A method for generating multi-level details of a BIM model

Abstract

The application relates to a BIM model multi-level detail generation method, which is based on a triangularized grid model of a BIM model to generate multi-level details, eliminates the influence of a production environment of a BIM professional design software and a multi-source heterogeneous storage format, and has universality; in the application, a component is taken as a basic unit, various types of components are extracted according to component attributes, and each level generated only splits the BIM model, and coordinate, geometric structure, attribute and material information are consistent with design information, so that the application meets related application requirements of the BIM model based on design characteristics and helps to improve rendering performance and work efficiency; the application also applies a volume cell grid to BIM model multi-level detail generation, and constructs an overall simplified model, the overall simplified model contains less data information and is easy to generate, the overall simplified model is generated in priority according to a generation order, so that the computer running burden is greatly reduced, and the rendering performance and efficiency are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of BIM model lightweight, in particular to a method for generating multi-level details of a BIM model. BACKGROUND

[0002] BIM model (Building Information Modeling) is a kind of building information model, which is generally modeled by components (basic elements in BIM model, representing an independent part or object in the building), expressed by solid model, can be parameterized designed or modified, has complete internal structure and external form, and contains complex design information such as geometry, physics, material, attribute and rule, and supports whole life cycle management of building information design, construction, operation and maintenance. Due to the factors such as multi-specialty integration, high modeling accuracy, rich details, complex design information, version iteration and design change of BIM model, the volume of BIM model is large, which brings great challenges to its digital application, especially the rendering performance problem affecting user experience and work efficiency.

[0003] In the actual digital application of BIM model, one part is based on the design characteristics of BIM model, which requires that the consistency of information such as coordinates, geometric structure, attributes and materials be ensured during the transfer process of BIM model from design software to digital platform, including model digital review, model association, simulation analysis and deepening design and other applications; the other part is based on the digital simulation characteristics of BIM model, which is not bound with design software, and focuses on the visualization effect and rendering loading efficiency of the model.

[0004] The current commonly used BIM model multi-level detail generation and organization scheme focuses on the digital simulation characteristics of BIM model, and mainly solves the problems of model volume and performance, but ignores the design characteristics of BIM model and related applications. The BIM model is treated as a general Mesh model, which is processed by blocking and grading according to the rules of GIS large scene application. The multi-level model generated in this way has problems such as geometric deformation, material loss, inconsistency with design coordinates, attribute association error and too many levels.

[0005] Therefore, there is an urgent need for a method for generating multi-level details of a BIM model to alleviate or even solve the above problems. SUMMARY

[0006] The main purpose of the present application is to provide a method for generating multi-level details of a BIM model, so as to solve the technical problems that the design performance of the model is difficult to be considered, the model information is easy to be lost and the level is too many in the prior art when generating multi-level details of a BIM model.

[0007] To achieve the above purpose, the present application provides a method for generating multi-level details of a BIM model, comprising the following steps:

[0008] S1, acquire a BIM target model, parse the BIM target model into a plurality of triangular mesh models with components as basic units, and determine a component set M;

[0009] S2, acquire the positions of components and the association relationship between components, and extract a component set M composed of non-closed components from the component set M according to the component positions and the association relationship; f a component set M composed of internal components t a component set M composed of external components d and a component set M d composed of components whose triangular mesh models are contained by other external components a ;

[0010] S3, acquire the vertex coordinates of the triangular mesh models of all components in the component set M d and the component set M f , determine the maximum and minimum values in the vertex coordinates, acquire a preset division length d, and construct a voxel grid G according to the maximum value, the minimum value, and the preset division length d;

[0011] S4, acquire the boundary voxels in the voxel grid G, extract the center points of all boundary voxels to construct a triangular mesh, and obtain an overall simplified model T after texture remapping;

[0012] S5, determine the generation order of the BIM target model according to the component set M f , the component set M t , the component set M a , the component set M d , and the overall simplified model T, and generate the multi-level details of the BIM target model in sequence according to the generation order.

[0013] Further, the step S1 further includes the following steps:

[0014] The geometric and material information in the BIM target model is parsed into a first format file, and the attributes in the triangular mesh model are parsed into a second format file. The first format file and the second format file are associated by a unique ID.

