Block automatic generation method and system
By setting the initial block outside the target geometric solid model, automatically identifying and modifying the block to meet quality requirements, the problem of difficult hexahedral meshing is solved, and efficient block automatic generation and meshing is achieved.
Patent Information
- Application Number
- CN202510512783.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-08-05
AI Technical Summary
In the prior art, hexahedral meshing is difficult, traditional methods operate cumbersome and rely on user experience. The method of automatically generating PolyCube has low success rate on complex geometric models and poor mesh quality.
By setting the initial block outside the target geometric solid model, geometric features are automatically identified, blocks are mapped and quality is evaluated. If the requirements are not met, the block is modified until the preset conditions are met, and hexahedral meshing is achieved.
It significantly improves the fit between the Block and the target geometric solid model, shortens the generation time, improves the efficiency of grid division, and improves the success rate of Block generation.
Smart Images
Figure CN120431291A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of finite element analysis, and in particular to a method and system for automatically generating blocks. Background Art
[0002] Meshing is a key step in finite element analysis. Especially for complex geometric solid models, generating high-quality hexahedral meshes is challenging.
[0003] Implementing hexahedral meshing through blocks and mapping them to geometric models is a good solution. However, traditional commercial software (such as ANSYS ICEM) relies entirely on manual operations to generate blocks, requiring users to construct blocks in a "top-down" or "bottom-up" manner. This method is cumbersome, inefficient, and reliant on user experience. In the field of scientific research, scientists automatically generate Polycubes and then Blocks by deforming the meshes of tetrahedrons of complex geometric solid models. However, this automatic generation method is used for complex geometric models, and the computational complexity of mesh deformation is very high. The probability of successfully generating PolyCubes is low, and its applicability and mesh quality for complex geometries still need to be improved.
[0004] Based on this, the inventors of this application designed a Block automatic generation method and system to overcome the above technical problems. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to overcome the defect of the difficulty in hexahedral mesh division in the prior art and to provide a method and system for automatic block generation.
[0006] The present invention solves the above technical problems through the following technical solutions:
[0007] A first aspect of the present invention provides a method for automatically generating a block, comprising:
[0008] Step 1: setting an initial block outside a target geometric entity model and performing geometric feature recognition on the target geometric entity model;
[0009] Step 2: Map the block onto the target geometric entity model and determine the quality of the block and the hexahedral mesh. If the block quality and mesh quality meet the preset requirements, stop generating the block. If the block quality and mesh quality do not meet the preset requirements, proceed to the next step.
[0010] Step 3: Identify and modify areas with low block and mesh quality, and remap the modified block to the target geometric entity model. Repeat steps 2 to 3 until the generated block meets the block quality and mesh quality requirements.
[0011] According to one embodiment of the present invention, in step 1, the initial Block is a hexahedral structure and surrounds the target geometric entity model.
[0012] According to one embodiment of the present invention, in step 1, the features of the target geometric entity model are automatically identified; wherein the features include feature points, feature lines and special lines;
[0013] The characteristic line is the intersection line of two surfaces, and the surface normals on both sides of the characteristic line have sudden changes;
[0014] The characteristic point is the intersection of the characteristic lines, and there is a sudden change in the direction of the characteristic lines on both sides of the intersection;
[0015] The special line is the ridge line of the hyperbolic parabola and the inflection point boundary line of the surface curvature.
[0016] According to one embodiment of the present invention, in step 2, the points and lines on the surface of the Block are first mapped to the feature points, feature lines and special lines of the target geometric entity model, and then a projection algorithm is used to fit the surface elements of the Block to the surface of the geometric entity model. The elements inside the Block are adjusted according to the position of the surface elements so that the angles between the lines at each point are close.
[0017] According to one embodiment of the present invention, in step 2, the quality of the Block is judged by measuring the line-to-line angle of the Block, the fit between the surface of the Block and the surface of the target geometric solid model, the capture rate between the surface elements of the Block and the geometric feature elements of the target geometric solid model, and the filling rate of the Block in the geometric solid model;
[0018] The quality of the generated hexahedral mesh is evaluated by measuring the mesh's orthogonality, twist angle, and slenderness ratio.
[0019] According to one embodiment of the present invention, the modification includes the following four modification methods:
[0020] 1. Move the point or line of the Block;
[0021] Second, use O-shape, C-shape, and L-shape to divide the Block to increase its fit with the geometric solid model;
[0022] 3. Split along the edge of the Block;
[0023] 4. Stretch along the edge or face of the Block.
