CN117893712B - Surface structure grid generation method and device - Google Patents
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Abstract
The invention belongs to the technical field of computer graphics processing. The invention discloses a method and a device for generating a surface structure grid, wherein the method comprises the following steps: performing surface triangularization on the imported three-dimensional model to be processed to generate an initial surface triangularization grid; initializing curved surface measurement parameters, and conformally mapping the initial curved surface triangulated mesh to a two-dimensional parameter domain; dividing the transformed grid into areas, calculating the compression ratio of unit area, and drawing a cloud picture corresponding to the transformed grid to extract the partition boundary line of the transformed grid; dispersing the partition boundary lines and automatically generating a structured grid corresponding to the transformed grid; and reversely mapping the generated structured grid onto a three-dimensional curved surface to obtain a surface structure grid corresponding to the three-dimensional model to be processed. The invention can automatically generate the surface structure grid, greatly shortens the surface grid generation time, improves the automation degree of grid generation and reduces the generation difficulty of the structure grid.
Description
Technical Field
The application belongs to the technical field of computer graphics processing, and particularly relates to a method and a device for generating a surface structure grid.
Background
In the prior art, a complex model is used in computational fluid dynamics (CFD, computational Fluid Dynamics) to generate a high-quality grid technology, and the flow field analysis can be greatly accelerated by generating a structured grid, and a result with better precision can be obtained, but the problems of low generation efficiency, high cost and the like exist.
In addition, in the existing quadrilateral mesh generation technology, an indirect method is mainly adopted, triangular meshes are generated first, then triangular mesh units are converted into quadrilateral meshes in a certain mode, and in fact, a partitioning technology is introduced for applying a complex model. However, the reliability of the existing partitioning algorithm is not high, and as the complexity of the model is continuously increased, the grid scale is also continuously increased, the generation time is excessively long, more memory is occupied, and the requirement of large-scale numerical simulation cannot be met. In addition, in mesh generation, there are problems such as low rationality of mesh density distribution, formation of ineffective mesh cells, and the like due to demands for calculation accuracy and efficiency.
Therefore, there is a need to provide a new surface structure grid generation method to solve the above-mentioned problems.
Disclosure of Invention
The method aims to solve the technical problems that in the existing method, the reliability of a partitioning algorithm for converting the triangular grid into the quadrilateral grid is low, the generation time is too long, the occupied memory is more along with the continuous increase of the grid scale, the requirement of large-scale numerical simulation cannot be met, the rationality of grid density distribution caused by the calculation precision and efficiency requirement is low, and even ineffective grid units are formed. The application provides a method and a device for generating a surface structure grid.
The technical effects to be achieved by the application are realized by the following scheme:
The first aspect of the present invention provides a method for generating a surface structure grid, including: performing curved surface triangularization on the imported three-dimensional model to be processed to generate an initial curved surface triangularization grid, wherein the three-dimensional model to be processed comprises three-dimensional models related to wing tips and ship propeller blades; initializing curved surface measurement parameters, and conformally mapping the generated initial curved surface triangulated mesh to a two-dimensional parameter domain, wherein the method comprises the following steps of repeatedly executing: calculating a curved surface Ricci flow of the initial curved surface triangulated mesh to determine whether to update the curved surface metric parameter; executing conformal mapping processing when the specified condition is met to obtain a transformed grid; dividing the transformed grid into areas, calculating the compression ratio of unit area, and drawing a cloud picture corresponding to the transformed grid to extract the partition boundary line of the transformed grid; discretizing the partition boundary lines and automatically generating a structured grid corresponding to the transformed grid; and reversely mapping the generated structured grid onto a three-dimensional curved surface to obtain a surface structure grid corresponding to the three-dimensional model to be processed.
According to an alternative embodiment, the gaussian curvature of each vertex of the initial surface triangulated mesh and the surface topology of the initial surface triangulated mesh satisfy the Gauss-Bonnet expression:
；
and the surface metric parameter for any vertex satisfies the following expression:
；
Wherein K i represents the target gaussian curvature of the ith vertex of the initial curved surface triangulated mesh M, i is a positive integer, and M represents the initial curved surface triangulated mesh; x represents the euler-diagram number; a circle fill measure representing the mesh edge e of any vertex.
According to an alternative embodiment, the initial surface is triangulated into a stream of surfaces Ricci for each vertex of the meshDefined as the absolute value of the difference between the calculated value of gaussian curvature of each vertex and the target gaussian curvature, and forming a specified condition for performing conformal mapping processing, expressed by the following expression:
；
Wherein, A stream of surfaces Ricci representing each vertex of the initial surface triangulated mesh, u i representing an ith conformal factor, i being a positive integer, t representing time, the curvature of each vertex varying over time; /(I)A calculated value representing the gaussian curvature of the ith vertex of the initial curved surface triangulated mesh M; k (v i, t) represents the target Gaussian curvature of the ith vertex of the initial curved surface triangulated mesh M, i is a positive integer, and M represents the initial curved surface triangulated mesh;
when the specified condition is not met, updating the curved surface measurement parameter, and repeatedly executing the step of calculating the curved surface Ricci flow of the initial curved surface triangulated mesh;
and when the specified condition is met, saving the numerical value of the curved surface measurement parameter, and executing conformal mapping processing.
