JP5595070B2 - CAD data transmission method, CAD data reception method, CAD data transmission device, CAD data reception device, CAD data transmission program, CAD data reception program, and data structure - Google Patents

Description

  The present invention relates to a transmission / reception method, a transmission / reception apparatus, a transmission / reception program, and a data structure of CAD data used for transmitting / receiving three-dimensional CAD data between different CAD systems.

In the mechanical industry, for example, three-dimensional CAD data is exchanged between different CAD (Computer Aided Design) systems and between different CAD applications, such as between a machine manufacturer and a component manufacturer.
Currently, as a CAD data format, a manufacturer-specific format such as Autodesk DXF and an IEEE standard format such as IGES and STEP are known. The data structure in these formats is composed of geometric information based on primitive shapes and polynomial approximation, and phase information such as trim positions such as mother shapes and trim curve groups.

  However, the geometric information has a problem that, since the shape generation model is different for each CAD, when data is exchanged between CAD systems that handle the geometric information differently, the data cannot be exchanged with high accuracy. For example, when CAD data is passed from a CAD system that handles a primitive curved surface as geometric information to a CAD system that handles a Bezier curved surface (polynomial approximation) as geometric information, an approximation error due to polynomial approximation occurs. Further, even when a primitive shape is handled as geometric information between different CAD systems, there is a problem that a conversion error occurs when the expression of the primitive shape is different.

  For this reason, the Japan Automobile Manufacturers Association has established PDQ (Product Data Quality) guidelines and is making efforts to improve CAD data quality problems during data exchange. This PDQ guideline indicates PDQ evaluation items such as “gap between edges” and “bending of the surface” and a reference value indicating what value should be used for each evaluation item.

  However, the above PDQ guideline only allows an error range that does not cause a practical problem in manufacturing operations such as processing and assembly, and is not intended to convey accurate shape information.

  On the other hand, Patent Document 1 discloses a triangular mesh with normal vectors that can be subjected to processing such as compression, storage, transfer, and decompression on triangular mesh data with normal vectors generated from a free-form surface of a three-dimensional shape model. A data structure representing is disclosed.

JP 2004-54736 A

  However, Patent Document 1 described above stores the data structure of a triangular mesh, and cannot store the characteristics of a three-dimensional free-form surface. In order to give accurate information about curved surfaces to triangular meshes, the size of triangular meshes is such that a free-form surface (non-developable surface) can be regarded as a developable surface, that is, a mathematically isothermal coordinate system. However, there is a problem that the amount of CAD data increases because the number of triangular meshes increases due to this subdivision.

  The present invention has been made to solve the above-described problem, and is a CAD data transmission method, CAD data reception method, and CAD data transmission capable of exchanging data between different CADs with high accuracy and a small amount of data. An apparatus, a CAD data receiving apparatus, a CAD data transmitting program, a CAD data receiving program, and a data structure are provided.

In order to solve the above problems, the present invention employs the following means.
A first aspect of the present invention is a CAD data transmission method for transmitting CAD data from a first CAD system to a second CAD system, wherein the computer represents three-dimensional coordinate information representing a curved surface of an object. Based on the representative point selection process of selecting a plurality of representative points from the point group consisting of, and the positional relationship between each of the representative points and a plurality of points in the point group existing around the representative point, A main curvature calculation process for calculating a principal curvature at each representative point, a curvature line creation process for creating a curvature line based on the main curvature at each representative point, a curvature line intersection where the curvature lines intersect, and the curvature A basic quantity calculation process for calculating a first basic quantity and a second basic quantity associated with the representative point in the vicinity of a line intersection; a coordinate value of each curvature line intersection; and the first basic quantity at each curvature line intersection Quantity and Said second basic amount created as CAD data, the CAD data transmission process of transmitting the CAD data, is executed, and the representative point of the line of curvature near an intersection is that it does not necessarily included in the CAD data This is a CAD data transmission method characterized by the above.

  According to the first aspect of the present invention, the CAD data transmitted to the second CAD system includes the coordinate value of the curvature line intersection, and the original CAD given to the curvature line intersection and the first CAD system. A positional parameter (that is, the first basic quantity and the second basic quantity) indicating the relevance of the representative points included in the data can be transmitted. Therefore, it is possible to transmit curved surface information (coordinates of intersections of curvature line grids) restored from the original CAD data with a small amount of data, and information on given points (coordinate values) included in the original CAD data. ) Can be accurately transmitted to the second CAD system.

  According to a second aspect of the present invention, there is provided CAD data for the second CAD system to receive the CAD data created by the CAD data transmission method according to the first aspect of the present invention from the first CAD system. A curved surface reproduction process in which a computer generates a curvature line lattice including a curvature line and a curvature line from each intersection of the curvature lines included in the CAD data, and reproduces a curved surface from the curvature line lattice; A representative that restores the coordinate value of the representative point based on the first basic quantity and the second basic quantity that are positional parameters representing the relationship between the intersection of each curvature line included in the CAD data and the representative point A CAD data receiving method characterized by executing a point restoration process.