[0024] According to one embodiment of the present invention, when making a modification, the four modification methods are used cyclically; or at least one of the four modification methods is selected for modification;
[0025] After the block modification is completed, the quality of the block and the mesh are judged until the block and mesh quality that meet the quality requirements are generated.
[0026] According to one embodiment of the present invention, after the modified Block is mapped, meshing is set in the Block, and hexahedral meshing of the target geometric entity model is achieved according to the mapping.
[0027] A computer program product according to a second aspect of the present application includes a computer program, which, when executed by a processor, implements the steps performed by a computer in the method according to the first aspect.
[0028] According to a third aspect of the present application, a computer-readable storage medium has a computer program, which, when executed by a processor, implements the steps performed by the computer in the method described in the first aspect.
[0029] A control system according to a fourth aspect of the present application includes: a memory capable of storing instructions executable by a processor; and a processor capable of executing the instructions to implement the steps performed by a computer in the method described in the first aspect.
[0030] The positive progress effect of the present invention is:
[0031] The automatic block generation method of the present invention automatically divides blocks according to the target geometric entity model, and gradually generates the final block through block quality assessment and automatic block modification, thereby improving the block fit, greatly reducing the time for block and mesh division, and significantly improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:
[0033] Figure 1 This is a flowchart of the Block automatic generation method of the present invention;
[0034] Figure 2 This is a diagram of the initial Block settings;
[0035] Figure 3This is a schematic diagram of the initial block being attached to the target geometric solid model;
[0036] Figure 4 This is a schematic diagram of the Block being fitted with the target geometric solid model after cutting;
[0037] Figure 5 This is a schematic diagram of the Block surface being stretched and fitted with the target geometric solid model;
[0038] Figure 6 This is a schematic diagram of the blocks generated step by step after the iteration is completed and fitted to the target geometric entity model;
[0039] Figure 7 This is a schematic diagram of the Block that finally meets the requirements;
[0040] Figure 8 Schematic diagram of the hexahedral mesh generated by the final Block mapping;
[0041] Figure 9 This is a schematic diagram of the mesh in the area where the surface curvature changes greatly;
[0042] Figure 10 This is a structural diagram of the control system. DETAILED DESCRIPTION
[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.
[0044] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Reference will now be made in detail to preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to represent the same or similar parts. In addition, although the terms used in the present invention are selected from commonly known and commonly used terms, some of the terms mentioned in this specification may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description herein. Furthermore, it is required that the present invention be understood not only by the actual terms used, but also by the meaning implied by each term.
[0045] The following are some of the nouns that appear in the present invention:
[0046] Blocking: When using HyperMesh meshing, complex geometric solid models are divided into independent mappable sub-regions by cutting to achieve hexahedral meshing. Sub-regions refer to geometric regions that can be parameterized as logical hexahedrons, which are called blocks of complex geometry.
[0047] When using ANSYS ICEM software to divide the grid, multiple blocks are used and mapped to the complex geometric solid model to achieve hexahedral grid division of the entire geometric model. Each block is composed of hexahedrons, which is called a block.
[0048] PolyCube generation algorithm: Decomposes a complex geometric model into several subdomains that are topologically equivalent to cubes. A structured mesh is generated within each subdomain, and the meshes between subdomains are aligned to ensure overall mesh continuity. The subdomains corresponding to the complex geometric model are called PolyCubes. The complex geometric model is divided into tetrahedrons; these tetrahedrons are deformed using the direction field of the geometric surface to generate several subdomains, resulting in a PolyCube with aligned meshes between the subdomains. This algorithm is called the PolyCube generation algorithm.
[0049] Reference Figure 1 The present invention proposes a method for automatically generating a block, comprising:
[0050] S1. Set an initial block outside the target geometric entity model and perform geometric feature recognition on the target geometric entity model.
[0051] Reference Figure 2 The present invention uses an oriented bounding box of the target geometric solid model or a similar method to generate an initial block. The initial block is a simple hexahedron that completely encloses the target geometric solid model. An oriented bounding box considers the orientation of the target geometric solid model in space and generates a bounding box that better fits its shape. For example, in the modeling scenario of complex parts, using an oriented bounding box can more tightly enclose the part, reducing redundant space in subsequent processing and improving computational efficiency.