According to an alternative embodiment, the initializing the curved surface metric parameter includes:
Initializing a circle filling measure and a discrete conformal factor, and determining an initial value of the circle filling measure according to the minimum size of the cells of the initial curved surface triangulating grid.
According to an alternative embodiment, the specified conditions further comprise calculating a discrete conformal factor；
Calculating the discrete surface Ricci flow is equivalent to solving a convex optimization problem, and the discrete conformal factor update rule is:
;
wherein u k represents the kth conformal factor; represents the k+1th conformal factor; f (u k) represents the entropy energy of the conformal factor u k; f (u) is the entropy energy of the conformal factor u, its gradient flow is the discrete Ricci flow; u i denotes the ith conformal factor, i and k are positive integers.
According to an alternative embodiment, the area compression ratio of each triangular patch, i.e., the compression ratio of each vertex, before and after the conformal mapping process is calculated using the following expression:
;
Wherein Diff (v i) represents the compression ratio of the ith vertex; area N(vi) represents the Area of the triangular patch where the i-th vertex v i is located in the parameterized two-dimensional mesh; area M(vi) represents the Area of the triangular patch where the i-th vertex v i is located in the initial curved surface triangulated mesh M; max (Area N(vi)) represents the largest Area of the triangular patch where all vertices v i are located in the parameterized two-dimensional mesh; drawing a cloud picture of the transformed grid according to the calculated area compression ratio; partition boundary lines are extracted from the drawn cloud image.
According to an alternative embodiment, the following expression is used to represent the size of each vertex:
;
Wherein size (v i) represents the size of the ith vertex v i; sumSize N(vi) represents the dimensions of all edges around the i-th vertex v i in the parameterized two-dimensional mesh, sum N(vi) represents the number of all edges around the i-th vertex v i in the two-dimensional mesh, and max (Size N(vi)) represents the maximum dimensions of all edges around all vertices v i in the parameterized two-dimensional mesh.
According to an alternative embodiment, the transformed mesh is divided into a plurality of sub-areas; reconstructing the plurality of sub-regions using a grid topology association constraint on the plurality of sub-regions; and filling the plurality of subareas by adopting a grid template filling method.
A second aspect of the present invention provides a surface structure mesh generation apparatus for implementing the surface structure mesh generation method of the first aspect of the present invention, the surface structure mesh generation apparatus comprising: generating a processing model, namely performing curved surface triangulation on the imported three-dimensional model to be processed to generate an initial curved surface triangulated grid, wherein the three-dimensional model to be processed comprises three-dimensional models related to wing tips and ship propeller blades; the conformal mapping processing module initializes the curved surface measurement parameters and conformally maps the generated initial curved surface triangulated mesh to the two-dimensional parameter domain, and comprises the following steps of repeatedly executing: calculating a curved surface Ricci flow of the initial curved surface triangulated mesh to determine whether to update the curved surface metric parameter; executing conformal mapping processing when the specified condition is met to obtain a transformed grid; the calculation processing module is used for carrying out region division on the transformed grid, calculating the compression ratio of unit area, and drawing a cloud picture corresponding to the transformed grid so as to extract the partition boundary line of the transformed grid; the area compression ratio of each triangular patch, that is, the compression ratio of each vertex before and after the conformal mapping process is calculated using the following expression:
;
Wherein Diff (v i) represents the compression ratio of the ith vertex; area N(vi) represents the Area of the triangular patch where the i-th vertex v i is located in the parameterized two-dimensional mesh; area M(vi) represents the Area of the triangular patch where the i-th vertex v i is located in the initial curved surface triangulated mesh M; max (Area N(vi)) represents parameterization; discretizing the partition boundary lines and automatically generating a structured grid corresponding to the transformed grid; and the second generation processing module is used for reversely mapping the generated structured grid to the three-dimensional curved surface to obtain the surface structure grid corresponding to the three-dimensional model to be processed.
A third aspect of the invention provides an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the surface texture grid generating method according to the first aspect of the invention when the program is executed.
A fourth aspect of the invention provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the surface structure grid generation method according to the first aspect of the invention.
Technical effects
Compared with the prior art, the method and the device have the advantages that the initial curved surface triangulated grid is generated by triangulating the imported three-dimensional model to be processed, the transformed grid is obtained by conformally mapping the initial curved surface triangulated grid to the two-dimensional parameter domain according to whether the specified condition is met, the transformed grid is subjected to regional division, the unit area compression ratio is calculated, the cloud image corresponding to the transformed grid is drawn to extract the partition boundary line of the transformed grid, the partition boundary line is discrete, the structured grid corresponding to the transformed grid is automatically generated, and the surface structure grid can be automatically generated according to the set grid generation parameters in the surface structure grid generation process, so that the surface grid generation time is greatly shortened, the automation degree of grid generation is improved, the generation difficulty of the structure grid is reduced, and the method and the device have great engineering practicability.