  According to the second aspect of the present invention, in the second CAD system, the curved surface can be restored from the coordinates of the intersection of the curvature line lattice, and the first basic quantity set at the lattice intersection of each curvature line And the coordinate value of the representative point can be accurately identified from the second basic quantity. That is, the position information of the point sequence and point group included in the original CAD data given to the first CAD system can be compensated for the curved surface reproduced by the second CAD system.

According to a third aspect of the present invention, there is provided a CAD data transmission method for transmitting CAD data from a first CAD system to a second CAD system, wherein the computer represents three-dimensional coordinate information representing a curved surface of an object. Based on the representative point selection process of selecting a plurality of representative points from the point group consisting of, and the positional relationship between each of the representative points and a plurality of points in the point group existing around the representative point, A main curvature calculation process for calculating a principal curvature at each representative point, a curvature line creation process for creating a curvature line based on the main curvature at each representative point, a curvature line intersection where the curvature lines intersect, and the curvature Adjacent curvature line lattice compression process for calculating a first basic quantity and a second basic quantity between adjacent curvature line intersections adjacent to the line intersection, and the first basic quantity and the second basic quantity at each of the curvature line intersections And each of the above Run the CAD data transmission process of transmitting the coordinate values of the rate line intersections as CAD data, and the adjacent line of curvature intersection, the CAD data transmitting method which is characterized in that in that it does not necessarily included in the CAD data is there.

  According to the third aspect of the present invention, the first basic quantity and the second basic quantity between the intersection of the curvature line and the intersection of the adjacent curvature line grid adjacent to the curvature line intersection are calculated and transmitted as CAD data. Therefore, it is not necessary to transmit information (coordinate values and basic amounts) at the intersections of adjacent curvature line grids, and the amount of transmission data can be reduced.

  According to a fourth aspect of the present invention, there is provided CAD data for the second CAD system to receive the CAD data created by the CAD data transmission method according to the third aspect of the present invention from the first CAD system. A receiving method, wherein a computer generates a curvature line lattice based on each intersection of curvature lines included in the CAD data and reproduces a curved surface, and the first basic at each intersection of the curvature lines A method of receiving CAD data, comprising: performing an adjacent curvature line intersection restoring process of restoring the coordinate value of the adjacent curvature line intersection based on a quantity and the second basic quantity.

  According to the fourth aspect of the present invention, in the second CAD system, from the intersection of the curvature line included in the transmitted CAD data, the first basic quantity, and the second basic quantity, at the intersection of the adjacent curvature line grids. Information can be identified. Thereby, the information (coordinate value and basic quantity) at the intersection of adjacent curvature line grids that are not transmitted can be restored.

According to a fifth aspect of the present invention, there is provided a data structure for causing a computer to transmit / receive CAD data between a first CAD system and a second CAD system, wherein the data structure is a curved surface of an object. A point in the point group consisting of the coordinate value of the point in the point group consisting of three-dimensional coordinate information representing the point or the point on the curved surface of the object near the point and the three-dimensional coordinate information representing the curved surface of the target or wherein the said point the one or more data sets of the first basic weight and the second base quantities associated with the coordinate value of a point on the curved surface of the object in the vicinity, and the first basic weight and the second Curvature line intersections where the curvature lines calculated from the principal curvatures at each representative point selected from within the point group intersect, and the adjacent curvatures adjacent to the representative points near the curvature line intersections or the curvature line intersections This parameter indicates the positional relationship with the line intersection Ri, the data set of the coordinate values and the first basic weight and the second base amount, by the computer, with use in the process of restoring the line of curvature in advance the second CAD system, is estimated from the line of curvature It is a data structure used for processing for restoring points on a curved surface.

  According to the fifth aspect of the present invention, the coordinate value and the first basic quantity and the second basic quantity calculated in advance can be stored in the table, and the CAD data can be transmitted and received. It is possible to transmit / receive not only the coordinate value information but also the information (first basic quantity and second basic quantity) of an arbitrary point on one or more curved surfaces corresponding to the coordinate value. An arbitrary point on one or more curved surfaces can be restored.

According to a sixth aspect of the present invention, there is provided a CAD data transmitting apparatus for transmitting CAD data from a first CAD system to a second CAD system, wherein the computer represents three-dimensional coordinate information representing a curved surface of an object. A representative point selecting means for selecting a plurality of representative points from a point group consisting of: and each positional relationship between the representative points and a plurality of points in a point group existing around the representative points. A main curvature calculating means for calculating a principal curvature at each representative point; a curvature line creating means for creating a curvature line based on the principal curvature at each representative point; a curvature line intersection where the curvature lines intersect; and the curvature A basic quantity calculating means for calculating a first basic quantity and a second basic quantity associated with the representative point in the vicinity of a line intersection; a coordinate value of each curvature line intersection; and the first basic quantity at each curvature line intersection Quantity and Said second basic amount created as CAD data, the CAD data transmitting means for transmitting the CAD data, is executed, and the representative point of the line of curvature near an intersection is that it does not necessarily included in the CAD data This is a CAD data transmitting apparatus characterized by the above.