[0052] When geometric feature recognition is performed on a target geometric entity model, the features of the target geometric entity model are automatically identified. The features specifically include feature points, feature lines and special lines.
[0053] A feature line is the intersection of two surfaces. A key criterion for identifying a feature line is a sudden change in the surface normals on either side. A feature point is the intersection of feature lines, where there is a sudden change in the direction of the feature lines on either side of the intersection. Special lines primarily include the ridge of a hyperbolic paraboloid and the inflection point boundary of a surface's curvature.
[0054] It can be seen that in the context of geometric feature recognition, "mutation" refers to a sharp and significant change in geometric properties at a specific location. This change is an important basis for determining feature lines and feature points:
[0055] Regarding feature lines: A feature line is the intersection of two faces. The basis for determining a feature line is the presence of a sudden change in the surface normal on both sides. The surface normal is a vector perpendicular to the tangent plane at a certain point on the surface. On a smooth surface, the direction of the normal vector changes continuously. When a feature line exists, taking a cube as an example, its edge is the feature line. The direction of the normal vector can be determined by vector calculation. For the faces on both sides of the edge of the cube, the normal vectors of the points on the surface are calculated. It will be found that the directions of these normal vectors are obviously different. This significant change in the direction of the normal vector is a sudden change. In actual engineering, feature lines can accurately define the boundaries of different surfaces. Determining feature lines is beneficial to subsequent surface treatment.
[0056] Feature points are intersections of feature lines. At a feature point, when transitioning from one feature line to another, there is a sudden change in direction, known as a "mutation." For example, in a polyhedron formed by the intersection of multiple planes, the vertices are feature points. This sudden change can be visualized by calculating the direction vectors of the intersecting edges and observing the change in angle between these vectors at the vertex.
[0057] Special lines include the ridge line of a hyperbolic paraboloid and the inflection point boundary of a surface's curvature. The ridge line of a hyperbolic paraboloid is crucial for ensuring structural stability and mechanical properties. The inflection point boundary of a surface's curvature can help designers identify key locations where a product's surface curvature changes.
[0058] S2. Map the block onto the target geometric entity model and determine the quality of the block and the hexahedral mesh. If the block quality and mesh quality meet the preset requirements, stop generating the block. If the block quality and mesh quality do not meet the preset requirements, proceed to the next step.
[0059] Reference Figure 3 During block mapping, points and lines on the block surface are preferentially mapped to the feature points, feature lines, and special lines of the target geometric solid model. A projection algorithm is used to align the surface elements of the block with the surface of the target geometric solid model. Elements within the block are adjusted based on the position of the block's surface elements, so that the angles between lines at each point are close.
[0060] Specifically, the surface elements of the Block can be made to fit the surface of the target geometric solid model through algorithms such as the nearest point and normal projection.
[0061] That is, after adjusting the internal elements of the Block according to the position of the surface elements, the angles between the relevant lines at each point of the surface elements are close to each other, which facilitates the subsequent meshing process.
[0062] It should be noted that after the mapping is completed, it is necessary to judge the quality of the block and evaluate the quality of the grid.
[0063] When judging the quality of a Block, we use the line-to-line angle of the Block, the fit between the Block's surface and the surface of the target geometric solid model, the capture rate of the Block's surface elements and the geometric feature elements of the target geometric solid model, and the filling rate of the Block in the geometric solid model to make the judgment.
[0064] If the quality of the block meets the preset requirements, meshing can be performed. After the hexahedral meshing is completed, the quality of the generated hexahedral mesh can be evaluated. The evaluation indicators mainly include the orthogonality, torsion angle, aspect ratio, etc. of the mesh.
[0065] If the quality of the block and the mesh quality meet the preset requirements, the block generation is stopped; if not, the next step is to modify the block.
[0066] S3. Identify and modify areas with low block and mesh quality, and remap the modified block to the target geometric entity model. Repeat steps 2 to 3 until the generated block meets the block quality and mesh quality requirements.
[0067] That is, the present invention determines the blocks and areas with low mesh quality based on the evaluation results of fit and mesh quality, and modifies them. The modification method can be done manually or by connecting to an external computer program, which is not limited here.
[0068] Modification methods include but are not limited to the following four:
[0069] 1. Move the points or lines of the Block to adjust the shape of the Block and optimize its adaptability to the target geometric entity model.
