Fabricated building management method and system based on BIM and cloud service

Abstract

The fabricated building management method based on the BIM and the cloud service is characterized by comprising the following steps: step 1, constructing a heterogeneous data management model based on the cloud service; step 2, realizing multi-party collaborative fabricated building management based on the data management model; step 3, performing intelligent production and distribution optimization of the fabricated components based on the BIM; step 4, cross-platform lightweight model rendering and interaction based on the BIM, wherein the step 4 comprises the following steps: 4.1, constructing a heterogeneous BIM geometrical relationship model; 4.2, carrying out adaptive streaming transmission; 4.3, multiplexing and rendering the heterogeneous grids; 4.4, on the basis of vision field-first progressive rendering, an overall solution of multi-granularity grid simplification, self-adaptive rendering, vision field-first progressive rendering and multi-terminal response type interaction is provided, geometric topology information and semantic attribute information of the BIM model are brought into full play, the data scale is simplified to the maximum extent, and the rendering efficiency is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of construction project management, and more specifically, to a prefabricated building management method and system based on BIM and cloud services. Background Art

[0002] In recent years, prefabricated buildings have received extensive attention and promotion at home and abroad for their advantages such as high efficiency, environmental protection and high quality. The Chinese government has also issued a series of policies to support the development of prefabricated buildings. However, the design, production, construction, operation and maintenance of prefabricated buildings involve multiple professions and participating entities, various information systems and management platforms are diverse, data standards are not unified, information flow is not smooth, and collaborative management is difficult to achieve. This has led to fragmentation and inefficiency in the management of prefabricated buildings.

[0003] With the development of information technology such as BIM, some scholars and enterprises have tried to introduce BIM into the design stage of prefabricated buildings, realize the rapid and accurate design of components through parametric modeling, and realize the visualization of prefabricated building scheme analysis and optimization based on BIM. However, most of the existing BIM applications are limited to the design stage, and lack comprehensive support for the production, construction, operation and maintenance of prefabricated buildings. For example, in the component production stage, the traditional production management system cannot directly apply BIM model data, and the key links such as component production scheduling and processing technology still rely on manual experience; in the logistics distribution stage, the transportation strategy and stacking order of components are often arbitrarily decided, and there is a lack of optimization methods; at the construction site, there is a lack of effective means to grasp the logistics information such as the arrival time and stacking location of components in real time, which affects the construction scheduling. In short, the existing information management of prefabricated buildings lacks overall coordination and system integration, and the potential value of BIM has not been fully utilized.

[0004] In addition, with the increase in the scale and complexity of prefabricated buildings, the amount of data in BIM models is increasing, which poses a severe challenge to the lightweight display and real-time interaction of models on multiple platforms. Traditional BIM software mostly uses local rendering, which requires downloading the complete BIM model data from the server to the local client, and parsing and rendering it locally. This method not only consumes a lot of network bandwidth, but also brings a heavy computing and storage burden to the client, resulting in slow loading speed and poor interactive response of BIM models, especially on mobile and Web terminals. Some researchers have tried to use multi-resolution models, mesh simplification and other methods to alleviate the above problems to a certain extent, but for the increasingly complex BIM models of prefabricated buildings, the existing model simplification methods are still rough and the rendering effect is not satisfactory.

[0005] New generation information technologies such as cloud computing, mobile Internet, and the Internet of Things provide new ideas for solving the above problems. Some scholars have proposed a cloud-based BIM collaborative management platform, where multiple participants can share BIM model data through the cloud to achieve cross-regional and cross-professional collaborative design and project management. Some scholars have also explored the application of Internet of Things technology in the logistics management of prefabricated buildings. In general, the deep integration of new generation information technology and prefabricated buildings is still in its infancy, lacking a global top-level design and systematic technical architecture, and has not formed a complete theoretical system and mature application solutions.

[0006] In summary, how to integrate new generation information technologies such as BIM, cloud computing, and the Internet of Things, and develop a set of collaborative, efficient, intelligently optimized, technologically advanced, practical and reliable prefabricated building information management systems for the design, production, construction, operation and maintenance of prefabricated buildings, and realize the interconnection and interoperability of information in various stages such as design, production, construction, operation and maintenance, and closed-loop management of the entire life cycle, has become an urgent task for the information transformation of the prefabricated building industry, and is also an important way to promote the transformation and upgrading of my country's building industrialization. It is in this context that the present invention is proposed, aiming to carry out systematic innovation in terms of top-level architecture, key technologies and system functions, and develop a set of technologically advanced, practical and efficient prefabricated building information management systems.