The seventh aspect of the present invention is the CAD data for the second CAD system to receive the CAD data created by the CAD data transmitting apparatus according to the sixth aspect of the present invention from the first CAD system. a receiver, computer, wherein generating the curvature line grid of curvature lines and curvature lines from each of said line of curvature intersections included in the CAD data, and a curved reproducing means for reproducing a curved surface from the curvature line grating, the A representative that restores the coordinate value of the representative point based on the first basic quantity and the second basic quantity that are positional parameters representing the relationship between the intersection of each curvature line included in the CAD data and the representative point A CAD data receiving apparatus characterized by executing point restoring means.

According to an eighth aspect of the present invention, there is provided a CAD data transmitting apparatus for transmitting CAD data from a first CAD system to a second CAD system, wherein the computer represents three-dimensional coordinate information representing a curved surface of an object. A representative point selecting means for selecting a plurality of representative points from a point group consisting of: and each positional relationship between the representative points and a plurality of points in a point group existing around the representative points. A main curvature calculating means for calculating a principal curvature at each representative point; a curvature line creating means for creating a curvature line based on the principal curvature at each representative point; a curvature line intersection where the curvature lines intersect; and the curvature Adjacent curvature line lattice compression means for calculating a first basic quantity and a second basic quantity between adjacent curvature line intersections adjacent to the line intersection, and the first basic quantity and the second basic quantity at each of the curvature line intersections And each of the above Run the CAD data transmitting means for transmitting the coordinate values of the rate line intersections as CAD data, and the adjacent line of curvature intersection, in the CAD data transmitting apparatus characterized by a point that is not necessarily included in the CAD data is there.

  According to a ninth aspect of the present invention, there is provided CAD data for the second CAD system to receive the CAD data created by the CAD data transmitting apparatus according to the eighth aspect of the present invention from the first CAD system. A receiving device, wherein the computer generates a curvature line lattice based on each intersection of the curvature lines included in the CAD data, and reproduces a curved surface, and the first basic at each intersection of the curvature lines A CAD data receiving apparatus, comprising: an adjacent curvature line intersection restoring unit that restores a coordinate value of the adjacent curvature line intersection based on a quantity and the second basic quantity.

According to a tenth aspect of the present invention, there is provided a CAD data transmission program for transmitting CAD data from a first CAD system to a second CAD system, wherein the computer represents three-dimensional coordinate information representing a curved surface of an object. A representative point selection step of selecting a plurality of representative points from a point group consisting of: and each positional relationship between the representative points and a plurality of points in a point group existing around the representative points. A main curvature calculating step for calculating a principal curvature at each representative point; a curvature line creating step for creating a curvature line based on the main curvature at each representative point; a curvature line intersection at which the curvature lines intersect; and the curvature A basic quantity calculating step for calculating a first basic quantity and a second basic quantity associated with the representative point in the vicinity of the line intersection; a coordinate value of each curvature line intersection; and each curvature line intersection. Said first base weight and said second basic amount created as CAD data that includes a CAD data transmitting step of transmitting the CAD data, is executed, and the representative point of the line of curvature near an intersection is the CAD data A CAD data transmission program characterized in that it is not necessarily included .

  An eleventh aspect of the present invention is the CAD for the second CAD system to receive the CAD data created by the CAD data transmission program according to the tenth aspect of the present invention from the first CAD system. A data reception program, wherein the computer generates a curvature line grid composed of a curvature line and a curvature line from each intersection of the curvature lines included in the CAD data, and reproduces a curved surface from the curvature line grid; and The coordinate value of the representative point is restored based on the first basic quantity and the second basic quantity that are positional parameters representing the relationship between the intersection of each curvature line included in the CAD data and the representative point. A CAD data receiving program characterized by executing a representative point restoration step.

A twelfth aspect of the present invention is a CAD data transmission program for transmitting CAD data from a first CAD system to a second CAD system, wherein the computer expresses a three-dimensional coordinate representing a curved surface of an object. Based on the representative point selection step of selecting a plurality of representative points from the point group consisting of information, and the positional relationship between each of the representative points and a plurality of points in the point group existing around the representative point, A main curvature calculating step for calculating a principal curvature at each representative point; a curvature line creating step for creating a curvature line based on a main curvature at each representative point; a curvature line intersection at which the curvature lines intersect; and Adjacent curvature line lattice compression step for calculating a first basic quantity and a second basic quantity between adjacent curvature line intersections adjacent to the curvature line intersection; the first basic quantity at each of the curvature line intersections; and Two basic weight and the coordinate values of each of said line of curvature intersection running a CAD data transmitting step of transmitting as CAD data, and the adjacent line of curvature intersection, and wherein a is a point that is not necessarily included in the CAD data This is a CAD data transmission program.

  In a thirteenth aspect of the present invention, the second CAD system receives the CAD data created by the CAD data transmission program according to the twelfth aspect of the present invention from the first CAD system. A CAD data receiving program, wherein a computer generates a curvature line lattice based on each curvature line intersection included in the CAD data, and reproduces a curved surface, and the first at each intersection of the curvature lines. A CAD data receiving program that executes an adjacent curvature line intersection restoring program that restores the coordinate value of the adjacent curvature line intersection based on one basic quantity and the second basic quantity.