[0070] Second, use O-shaped, C-shaped, and L-shaped methods to divide the Block, thereby improving the fit between the Block and the geometric solid model.
[0071] 3. Perform a split operation along the edge of the Block to change the structure of the Block so that it better fits the shape of the target geometric entity model.
[0072] 4. Stretch along the edge or face of the Block to form a new Block shape that meets the fit and quality requirements of the target geometric solid model.
[0073] Specific reference Figures 4 to 6 , Figure 4 Figure 4 The diagram shows how the block fits into the target geometric solid model after cutting. Figure 5 A schematic diagram of the block surface being stretched and fitted with the target geometric solid model is presented; Figure 6 It depicts the schematic process of fitting the gradually generated blocks to the target geometric entity model after the iterations of the above four modification methods are completed.
[0074] As can be seen, each time a modification is completed, the modified block must be remapped to the target geometric solid model and a series of operations such as geometric feature recognition, mapping, and quality assessment must be performed again. This process is repeated until the generated block meets both the preset block quality requirements and the mesh quality requirements.
[0075] in, Figure 7 The final Block.
[0076] in, Figure 7 The figure shows the final block. Once the block mapping is complete, meshing is performed based on the block. Based on the mapping, the hexahedral meshing of the target geometric solid model is achieved, thus completing the meshing phase of the entire modeling process.
[0077] Please refer to Figure 8 and Figure 9 , Figure 8 The hexahedral mesh generated by the final Block mapping is shown. Figure 9 The mesh is shown in areas where the surface curvature varies greatly.
[0078] This method automatically maps a block onto the target geometric solid model by accurately capturing its characteristic points and lines. Based on this, it automatically analyzes the fit between the block and the target geometric solid model, precisely identifying areas of poor fit. Subsequently, based on criteria such as fit and mesh quality, it intelligently selects the appropriate method for modifying the block, including splitting, stretching, and merging.
[0079] The above method significantly shortens the time required for manual block generation and effectively improves the efficiency of finite element analysis.
[0080] Traditional block construction methods, such as ANSYS ICEM, rely heavily on manual experience. When faced with complex geometries, block construction often takes days. This approach is not only inefficient but also requires a high level of operator expertise, increasing both labor and time costs, and posing significant challenges in managing project progress.
[0081] The present invention imitates the manual construction process, automatically divides blocks according to geometric features, and gradually generates the final block through block quality evaluation and automatic block modification. This process effectively improves the fit between the block and the target geometric entity model, while greatly shortening the time spent on block construction and mesh division, thereby significantly improving overall work efficiency.
[0082] Furthermore, existing automatic hexahedral mesh generation methods have limited adaptability to complex geometries such as non-convex structures and porous models with large curvature variations. However, the present invention ensures block fit by capturing elements such as feature points, feature lines, and special lines. Furthermore, through block heuristic modification and comprehensive modification evaluation, the appropriate modification method is determined, ensuring the rationality of the gradual generation of blocks. Compared to existing automatic PolyCube generation methods (with a success rate of approximately 55%), the present invention achieves a higher success rate (nearly 90%) for block generation in complex geometric models.
[0083] Furthermore, the present invention uses a generative, step-by-step approach to build blocks, allowing them to iteratively evolve and conform to the geometric model, thereby improving block quality. Because each step of block modification is relatively independent, manual intervention and the insertion of new control programs to modify the blocks are facilitated.
[0084] refer to Figure 10 As shown, the present application also provides a control system 1000, including a memory 1001 and a processor 1002, wherein the memory can store instructions that can be executed by the processor 1002; the processor 1002 can execute instructions to implement the steps performed by the computer in the Block automatic generation method introduced in the above embodiment.
[0085] It is understood that it is important to note that the aforementioned memory and processor are not limited to a specific memory or processor. Furthermore, in embodiments employing a distributed structure, the specific execution terminal of each step can be adjusted according to actual circumstances, and the specific implementation of each step on a specific terminal should not limit the scope of protection of this application.
[0086] According to another aspect of the present application, the present application also provides a computer-readable medium.
[0087] The computer-readable medium provided in this application has computer instructions thereon. When the computer instructions are executed by a processor, the program can be executed by the processor to implement the steps performed by the program in the method described in the above embodiment.
