JP2002328958A - Mesh generation method, program, recording medium, and mesh generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a continual polygon mesh which is suited for CAE analysis easily and efficiently from CAD data whose connection is incomplete between surfaces. SOLUTION: On a mesh generation method, which generates the polygon mesh for CAE analysis using a surface model that is created by CAD and describes surface form of a certain material with plural surfaces, a computer 1 generates point group data, which is distributed all over the surface, according to the surface model. And, the computer 1 generates the polygon mesh, in which the point group is considered to be a node point, according to the point group data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating a polygon mesh, a generation system, a program, and a recording medium on which the program is recorded. Using, C
The present invention relates to a method for generating mesh data for AE analysis.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Publication No. Hei 9-185729 discloses a method of generating orthogonal difference mesh three-dimensional model data required for analysis by a CAE system using three-dimensional solid model data generated by a CAD system. Is disclosed. In this method, first, an intersection between a three-dimensional solid model generated by a CAD system and a three-axis orthogonal line formed at an arbitrary pitch is obtained, and the outermost point of the three-dimensional solid model is calculated. Next, an inner / outer positional relationship between the outermost surface point and a virtual difference mesh having a representative point of the difference mesh is determined. An attribute is assigned to the virtual difference mesh according to the determination result, and a single difference mesh model is created.
Then, a conditional expression for determining a connection state of a single unit to be a target of a desired analysis model is given to the difference mesh model to make a condition determination, and an orthogonal difference mesh is created.

[0003] Japanese Patent Application Laid-Open No. 2000-132582 discloses a technique for converting meshed CAD data into a surface model. In this method, first, a plurality of meshes are divided into one or more regions based on a mesh model including coordinate values of a plurality of grids representing the shape of the structure and an adjacency relationship between the plurality of meshes representing the shape. I do. This division is performed by calculating an inner product based on coordinate values of a plurality of grids, calculating an angle between a pair of meshes adjacent to each other, and comparing the angle with a predetermined value. Next, an outer peripheral line is calculated for each of the divided areas. Then, by calculating a function formula of a curved surface that satisfies the calculated outer peripheral line and the coordinate values of the inner grid, an interface having a surface model corresponding to a region constituting one member is obtained. .

Further, Japanese Patent Application Laid-Open No. 9-44696 discloses a method for connecting three-dimensional shapes represented by polygons. In this method, first, the vertices of two polygon meshes to be connected are associated with each other, and a new vertex is generated between the associated vertices. Next, a polygon having the newly generated vertices as vertices is newly generated. Then, unnecessary vertices are deleted as a result of generating a new polygon.

[0005]

SUMMARY OF THE INVENTION From CAD data to CA
When generating a mesh for E-analysis, first, it is necessary to correct (healing) the gap or overlap between surfaces and sides in the CAD data as the base, and then generate the mesh. This is because the original CAD data created by the CAD designer often has gaps or overlaps between the surfaces to be abutted, and if this data is used as it is, the mesh for CAE analysis becomes discontinuous. It is because. In order to correct such a defect, for example, when a gap between adjacent surfaces is equal to or smaller than a predetermined allowable value, a method of automatically correcting the defect on a computer is considered assuming that the surfaces are connected to each other. . For a large gap or surface data missing during data conversion, a method of generating a new surface in that part can be considered. Further, with respect to the overlapped portion, a method of adding a missing surface and then trimming the surfaces or deleting an unnecessary surface can be considered.

However, as shown in FIG. 12A, when the sides of the surfaces to be connected do not match, there is a disadvantage that the gap between the surfaces cannot be automatically corrected. In such a case, prior to coupling with a pair of adjacent surfaces S1 and S2, first,
It is necessary to match each other's sides. As an example, as shown in FIG. 4B, the horizontal side E1 on the surface S1 is separated at the newly added division point d. After creating the separated horizontal side E1 '(shown by a dotted line), the horizontal side E1' and the vertical side E2 are connected. Then, the connection side on the surface S1 side obtained thereby and the side on the surface S2 side opposite thereto are connected. In general, large-scale CAD data such as a vehicle body shape has at least several hundred surfaces and several times as many sides. Therefore, performing the above-described correction process manually (manually) requires a great deal of labor and time. Furthermore, since the surface correction in the overlapping portion is almost manual, the manual correction is complicated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a new method capable of generating a good CAE analysis mesh using CAD data.