According to the present invention, it is possible to exchange data between different CADs with high accuracy and a small amount of data.
In addition, according to the present invention, curved surface data such as curved surface shape data and characteristic lines defined on the curved surface are transmitted and received as curved surface points (coordinate values) and characteristic information (first basic amount and second basic amount). Can do. That is, all the CAD data related to the shape to be transmitted / received is handled as point information, and a curve or a curved surface can be handled using only the information on these points.

1 is a block diagram showing a schematic configuration of a CAD system according to a first embodiment of the present invention. It is the flowchart which showed the procedure of the transmission method in the CAD system which concerns on 1st embodiment of this invention. It is explanatory drawing for demonstrating a representative point. It is explanatory drawing for demonstrating the main curvature calculation process. It is the flowchart which showed the procedure of the main curvature calculation process. It is explanatory drawing for demonstrating the main curvature calculation process. It is a figure which shows an example of an angle-curvature table. It is the flowchart which showed the procedure of the receiving method in the CAD system which concerns on 1st embodiment of this invention. It is a schematic diagram which shows the relationship between the curvature line grating | lattice and input point sequence grating | lattice which concern on 1st embodiment of this invention. It is a figure showing the three-dimensional coordinate value of nine measurement points in a torus surface. FIG. 11 is a diagram showing element vectors from nine measurement points and reference points shown in FIG. 10. FIG. 11 is a diagram showing a basic quantity, a main curvature, a Gaussian curvature, and an average curvature calculated based on the nine measurement points shown in FIG. 10. It is a figure showing the three-dimensional coordinate value of nine measurement points in a torus surface. FIG. 14 is a diagram showing element vectors from nine measurement points and reference points shown in FIG. 13. FIG. 14 is a diagram showing a basic quantity, a main curvature, a Gaussian curvature, and an average curvature calculated based on the nine measurement points shown in FIG. 13. It is the flowchart which showed the procedure of the transmission method in the CAD system which concerns on 2nd embodiment of this invention. It is the flowchart which showed the procedure of the receiving method in the CAD system which concerns on 2nd embodiment of this invention. It is a schematic diagram which shows the relationship between the curvature line grating | lattice which concerns on 2nd embodiment of this invention, and an adjacent curvature line grating | lattice. It is a schematic diagram for demonstrating the calculation method of the normal line which concerns on 3rd embodiment of this invention. It is a schematic diagram which shows the relationship between the curvature line grating | lattice based on 4th embodiment of this invention, an adjacent curvature line grating | lattice, and an input point sequence grating | lattice. It is a figure which shows the characteristic line in a ship form. It is a schematic diagram which shows the relationship between the curvature line grating | lattice and specific data information which concern on 5th embodiment of this invention.

[First embodiment]
Hereinafter, a first embodiment of a CAD system for realizing a CAD data transmission method and reception method according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a CAD system according to the first embodiment of the present invention. As shown in FIG. 1, a CAD system according to this embodiment includes a CPU (Central Processing Unit) 1, a main storage device 2 such as a RAM (Random Access Memory), and an auxiliary storage device such as an HDD (Hard Disk Drive). 3. An input device 4 such as a keyboard and a mouse, an output device 5 such as a monitor and a printer, and the like.
Various programs are stored in the auxiliary storage device 3, and the CPU 1 reads out the programs from the auxiliary storage device 3 to the main storage device 2 such as a RAM and executes them, thereby realizing various processes.

  A CAD data transmission / reception process (CAD data transmission method and CAD data reception method) for transmitting CAD data to another CAD system in the CAD system having the above-described configuration will be described with reference to the drawings. The processing shown below is realized, for example, by reading a point sequence generation program stored in the auxiliary storage device 3 in the CPU 1 into the main storage device 2 such as a RAM and executing it.

  First, the CPU 1 acquires point cloud data composed of three-dimensional coordinate information that represents a curved surface of an object included in given CAD data. The point cloud data may be stored in advance in a memory such as the auxiliary storage device 3 built in the CAD system, or may be captured online from another external device. In the present invention, the method for acquiring the point cloud data is not particularly limited.

  When the point cloud data (hereinafter referred to as “point cloud”) is acquired as described above, a plurality of representative points are selected from these point clouds (step SA1: representative point selection process in FIG. 2). For example, in the point group as shown in FIG. 3, a plurality of points are selected as the representative point P0. Subsequently, the main curvature at each representative point P0 is calculated based on the positional relationship between each representative point P0 selected in step SA1 and a plurality of points existing around this representative point P0 (step in FIG. 2). SA2: main curvature calculation process).

Hereinafter, the details of the main curvature calculation process will be described by taking, as an example, a point group belonging to an arbitrarily selected area Q among the point groups shown in FIG.
First, as shown in FIG. 4, element vectors L01, L02, L03, and L04 are generated by connecting the representative point P0 and the respective points P1, P2, P3, and P4 existing around the representative point P0 (FIG. 5). Step SB1).