[0007] Especially in the lightweight rendering of BIM models, the existing technology has the following technical difficulties:

[0008] (1) For the original complex and large BIM model, the simple uniform sorting mesh simplification method will cause obvious rendering quality loss and cannot meet the requirements of engineering applications. Although the complex simplification method can ensure a certain model accuracy, it has low computational efficiency and is not suitable for large-scale BIM scenarios. How to balance rendering efficiency and rendering quality is a technical challenge that needs to be solved urgently.

[0009] (2) Most existing mesh simplification methods use Graphics Processing Unit (GPU) acceleration, but for mobile devices, it is difficult to take advantage of GPU parallel computing due to the limited GPU computing resources. How to design a lightweight and efficient mesh simplification algorithm based on the hardware characteristics of mobile terminals is also a problem to be studied.

[0010] (3) Currently, most rendering optimization algorithms for BIM models are based on PC-based considerations and lack special optimization for mobile operating systems such as Android and iOS. To achieve efficient rendering of BIM models on mobile terminals, it is necessary to fully consider the resource limitations of mobile devices such as energy consumption, bandwidth, and cache, which is still rare in existing technologies.

[0011] (4) With the promotion and application of BIM in the field of prefabricated buildings, the number of BIM models generated by various participating units is increasing, and the data format, precision, and reference coordinates are different. How to achieve the integration and integrated application of multi-source heterogeneous BIM models has also become a new technical challenge. Most of the existing BIM software is oriented to a single platform and lacks a cross-platform BIM data management and conversion mechanism. Summary of the invention

[0012] The present invention is aimed at the above technical problems and proposes a method and system for prefabricated building management based on BIM and cloud services. On the one hand, for lightweight rendering of BIM models, the present invention realizes adaptive extraction of key features of BIM models based on Graph Attention Network (GAT) and progressive mesh simplification based on Kullback-Leibler (KL) divergence on the mobile terminal, and introduces distributed BIM data indexing technology based on MapReduce on the cloud, forming a lightweight processing architecture of BIM models in end-cloud collaboration, which well balances rendering efficiency and rendering quality. On the other hand, for the integrated management of multi-source heterogeneous BIM models, the present invention realizes semantic mapping and conversion of different BIM models by constructing BIM semantic ontology, and develops BIM data standards and interfaces that support multi-platform and multi-terminal use. In addition, the present invention also associates BIM model data with real-time data of the Internet of Things, enhances the semantics of BIM models through visualization, digital twins and other technologies, and realizes accurate mapping of BIM models with physical entities of prefabricated buildings. Through the above innovative work, the present invention has better solved the limitations of the existing technology and formed a new set of prefabricated building information management technology solutions, which is of great significance for promoting the upgrading of my country's prefabricated building industry and the transformation of building industrialization.

[0013] The present invention provides a prefabricated building management method based on BIM and cloud services. 1. The prefabricated building management method based on BIM and cloud services is characterized by comprising the following steps:

[0014] Step 1: Build a heterogeneous data management model based on cloud services;

[0015] Step 2: Implement multi-party collaborative prefabricated building management based on the data management model;

[0016] Step 3: Intelligent production and distribution optimization of prefabricated components based on BIM;

[0017] Step 4: Cross-platform lightweight model rendering and interaction based on BIM, said step 4 includes:

[0018] 4.1. Constructing a heterogeneous BIM geometric relationship model; 4.2. Adaptive streaming; 4.3. Heterogeneous grid reuse and rendering; 4.4. Progressive rendering based on view priority.

[0019] Specifically, the step 1 comprises:

[0020] Collect heterogeneous data at various stages of prefabricated buildings, including BIM model data, progress data, quality data, and logistics data;

[0021] Uploading the heterogeneous data to the cloud, and storing and managing them in a manner based on a combination of document and graphic databases;

[0022] The heterogeneous data are cleaned, converted and integrated in the cloud to build a unified data management model.

[0023] Specifically, the step 2 comprises:

[0024] Build a collaborative management platform based on cloud services to support multiple parties to access and operate cloud data through browsers or mobile apps;

[0025] Using the semantic association information in the data management model, data interconnection and intercommunication across disciplines and stages can be achieved;

[0026] Based on role and authority control, provide personalized data views and operation interfaces for different subjects;

[0027] It integrates BIM model browsing, progress simulation, quality problem marking, logistics tracking and other functions to achieve visualization and interactive management of the production, construction and management processes of prefabricated buildings.

[0028] Specifically, the step 3 comprises:

[0029] Based on the BIM model of prefabricated buildings, the geometric parameters, material properties, processing requirements and other information of components are extracted to automatically generate production design files of components;

[0030] Optimize the production schedule and batch division of components, formulate a periodic rolling production plan with the order delivery time and production balance as the goal;

[0031] Optimize the transportation routes and delivery time of components based on the logistics information of components in the BIM model;

[0032] Integrate barcode and RFID Internet of Things technologies to conduct information management and real-time tracking of component production, transportation, storage and other links.