It is another object of the present invention to improve the efficiency of the work of correcting surface defects in CAD data.

[0009]

Means for Solving the Problems In order to solve the above problems, a first invention uses a surface model created by CAD and expressing the surface shape of a certain member by a plurality of surfaces, for CAE analysis. In a mesh generation method for generating a polygon mesh, a first step in which a computer generates point cloud data in which a point cloud is distributed on a surface based on a surface model; And a second step of generating a polygon mesh having a group as a node.

A second invention is a program for causing a computer to execute a mesh generation method for generating a polygon mesh for CAE analysis using a surface model created by CAD and expressing a surface shape of a member by a plurality of surfaces. In, based on the surface model,
A first step of generating point cloud data in which a point cloud is distributed on a surface; and a second step of generating a polygon mesh having the point cloud as a node based on the point cloud data.
And a program for executing the mesh generation method having the steps of:

A third invention is a program for causing a computer to execute a mesh generation method for generating a polygon mesh for CAE analysis using a surface model created by CAD and expressing a surface shape of a member by a plurality of surfaces. A first step of generating point cloud data in which point clouds are distributed on a surface, based on a surface model, on a recording medium on which
And a second step of generating a polygon mesh having the point group as a node based on the point group data.

According to a fourth aspect of the present invention, there is provided a mesh generation system for generating a polygon mesh for CAE analysis using a surface model created by CAD and expressing the surface shape of a member by a plurality of surfaces. Means for generating point cloud data in which point clouds are distributed on a surface; and generating a polygon mesh having the point cloud as a node based on the point cloud data generated by the point cloud data generating means. A mesh generation system having a mesh generation unit is provided.

Here, in any of the first to fourth inventions, when a boundary line surrounding each surface constituting the surface model is set in the surface model, a point group is also arranged on the boundary line. Is preferred.

When a character line indicating an edge portion of a member is set in a surface model, it is preferable to arrange a point group also on the character line. In this case, when the characteristic angle between a pair of adjacent surfaces is smaller than a predetermined determination angle, it is desirable to determine that an edge is formed at the boundary of the surface, and to set a character line at the boundary.

In any one of the first to fourth inventions described above, when the operator sets a new line by connecting a plurality of points to the generated point group data,
If the set line intersects the boundary line or the character line, it is preferable to additionally set a new point at the intersection.

In any one of the first to fourth aspects of the present invention, it is preferable that the generation of the polygon mesh is performed in consideration of a boundary line or a character line. It is desirable to set the distribution density according to.

In any one of the first to fourth inventions described above, when the operator designates point cloud data relating to another member, the point cloud data relating to a certain member and the point cloud data relating to another member are superimposed. It is desirable to generate a polygon mesh based on the point cloud data obtained by the superposition.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (System Configuration) FIG. 1 is an overall configuration diagram of a mesh generation system. This generation system includes a computer 1, an input device 2 such as a keyboard and a mouse, a display device 3 such as a CRT and a liquid crystal display, and a storage device 4 such as a magnetic disk. The computer 1 mainly includes a CPU, a RAM, a ROM, an input / output interface, and the like, and performs a mesh generation process described later. The operator performs necessary instructions and operations via the input device 2 while confirming on the display device 3 the processing results sequentially displayed in the process. The storage device 4 stores “C”, which is input data of the mesh generation process.
“AD data”, “mesh data” for CAE analysis output as a processing result, “point group data” generated in an intermediate process, and “separate member data” are stored.