[0015] Further, the step S1 further includes the following steps:

[0016] Determine the bounding box of the component M i according to the triangular mesh model of the component M i , and traverse each component in the component set M to determine the corresponding bounding box of each component; wherein the component M iLet i be the i-th component in the component set M, where 1 ≤ i ≤ n, and n is the number of components, i = 1, 2, 3, ..., n.

[0017] More preferably, in step S2, component set M is extracted from the component set M. f Specifically, it includes the following steps:

[0018] Iterate through each component M in the component set M. i Determine component M i In the triangular mesh model, are all sides of the triangles shared by the triangular mesh models of adjacent components?

[0019] If so, then determine component M. i For closed components; extract all closed components to obtain the component set M. c The number of components is n c ;

[0020] If not, then determine component M. i For non-closed components; extract all non-closed components to obtain the component set M. f The number of components is n f .

[0021] More preferably, in step S2, component set M is extracted from the component set M. t and M d Specifically, it includes the following steps:

[0022] Traverse the component set M c Each component M ci Determine component M ci Does it intersect with the bounding box of other components? If it intersects, then component M... ci If they do not intersect, then assign component M to the first set; if they do not intersect, then assign component M to the first set. ci They are assigned to the second set; where 1 ≤ i ≤ n c ;

[0023] Determine whether the bounding boxes of intersecting components in the first set have an inclusion relationship. If an inclusion relationship exists, extract all components whose bounding boxes are included to obtain the inner component set M. t If no containment relationship exists, extract all components whose bounding boxes are not contained within the second set to obtain the component set M. d The number of components is n d .

[0024] More preferably, in step S2, component set M is extracted from the component set M. a Specifically, it includes the following steps:

[0025] Traverse the component set Md Each component M in di Determine component M di In a triangular mesh model, are all the vertices of the triangle contained in the component set M? d If the bounding boxes of other components contain the triangle, then extract the components whose triangle vertices are fully contained to obtain the third set; otherwise, extract the components whose triangle vertices are not fully contained to obtain the component set M. a The number of components is n a Where 1≤i≤n d .

[0026] More preferably, step S3 specifically includes the following steps:

[0027] Get the component set M d and component set M f The maximum value among all component vertex coordinates and minimum value Obtain the preset partition length d, and then construct a voxel grid G ​​with n voxels. G ;

[0028] Wherein, the volumetric grid G ​​is represented as an array V(a,b,c), with a default value of False; where 'a' is the volumetric X-axis index, and the index range is... b is the Y-axis index of the volume element, and the index range is... ;c is the Z-axis index of the volume element, and the index range is The coordinates of the center point are .

[0029] More preferably, step S4 specifically includes the following steps:

[0030] Traverse each volume element G in the volume grid G j Obtain the body element G j With the component set M d Component M in di Intersecting or being component M di Includes the first volume element, and volume element G j With the component set M f Middle component M fi The second volume element intersects, and the values ​​of the first and second volume elements are set to true; where 1≤j≤n G The values ​​of all voxels in the voxel grid G ​​are set to dummy values;

[0031] Determine the volume element G j The values ​​and index ranges of adjacent volume elements along the X, Y, and Z axes are considered. If an adjacent volume element has a false value or exceeds the index range, then volume element G is determined to be false. jFor the boundary body element, the center points of all the boundary body elements are extracted to construct a triangular mesh and obtain the whole simplified model T after texture remapping.

[0032] Further preferably, the step S5 comprises the following steps:

[0033] According to the component set M f , the component set M t , the component set M a , the component set M d and the whole simplified model T, the generation order of the BIM target model is determined: the component set M f has a level D1, the component set M t has a level L1, the component set M d has a level L2, the component set M a has a level L3, and the whole simplified model T has a level L4; and the multi-level details of the BIM target model are generated in sequence according to the generation order; wherein the D1 level and the L1 to L4 levels are parallel levels, the higher the level number in the L1 to L4 levels, the lower the precision, and the more prior the generation order.