[0033] Specifically, the heterogeneous BIM geometric relationship model in step 4.1 is represented by a multi-level directed acyclic graph G=(y, E, L), where y represents the component instance node in the BIM model, E represents the topological relationship edge between components, and L represents the relationship type; for the node v at the i-th layer, i ∈y, its characteristic vector fv i for:

[0034] f i =[gv i , sv i , rv i ,tv i ]∈R

[0035] Among them, gv i Represents the geometric parameters sv of the node i Represents the semantic attributes of the node, rv i Represents the relationship characteristics of the nodes, tv i Represents the topological characteristics of the node; for edge e ij ∈E, its characteristic vector feij is:

[0036] feij=[reij,teij]∈R p

[0037] Among them, reij represents the relationship characteristics of the edge, and teij represents the topological characteristics of the edge.

[0038] Specifically, in step 4.2, the node v is calculated according to the user's interaction parameters. i ∈V is the correlation measure with the viewpoint

[0039]

[0040] Among them, pv i For node v i The geometric center, vc is the viewpoint position, dc is the line of sight direction, Represents node v i Importance in BIM model, W 1 , W 2 , W 3 is the balance weight; based on the correlation measure ρv i The improved breadth-first search algorithm is used to generate the key node set V k′ And sort them in topological dependency order to form a transmission sequence Sk; assemble the data stream according to the transmission sequence Sk, and dynamically adjust the data packet size S i

[0041]

[0042] Among them, Si-1 is the size of the previous data packet T r and T t The target rendering time and the actual transmission time are respectively r and F t are the target frame rate and actual frame rate respectively, and α and β are the balance factors.

[0043] Specifically, in step 4.3, for the received grid data M i , calculate its difference with the cached grid M j The similarity Sim(M i , M j ):

[0044]

[0045] Among them, V i and V j is the vertex set F of the two meshes i and F j is the face set of two meshes, c i and c j is the geometric center of the two grids, λ is the attenuation factor of the centroid distance; when Sim(M i , M j ) is greater than a given threshold δ, multiplexing M j Rendering result; otherwise, according to the grid M i The mesh simplification parameter σ is adaptively generated based on the geometric characteristics and performance parameters of the rendering device. i , and adopts the improved quadratic error metric grid simplification algorithm to i Simplify and generate the edge collapse error less than σ i , the number of patches is reduced to the original mesh r i Lightweight mesh

[0046] Specifically, in step 4.4, the lightweight grid is determined according to the topological order of the data stream and the user's current field of view. The rendering priority P i :

[0047]

[0048] Among them, ρv i The node v to which the grid belongs i The correlation measure of is the visible area A of the grid 0 is the total area of ​​the viewshed is the number of mesh faces γ 1 , γ 2 , γ 3The weight coefficient is 2 according to the rendering priority P i Sort the lightweight meshes into a rendering sequence, and render the meshes in sequence according to the rendering sequence; during the rendering process, monitor the rendering frame rate F in real time r，当 F r Below target frame rate F t When F r Higher than F t When the user's perspective changes, the rendering accuracy of subsequent meshes is adaptively improved or some high-priority meshes are rendered. For low-priority meshes outside the field of view, a delayed loading strategy is adopted to render them when the user's perspective changes.

[0049] Specifically, the BIM model adopts the IFC standard format, the cloud adopts Alibaba Cloud server, the mobile APP is developed based on the Android operating system, the Internet of Things technology includes RFID and QR code, and the database includes MySQL and Redis.

[0050] A prefabricated building management system based on BIM and cloud services, comprising: a heterogeneous data management model construction module, a multi-party collaborative management module, a prefabricated component intelligent production and distribution optimization module, and a cross-platform lightweight model rendering and interaction module. The cross-platform lightweight model rendering and interaction module comprises a heterogeneous BIM geometric relationship model construction unit, an adaptive streaming unit, a heterogeneous grid reuse and rendering unit, and a progressive rendering unit based on view priority; the system is used to implement the prefabricated building management method based on BIM and cloud services.

[0051] The present invention has the following beneficial effects:

[0052] (1) The heterogeneous data management model built using cloud services provides all participants with a unified data access portal and an integrated data management solution, breaking down the data barriers between different professions and stages, and realizing the interconnection and real-time sharing of heterogeneous data such as BIM.

[0053] (2) Introduce BIM into key links such as component production and logistics distribution of prefabricated buildings, and rely on BIM models to carry out production scheduling optimization, transportation route planning, etc., thereby reducing costs while improving production efficiency and management accuracy.

[0054] (3) An innovative overall solution of multi-granularity grid simplification, adaptive rendering, view-priority progressive rendering, and multi-terminal responsive interaction was proposed, which fully utilized the geometric topological information and semantic attribute information of the BIM model, simplified the data scale to the maximum extent, and optimized the rendering efficiency, thus achieving lightweight, high-fidelity rendering and smooth browsing of large-scale and complex BIM models on multiple platforms.