Here, the "CAD data" is data relating to a surface model created by CAD and expressing the surface shape of a member by a plurality of surfaces. “Point cloud data” is data relating to a point cloud obtained by dispersing a large number of points on the entire surface or a partial surface designated by the operator in the surface model. The “separate member data” is point cloud data related to another member that is required in a case where a mesh model for an assembly in which a plurality of members are assembled is generated. The point cloud data may be generated by the mesh generation method according to the present embodiment, or may be obtained by three-dimensionally scanning the shape of another member. The “mesh data” is data based on a polygon mesh that is generated based on the point cloud data and has the point cloud as a node. The mesh data finally generated in the mesh generation process is used for collision analysis, vibration analysis,
Various CAEs such as flow analysis, strength / rigidity analysis, and heat conduction analysis
Widely available for analysis.

(First Embodiment) FIG. 2 is a flowchart of a mesh generation process executed in the computer 1. Hereinafter, four surfaces S1 to S1 shown in FIG.
This processing will be described in detail with reference to a surface model expressing the surface shape of the member in S4 as appropriate.

First, the operator selects, from the CAD data stored in the storage device 4, data relating to a member to be processed. By this action, step 1 is executed, and the computer 1 reads the CAD data designated by the operator from the storage device 4 and displays the surface model on the display device 3.

Next, the operator operates the input device 2 while referring to the displayed surface model, and
Boundary lines BL and character lines CL are set at arbitrary positions in the AE analysis mesh (see FIG. 3). These lines BL and CL can be set separately, but in that case, a correction in step 7 described later is necessary. By this action, step 2 is executed, and the computer 1 adds the lines BL and CL specified by the operator to the surface model. The added lines BL and CL are reflected on the display screen of the display device 3.

Here, the "boundary line BL" is a calculation line surrounding each surface constituting the surface model. Therefore, each surface in the CAD data is surrounded by the boundary line. The “character line CL” is a line indicating an edge portion where the surface is bent to some extent.
It corresponds to a bent curve.

The boundary line BL in the state of the surface model
The reason why the character line CL is set is to improve the shape reproducibility and increase the degree of freedom in setting the lines BL and CL. Without providing the character line CL indicating the edge portion of the member (or by using this line CL
Creating a polygon mesh (without considering the
The reproducibility of the surface shape of the member deteriorates. For example, there are some cases where a node (node) of a polygon mesh is selected at a corner. At this time, if a polygon mesh is created without any restrictions, the actual character line CL (shown by a dotted line) may be cut as shown in FIG. As a result, it becomes difficult to appropriately represent the edge portion with a polygon. Therefore, regarding the edge part,
A character line CL is specified at the surface model stage, and as described later, generation of a polygon mesh that straddles this line CL is restricted. On the other hand, the boundary line BL
Must be set in advance to set material characteristics (characteristics such as Young's modulus, Poisson's ratio, density, and plate thickness) and load conditions (load and its input direction) in the CAE analysis mesh. In this case, although it is possible to set the boundary line BL in step 7, it is possible to improve the degree of freedom of the shape of the boundary line BL by setting the boundary line BL in the state of the surface. At the same time, setting of boundary conditions in CAE analysis can be made more efficient.

Next, the operator designates a target area where points in the surface model are scattered. The target area can specify the entire surface of the surface model, but can also specify a part of the surface while referring to the display screen of the display device 3. Step 3 is executed by this action, and the computer 1 distributes the point cloud as a whole in the designated target area, and stores the generated point cloud data in the storage device 4. At the same time, a processing result as shown in FIG. Note that the display example in plan view of FIG. 5 shows a state in which all surfaces are designated as target regions, and point groups are uniformly and entirely distributed over all surfaces.

The point group set in step 3 is a virtual point group necessary for reconstructing the surface, and corresponds to a mesh node candidate when creating a polygon mesh. The computer 1 uniformly distributes the point cloud on the target area according to a predetermined distribution rule. The distribution density of point groups (corresponding to the interval between adjacent points) needs to be set to an interval smaller than the target mesh size of the mesh for CAE analysis to be generated, but is not more than half the target mesh size ( In other words, it is preferable to set the interval to at least four times the distribution density of the mesh nodes. When the boundary line BL and the character line are set on the considered CL surface, a point group is also arranged on these lines BL and CL (see FIG. 5). The reason for this is to form a mesh with the lines BL and CL as sides when generating a mesh in step 8 described later, and to match the nodes of the mesh adjacent to the lines BL and CK. .