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In order to more clearly illustrate the embodiments of the application or the prior art solutions, the drawings which are used in the description of the embodiments or the prior art will be briefly described below, it being obvious that the drawings in the description below are only some of the embodiments described in the present application, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.
FIG. 1 is a flow chart of a method of generating a surface texture grid according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an example of a curved triangulated mesh generated by applying a surface structured mesh generation method of an embodiment of the present invention;
FIG. 3 is a schematic diagram of an example of a two-dimensional grid generated by a surface structured grid generation method applying an embodiment of the present invention;
FIG. 4 is a schematic diagram of an example of a cloud image generated in a surface structure grid generation method to which an embodiment of the present invention is applied;
FIG. 5 is a schematic diagram of an example of cloud image contours extracted by a surface structure grid generation method applying an embodiment of the present invention;
FIG. 6 is a schematic diagram of an example of a surface structure network generated by a surface structure grid generation method applying an embodiment of the present invention;
FIG. 7 is a schematic diagram of an example of a surface texture grid generating device according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of an electronic device according to an embodiment of the present application.
Detailed Description
The application will be described in further detail below with reference to the drawings by means of specific embodiments. Wherein like elements in different embodiments are numbered alike in association. In the following embodiments, numerous specific details are set forth in order to provide a better understanding of the present application. The numbering of the components itself, e.g. "first", "second", etc., is used herein merely to distinguish between the described objects and does not have any sequential or technical meaning. The term "coupled" as used herein includes both direct and indirect coupling (coupling), unless otherwise indicated.
In view of the above problems, the present invention provides a method for generating a surface structure grid, which maps any complex three-dimensional curved surface (particularly, three-dimensional curved surfaces related to wing tips, ship propeller blades, etc.) into a two-dimensional parameter domain plane through a conformal mapping technology, and provides a new topology region division concept. The conformal mapping conformal geometric transformation compresses geometric metrics at the same time, the degree of the compressed transformation is closely related to the measurement characteristics (local curvature, association relation of curved surface structures and the like) of the original geometric shapes, a cloud image of the change rate of the curved surface area is constructed by utilizing the association, an equivalent region is extracted, geometric region decomposition matched with the geometric characteristics is obtained, then the region decomposition is utilized to construct a corresponding grid topology, the whole surface geometry is divided into a plurality of sub-regions which are mutually related and have simple geometric forms, sub-region grids are constructed through grid templates, and the full-structure grid generation of the whole region is realized by utilizing the association constraint (such as that the grid size is smaller than a specific size, the geometric characteristics are the combination of one or more three-dimensional bodies) of each sub-region.
The surface structure grid generating method of the present invention is particularly suitable for, for example, a three-dimensional curved surface of a wing tip portion of an aircraft wing, a curved surface of a propeller blade, and the like.
Various non-limiting embodiments of the present application are described in detail below in conjunction with fig. 1-6.
As shown in fig. 1, the method of the present invention includes the following steps.
First, in step S101, an initial curved triangulated mesh is generated by curved triangulating an imported three-dimensional model to be processed, including three-dimensional models related to wing tips and ship propeller blades.
In one embodiment, a CAD digital-analog file of a part of the curved surface of, for example, a wing tip of an aircraft is imported.
The three-dimensional model to be processed includes a three-dimensional model related to a wing tip and a ship propeller blade, in this example, but not limited to, a partially curved surface of the wing tip, and in other embodiments, may be other three-dimensional curved surfaces of other flying devices or apparatuses, for example. The foregoing is illustrative only and is not to be construed as limiting the invention.
Specifically, curved surface triangulation is performed on the imported three-dimensional model to be processed, wherein the curved surface triangulation refers to triangulation of the imported complex three-dimensional geometric model.
And carrying out surface triangularization according to the set parameters to generate an initial surface triangularization grid. Parameters of triangulation are set according to different application scenes (such as application to aircraft wings and the like), and the parameters specifically comprise parameters of target size, minimum size, self-adaptive angle, growth rate and the like.
In one embodiment, for example, an initial surface triangulated mesh, particularly a double ellipsoidal surface triangulated mesh, is generated as shown in FIG. 2.
Next, in step S102, initializing the surface metric parameters, conformally mapping the generated initial surface triangulated mesh to the two-dimensional parameter domain, including repeatedly performing the steps of: calculating a curved surface Ricci flow of the initial curved surface triangulated mesh to determine whether to update the curved surface metric parameter; and executing conformal mapping processing when the specified condition is met, and obtaining the transformed grid.
Specifically, a surface metric parameter (e.g., a circle fill metric) is initialized, and an initial value of the surface metric parameter is determined based on a minimum cell size of the initial surface triangulated mesh.
In an alternative embodiment, a circle fill measure, a discrete conformal factor, is initialized and an initial value of the circle fill measure is determined based on a minimum cell size of the initial curved triangulated mesh.
Specifically, according to the application scene and the shape of the three-dimensional model to be processed, a target Gaussian curvature K of the initial curved surface triangularization grid is configured.