[0055] (4) It comprehensively covers all stages of prefabricated building design, production, construction, operation and maintenance, and gives full play to the integrated advantages of new generation information technologies such as cloud computing, big data, and the Internet of Things, forming an overall solution for the intelligent construction of prefabricated buildings with multi-participating entity collaboration and closed-loop management throughout the entire life cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a flow chart of the prefabricated building management method based on BIM and cloud services of the present invention.

[0057] Figure 2 This is a schematic diagram of the framework of the prefabricated building management system based on BIM and cloud services of the present invention. DETAILED DESCRIPTION

[0058] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the specific implementation method, structure, features and effects of the prefabricated building management method based on BIM and cloud services proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0059] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0060] The specific scheme of the prefabricated building management method based on BIM and cloud service provided by the present invention is described in detail below with reference to the accompanying drawings.

[0061] Example 1

[0062] See also Figure 1 The purpose of the present invention is to provide a prefabricated building management method based on BIM and cloud services, so as to solve the technical problems existing in traditional prefabricated building management, such as the difficulty in integrating and sharing heterogeneous data, the low efficiency of multi-party collaborative management, the difficulty in accurately optimizing component production and distribution, and the difficulty in lightweight display of large-scale BIM models, so as to realize the refined management and visualization application of the whole life cycle of prefabricated buildings.

[0063] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a method for prefabricated building management based on BIM and cloud services, comprising the following steps: Step 1: constructing a heterogeneous data management model based on cloud services; Step 2: realizing multi-party collaborative prefabricated building management based on the data management model; Step 3: intelligent production and distribution optimization of prefabricated components based on BIM; Step 4: cross-platform lightweight model rendering and interaction based on BIM, Step 4 includes: 4.1 constructing a heterogeneous BIM geometric relationship model; 4.2 adaptive streaming transmission; 4.3 heterogeneous grid reuse and rendering; 4.4 progressive rendering based on view priority.

[0064] In step 1, heterogeneous data of each stage of prefabricated buildings are collected, uploaded to the cloud and managed by combining documents and graph databases, and the heterogeneous data are cleaned, converted and integrated in the cloud, and finally a unified data management model is constructed. Among them, heterogeneous data includes but is not limited to BIM model data, progress data, quality data and logistics data. The present invention does not limit the source format of heterogeneous data, and may include multiple general data formats such as IFC, XML, and JSON. Considering the scale and query characteristics of BIM model data, the present invention preferably uses document databases such as MongoDB for storage, and for other structured management data, the present invention preferably uses graph databases such as Neo4j for storage to make full use of the advantages of graph databases in processing association relationships. The cleaning, conversion and integration process of cloud data can adopt mainstream data integration technologies such as ETL, and the present invention does not limit this. The modeling method of the data management model can be combined with knowledge representation technologies such as ontology and semantic network to achieve the scalability and versatility of the data model.

[0065] In step 2, a collaborative management platform is built on the cloud to support all participants to remotely access cloud data resources through a browser or mobile APP, and to achieve seamless data interconnection across disciplines and stages with the help of semantic association information contained in the data management model. The platform supports flexible role authority management, and provides differentiated data services for users of different roles by customizing personalized data views and operation interfaces. In addition, the collaborative platform integrates various business management functions such as BIM model browsing, progress management, quality management, and logistics management, and realizes the refinement, visualization, and integrated management of the entire process of prefabricated building production, construction, and operation and maintenance. The development technology of the collaborative platform is not limited by the present invention, and mainstream development frameworks such as Java and .NET can be used. The operating system platform of the mobile APP can be Android, iOS, etc. Considering the large file characteristics of the BIM model, the present invention preferably adopts model streaming technology when realizing the model browsing function to improve the loading speed and response performance of the model on the mobile terminal.

[0066] In step 3, firstly, various attribute parameters of prefabricated components, such as size parameters, material attributes, reserved embedded parts information, etc., are extracted from the BIM model of the prefabricated building, and after calculation and processing, structured production design files, such as processing drawings, numerical control programs, etc., are automatically generated to realize the automation of production design. On this basis, the present invention combines constraints such as order delivery period and production resources to optimize the scheduling of component production tasks and formulate a scientific and reasonable production plan. Among them, the scheduling optimization can select a variety of operational optimization theories and methods such as linear programming, integer programming, heuristic search, and reinforcement learning, which are not specifically limited in the present invention. At the same time, the present invention also makes full use of the spatial information such as component assembly relationship and on-site road layout contained in the BIM model to finely optimize the distribution process of prefabricated components. For example, the optimal distribution plan can be generated by using intelligent optimization algorithms such as genetic algorithms based on factors such as the stacking order of components, on-site transportation distance, and hoisting height. In order to realize the transparent management of component production and distribution process, the present invention integrates Internet of Things technologies such as barcodes and RFID to collect information and monitor the production and logistics distribution process in real time. Among them, barcode technology is mainly used for component identification and association in the manufacturing stage, and can be implemented in the form of one-dimensional code, two-dimensional code, DM code, etc. RFID technology is more used in the logistics and distribution stage, and by attaching electronic tags to physical entities such as components, vehicles, and storage equipment, it can achieve management functions such as accurate positioning of entities, automatic inventory, and intelligent scheduling.