In step 3, by converting the data into a set of "points", which are the minimum units of the shape, the inconvenience relating to the gap between the surface and the line can be eliminated, and the CAD data can be easily corrected. Note that, for example, in a place where adjacent surfaces overlap each other, points are excessively dense because point groups are generated in an overlapping manner. In such a case, overlapping points are deleted in step 7 described later.

In step 3, the distribution density may be changed according to the curvature of the surface as shown in FIG. 6 without uniformly distributing the point groups. In this case, while increasing the distribution density of a portion having a large curvature (a small radius of curvature), the distribution density of a portion having a small curvature (a large radius of curvature) has a low distribution density, which is smaller than the mesh size of the mesh data for analysis. Distribute points at large intervals. As a specific method, for example, on a curved surface, points are arranged so that a change in the direction of a normal vector of each point is constant, and on a plane, points are arranged at predetermined intervals. As a result, the mesh side formed by connecting adjacent points becomes smooth, and the fitting to the CAD surface is improved.

Subsequently, when the operator desires to generate a CAE analysis mesh for an assembly in which a plurality of members are combined, the operator additionally designates point group data for members other than the members specified in step 1. As described above, the point cloud data of another member is stored as separate member data in the storage device 4, and the CA related to the designated member is
D data is read. The computer 1 proceeds to the process of step 5 when the point cloud data of another member is designated by the operator, and skips step 5 when it is not designated.

In step 5, the computer 1
Point cloud data of each member constituting the assembly is superimposed while taking into account the position between members designated by a manual operation of an operator, and point cloud data of the assembly is automatically generated. The point cloud obtained by this polymerization process is displayed on the display device 3. In step 5, since the three-dimensionally scanned shape data can be used as separate member data,
It is possible to easily combine the three-dimensionally scanned shape and the existing CAD shape.

Subsequently, when the operator desires to correct the point cloud data or the line data such as the boundary line BL and the character line CL, the operator instructs the computer 1 via the input device 2 to that effect. In response to this, when receiving the correction instruction, the computer 1 proceeds to step 7
If no correction designation has been received, step 7 is skipped.

In step 7, the computer 1
The point cloud data or line data is corrected according to the manual operation of the operator, and the correction result is displayed on the display device 3. Modifications of point cloud data include deleting some overlapping or overly dense points, moving or adding points, etc. in order to improve the quality of polygon meshes (regular triangles have the best quality). This is necessary work. Correction of the point cloud can be performed more efficiently than correction of CAD data if the correction is small. In addition, as the correction of the line data, the lines BL,
Correction of CL, creation of a new line (broken line or B-Spline curve) connecting adjacent points, and the like. By such a line correction, a boundary surface can be generated at the time of generating the mesh for CAE analysis, and the object shape accuracy can be improved.

At step 8, the computer 1
For example, a polygon mesh shown in FIG. 7 is generated based on the point group set on the surface, and the mesh data is output. This mesh data is stored in the storage device 4, and a polygon mesh model based on this data is displayed on the display device 3, and a series of processing ends.

In step 8, a triangle or quadrilateral polygon mesh having nodes as the nodes forming the point group corrected in step 7 is generated. As described above, since the point cloud is also arranged on the boundary line BL and the character line CL, the surface shape in consideration of these lines BL and CL can be reconstructed. That is, as shown in FIG. 7, the generated mesh has the lines BL and CL as sides and the nodes of the mesh adjacent to the lines BL and CK are coincident. Further, even if there is a defect in the surface model that does not need to be corrected on the CAD (has no great influence on the CAE analysis), it is possible to form a surface.