The gaussian curvature of each vertex of the initial surface triangulated mesh and the surface topology of the initial surface triangulated mesh need to satisfy the following expressions (1) and (2) simultaneously.
Specifically, the Gauss-Bonnet expression is satisfied, that is, expression (1) is satisfied.
（1）
Wherein K i represents the target gaussian curvature of the ith vertex of the initial curved surface triangulated mesh M, i being a positive integer; x represents the euler-diagram number; m represents an initial surface triangulated mesh.
The surface metric parameters for any vertex satisfy the following expression:
（2）
Wherein K i represents the target gaussian curvature of the ith vertex of the initial curved surface triangulated mesh M, i is a positive integer, and M represents the initial curved surface triangulated mesh; x represents the euler-diagram number; a circle fill measure representing the mesh edge e of any vertex.
It should be noted that, according to the target gaussian curvature K, in the discrete case, the gaussian curvature of each vertex may be arbitrary, but the sum of the gaussian curvatures is closely related to the topology of the curved surface, satisfying the Gauss-Bonnet formula, that is, the sum of the discrete gaussian curvatures is equal to the product of 2 and the euler's representation number.
Flow of surfaces Ricci per vertex of the initial surface triangulated meshDefined as the absolute value of the difference between the calculated value of gaussian curvature of each vertex and the target gaussian curvature, and forming a specified condition for performing conformal mapping processing, expressed by the following expression:
（3）
Wherein, A flow of surfaces Ricci representing each vertex of the initial surface triangulated mesh (i.e., a calculated value of gaussian curvature for each vertex), v i represents the ith vertex, u i represents the ith conformal factor, i is a positive integer, and t represents time; A calculated value representing the gaussian curvature of the ith vertex v i of the initial curved-surface triangulated mesh M; k (v i, t) represents the target Gaussian curvature of the ith vertex of the initial surface triangulated mesh M, i is a positive integer, M represents the initial surface triangulated mesh;) Representing specified error thresholds that match different three-dimensional models to be processed.
Further, the following steps are repeatedly performed until the specified condition is satisfied.
And specifically calculating a curved surface Ricci flow of the initial curved surface triangulated mesh to judge whether to update the curved surface measurement parameters.
And executing conformal mapping processing when the specified condition is met, and obtaining the transformed grid.
The specified conditions further include calculating a discrete conformal factor；
Calculating the discrete surface Ricci flow is equivalent to solving a convex optimization problem, and the discrete conformal factor update rule is:
;
wherein u k represents the kth conformal factor; represents the k+1th conformal factor; f (u k) represents the entropy energy of the conformal factor u k; f (u) is the entropy energy of the conformal factor u, its gradient flow is the discrete Ricci flow; u i denotes the ith conformal factor, i and k are positive integers.
Specifically, when the specified condition is satisfied, the numerical value of the curved surface measurement parameter is saved, and conformal mapping processing is performed.
The transformed mesh (e.g., the triangulated mesh shown in fig. 3) is obtained by performing a conformal mapping process, specifically, conformally mapping the generated initial curved triangulated mesh to a two-dimensional parameter domain.
And when the specified condition is not met, updating the curved surface measurement parameter, and repeatedly executing the step of calculating the curved surface Ricci flow of the initial curved surface triangulated mesh. Wherein, repeatedly calculating the curved surface Ricci flow of the initial curved surface triangulated mesh until the curvature obtained based on the calculated curved surface Ricci flow satisfies the precision error value, stopping repeatedly executing the steps.
Specifically, when a two-dimensional parameterized grid (such as the triangulated grid shown in fig. 3) is obtained, the curved surface measurement parameters are updated, and all points after conformal mapping are paved to the two-dimensional parameter domain, so as to obtain the grid after conformal mapping (i.e. the grid after transformation). The transformed grid is a two-dimensional grid that is compressed from a three-dimensional grid.
It should be noted that the foregoing is merely illustrative of the present invention and is not to be construed as limiting thereof.
Next, in step S103, the transformed mesh is area-divided, a unit area compression ratio is calculated, and a cloud image corresponding to the transformed mesh is drawn to extract a partition boundary line of the transformed mesh.
Specifically, after the three-dimensional grid is compressed into a two-dimensional grid, a change in area density may result. Thus, the transformed mesh in the two-dimensional parametric domain is divided into a plurality of partitions, i.e. into a plurality of sub-regions, with a density variation gradient.
Further, the area compression ratio of each triangular patch before and after the conformal mapping process is calculated, that is, the compression ratio of the corresponding unit before and after the transformation is calculated.
Specifically, the area compression ratio of each triangular patch in the parameterized two-dimensional mesh (e.g., mesh N) to the initial curved triangulated mesh M is calculated. In the compression process, the area density is changed due to the conformal mapping of each triangular patch, and the area ratio before and after transformation of each triangular patch, namely the compression rate of each vertex, is calculated.