[0034] Further, the steps S4 and S5 further comprise the following steps:

[0035] The circumcircle radius of the maximum allowed vertex of a single component is r, and each component in the component set M f , the component set M t , the component set M a and the component set M d is taken as a to-be-split component, and whether the bounding box side length L of the to-be-split component is greater than r is judged.

[0036] If the bounding box side length L of the to-be-split component is greater than r, the set P of the division points of the bounding box side length L is obtained with r as the division length, the number of the division points is n p , each point P i in the set P of the division points is traversed, the to-be-split component is split by constructing a plane passing through the point P i and perpendicular to L, and the unique ID of the to-be-split component before and after the splitting remains unchanged.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] The application is based on the grid model after the triangulation of the BIM model to generate multi-level details, eliminates the influence of the production environment of the BIM professional design software and the multi-source heterogeneous storage format, and has universality; in the application, components are taken as basic units, various types of components are extracted according to the component properties, and each level generated only splits the BIM model, and the coordinate, geometric structure, property and material information are consistent with the design information, which meets the related application requirements of the BIM model based on the design characteristics and helps to improve the rendering performance and work efficiency; the application also applies the voxel grid to the multi-level detail generation of the BIM model, and constructs the overall simplified model, the overall simplified model contains less data information and is easy to generate, the overall simplified model is generated in priority according to the generation order, which greatly reduces the computer running burden and improves the rendering performance and efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor based on the drawings shown.

[0040] Figure 1 The flowchart of the multi-level detail generation method of the BIM model in an embodiment of the present application;

[0041] Figure 2 The original BIM model in an embodiment of the present application, corresponding to L1 level;

[0042] Figure 3 The external model (not contained) processed by using the voxel grid in an embodiment of the present application, corresponding to L2 or L3 level;

[0043] Figure 4 The overall model generated by the voxel grid in an embodiment of the present application, corresponding to L4 level;

[0044] Figure 5 The further simplified model based on the L4 level in an embodiment of the present application.

[0045] The purpose of the present application, the functional characteristics and the advantages will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0046] It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0047] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0048] It should be noted that all the direction indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, motion condition, etc. between components in a certain posture (as described in the drawings), if the certain posture changes, the direction indications also change accordingly.

[0049] In addition, the description of "first", "second" and the like in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of those skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the present application.

[0050] Please refer to Figure 1 The embodiment provides a method for generating multi-level details of a BIM model, comprising the following steps:

[0051] S1, obtaining a BIM target model, parsing the BIM target model into a plurality of triangular mesh models with components as basic units, so as to determine a component set M;

[0052] S2, extracting component set M f , component set M t , component set M a and component set M d from the component set M respectively;

[0053] S3, obtaining vertex coordinates of triangular mesh models of all components in the component set M d and the component set M f , determining the maximum value and the minimum value in the vertex coordinates, obtaining a preset division length d, and constructing a voxel grid G according to the maximum value, the minimum value and the preset division length;

[0054] S4, obtaining boundary voxels in the voxel grid G, extracting the center points of all boundary voxels to construct a triangular mesh and obtain an overall simplified model T after texture remapping;

[0055] S5、according to the component set M f , the component set M t , the component set M a , the component set M d and the whole simplified model T determine the generation order of the BIM target model, and the multi-level details of the BIM target model are generated in sequence according to the generation order.

[0056] The application generates multi-level details based on the triangular grid model after the BIM model is triangulated, eliminates the influence of the production environment of the BIM professional design software and the multi-source heterogeneous storage format, and has universality; in the application, components are taken as basic units, and various types of components are extracted according to component properties, the whole process only splits the BIM model, and the coordinate, geometric structure, property and material information are consistent with the design information, which meets the related application requirements of the BIM model based on the design characteristics and helps to improve the rendering performance and work efficiency; the application also applies the voxel grid to the multi-level detail generation of the BIM model, and constructs the whole simplified model, the data information contained in the whole simplified model is less and easy to generate, the whole simplified model is generated in priority according to the generation order, which greatly reduces the computer running burden and improves the rendering performance and efficiency.

[0057] Further, the step S1 specifically includes the following steps:

[0058] The geometric and material information in the BIM target model is parsed into a first format file, and the attribute in the triangular grid model is parsed into a second format file, and the first format file and the second format file are associated through a unique ID.