[0088] According to yet another aspect of the present application, the present application also provides a computer program product.
[0089] The computer-readable medium provided in the present application includes a computer program. When the computer program is executed by a processor, the program can implement the steps executed by the program in the method described in the above embodiment.
[0090] The various illustrative logic modules and circuits described in conjunction with the embodiments disclosed herein may be implemented or executed using a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
[0091] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read and write information from / to the storage medium. In an alternative, the storage medium may be integrated into the processor. The processor and storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and storage medium may reside in a user terminal as discrete components.
[0092] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software as a computer program product, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, including any media that facilitates the transfer of a computer program from one location to another. A storage medium may be any available medium that can be accessed by a computer. By way of example and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Any connection is also properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves are included in the definition of medium. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks typically reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
[0093] Although the present application is disclosed above with reference to preferred embodiments, this is not intended to limit the present application. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application shall fall within the scope of protection defined by the claims of the present application.
Claims
1. A method for automatic block generation, characterized in that: include: Step 1: setting an initial block outside a target geometric entity model and performing geometric feature recognition on the target geometric entity model; Step 2: Map the Block onto the target geometric entity model and determine the quality of the Block and the quality of the hexahedral mesh; If the quality of the block and the mesh quality meet the preset requirements, the block generation is stopped; if the quality of the block and the mesh quality do not meet the preset requirements, the next step is entered; Step 3: Identify and modify areas with low block and mesh quality, and remap the modified block to the target geometric entity model. Repeat steps 2 to 3 until the generated block meets the block quality and mesh quality requirements.
2. The automatic block generation method according to claim 1, characterized in that: In step 1, the initial Block is a hexahedral structure and surrounds the target geometric entity model.
3. The automatic block generation method according to claim 1, characterized in that: In the step 1, the features of the target geometric entity model are automatically identified; wherein the features include feature points, feature lines and special lines; The characteristic line is the intersection line of two surfaces, and the surface normals on both sides of the characteristic line have sudden changes; The characteristic point is the intersection of the characteristic lines, and there is a sudden change in the direction of the characteristic lines on both sides of the intersection; The special line is the ridge line of the hyperbolic parabola and the inflection point boundary line of the surface curvature.
4. The automatic block generation method according to claim 3, characterized in that: In step 2, the points and lines on the surface of the Block are first mapped to the feature points, feature lines and special lines of the target geometric solid model, and then a projection algorithm is used to fit the surface elements of the Block to the surface of the geometric solid model. The elements inside the Block are adjusted according to the positions of the surface elements so that the angles between the lines at each point are close.
5. The automatic block generation method according to claim 1, characterized in that: In step 2, the quality of the Block is judged by the line-to-line angle of the Block, the fit between the surface of the Block and the surface of the target geometric solid model, the capture rate of the surface elements of the Block and the geometric feature elements of the target geometric solid model, and the filling rate of the Block in the geometric solid model; The quality of the generated hexahedral mesh is evaluated by measuring the mesh's orthogonality, twist angle, and slenderness ratio.
6. The automatic block generation method according to claim 1, characterized in that: The modification includes the following four modification methods:
1. Move the point or line of the Block; Second, use O-shape, C-shape, and L-shape to divide the Block to increase its fit with the geometric solid model; 3. Split along the edge of the Block; 4. Stretch along the edge or face of the Block.
7. The automatic block generation method according to claim 6, characterized in that: When making a modification, cyclically use the four modification methods to make the modification; or, select at least one of the four modification methods to make the modification; After the block modification is completed, the quality of the block and the mesh are judged until the block and mesh quality that meet the quality requirements are generated.
8. The automatic block generation method according to claim 1, characterized in that: After step 3, the method further includes: After the corrected Block mapping is completed, the meshing is set in the Block, and the hexahedral meshing of the target geometric entity model is achieved according to the mapping.
9. A computer program product, characterized in that The method comprises a computer program, which, when executed by a processor, implements the steps performed by a computer in the method according to any one of claims 1 to 8.
10. A computer-readable storage medium, characterized in that The invention provides a computer program, which, when executed by a processor, implements the steps executed by a computer in the method according to any one of claims 1 to 8.
11. A control system, characterized in that: include: a memory capable of storing instructions executable by a processor; A processor capable of executing the instructions to implement the steps performed by a computer in the method according to any one of claims 1 to 8.