[0067] In step 4, considering that the massive heterogeneous BIM model data centrally stored in the cloud puts forward extremely high requirements for lightweight display and responsive interaction on multiple platforms, the present invention innovatively proposes a complete cross-platform BIM lightweight rendering optimization solution. The solution first constructs a heterogeneous geometric relationship model of the BIM model, and then combines the user's real-time interaction parameters, through adaptive streaming, heterogeneous grid reuse, progressive rendering and other progressive optimization strategies, and finally realizes efficient, stable and realistic cross-platform rendering display of massive heterogeneous BIM models. The core steps of the rendering optimization solution are described in detail below:

[0068] In step 4.1, it is considered that the BIM models gathered in the cloud often come from different design software, use different data formats, and have significant heterogeneous characteristics. In order to overcome the "information island" problem of heterogeneous BIM models and realize the interconnection and interoperability of BIM models, the present invention first performs geometric analysis on these heterogeneous model data, extracts and reconstructs the topological relationship between its core geometric elements (such as points, lines, surfaces, etc.), and builds a unified heterogeneous geometric relationship model at the model granularity. The heterogeneous geometric relationship model is represented by a multi-level directed acyclic graph (Multi-level DAG), denoted as G=(V, E, L). Among them, V represents the component instance node in the BIM model, E represents the topological relationship edge between component instances, and L represents a set of relationship types (such as support, intersection, connection, etc.). Taking into account the multi-granularity characteristics of the BIN model, the present invention adopts a multi-level graph model expression, that is, each coarse-grained component node can continue to contain multiple fine-grained sub-component nodes downward. For any level of node v i ∈V, introduce the feature vector Describe its characteristic attributes

[0069]

[0070] in, Represents node v i Geometric parameters (such as centroid coordinates, size, etc.) Indicates semantic attributes (component type, material, etc.) Indicates the relationship characteristics with other component nodes (such as support method, connection type, etc.), Indicates topological features (degree, clustering coefficient, etc.). Similarly, for the relationship edge e ij ∈E, introduce the feature vector Describe its characteristic attributes

[0071]

[0072] in, Represents edge e ij relationship characteristics (such as support force, connection strength, etc.), Represents topological features (such as directionality, etc.). The specific components of the node feature vector and edge feature vector can be flexibly defined in combination with the actual project and automatically extracted and calculated from the original BIM model data through aggregation operations such as averaging, maximum value, and minimum value. The construction of heterogeneous geometric relationship models can be completed in the cloud or in the terminal. The present invention does not limit this.

[0073] In step 4.2, in view of the massive data size of heterogeneous BIM models, the present invention proposes an adaptive streaming transmission strategy, which adaptively determines the model transmission granularity and priority according to the user's real-time interaction parameters, such as viewpoint position, line of sight direction, field of view, etc., and dynamically adjusts the size of the streaming data packet, in order to minimize the data transmission volume while ensuring a good interactive experience. First, the node correlation measurement index is introduced Measuring any node v i Relevance to the current user's viewpoint:

[0074]

[0075] in, For node v i The geometric center coordinates, v c is the user's viewpoint position, d c is the sight direction, Represents node v i Importance in BIM model, w 1 ,w 2 ,w 3 is the balance weight coefficient. It can be calculated by the following formula:

[0076]

[0077] Among them, Area(v i ) is the component v i Intuitively, the node correlation measure The distance from the node to the viewpoint, the angle between the node and the line of sight, and the importance of the node itself are comprehensively considered. On this basis, the present invention improves the classic breadth-first search (BFS) algorithm to extract key nodes related to the view area on the heterogeneous geometric relationship model G. The improved BFS algorithm extracts the key nodes related to the view area from the nodes with the highest correlation measure. Start by recursively searching its adjacent nodes until one of the following termination conditions is met: (1) The cumulative number of nodes reaches the preset maximum number of key nodes N k ; (2) The correlation metric value of the newly expanded node is lower than the preset correlation threshold ρ min ; (3) The number of BFS search layers reaches the preset maximum number of layers D max The final set of key nodes is recorded as V kv And according to the correlation metric The order from high to low forms an ordered sequence Next, the present invention uses S k The key nodes v are transmitted in order. iThe geometric data, semantic data, relational data, etc. are assembled into several data packets and transmitted in batches through the streaming channel. Taking into account the volatility of network conditions and rendering performance, the present invention dynamically adjusts the data packet size S during the streaming process. i :