[0059] Specifically, the geometric and material information is parsed into an OBJ format file in a digital-analog separation manner, and the attribute is parsed into a separate JSON format file, and the two are associated through a unique ID, so as to ensure consistency with the related information of the design software. Each BIM model design platform can parse based on its own tool or secondary development interface, for example, the Bentley platform can realize complete parsing of the BIM model information based on MDL development.

[0060] In one embodiment, the step S1 further includes the following steps:

[0061] The OBJ format file is parsed, the bounding box of the component M i is determined according to the triangular grid model of the component M i , and the bounding box corresponding to all components in the component set M is determined by traversing each component in the component set M; wherein the component M iFor the components in the component set M, 1≤i≤n, n is the number of components, i=1, 2, 3...n. The bounding box in the embodiment is an OBB bounding box, which is a kind of cuboid that can tightly enclose a triangular mesh model and can be arbitrarily rotated.

[0062] As further preferred, the step S2 of extracting component sets M f from the component set M specifically includes the following steps:

[0063] Traverse each component M i in the component set M i , and determine whether each edge of the triangles in the triangular mesh model of the component M i is shared by the triangular mesh model of the adjacent component; if yes, the component M i is determined to be a closed component; if no, the component M c is determined to be a non-closed component; extract all closed components to obtain the component set M c , and the number of components is n f ; extract all non-closed components to obtain the component set M f , and the number of components is n t .

[0064] In the embodiment, the step S2 of extracting component sets M t and M d from the component set M specifically includes the following steps:

[0065] Traverse each component M c in the component set M ci , and determine whether the component M ci intersects with the bounding box of other components; if yes, the component M ci is classified into the first set; if no, the component M ci is classified into the second set; wherein 1≤i≤n c ;

[0066] Determine whether the bounding boxes of the intersecting components in the first set have a containing relationship; if yes, extract all components whose bounding boxes are contained to obtain the internal component set M t ; if no, extract all components whose bounding boxes are not contained and the second set to obtain the component set M d , and the number of components is n d .

[0067] In the embodiment, the CGAL library function is used to perform a difference set operation on the two components with the bounding box intersection relationship, so as to determine whether the bounding boxes have a containing relationship, i.e., if all vertices, edges and triangular faces of the mesh B are located inside or on the surface of the mesh A, then A contains B.

[0068] More preferably, in step S2, component set M is extracted from the component set M. a Specifically, it includes the following steps:

[0069] Traverse the component set M d Each component M in di Determine component M di In a triangular mesh model, are all the vertices of the triangle contained in the component set M? d If the bounding boxes of other components contain the triangle, then extract the components whose triangle vertices are fully contained to obtain the third set; otherwise, extract the components whose triangle vertices are not fully contained to obtain the component set M. a The number of components is n a Where 1≤i≤n d .

[0070] In this embodiment, as a further preferred embodiment, step S3 specifically includes the following steps:

[0071] Get the component set M d and component set M f The maximum value among all component vertex coordinates and minimum value Obtain the preset partition length d, and then construct a voxel grid G ​​with n voxels. G ;

[0072] Here, G can be represented as a three-dimensional Boolean array V(a,b,c), with a default value of False; where a is the X-axis index of the volume element, and the index range is... b is the Y-axis index of the volume element, and the index range is... ;c is the Z-axis index of the volume element, and the index range is The coordinates of the center point are .

[0073] Iterate through each voxel in G. j Obtain the body element G j With the component set M d Component M in di Intersecting or being component M di Includes the first volume element, and volume element G j With the component set M f Middle component M fi The second volume element intersects, and the values ​​of the first and second volume elements are set to true; where 1≤j≤n G ;

[0074] Determine the volume element G jThe value and index range of the adjacent voxels in the X, Y and Z axis directions, if the adjacent voxels have a false value or exceed the index range, then determine the voxel G j The center points of all the boundary voxels are extracted to construct a triangular mesh and perform texture remapping to obtain the overall simplified model T.

[0075] Specifically, a preset division length of 1 meter is set, a voxel grid G is constructed, the boundary voxels of the voxel grid G are calculated, the center points of the boundary voxels are constructed into a triangular mesh model, and the original texture information of the BIM target model is combined to perform texture remapping and stored as a new model, i.e., the overall simplified model T.