In the polygon mesh generation step in step 8, it is preferable to change the attribute of the polygon inside and outside the closed line. The reason for this is that, at this stage, if you divide the surface to be regenerated for each attribute,
This is because separation of the boundary surface in the CAE analysis becomes easy. For the same reason, it is preferable to change the attribute of the three-dimensional free-form surface generated based on the polygon according to the attribute of the polygon.

This polygon mesh is used for purposes other than CAE analysis, such as stereolithography data (STL data) and CG.
It can also be used as application data (OBJ data). Further, a three-dimensional free-form surface may be generated based on the generated polygon mesh. Specifically, a three-dimensional free-form surface (for example,
NURBS data, B-spline data, etc.)
Rebuild the CAD surface. The composition of the surface is
It may be the same as the surface configuration at the time of input, but may be different.

As described above, according to the present embodiment, the CAD
Is once replaced with a point group, and a polygon mesh for CAE analysis is reconstructed from this point group. As a result, the work of correcting surface defects in CAD data can be made more efficient, and good surface data in which individual surfaces are continuously connected can be obtained. Further, when distributing the point group on the surface, the point group is also arranged on the boundary line BL, and a polygon mesh is generated using the point group as a node. Therefore, the boundary line B corresponding to the boundary between adjacent surfaces
Since the point cloud is always arranged on L, even if the connection between the surfaces in the CAD data is uncertain, the polygon mesh data for CAE analysis in which it is securely connected is easily and efficiently generated. It is possible to do. Further, when distributing the point group on the surface, the point group is also arranged on the character line CL indicating the edge portion, and a polygon mesh is generated using the point group as a node. Therefore, since the character line CL coincides with the side of the element, it is possible to appropriately represent an edge portion by a mesh.

(Second Embodiment) In the first embodiment described above, the setting of the character line CL in step 2 of FIG. 2 was performed manually. On the other hand, in the present embodiment, the computer 1 performs an edge determination based on an angle between a pair of surfaces adjacent to each other (hereinafter, referred to as “feature angle”), and automatically generates a character line CL indicating an edge portion of the member. Is to be set dynamically. FIG. 8 is a flowchart of a character line CL setting process executed in the computer 1.

First, in step 11, based on a value input by the operator, the computer 1 sets a determination angle θth serving as a threshold value for edge determination. If the determination angle θth is set to a fixed value without being made variable, this step 11 becomes unnecessary.

Next, in step 12, the computer 1 calculates a characteristic angle θ between adjacent pairs of surfaces to be subjected to edge determination. FIG. 9 shows the characteristic angle θ.
FIG. A pair of surfaces S1 and S2 adjacent to each other are specified as a determination target among a plurality of surfaces constituting the surface model of the member. Then, the characteristic angle θ of the surface pair S1, S2 (0 ° <θ ≦ 180 °)
Is calculated based on a known method (for example, calculating an angle formed by a normal vector).

In step 13, the computer 1
Determines whether or not an edge is an edge based on the calculated characteristic angle θ. When the characteristic angle θ is smaller than the determination angle θth (0
° <θ <θth), it is determined that an edge is formed at the boundary between the surface pairs, and a character line CL is set at this boundary (step 14). Information about the edge is stored in the storage device 4. On the other hand, the characteristic angle θ
Is greater than or equal to the determination angle θth (θth ≦ θ ≦ 180 °), the step 14 is skipped.

In step 15, the computer 1
Sets the determined flag relating to the surface pair determined this time from “0” to “1”. The determined flag is provided in association with all surface pairs in the surface model. “0” means undetermined, and “1” means determined.

Then, in step 16, the computer 1 determines whether or not all the surface pairs to be determined have been determined based on the determined flag. Step 16
If the determination is negative, ie, if all the determined flags are not set to “1”, an undetermined surface pair is set as a new determination target (step 17), and the process proceeds to step 12. Return. Then, the procedure from step 12 described above is executed on the new determination target. On the other hand, if the determination in step 16 is affirmative, that is, if the edge determination has been completed for all surface pairs, the setting process ends.