[0078]

[0079] Among them, S i-1 is the size of the data packet in the previous batch, T r and T t are the target response time and actual response time of the rendering end, respectively. r and F t are the target frame rate and actual frame rate of the rendering end, respectively, and a and β are the balance factors. It can be seen that when the actual response time of the rendering end is greater than the target response time (i.e., T t >T r ) or the actual frame rate is lower than the target frame rate (i.e. F t <F r ), it means that the current network transmission rate or rendering performance is insufficient, so the size of subsequent data packets needs to be appropriately reduced. On the contrary, the size of the data packet can be appropriately increased. α and β control the degree of influence of transmission performance and rendering performance on data packet size adjustment, and can be set according to specific application scenarios. The present invention can minimize the amount of data transmission and save network bandwidth while ensuring a good interactive experience through the above-mentioned adaptive streaming transmission strategy.

[0080] In step 4.3, after receiving the streaming BIM component data, the rendering end first performs geometric analysis to extract the geometric elements such as mesh facets, vertex coordinates, texture maps, etc. of each component. Considering the scale and complexity of the BIM model, the geometric mesh data of the same component may be repeatedly transmitted and rendered multiple times, resulting in a waste of resources. To this end, the present invention proposes a heterogeneous mesh reuse method based on content similarity. Specifically, a mesh cache collection is maintained at the local rendering end. Store the received component mesh data. For the newly received component mesh M i , first calculate its There is already a grid M in j Similarity

[0081]

[0082] Among them, V i and V j The grid M i and M j The vertex set F i and F j are the face sets of the two respectively, ci and c j are the geometric center coordinates of the two grids, and λ is the attenuation factor. i , M j ) has a value range of [0, 1]. Intuitively, Sim(M i , M j ) comprehensively measures the degree of overlap between two meshes in terms of vertices, faces, positions, etc. i , M j ) is greater than the preset similarity threshold δ (such as δ = 0.9), it can be considered that the grid M i With M j Geometrically similar, so M can be directly reused j The rendering result does not need to be repeated. i If Sim(M i , M j ) is less than the similarity threshold δ, then M i Add to cache collection Considering the differences in hardware configurations of different terminal devices (such as CPU / GPU frequency, memory size, etc.), and the differences in geometric features of different BIM models (such as the number of vertices, texture size, etc.), it is difficult to achieve both high efficiency and high quality by using unified rendering parameters. To this end, the present invention adopts an adaptive rendering strategy to target different mesh data M i , dynamically generate rendering parameters σ that match it i Among them, the rendering parameter σ i It may include lighting parameters (such as light source type, intensity, etc.), material parameters (such as diffuse reflection coefficient, highlight coefficient, etc.), camera parameters (such as field of view angle, depth of field, etc.), etc. Rendering parameters σ i The generation of is achieved through the following formula:

[0083] σ i =f(g i , d i , e i )

[0084] Among them, g i For the grid M i Geometric features such as the number of vertices, normal vectors, etc.), d i is the performance parameters of the rendering device (such as CPU frequency, GPU model, etc.), i is the application environment parameter (such as lighting conditions, scene type, etc.), and f(·) is the rendering parameter generation function. The generation function f(·) can be learned from a large number of rendering cases using machine learning methods, or can be customized by graphics experts based on experience. The present invention does not limit this. Based on the adaptive rendering parameter σ i′The present invention can determine the rendering strategy according to the different mesh data, and ensure the rendering quality as much as possible while rendering efficiently. Furthermore, in order to improve the efficiency of rendering, the present invention also introduces a mesh simplification method based on error measurement. Generate a series of simplified multi-resolution meshes through iterative edge collapse operations The superscript indicates the simplification level. The higher the level, the greater the simplification degree and the fewer mesh faces. Each edge collapse operation corresponds to a local simplification error ΔE:

[0085]

[0086] Among them, p 1 and p 2 is the coordinates of a pair of vertices that undergo collapse transformation, is the target vertex coordinate after collapse, usually p 1 and p 2 The midpoint of . Each time, the vertex pair with the minimum simplification error ΔE is selected for edge collapse until the simplified mesh satisfies the number of facets reduced to ∈ times (such as 10%) of the original mesh. The above iterative edge collapse process can be implemented through the error metric matrix Q. For any vertex v, its simplification error is calculated by the following formula:

[0087] E(v)=v T Q

[0088] Among them, the matrix Q is the sum of the error metric matrices of all edge collapse transformations associated with vertex v:

[0089]

[0090] Among them, C is the set of all collapse transformations to which the vertex v belongs, and the matrix on the right corresponds to a quadratic surface, whose coefficient a ij ,b ij ,c ij ,d ij ,e ij ,f ij Based on the above mesh simplification method, the present invention can adaptively generate simplified versions of different resolutions for different mesh data, dynamically adjust the simplification level according to device performance and interaction requirements during rendering, and achieve a dynamic balance between rendering efficiency and fidelity.