[0076] In one embodiment, the step S5 includes the following steps:

[0077] Referring to Figures 2 to 4 , the generation order of the BIM target model is determined according to the component set M f , the component set M t , the component set M a , the component set M d and the overall simplified model T: the component set M f has a level D1, the component set M t has a level L1, the component set M d has a level L2, the component set M a has a level L3, and the overall simplified model T has a level L4; and the multi-level details of the BIM target model are generated in sequence according to the generation order; wherein the D1 level and the L1 to L4 levels are parallel levels, the greater the number of levels in the L1 to L4 levels, the lower the precision, and the more prior the generation order.

[0078] If the volume of the overall simplified model T cannot meet the actual rendering requirements, the model T can be further simplified to obtain a new level, as shown in Figure 5 .

[0079] Finally, the rendering result is output as a 3D tiles format file, and when a technician opens the BIM model, the L4 level and the D1 level are first rendered and generated, the technician zooms in on a local position, and the details of the L3, L2 and L1 levels are generated in sequence. In the entire generation process, each component has a unique ID for association, the details of the BIM model are generated in multiple levels without loss of the design performance of the BIM model, the rendering efficiency is improved, and the load of the computer is reduced.

[0080] In one embodiment, the steps S4 and S5 further include the following steps:

[0081] The circumcircle radius of the maximum allowed vertex of a single component is r, and the circumcircle radius of the maximum allowed vertex of the component set Mf a component set M t a component set M a a component set M d each component in the component set M is regarded as a component to be cut, and whether the length L of the bounding box of the component to be cut is greater than r is determined;

[0082] if the length L of the bounding box of the component to be cut is greater than r, a set P of points of division of the length L of the bounding box is obtained with r as the length of division, and the number of points of division is n p each point P in the set P of points of division is traversed i a plane perpendicular to L is constructed through the point P i the component to be cut is cut by the plane, and the unique ID of the component to be cut before and after the cutting remains unchanged.

[0083] The skilled person can also cut the whole simplified model T by the same cutting method, and the generation efficiency of the whole simplified model T is further improved. The specific process is similar, and thus is not described in detail here.

[0084] The above is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is based on the content of the specification and drawings of the present application, is also included in the patent protection scope of the present application.

Claims

1. A method for generating multi-level details of a BIM model, characterized in that, Comprise the following steps: S1, acquire BIM target model, parse BIM target model into several triangular mesh models with component as basic unit, so as to determine component set M; S2, acquiring the position of each component and the correlation between components, and extracting a component set M composed of non-closed components from the component set M according to the component position and the correlation f , a component set M composed of internal components t , a component set M composed of external components d , and a component set M composed of components in which the vertices of the triangular mesh model are contained by other external components d a ;​ S3, obtaining the component set M d and the component set M f determining the maximum value and the minimum value in the vertex coordinates, obtaining a preset division length d, and constructing a voxel grid G according to the maximum value, the minimum value, and the preset division length d; S4, obtain the boundary volume element in the volume element grid G, extract the center point of all boundary volume elements to build triangular mesh and obtain the overall simplified model T after texture remapping; S5、determining a generation order of the BIM target model according to the component set M f , the component set M t , the component set M a , the component set M d and the overall simplified model T determines the generation order of the BIM target model, and the multi-level details of the BIM target model are generated in sequence according to the generation order; Wherein, step S4 specifically comprises the following steps: Traverse each volume element G in the volume grid G j Obtain the volume element G j With the component set M d Component M in di Intersecting or being component M di Includes the first volume element, and volume element G j With the component set M f Middle component M fi The second volume element intersects, and the values ​​of the first and second volume elements are set to true; where 1≤j≤n G ; Determine the value of the body element G j The value and index range of the adjacent body element in X, Y and Z axis direction, if the adjacent body element has a false value or exceeds the index range, then determine the body element G j As a boundary body element, extract the center point of all boundary body elements to construct a triangular mesh and obtain the overall simplified model T after texture remapping; Step S5 comprises the following steps: According to the component set M f , the component set M t , the component set M a , the component set M d and the whole simplified model T determine the generation order of the BIM target model; wherein the level of the component set M f is D1, the level of the component set M t is L1, the level of the component set M d is L2, the level of the component set M a is L3, and the level of the whole simplified model T is L4. According to the generation order, generate the multi-level details of BIM target model in turn;Wherein, D1 level and L1 to L4 level are parallel levels, the greater the level number in L1 to L4 level, the lower the precision, and the more prior the generation order.