The compression rate of each vertex is expressed using the following expression:
;
Wherein Diff (v i) represents the compression ratio of the ith vertex; area N(vi) represents the Area of the triangular patch where the ith vertex v i is located in the parameterized two-dimensional mesh (e.g., mesh N); area M(vi) represents the Area of the triangular patch where the i-th vertex v i is located in the initial curved surface triangulated mesh M; max (Area N(vi)) represents the largest Area of the triangular patch in which all vertices v i are located in a parameterized two-dimensional mesh (e.g., mesh N).
Optionally, in addition to considering the area variation, attention is paid to parameter constraints such as dimensional field variation caused by non-uniformity of the curved surface. The size of each vertex is expressed using the following expression:
;
Wherein size (v i) represents the size of the ith vertex v i; sumSize N(vi) represents the dimensions of all edges around the i-th vertex v i in a parameterized two-dimensional mesh (e.g., mesh N), sum N(vi represents the number of all edges around the i-th vertex v i in a two-dimensional mesh (e.g., mesh N), and max (Size N(vi)) represents the maximum dimensions of all edges around all vertices v i in a parameterized two-dimensional mesh (e.g., mesh N).
And calculating the dihedral angle between each triangular patch and the adjacent patches in the initial curved surface triangularization grid M by adopting the dihedral angle discrimination technology of the adjacent units. Wherein, when the calculated dihedral angle is smaller than a predetermined threshold value, it is determined as a feature of the initial curved surface triangulated mesh M. Such as a concave portion of a wing, etc.
Further, information such as a compression ratio Diff (v i) of each triangular patch in the parameterized two-dimensional mesh (e.g., mesh N) and the initial curved surface triangulated mesh M, a size field of mesh N, and a feature edge is displayed on a cloud image.
And drawing a cloud image (such as the cloud image shown in fig. 4) of the transformed grid according to the calculated area compression ratio (the compression ratio of each vertex) and the size of each vertex, and displaying the cloud image.
Next, partition boundary lines, that is, cloud image contours (for example, cloud image contours shown in fig. 5) are extracted from the drawn cloud images as partition boundary lines of the respective areas. Specifically, three different field information including a compression ratio Diff (v i), a size field of a grid N and a characteristic edge are respectively extracted from cloud image contours, the extracted cloud image contours are subjected to smoothing and filtering treatment, the contours of different fields are mutually staggered to divide a parameter area into a plurality of sub-subareas, and topological subareas of a parameter domain structure grid (namely a parameterized two-dimensional grid, specifically a two-dimensional grid formed by mapping a three-dimensional grid to a two-dimensional plane area) are formed.
And carrying out sectional quantification on the partition boundary lines of the formed topological partitions, and carrying out structural grid filling on each topological partition by adopting a structural grid filling method such as a grid template method.
It should be noted that the foregoing is merely illustrative of the present invention and is not to be construed as limiting thereof.
Next, in step S104, the partition boundary line is discretized, and a structured mesh corresponding to the transformed mesh is automatically generated.
Reconstructing the plurality of sub-regions using association constraints of the grid topology on the plurality of sub-regions.
The relevance constraint includes that the boundary curvature of the sub-region is smaller than a specific value, the area of the sub-region is larger than a specified value, and the like.
Specifically, the structured grid is generated using, for example, a grid template method based on discretizing the partition boundaries.
Optionally, the boundary line of the partition is subjected to fairing processing, and the boundary line of the partition is subjected to fairing processing by adopting a Laplace fairing algorithm.
And carrying out secondary discrete processing on the boundary line subjected to smooth processing by adopting the partition boundary subjected to smooth processing according to the size field information, and regenerating a structured grid corresponding to the grid after conversion.
Next, in step S105, the generated structured grid is inversely mapped onto a three-dimensional curved surface, so as to obtain a surface structure grid corresponding to the three-dimensional model to be processed.
Specifically, for example, the generated structured grid is inversely mapped (for example, the gravity center inverse mapping) onto the three-dimensional curved surface by using gravity center weighted inverse transformation, so as to obtain a surface structure grid (for example, the surface structure grid shown in fig. 6) corresponding to the three-dimensional model to be processed, namely, the surface structure grid is automatically generated.
It is noted that the figures are only schematic illustrations of processes involved in a method according to an exemplary embodiment of the invention and are not intended to be limiting. It will be readily understood that the processes shown in the figures do not indicate or limit the temporal order of these processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, for example, among a plurality of modules.
Compared with the prior art, the method and the device have the advantages that the initial curved surface triangulated grid is generated by triangulating the imported three-dimensional model to be processed, the transformed grid is obtained by conformally mapping the initial curved surface triangulated grid to the two-dimensional parameter domain according to whether the specified condition is met, the transformed grid is subjected to regional division, the unit area compression ratio is calculated, the cloud image corresponding to the transformed grid is drawn to extract the partition boundary line of the transformed grid, the partition boundary line is discrete, the structured grid corresponding to the transformed grid is automatically generated, and the surface structure grid can be automatically generated according to the set grid generation parameters in the surface structure grid generation process, so that the surface grid generation time is greatly shortened, the automation degree of grid generation is improved, the generation difficulty of the structure grid is reduced, and the method and the device have great engineering practicability.