[0091] In step 4.4, after the parsing, reuse and simplification of the BIM component mesh data are completed, the simplified mesh data needs to be rendered and displayed. Considering that the user's viewpoint position and line of sight direction are changing at any time, and the importance of different components is different, in order to achieve high efficiency and interactivity of rendering, the present invention adopts a progressive rendering method based on view priority. First, according to the topological order of the data stream and the user's current view range, each simplified mesh is calculated. The rendering priority P i :

[0092]

[0093] in, For Grid Belonging node v i The correlation measure of (see formula (2)), For Grid Visible area A 0 is the total area of ​​the viewshed For Grid The number of patches γ 1 ,γ 2 ,γ 3 is the weight coefficient. Intuitively, formula (7) comprehensively considers the three factors of grid relevance, visibility and complexity: the relevance metric The larger the visible area The larger the number of patches, The smaller the value, the higher the rendering priority of the mesh. i , the simplified mesh data can be sorted to obtain a progressive rendering sequence Then, the grid data is rendered in sequence according to the sequence, that is, the important grids with high priority are rendered first, and then the secondary grids with low priority are rendered. Due to the changes in viewpoints and sight lines, the rendering priority will also change dynamically. Therefore, during the rendering process, it is also necessary to monitor the rendering performance indicators (such as frame rate) in real time and dynamically adjust the rendering strategy. Specifically, when the rendering frame rate is lower than the preset fluency threshold (such as 25FPS), the rendering response of high-priority grids is prioritized, and the rendering of low-priority grids is reduced or suspended: when the rendering frame rate is higher than the fluency threshold, the rendering frequency of low-priority grids can be appropriately increased to improve the integrity and fidelity of the rendering. In addition, for grid data beyond the field of view, a delayed loading strategy can be adopted, that is, its rendering is triggered only when the viewpoint moves and causes it to enter the field of view, rather than blindly rendering. Based on the above-mentioned progressive rendering strategy, the present invention can adaptively balance rendering efficiency and rendering quality, while ensuring the real-time response of key data, and improve the rendering accuracy of non-critical data as much as possible, thereby obtaining a better user experience.

[0094] Although the above steps 4.1 to 4.4 are for PC, similar ideas can be adopted for mobile terminals, that is, first screen key data, and then use strategies such as progressive rendering and view priority to achieve efficient, stable and fidelity mobile terminal BIM model browsing. The difference is that due to the more limited computing, storage, display and other resources of mobile terminals, mesh simplification, rendering parameter setting, delayed loading and other aspects will be more aggressive, and mobile graphics optimization technologies such as skeleton extraction and contour edge rendering can also be introduced to further reduce rendering complexity.

[0095] See also Figure 2 The present invention also discloses an assembled building management system based on BIM and cloud services, comprising: a heterogeneous data management model construction module 1, a multi-party collaborative management module 2, an assembled component intelligent production and distribution optimization module 3, and a cross-platform lightweight model rendering and interaction module 4. The cross-platform lightweight model rendering and interaction module 4 includes a heterogeneous BIM geometric relationship model construction unit, an adaptive streaming unit, a heterogeneous grid reuse and rendering unit, and a progressive rendering unit based on view priority; the system is used to implement the assembled building management method based on BIM and cloud services.

[0096] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. The prefabricated building management method based on BIM and cloud services is characterized by , including the following steps: Step 1: Build a heterogeneous data management model based on cloud services; Step 2: Implement multi-party collaborative prefabricated building management based on the data management model; Step 3: Intelligent production and distribution optimization of prefabricated components based on BIM; Step 4: Cross-platform lightweight model rendering and interaction based on BIM, said step 4 includes: 4.

1. Constructing heterogeneous BIM geometric relationship model; 4.

2. Adaptive streaming; 4.

3. Heterogeneous grid reuse and rendering; 4.

4. Progressive rendering based on viewport priority.

2. The method according to claim 1, characterized in that , the step 1 comprises: Collect heterogeneous data at various stages of prefabricated buildings, including BIM model data, progress data, quality data, and logistics data; Uploading the heterogeneous data to the cloud, and storing and managing them in a manner based on a combination of document and graphic databases; The heterogeneous data are cleaned, converted and integrated in the cloud to build a unified data management model.