As described above, according to the present embodiment, the computer 1 automatically determines an edge existing in the surface model, and can set a necessary character line CL at a time. Therefore, compared to the first embodiment described above,
The labor of the operator can be saved, and the operation efficiency can be improved.

(Third Embodiment) In the present embodiment, in step 7 of the above-described first embodiment, as shown in FIG.
It relates to a correction process executed when L '(or character line CL') is additionally set. Computer 1
Executes the correction processing shown in the flowchart of FIG. 11 when the additional lines BL ′ and CL ′ are added in step 7.

First, in step 21, the computer 1 checks the lines BL ', added by the operator.
It is determined whether or not CL ′ straddles the adjacent surfaces S1 and S2, in other words, whether or not it crosses the preset character line CL. If such an intersection does not occur, the processing is terminated without making any corrections on the additional lines BL ′ and CL ′.

On the other hand, additional lines BL 'and CL'
Is a preset character line CL (boundary line BL '
May be intersected, a point P is additionally set at the intersection of the two lines (step 22). Then, in the subsequent step 23, the two additional lines are reset by separating the additional lines BL 'and CL' at the additional point P, and the processing is terminated.

According to the present embodiment, it is possible to prevent the state shown in FIG. 4, that is, the generation of the polygon mesh by cutting the character line CL. Further, by separating the additional lines BL ′ and CL ′, it is possible to generate a good B-Spline curve fitted to the surface.

It should be noted that a recording medium on which a computer program for realizing the functions described in the above embodiments may be supplied to the computer 1. In this case, by reading and executing the computer program stored in the recording medium in the computer 1, the object of the present invention can be achieved. Therefore, since the computer program itself read from the recording medium realizes the novel functions of the present invention, the recording medium on which the program is recorded constitutes the present invention. Examples of the recording medium on which the computer program is recorded include a CD-ROM, a floppy (registered trademark) disk,
Hard disk, memory card, optical disk, DVD-
ROM, DVD-RAM, and the like. Further, the computer program itself for realizing the functions of the above-described embodiments also has new functions.

[0050]

According to the present invention, a number of virtual points are scattered on a surface model created by CAD, the surface is temporarily replaced with a point group, and a polygon mesh having the point group as a node is regenerated. I do. As a result, even if the connection between the surfaces is incomplete, a continuous polygon mesh suitable for CAE analysis can be easily and efficiently generated from such CAD data.
At the same time, the work of correcting the surface defect in the CAD data can be made more efficient.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a mesh generation system.

FIG. 2 is a flowchart of a mesh generation process.

FIG. 3 is a display example of a surface model of a member

FIG. 4 is an example of generating a polygon mesh obtained by cutting a character line.

FIG. 5 is a display example of a point cloud set on a surface model.

FIG. 6 is a display example of a point cloud set according to the curvature of a surface.

FIG. 7 is a display example of a generated polygon mesh.

FIG. 8 is a flowchart of a character line setting process.

FIG. 9 is an explanatory diagram of a characteristic angle.

FIG. 10 is an explanatory diagram relating to processing of a newly added line.

FIG. 11 is a flowchart of an additional line process.

FIG. 12 is a diagram illustrating a conventional surface connection method.

[Explanation of symbols]

 1 computer, 2 input device, 3 display device, 4 storage device, BL boundary line, CL character line

Claims (19)