The following are examples of the apparatus of the present invention that may be used to perform the method embodiments of the present invention. For details not disclosed in the embodiments of the apparatus of the present invention, please refer to the embodiments of the method of the present invention.
Fig. 7 is a schematic structural view of an example of a surface structure mesh generating apparatus according to the present invention.
Referring to fig. 7, a second aspect of the present disclosure provides a surface structure grid generating device 700.
The surface structure grid generating device 700 is configured to implement the surface structure grid generating method according to the present invention, where the surface structure grid generating device 700 includes a first generating processing model 710, a conformal mapping processing module 720, a calculating processing module 730, a second generating processing module 740, and an inverse mapping processing module 750.
Specifically, the first generation processing model 710 performs surface triangulation on the imported three-dimensional model to be processed, and generates an initial surface triangulated mesh, where the three-dimensional model to be processed includes three-dimensional models related to wing tips and ship propeller blades. The conformal mapping processing module 720 initializes the surface metric parameters and conformally maps the generated initial surface triangulated mesh to the two-dimensional parameter domain, including repeatedly performing the steps of: calculating a curved surface Ricci flow of the initial curved surface triangulated mesh to determine whether to update the curved surface metric parameter; and executing conformal mapping processing when the specified condition is met, and obtaining the transformed grid. The calculation processing module 730 performs region division on the transformed grid, calculates a compression ratio of a unit area, and draws a cloud image corresponding to the transformed grid to extract a partition boundary line of the transformed grid; the area compression ratio of each triangular patch, that is, the compression ratio of each vertex before and after the conformal mapping process is calculated using the following expression:
;
wherein Diff (v i) represents the compression ratio of the ith vertex; area N(vi) represents the Area of the triangular patch where the ith vertex v i is located in the parameterized two-dimensional mesh (e.g., mesh N); area M(vi) represents the Area of the triangular patch where the i-th vertex v i is located in the initial curved surface triangulated mesh M; max (Area N(vi)) represents parameterization. The second generation processing module 740 discretizes the partition boundary line and automatically generates a structured grid corresponding to the transformed grid. The inverse mapping processing module 750 inversely maps the generated structured grid onto the three-dimensional curved surface to obtain a surface structure grid corresponding to the three-dimensional model to be processed.
Specifically, a cloud image of the transformed mesh is drawn according to the calculated area compression ratio. Partition boundary lines are extracted from the drawn cloud image.
According to an alternative embodiment, the following expression is used to represent the size of each vertex:
;
Wherein size (v i) represents the size of the ith vertex v i; sumSize N(vi) represents the dimensions of all edges around the i-th vertex v i in the parameterized two-dimensional mesh, sum N(vi) represents the number of all edges around the i-th vertex v i in the two-dimensional mesh, and max (Size N(vi)) represents the maximum dimensions of all edges around all vertices v i in the parameterized two-dimensional mesh.
The method in the apparatus embodiment of the present invention is substantially the same as the method in the method embodiment of the present invention, and therefore, the description of the same parts is omitted.
Compared with the prior art, the method and the device have the advantages that the initial curved surface triangulated grid is generated by triangulating the imported three-dimensional model to be processed, the transformed grid is obtained by conformally mapping the initial curved surface triangulated grid to the two-dimensional parameter domain according to whether the specified condition is met, the transformed grid is subjected to regional division, the unit area compression ratio is calculated, the cloud image corresponding to the transformed grid is drawn to extract the partition boundary line of the transformed grid, the partition boundary line is discrete, the structured grid corresponding to the transformed grid is automatically generated, and the surface structure grid can be automatically generated according to the set grid generation parameters in the surface structure grid generation process, so that the surface grid generation time is greatly shortened, the automation degree of grid generation is improved, the generation difficulty of the structure grid is reduced, and the method and the device have great engineering practicability.
Fig. 8 is a schematic structural view of an electronic device according to an embodiment of the present application. Referring to fig. 8, at the hardware level, the electronic device includes a processor, and optionally an internal bus, a network interface, and a memory. The Memory may include a Memory, such as a Random-Access Memory (RAM), and may further include a non-volatile Memory (non-volatilememory), such as at least 1 disk Memory. Of course, the electronic device may also include hardware required for other services.
The processor, network interface, and memory may be interconnected by an internal bus, which may be an ISA (Industry Standard Architecture ) bus, a PCI (PERIPHERAL COMPONENTINTERCONNECT, peripheral component interconnect standard) bus, or EISA (Extended Industry Standard Architecture ) bus, among others. The buses may be classified as address buses, data buses, control buses, etc. For ease of illustration, only one bi-directional arrow is shown in FIG. 8, but not only one bus or type of bus.
And the memory is used for storing programs. In particular, the program may include program code including computer-operating instructions. The memory may include memory and non-volatile storage and provide instructions and data to the processor.
The processor reads the corresponding computer program from the nonvolatile memory into the memory and then runs the computer program to form a model surface grid fairing processing method on a logic level. And the processor is used for executing the program stored in the memory and particularly used for executing the surface grid fairing processing method of any model.