  Subsequently, a normal vector group (not shown) at the representative point P0 is obtained by calculating the outer product of the element vectors L01, L02, L03, and L04 in all combinations (step SB2 in FIG. 5). Subsequently, an average vector of the normal vector group is obtained, and this average vector is determined as a normal vector n at the representative point P0 (step SB3 in FIG. 5).

  Next, the main curvature is obtained based on the relationship between the normal vector n and the element vectors L01, L02, L03, and L04. Specifically, a tangent vector t orthogonal to the normal line n is set, and an angle formed by the tangent vector t and each of the element vectors L01, L02, L03, and L04 around the normal line n is calculated. Is calculated as a curvature (step SB4 in FIG. 5). The angle formed by the tangent plane including, and the plane including each of the element vectors L01, L02, and L04 is calculated.

For example, when the element vector L02 shown in FIG. 4 has a relationship as shown in FIG. 6 with respect to the representative point P0, the angle formed by the vector component L02 (XY) and the tangent vector t in the tangent plane of the element vector L02. While calculating θ2, the angle formed by the plane including the element vector L02 and the tangent plane including the tangent vector t is obtained as the curvature K2.
Similarly, the angle θ and the curvature K are calculated for the points P1, P3, and P4 shown in FIG.

  When the calculation for points existing around the representative point P0 is completed in this way, these calculation results are plotted in an angle-curvature table in which the angle θ is plotted on the horizontal axis and the curvature K is plotted on the vertical axis. An angle-curvature table is created by connecting the plots by applying Euler's law (step SB5 in FIG. 5). As a result, for example, an angle-curvature table as shown in FIG. 7 is obtained. Note that the plotting to the angle-curvature table may be performed in parallel with the calculation.

Subsequently, in this angle-curvature table, the maximum curvature Kmax and the minimum curvature Kmin are acquired as the main curvature (step SB6 in FIG. 5).
The maximum curvature Kmax and the minimum curvature Kmin at each representative point are obtained by performing the above-described main curvature calculation process for each representative point determined in the point group shown in FIG.
Then, the main direction is determined from the main curvature at each representative point (the maximum and minimum main directions of the main curvature are orthogonal to each other from Euler's formula). By connecting lines along the maximum and minimum main directions determined for each representative point, curvature lines orthogonal to each other are created at each representative point (step SA3 in FIG. 2: curvature line creation process). .

  FIG. 9 shows the curvature line grid generated by the orthogonal curvature lines set at the representative point P0 and the orthogonal curvature lines set at the other representative points, and the input to the transmitting-side CAD system (first CAD system). The schematic diagram with the input point sequence | arrangement grid | lattice contained in the original CAD data which were performed is shown. Here, an example is shown in which the orthogonal coordinate system (uv coordinate) of the curvature line lattice is different from the coordinate system (u′v ′ coordinate) of the input point sequence lattice. As the curvature line, not all the curvature lines set at each representative point are adopted, but they can be thinned out as necessary. Therefore, the coordinates of the intersection of the input point string lattice and the intersection of the curvature line lattice do not always match.

Here, based on the coordinate value of each intersection of the curvature line grid and the coordinate value of each intersection of the input point string grid, the first basic quantity and the second basic quantity corresponding to the parameters indicating the positional relationship between them are calculated ( Step SA4 in FIG. 2: Basic amount calculation process). The first basic quantities are E = s _u ² and F = s _u · s _v , where s _u = ∂s / ∂u and s _v = ∂s / ∂v on the curved surface s (u, v). , G = s _v ² are three parameters. The second basic quantity is a unit normal vector on the curved surface expressed as n = (s _u × s _v ) / | s _u × s _v |, su _u = ∂ ² s / ∂ _u ² , s _uv = ∂ ² s / _∂U∂v, When ^{_{s vv = ∂ 2 s / ∂v}} 2, the three parameters that are defined _{L = n · s uu, M} = n · s uv, with n = n · _{s vv.}
Thus, the basic quantity is not uniquely determined from the curved surface shape, such as the main curvature, but has a property that the value varies depending on the positional relationship between the reference point and the reference point. However, conversely, the basic quantity is uniquely determined if the reference point and the reference point are determined. From such a characteristic of the basic quantity, the basic quantity can be used as a parameter representing the positional relationship between the reference point and the reference point.

  Hereinafter, with respect to the characteristics of the main curvature, the Gaussian curvature, and the average curvature calculated based on the first basic quantity and the second basic quantity described above, and these basic quantities, FIG. 10 to FIG. 12 and FIG. 13 to FIG. A specific description will be given with reference.

In FIG. 10, a certain point on the torus surface having a small circle radius of 2000 mm and a large circle radius of 4000 mm is defined as a reference point (point sequence No. 5 in FIG. 10), and eight points (reference points) in the vicinity of this reference point. Is the three-dimensional coordinate value of the measured data. These nine measurement data are arranged along the main direction as shown in FIG. 11, and the element vectors du and dv from the reference point are orthogonal.
FIG. 12 shows the first basic amounts E ₁ , F ₁ , G ₁ and the second basic amounts L ₁ , M ₁ , N ₁ calculated from the measurement data of FIG. 10 and the two calculated from these basic amounts. The main curvatures c ₁₁ and κ ₂₁ , the Gaussian curvature κ _G1 , and the average curvature κ _m1 are shown.