3. The method according to claim 1, characterized in that , the step 2 comprises: Build a collaborative management platform based on cloud services to support multiple parties to access and operate cloud data through browsers or mobile apps; Using the semantic association information in the data management model, data interconnection and intercommunication across disciplines and stages can be achieved; Based on role and authority control, provide personalized data views and operation interfaces for different subjects; It integrates BIM model browsing, progress simulation, quality problem marking, logistics tracking and other functions to achieve visualization and interactive management of the production, construction and management processes of prefabricated buildings.

4. The method according to claim 1, characterized in that , the step 3 comprises: Based on the BIM model of prefabricated buildings, the geometric parameters, material properties, processing requirements and other information of components are extracted to automatically generate production design files of components; Optimize the production schedule and batch division of components, formulate a periodic rolling production plan with order delivery time and production balance as the goal ； Optimize the transportation routes and delivery time of components based on the logistics information of components in the BIM model; Integrate barcode and RFID Internet of Things technologies to conduct information management and real-time tracking of component production, transportation, storage and other links.

5. The method according to claim 1, characterized in that The heterogeneous BIM geometric relationship model in step 4.1 is represented by a multi-level directed acyclic graph G=(V, E, L), where V represents the component instance node in the BIM model, E represents the topological relationship edge between components, and L represents the relationship type; for the node v at the i-th layer, i ∈V, its characteristic vector fv i for: fv i =[gv i ,sv i ,rv i ,tv i ]∈R Among them, gv i Represents the geometric parameters sv of the node i Represents the semantic attributes of the node, rv i Indicates the relationship characteristics of the nodes, tv i Represents the topological characteristics of the node; for edge e ij ∈E, its characteristic vector feij is: feij=[reij,teij]∈R p Among them, reij represents the relationship characteristics of the edge, and teij represents the topological characteristics of the edge.

6. The method according to claim 1, characterized in that In step 4.2, the node v is calculated according to the user's interaction parameters. i ∈V is the correlation measure with the viewpoint Among them, pv i For node v i The geometric center, v c is the viewpoint position, dc is the sight direction, Represents node v i The importance in the BIM model, w1, w2, w3 are balance weights; based on the correlation metric ρv i The improved breadth-first search algorithm is used to generate the key node set V k′ And sort them in topological dependency order to form a transmission sequence Sk; assemble the data stream according to the transmission sequence Sk, and dynamically adjust the data packet size S i Among them, Si-1 is the size of the previous data packet T r and T t The target rendering time and the actual transmission time are respectively r and F t are the target frame rate and actual frame rate respectively, and α and β are the balance factors.

7. The method according to claim 1, characterized in that In step 4.3, for the received grid data M i , calculate its difference with the cached grid M j The similarity Sim(M i , M j ): Among them, V i and V j is the vertex set F of the two meshes i and F j is the face set of two meshes, c i and c j is the geometric center of the two grids, λ is the attenuation factor of the centroid distance; when Sim(M i , M j ) is greater than a given threshold δ, multiplexing M j Rendering result; otherwise, according to the grid M i The mesh simplification parameter σ is adaptively generated based on the geometric characteristics and performance parameters of the rendering device. i , and adopts the improved quadratic error metric grid simplification algorithm to i Simplify and generate the edge collapse error less than σ i , the number of patches is reduced to the original mesh r i Lightweight mesh 8. The method according to claim 1, characterized in that In step 4.4, the lightweight grid is determined according to the topological order of the data stream and the user's current field of view. The rendering priority P i : Among them, ρv i The node v to which the grid belongs i The correlation measure of is the visible area of ​​the grid A0 is the total area of ​​the field of view is the number of mesh faces γ1, γ2, γ3 are weight coefficients 2 according to the rendering priority P i Sort the lightweight meshes into a rendering sequence, and render the meshes in sequence according to the rendering sequence; during the rendering process, monitor the rendering frame rate F in real time r，当 F r Below target frame rate F t When F r Higher than F t When the user's perspective changes, the rendering accuracy of subsequent meshes is adaptively improved or some high-priority meshes are rendered. For low-priority meshes outside the field of view, a delayed loading strategy is adopted to render them when the user's perspective changes.

9. The method according to any one of claims 1 to 8, characterized in that: The BIM model adopts the IFC standard format, the cloud uses Alibaba Cloud server, the mobile APP is developed based on the Android operating system, the Internet of Things technology includes RFID and QR code, and the database includes MySQL and Redis.

10. A prefabricated building management system based on BIM and cloud services, characterized in that , including: a heterogeneous data management model construction module, a multi-party collaborative management module, an assembly component intelligent production and distribution optimization module, and a cross-platform lightweight model rendering and interaction module. The cross-platform lightweight model rendering and interaction module includes a heterogeneous BIM geometric relationship model construction unit, an adaptive streaming unit, a heterogeneous grid reuse and rendering unit, and a progressive rendering unit based on view priority; The system is used to implement the prefabricated building management method based on BIM and cloud services as described in any one of claims 1 to 9.

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