The method disclosed in the embodiment of fig. 1 of the present application can be applied to a processor (i.e., a deletion control module in the present specification), or implemented by a processor. The processor may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware in a processor or by instructions in the form of software. The processor may be a general-purpose processor, including a central processing unit (Central Processing Unit, CPU), a network processor (Network Processor, NP), etc.; but also digital signal processors (DIGITAL SIGNAL processors, DSPs), application specific integrated circuits (ApplicationSpecific Integrated Circuit, ASICs), field-Programmable gate arrays (Field-Programmable GATE ARRAY, FPGA) or other Programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. The disclosed methods, steps, and logic blocks in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present application may be embodied directly in the execution of a hardware decoding processor, or in the execution of a combination of hardware and software modules in a decoding processor. The software modules may be located in a random access memory, flash memory, read only memory, programmable read only memory, or electrically erasable programmable memory, registers, etc. as well known in the art. The storage medium is located in a memory, and the processor reads the information in the memory and, in combination with its hardware, performs the steps of the above method.
The electronic device may also execute the method described in fig. 1 and implement the functions of the embodiment shown in fig. 1, which is not described herein.
The embodiments of the present application also provide a computer-readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by an electronic device comprising a plurality of application programs, enable the electronic device to perform the method of the embodiment of fig. 1, and in particular for performing any of the methods described above.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In one typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include volatile memory in a computer-readable medium, random Access Memory (RAM) and/or nonvolatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of computer-readable media.
Furthermore, the present invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the surface structure grid generation method according to embodiment 1 of the present invention.
In this example, non-transitory computer-readable storage media, i.e., computer-readable media, including in particular, non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technique. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Disks (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. Computer-readable media, as defined herein, does not include transitory computer-readable media (transmission media), such as modulated data signals and carrier waves.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises the element.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and variations of the present application will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.
Claims (9)
1. A method of generating a surface texture grid, comprising:
performing curved surface triangulation on the imported three-dimensional model to be processed, setting parameters of triangulation according to different application scenes, and generating an initial curved surface triangulation grid, wherein the three-dimensional model to be processed comprises a three-dimensional model related to wing tips and ship propeller blades, and the parameters specifically comprise target size, minimum size, self-adaptive angle and growth rate;
Initializing a circle filling measure and a discrete conformal factor, and determining an initial value of the circle filling measure according to the minimum size of a unit of the initial curved surface triangulating grid; specifically, according to the application scene and the shape of the three-dimensional model to be processed, the target Gaussian curvature of the initial curved surface triangularization grid is configured; conformally mapping the generated initial curved surface triangulated mesh to a two-dimensional parameter domain, comprising repeatedly performing the steps of: calculating a curved surface Ricci flow of the initial curved surface triangulated mesh to determine whether to update a curved surface measurement parameter; executing conformal mapping processing when the specified condition is met to obtain a transformed grid; flow of surfaces Ricci per vertex of the initial surface triangulated mesh Defined as the absolute value of the difference between the calculated value of gaussian curvature of each vertex and the target gaussian curvature, and forming a specified condition for performing conformal mapping processing, expressed by the following expression: Wherein/> Flow of surface Ricci representing each vertex of the initial surface triangulated mesh,/>Representing the i < th > conformal factor,/>Represents the ith vertex, i is a positive integer,/>Representing time, the curvature of each vertex varies with time; /(I)A calculated value representing the gaussian curvature of the ith vertex of the initial curved surface triangulated mesh M; The method comprises the steps of representing the target Gaussian curvature of the ith vertex of an initial curved surface triangulated mesh M, wherein i is a positive integer, and M represents the initial curved surface triangulated mesh;
the transformed mesh is subjected to region division, and the area compression ratio of each triangular patch before and after the conformal mapping process, namely the compression ratio of each vertex, is calculated: Wherein/> Representing the compression ratio of the ith vertex; /(I)Representing the i-th vertex/>, in the parameterized two-dimensional meshThe area of the triangular patch; /(I)Representing the i-th vertex/>, in the initial surface triangulated mesh MThe area of the triangular patch; /(I)Representing all vertices/>, in a parameterized two-dimensional meshDrawing a cloud picture corresponding to the transformed grid to extract a partition boundary line of the transformed grid; dividing the transformed grid into a plurality of sub-regions; reconstructing the plurality of sub-regions by utilizing a relevance constraint of grid topology on the plurality of sub-regions, wherein the relevance constraint comprises that the boundary curvature of the sub-region is smaller than a specific value and the area of the sub-region is larger than a specified value;
discretizing the partition boundary lines and automatically generating a structured grid corresponding to the transformed grid;
And reversely mapping the generated structured grid onto a three-dimensional curved surface to obtain a surface structure grid corresponding to the three-dimensional model to be processed.