On the other hand, in FIG. 13, as in FIG. 10 described above, a certain point on the torus surface having a small circle radius of 2000 mm and a large circle radius of 4000 mm is defined as a reference point (point sequence No. 5 in FIG. 13). And three-dimensional coordinate values of measurement data obtained by measuring eight neighboring points (reference points). The reference point in FIG. 13 is equal to the reference point in FIG. 10, but the nine measurement data in FIG. 13 are crossed with element vectors du and dv from the reference point as shown in FIG.
FIG. 15 shows the first basic amounts E ₂ , F ₂ , G ₂ and the second basic amounts L ₂ , M ₂ , N ₂ calculated from the measurement data of FIG. 13, and two calculated from these basic amounts. Main curvatures κ ₁₂ and κ ₂₂ , Gaussian curvature κ _G2 , and average curvature κ _m2 are shown.

  As can be seen by comparing FIGS. 10 to 12 and FIGS. 13 to 15, even if the coordinate values of the reference values on the same curved surface are equal, the first basic quantity and the Although the values of the two basic quantities change, the values such as the main curvature calculated from these basic quantities are equal.

  In FIG. 9, a reference point P′0 that is a curvature line lattice and a reference point R0 that is an input point sequence lattice in the vicinity of the reference point P′0 will be described as an example. From the reference point P′0 to the reference point R0. A first basic quantity which is a parameter representing the positional relationship between the reference point R0 and the reference point P′0 by using the element vector dr toward the reference point and the element vector dv along the v direction of the curvature line from the reference point P′0 A second basic quantity can be calculated.

  Similarly, the first basic quantity and the second basic quantity are calculated from the neighboring input point grid at each intersection of the curvature line grid. In FIG. 9, one input point array grid corresponds to each intersection of the curvature line grid. However, the present invention is not limited to this, and a plurality of input point array grids are provided per intersection of one curvature line grid. You may make it correspond.

  A data structure as shown in Table 1, with the coordinate values of the intersections of the curvature grid obtained as described above and the first and second basic quantities corresponding to these intersections as a set. Are transmitted to the receiving side CAD system (second CAD system) (step SA5 in FIG. 2: CAD data transmission process).

In Table 1, P _{# 1 to #n} are indexes corresponding to the representative points, and X 1 to _n , Y 1 to _n , and Z 1 to _n represent coordinate values. Moreover, E1- _n , F1- _n , G1- _n represents a 1st basic quantity, L1- _n , M1- _n , _N1-n represents a 2nd basic quantity. Kinds 1 to _n are used for classification, for example, whether the coordinate value is the coordinate data of the intersection of the curvature line grid or the coordinate data of the intersection of the input point string grid. In the case of the present embodiment, kind categories indicating coordinate data of intersections of the curvature grid are set in Kinds 1 to _n . The FLG can be used, for example, for function selection. In Table 1, one first basic quantity and second basic quantity are set for each coordinate value. However, the present invention is not limited to this, and a plurality of first basic quantities and one coordinate value are set for one coordinate value. A second basic amount may be set.

In the receiving side CAD system, first, a table having the above data structure is received (step SC1: CAD data receiving process in FIG. 8). A curvature line is restored based on the coordinate value of the intersection of the curvature line grid in the table and the intersection of the curvature line grid around the intersection (step SC2 in FIG. 8: curvature line restoration process).
Then, the curved surface is restored by the curved surface reproduction technique using the curvature line (step SC3 in FIG. 8: curved surface restoration process). For example, Gaussian mapping / inverse mapping is performed based on the curvature line to restore the curved surface. Specifically, after performing coordinate conversion to a parameter space where Euclidean geometry is established, the curved surface is restored by interpolating the curved surface.

  Thereafter, each representative point of the input point sequence grid is restored from the first basic quantity and the second basic quantity set at each intersection of the curvature line grid (step SC4 in FIG. 8: representative point restoration process). Specifically, each curvature line grid vicinity is searched on the curved surface restored in the curved surface restoration process, and the first basic quantity and the second basic quantity in the vicinity of each curvature line grid are stored in the table. A point corresponding to the first basic quantity and the second basic quantity corresponding to the line lattice is identified. Matched points become coordinates included in the input grid point sequence.

  According to the present embodiment, the CAD data transmitted to the receiving-side CAD system includes the coordinate value of the curvature line intersection and the position parameter (that is, the first basic quantity and the relationship between the curvature line intersection and the original CAD data). Second basic quantity) can be stored and transmitted. Therefore, it is possible to transmit the coordinate values of the points included in the original CAD data with a small amount of data, and to accurately transmit the curved surface information restored from the original CAD data to the receiving-side CAD system. Further, the receiving side CAD system can restore an accurate curved surface based on the CAD data transmitted from the transmitting side CAD system, and the coordinate values of the points included in the original CAD data or the coordinates of the measured points. The value can be restored.