2. The method for generating multi-level details of a BIM model according to claim 1, wherein, After step S1, further comprising the following steps: Parse the geometry and material information in the BIM target model into a first format file, and parse the attributes in the triangular mesh model into a second format file, the first format file and the second format file are associated by unique ID.

3. The method for generating multi-level details of a BIM model as claimed in claim 1, wherein, After step S1, further comprising the following steps: According to the triangular mesh model of the component M i , the bounding box of the component M i is determined, and each component in the component set M is traversed to determine the corresponding bounding box of each component; wherein the component M i is the i-th component in the component set M, 1≤i≤n, n is the number of components, i=1,2,3...n.

4. The method for generating multi-level details of a BIM model according to claim 3, wherein, extracting a set of components M in the set of components M in step S2 f , specifically comprising the following steps: traversing each component M in the set of components M i , determining whether each edge of a triangle in the triangular mesh model of component M i is shared by the triangular mesh model of an adjacent component; If so, the determining component M i is a closed component; extracting all closed components gives the component set M c , with n components c ; If not, the determining component M i is a non-closed component; extracting all non-closed components results in a component set M f , the number of components is n f .

5. The method for generating multi-level details of a BIM model according to claim 4, wherein, extracting a set of components M from the set of components M in step S2 t and M d , in particular comprising the following steps: traversing the set of primitives M c each primitive M ci i, judging whether the primitive M ci intersects with the bounding box of other primitives, if intersects, then the primitive M ci is classified into the first set; if not intersects, then the primitive M ci is classified into the second set; wherein, 1≤i≤n c ; determining whether the bounding box of the intersecting component in the first set has a containing relationship, if the containing relationship exists, extracting all components whose bounding boxes are contained to obtain an internal component set M t , if the containing relationship does not exist, extracting all components whose bounding boxes are not contained and the second set to obtain a component set M d , the number of components is n d .

6. The method for generating multi-level details of a BIM model according to claim 5, wherein, extracting a set of components M in the set of components M in step S2 a , specifically comprising the following steps: traverse each member M in the member set M d di , determine whether all triangle vertices in the triangular mesh model of member M di are contained by the bounding boxes of other members in the member set M d ; if yes, extract the member whose triangle vertices are all contained to obtain a third set; if no, extract the member whose triangle vertices are not all contained to obtain a member set M a , the number of members is n a ; wherein 1≤i≤n d .​ 7. The method for generating multi-level details of a BIM model according to claim 6, wherein, Step S3, specifically comprising the following steps: A set of acquisition components M d and the maximum value of all component vertex coordinates of the component set M f and the minimum value , a preset division length d is acquired, so as to construct a voxel grid G, the number of voxels is n G ;​ Wherein, the body element grid G is expressed as an array V(a, b, c), and the default value is a false value; wherein a is a body element X-axis direction index, the index range is ; b is a body element Y-axis direction index, the index range is ; c is a body element Z-axis direction index, the index range is ; and the center point coordinates are .

8. The method for generating multi-level details of a BIM model as claimed in claim 1, wherein, Between step S4 and step S5, further comprising the following steps: Between step S4 and step S5, further comprising the following steps: An outer circle radius r of a maximum allowed vertex of a single component is acquired, to form a component set M f , the component set M t , the component set M a , and each component in the component set M d is judged whether the bounding box side length L of a component to be cut is greater than r; If the bounding box side length L of the to-be-split component is greater than r, a set of points P of equal division of the bounding box side length L is obtained with r as the equal division length, and the number of points P is n p Each point P in the set of points P is traversed i The to-be-split component is split by a plane passing through the point P i and perpendicular to L, and the unique ID of the to-be-split component before and after the split remains unchanged.

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