2. The surface texture grid generating method according to claim 1, further comprising:
the Gaussian curvature of each vertex of the initial surface triangulated mesh and the surface topology of the initial surface triangulated mesh satisfy Gauss-Bonnet expression:
And the surface metric parameter for any vertex satisfies the following expression: Wherein/> The ith vertex/>, representing the initial surface triangulated mesh MTarget Gaussian curvature of/>M represents an initial curved surface triangularization mesh; /(I)Representing euler's illustrative number; /(I)A circle fill measure representing the mesh edge e of any vertex.
3. The method for generating a surface texture grid as claimed in claim 2, wherein,
When the specified condition is not met, updating the curved surface measurement parameter, and repeatedly executing the step of calculating the curved surface Ricci flow of the initial curved surface triangulated mesh;
and when the specified condition is met, saving the numerical value of the curved surface measurement parameter, and executing conformal mapping processing.
4. The method for generating a surface texture grid as claimed in claim 1, wherein,
Drawing a cloud picture of the transformed grid according to the calculated area compression ratio;
Partition boundary lines are extracted from the drawn cloud image.
5. The method for generating a surface texture grid as recited in claim 4, wherein,
The size of each vertex is expressed using the following expression: Wherein/> Represents the ith vertex/>Is a dimension of (2); /(I)Representing the i-th vertex/>, in the parameterized two-dimensional meshSize of all around,/>Representing the ith vertex/>, in a two-dimensional meshThe number of all sides around,Representing all vertices/>, in a parameterized two-dimensional meshMaximum size of all sides around.
6. A surface structure mesh generation apparatus for implementing the surface structure mesh generation method of any one of claims 1 to 5, the surface structure mesh generation apparatus comprising:
A first generation processing model, which is used for carrying out curved surface triangulation on an imported three-dimensional model to be processed, setting parameters of triangulation according to different application scenes, and generating an initial curved surface triangulation grid, wherein the three-dimensional model to be processed comprises three-dimensional models related to wing tips and ship propeller blades, and the parameters specifically comprise target size, minimum size, self-adaptive angle and growth rate; the conformal mapping processing module initializes the circle filling measure and the discrete conformal factor, and determines the initial value of the circle filling measure according to the minimum size of the cells of the initial curved surface triangulated mesh; specifically, according to the application scene and the shape of the three-dimensional model to be processed, the target Gaussian curvature of the initial curved surface triangularization grid is configured; conformally mapping the generated initial curved surface triangulated mesh to a two-dimensional parameter domain, comprising repeatedly performing the steps of: calculating a curved surface Ricci flow of the initial curved surface triangulated mesh to determine whether to update the curved surface metric parameter; executing conformal mapping processing when the specified condition is met to obtain a transformed grid; flow of surfaces Ricci per vertex of the initial surface triangulated mesh Defined as the absolute value of the difference between the calculated value of gaussian curvature of each vertex and the target gaussian curvature, and forming a specified condition for performing conformal mapping processing, expressed by the following expression: /(I)Wherein/>Flow of surface Ricci representing each vertex of the initial surface triangulated mesh,/>Representing the i < th > conformal factor,/>Represents the ith vertex, i is a positive integer,/>Representing time, the curvature of each vertex varies with time; /(I)A calculated value representing the gaussian curvature of the ith vertex of the initial curved surface triangulated mesh M; /(I)The calculation processing module performs region division on the transformed grid, and calculates the area compression ratio of each triangular patch before and after conformal mapping processing, namely the compression ratio of each vertex by adopting the following expression: /(I)Wherein/>Representing the compression ratio of the ith vertex; /(I)Representing the i-th vertex/>, in the parameterized two-dimensional meshThe area of the triangular patch; /(I)Representing the i-th vertex/>, in the initial surface triangulated mesh MThe area of the triangular patch; /(I)Representing parameterization; drawing a cloud image corresponding to the transformed grid to extract partition boundary lines of the transformed grid, and dividing the transformed grid into a plurality of subareas; reconstructing the plurality of sub-regions by utilizing a relevance constraint of grid topology on the plurality of sub-regions, wherein the relevance constraint comprises that the boundary curvature of the sub-region is smaller than a specific value and the area of the sub-region is larger than a specified value;
the second generation processing module is used for dispersing the partition boundary lines and automatically generating a structured grid corresponding to the transformed grid;
and the inverse mapping processing module is used for inversely mapping the generated structured grid to the three-dimensional curved surface to obtain the surface structure grid corresponding to the three-dimensional model to be processed.
7. The surface texture grid generating apparatus as claimed in claim 6, wherein,
Drawing a cloud picture of the transformed grid according to the calculated area compression ratio;
Extracting partition boundary lines from the drawn cloud image; wherein,
The size of each vertex is expressed using the following expression: Wherein/> Represents the ith vertex/>Is a dimension of (2); /(I)Representing the i-th vertex/>, in the parameterized two-dimensional meshSize of all around,/>Representing the ith vertex/>, in a two-dimensional meshThe number of all sides around,Representing all vertices/>, in a parameterized two-dimensional meshMaximum size of all sides around.
8. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the steps of the surface structure grid generation method of any one of claims 1-5 when the program is executed.
9. A non-transitory computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the surface structure grid generation method according to any one of claims 1-5.
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