[Second Embodiment]
Next, a CAD data transmission / reception method according to the second embodiment of the present invention will be described with reference to the drawings.
The CAD data transmission / reception method according to the present embodiment is different from the CAD data transmission / reception method according to the first embodiment in that the adjacent curvature line lattice compression processing (step SA4 ′ in FIG. 16: adjacent curvature line lattice compression in FIG. 16) is performed. In the process), the information of the curvature line lattice is compressed, and the compressed curvature line lattice is restored in the adjacent curvature line lattice restoration processing (step SC4 ′ in FIG. 17: adjacent curvature line lattice restoration process in FIG. 17) of the receiving CAD system. It is. In the basic quantity calculation process in the present embodiment, the first basic quantity and the second basic quantity are calculated based on the intersection of the curvature line lattice and the intersection of the curvature line adjacent to the intersection.

FIG. 18 shows a state where the process up to the curvature line creation process has been completed in the transmission-side CAD system. In FIG. 18, the curvature lines form an orthogonal uv coordinate system.
Hereinafter, as an example, the curvature line lattice point Pf1 of FIG. 18 will be specifically described.
At the curvature line lattice point Pf1, the first basic amount and the second basic amount are calculated based on the element vector dr for the adjacent curvature line lattice point R1 and the element vector dv along the v direction of the curvature line. The first basic quantity and the second basic quantity calculated here correspond to parameters representing the positional relationship of the reference point R1 with respect to the curvature line grid point Pf1. Therefore, the curvature line grid point Pf1 stores the first basic quantity and the second basic quantity between the curvature line grid point R1 and the adjacent curvature line grid point R1 in the transmission table, so that the reception side CAD system has the adjacent curvature line. Even without the coordinate value information of the lattice point R1, the adjacent curvature line lattice point R1 can be restored from the transmitted curvature line lattice point and the corresponding first basic amount and second basic amount.

  According to the present embodiment, as described above, the coordinates of the intersection of the curvature line lattice and the first basic amount and the second basic amount indicating the positional relationship between the intersections of the curvature line lattice adjacent to the intersection of the curvature line lattice, Therefore, the number of curvature line grids to be transmitted can be reduced. As a result, the transfer data can be compressed with high accuracy, and the amount of data and the calculation time can be reduced.

[Third embodiment]
The CAD data transmission / reception method according to the present embodiment is different from the CAD data transmission / reception method according to the second embodiment in that the normal calculation method used for curved surface reproduction is improved in the receiving-side CAD system. It is.
As shown in FIG. 19, when calculating the normal line N at the reference point P, which is a curvature line lattice point, first, the curvature line lattice point near the reference point Pf1 included in the CAD data transmitted from the transmitting-side CAD system. Based on Pf2, Pf3, Pf4, and Pf5, a normal vector nc is calculated by the outer product of the respective element vectors. Further, based on the points Qr1, Qr2, Qr3, and Qr4 restored by the first basic quantity and the second basic quantity stored in the reference point Pf1 and the curvature line lattice point in the vicinity of the reference point Pf1, the respective element vectors The normal nr is calculated from the outer product of. An average normal N is calculated from these normals nr and nc.

According to the present embodiment, in the receiving-side CAD system, not only the normal line is obtained from the element vector formed by the curvature line lattice, but also the reference curvature line lattice point and the curvature line lattice adjacent to the curvature line lattice point. It is possible to restore a point that has been compressed (thinned out) from the first basic quantity and the second basic quantity of points, and to obtain a normal using a newly created element vector.
Thereby, since the number of element vectors increases, the normal accuracy can be further increased. Further, the interval between the reference curvature line lattice point and the point restored from the first basic amount and the second basic amount is shorter than the interval between the reference curvature line lattice point and the four adjacent curvature line lattice points. Therefore, the lengths of the element vectors can be made substantially equal, and the normal accuracy can be increased.
Note that this normal calculation method can also be used in combination with the first embodiment described above.

[Fourth embodiment]
The CAD data transmission / reception method according to the fourth embodiment is a combination of the above-described CAD data transmission / reception methods according to the first embodiment and the second embodiment. That is, as shown in FIG. 20, at a certain reference point P0 on the curvature line lattice, the first basic quantity and the second basic amount based on the reference point P0 and the intersection P′1 of the curvature line lattice adjacent to the reference point P0. And calculating the first basic quantity and the second basic quantity based on the adjacent curvature line lattice point P′1 and the input point sequence lattice point R1 in the vicinity of the adjacent curvature line lattice point P′1, It is set in the transmission table as CAD data and transmitted to the receiving side CAD system.

  A table having the data structure shown in Table 1 can be used as the transmission table used here. However, in this case, since a plurality of first basic quantities and second basic quantities need to correspond to one reference point, a plurality of first basic quantities and second basic quantities are stored for one index. It will be.

