Access method of topological element of three-dimensional CSG-BRep (Constructive Solid Geometry-Boundary Representation) model

An access method and model technology, which is applied in special data processing applications, instruments, electrical digital data processing, etc., can solve the problems of lack of topological connection relationship inside the model, incomplete integration of topological and geometric information, and data redundancy, etc.

Inactive Publication Date: 2015-11-04
BEIJING UNIV OF CIVIL ENG & ARCHITECTURE
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  • Summary
  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

2) They only propose their own topology models, but do not explore how to access the topology
3) Although there are better methods for topological reconstruction of adjacent spatial volumes, it is difficult to reconstruct the topological relationship of intersecting spatial volumes
4) Realizing 3D reconstruction based on volume and images Although model reconstruction can be realized, the model is formed by simple stretching and does not have a fine structure, and the model only has a simple coordinate representation and lacks topological connections within the model
5) Most topological models have data redundancy, and the fusion of topological and geometric information is not comprehensive

Method used

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  • Access method of topological element of three-dimensional CSG-BRep (Constructive Solid Geometry-Boundary Representation) model
  • Access method of topological element of three-dimensional CSG-BRep (Constructive Solid Geometry-Boundary Representation) model
  • Access method of topological element of three-dimensional CSG-BRep (Constructive Solid Geometry-Boundary Representation) model

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Effect test

Embodiment 1

[0155] Access Mechanism of Topological Elements Based on Topological Model

[0156] 1. Construct a 3D fine voxel model

[0157] Before introducing the mechanism of accessing the topology, it is first necessary to construct a three-dimensional fine voxel model according to the topology model structure above. The present invention proposes to select a three-dimensional point in the point cloud, use the RANSAC improved algorithm, combine the linear least squares method to extract and fit the quadratic surface, improve the selection method of the initial iteration point in the RANSAC algorithm, and obtain the parameters of the quadratic surface for the first time Finally, according to the scanning density of the spatial points, the point cloud data is automatically segmented by an iterative method, and finally the exact value of the segmented quadratic surface parameters is calculated, and the linear least square method is used to accurately fit the segmented quadratic surface. T...

Embodiment 2

[0166] Access the parent set topology of shape

[0167] Because in the topological data structure of the CSG-BRep model designed by the present invention, it is all references from top to bottom (from CSG_Shell or CSG_Solid to CSG_Vertex), and the subset cannot be accessed directly from the subset elements like accessing the subset topology structure. The parent element of the set, so the present invention proposes such an algorithm to solve this problem, taking a square as an example, such as Image 6 As shown, in order to find three edges connected to a vertex located in a cube, the following steps need to be implemented:

[0168] a. Traverse the cube and find all edge structures located on the cube from the cube.

[0169] b. Continue to traverse the vertices located on the edge in the found edge structure.

[0170] c. Assign a code to the vertex found in b, and change the code to a unique identifier of the vertex.

[0171] d. Put the identity of the vertex in c and the e...

Embodiment 3

[0181] Conversion between models to internal topological relationships

[0182] According to the above algorithm, the construction and access of the topological relationship within a single model can be realized, but the topological relationship between models has not yet been processed. Using the well-known Boolean operations in CSG, the relationship between models can be skillfully handled. By performing Boolean operations on different models, the topological regression between models can be unified into the topology within the model. Naturally, the algorithm within the model can be used. solve.

[0183] 1. Express typical voxels with geometric parameter equations

[0184] The intersection operation is the core content of the Boolean operation to construct the CSG model, and its efficiency and accuracy will directly affect the effect of the Boolean operation, and then affect the reliability of the constructed entity. These include intersecting between straight line segment...

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Abstract

The invention discloses a CSG-BRep (Constructive Solid Geometry-Boundary Representation) model data structure, which can comprehensively record a topological relationship in a model in detail. The special data structure is comprehensively analyzed from aspects including a subset shape, a topology position, a topology orientation and the like, two algorithms are put forward to solve an access problem of a topological structure, and the invention discloses an access method of a topological element of the three-dimensional CSG-BRep model. In addition, the Boolean operation is utilized for appropriately processing a topology problem of spatial model intersection. Finally, a laser point cloud is taken as a model data source, the model data source is combined with the data structure put forward by the invention to construct a three-dimensional fine CSG-BRep model, and an improved RANSAC (RANdom SAmple Consensus) algorithm is utilized, or parameters are manually fit. Compared with a common triangular network model, the model is characterized in that each construction member can be disassembled, occupies small memory space, has a perfect topological relationship and realizes the query and the analysis of the topological information of a three-dimensional spatial object.

Description

technical field [0001] The invention relates to a method for accessing topological elements of a three-dimensional CSG-BRep model. Background technique [0002] The emergence of lidar makes the way of data acquisition fast and convenient. The current general modeling method is to simplify and construct a network based on the point cloud measured by the lidar. Although it can build a fine three-dimensional model. However, its disadvantages are that the constructed triangulation model has a large amount of data, is difficult to split, and has no topological relationship. Not only is it inconvenient to manage, but it also does not have a detailed description of the topological relationship of the model. Therefore, a new method to solve these problems is urgently needed. At present, many scholars have conducted research on the expression and construction of model topological relations. [0003] However, the three-dimensional space topology is still in its infancy. Although ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F19/00
Inventor 黄明王晏民张勇
Owner BEIJING UNIV OF CIVIL ENG & ARCHITECTURE
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