[Claims] 1. A mesh generation method for generating a polygon mesh for CAE analysis using a surface model created by CAD and expressing a surface shape of a member by a plurality of surfaces, wherein a computer is configured to execute the method based on the surface model. A first step of generating point cloud data in which a point cloud is distributed on the surface; and a second step of generating a polygon mesh having the point cloud as a node based on the point cloud data. And a mesh generation method. 2. The method according to claim 1, wherein the first step includes arranging a point cloud on the boundary line when a boundary line surrounding each surface constituting the surface model is set in the surface model. The mesh generation method according to claim 1, wherein: 3. The method according to claim 1, wherein the first step includes a step of arranging a point cloud on the character line when a character line indicating an edge portion of the member is set in the surface model. Item 7. The mesh generation method according to Item 1. 4. When the characteristic angle between a pair of surfaces adjacent to each other is smaller than a predetermined determination angle, the computer determines that an edge is formed at the boundary of the surface, and places the character line on the boundary. The method according to claim 3, further comprising a third step of setting. 5. When the operator sets a new line by connecting a plurality of points to the point cloud data generated in the first step, the computer determines whether the set line is the boundary line or the new line. The method according to any one of claims 2 to 4, further comprising a fourth step of, if the character line intersects, additionally setting a new point at the intersection position. 6. The method according to claim 2, wherein the second step is a step of generating a polygon mesh in consideration of the boundary line or the character line.
6. The mesh generation method according to any one of claims 1 to 5. 7. The mesh generation method according to claim 1, wherein said first step is a step of distributing a point group with a distribution density according to a curvature of said surface. 8. The method according to claim 8, further comprising: when the operator designates point cloud data relating to another member, superimposing the point cloud data generated in step 1 with the point cloud data relating to another member. Generating a polygon mesh based on the point cloud data obtained by the superimposition. 9. A program for causing a computer to execute a mesh generation method for generating a polygon mesh for CAE analysis using a surface model created by CAD and expressing a surface shape of a member by a plurality of surfaces, the program comprising: Distribute a point cloud on the surface based on the model, and place a point cloud on the boundary line when a boundary line surrounding each surface constituting the surface model is set in the surface model. When a character line indicating an edge portion of a member is set in the surface model, a first step of generating point group data by arranging a point group on the character line; Based on the data, a polygon mesh with the point group as a node is Program for executing a mesh generation method in a computer having a second step of forming. 10. A method according to claim 7, further comprising the step of setting a character line at a boundary between said surfaces when a characteristic angle between a pair of adjacent surfaces is smaller than a predetermined determination angle. The program according to claim 9, which is executed by a computer. 11. A recording medium on which the program according to claim 9 or 10 is recorded. 12. A mesh generation system for generating a polygon mesh for CAE analysis using a surface model created by CAD and expressing a surface shape of a member by a plurality of surfaces, wherein: Point cloud data generating means for generating point cloud data in which point clouds are distributed on a surface; and generating a polygon mesh having the point cloud as a node based on the point cloud data generated by the point cloud data generating means. And a mesh generating means. 13. The point cloud data generating means, when a boundary line surrounding each surface constituting the surface model is set in the surface model, arranges a point cloud on the boundary line. 13. The mesh generation system according to claim 12, wherein: 14. A method according to claim 14, wherein said point cloud data generating means arranges a point cloud on said character line when a character line indicating an edge portion of a member is set in said surface model. Item 13. A mesh generation system according to Item 12. 15. When a characteristic angle between a pair of surfaces adjacent to each other is smaller than a predetermined determination angle, it is determined that an edge is formed at a boundary of the surface, and an edge for setting the character line at the boundary is determined. The mesh generation system according to claim 14, further comprising a determination unit. 16. When an operator sets a new line by connecting a plurality of points to the point cloud data generated by the point cloud data generating means, the set line is the boundary line or the character. 16. The mesh generation system according to claim 13, further comprising a point cloud data correction unit that additionally sets a new point at the intersection position if the line intersects the line. 17. The apparatus according to claim 13, wherein said mesh generating means generates a polygon mesh in consideration of said boundary line or said character line.
A mesh generation system according to any one of the above. 18. The mesh generation system according to claim 12, wherein said point cloud data generating means distributes the point cloud at a distribution density according to a curvature of said surface. 19. The method according to claim 19, wherein, when an operator designates point cloud data relating to another member, the mesh generating unit superimposes the point cloud data generated by the point cloud data generating unit on the point cloud data relating to another member. 13. The mesh generation system according to claim 12, wherein a polygon mesh is generated based on the point cloud data obtained by the superimposition.