x x+H y y+H z z-(H x v x0 +H y v y0 +H z v z0 )=0; According to the standard equation of ellipse in three-dimensional space, the coordinate offset is (v x0 ,v y0 ,v z0 ), the scale scaling amount is The coordinates of the two foci are calculated from this Step S55: Based on the ellipse equation of the face plane in step S54: H x x+H y y+H z z-(H x v x0 +H y v y0 +H z v z0 )=0, and the mathematical constraint condition is that the distance from any point on the ellipse to the two foci is less than or equal to twice the length of the major semi-axis, and the constraint inequality is obtained: Combining the equations with the inequalities, we get the equation of the complete plane ellipse of the tunnel face: Step S56, calculate the length of the perpendicular line from point P (x, y, z) on the surface of the elliptical cylinder to the base ellipse of the elliptical cylinder. This L direction is The direction of the constraint is: is the generatrix of the elliptical cylinder surface, and the ellipse on the face plane is the directrix of the elliptical cylinder surface. c ,y c ,z c ), the generatrix equation passing through this point is: Combining the above constraints with the equation, we get an equation for the tunnel body in the construction section: Step S57, draw the tunnel bodies of each construction section one by one according to the equation in step S56, and then fit and splice the tunnel bodies of multiple construction sections together to obtain LOD2 level model data.

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