  According to this embodiment, the positional relationship with the points adjacent to the curvature line lattice points is given as the first basic amount and the second basic amount, and the adjacent curvature line lattice points are compressed (thinned out) to transmit data. However, since the adjacent curvature line lattice points can be restored at the time of curved surface reproduction in the receiving side CAD system, the curved surface can be reproduced with high accuracy while reducing the data amount and the calculation amount. Furthermore, it is possible to compensate for a point sequence / point group given as an input point sequence grid near the adjacent curvature line grid point.

[Fifth embodiment]
The CAD data transmission / reception method according to the fifth embodiment is different from the CAD data transmission / reception method according to the first embodiment described above in that the specific data information is embedded in the basic quantity calculation process. .
The specific data information is information related to feature lines such as contour lines, vertical cross section lines, horizontal cross section lines, and cross section lines. FIG. 21 shows an example of ship-type specific data information.

  The specific data information embedding process will be described below with reference to FIG. FIG. 22 is a schematic diagram illustrating a part of a curved surface generated in the transmission-side CAD system. There are 5 × 5 points of curvature line lattice points, and each of the curvature line lattice points is connected by a curvature line. In FIG. 22, three thick dotted lines running substantially to the left and right represent feature lines (corresponding to WL (horizontal section line) in FIG. 21).

In FIG. 22, the feature line located at the top will be described with focus. A point P _c2 having specific data information on the feature line inside the curvature line mesh formed by the four curvature line grids is selected, and on the feature line at a position opposite to each other with the curvature line grid point P _c3 on the feature line interposed therebetween Specific data _Pc4 is selected. Other feature lines are selected in the same manner, and a set of 9 points is selected as a whole. In order to use these as information of a given point sequence / point group, a curved surface analysis is performed using the set of these nine points, and the first basic quantity and the second basic quantity at P _c0 are calculated. These first basic quantity and second basic quantity are added as information of the curvature line intersection P _c0 and stored in the transmission table. This process is performed over the entire curved surface.

The calculation method of the first basic amount and the second basic amount in the present embodiment is not limited to the method of calculating using the 9-point set as described above. For example, the calculation is performed by the method described in the first embodiment. May be. That is, the first basic quantity and the second basic quantity may be calculated using an element vector from the reference point P _c0 to P _c1 and an element vector along one direction of the curvature line.

Note that when selecting specific data information on a feature line, a curved line has already been generated at the time of this processing, so it is possible to set a curvature line at an arbitrary position on the curved surface. Therefore, it is possible to select three points as specific data on the feature line and set the curvature line so that the center point (P _c0 , P _c3 , P _{c7 in} this embodiment) is a curvature line lattice. It becomes.
Thereby, it is possible to restore the feature data information on the feature line given in advance using the curvature line lattice point, the first basic quantity, and the second basic quantity in the reproduction-side CAD system.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and includes design changes and the like within a scope that does not depart from the gist of the present invention. .
In the above-described embodiment, the present invention includes a developable surface excluding a plane having a principal curvature of zero, that is, a curvature that is all zero with respect to a tangential plane, and a non-expandable surface except a spherical surface having the same principal curvature. Although it has been applied to free-form surfaces, for example, straight lines are used for planes instead of curvature lines, and geodesic lines are used for spherical surfaces, so that the intersections of each line are orthogonal to each other. Alternatively, it can be applied to a plane and a spherical surface by selecting a geodesic line.
Note that the main curvature is a normal curvature at which the normal curvature, which is the curvature of the normal section, is maximum and minimum.

1 CPU
2 Main storage device 3 Auxiliary storage device 4 Input device 5 Output device

Claims (13)

A CAD data transmission method for transmitting CAD data from a first CAD system to a second CAD system,
Computer
A representative point selection process for selecting a plurality of representative points from a group of points consisting of three-dimensional coordinate information representing the curved surface of the object;
A main curvature calculation process for calculating a principal curvature at each representative point based on a positional relationship between each representative point and a plurality of points in a point group existing around the representative point; and
A curvature line creation process for creating a curvature line based on the principal curvature at each representative point;
A basic quantity calculation step of calculating a first basic quantity and a second basic quantity that are associated between a curvature line intersection where the curvature lines intersect each other and the representative point in the vicinity of the curvature line intersection;
A CAD data transmission step of creating the coordinate value of each curvature line intersection and the first basic quantity and the second basic quantity at each curvature line intersection as CAD data and transmitting the CAD data;
Run
The CAD data transmission method, wherein the representative point in the vicinity of the intersection of the curvature lines is a point that is not necessarily included in the CAD data. The CAD data receiving method for receiving the CAD data created by the CAD data transmitting method according to claim 1, wherein the second CAD system is from the first CAD system,
Computer
A curved surface reproduction process of generating a curvature line grid composed of a curvature line and a curvature line from each of the intersections of the curvature lines included in the CAD data, and reproducing a curved surface from the curvature line grid;
The coordinate value of the representative point is restored based on the first basic quantity and the second basic quantity that are positional parameters representing the relationship between the intersection of each curvature line included in the CAD data and the representative point. Representative point restoration process,
The CAD data receiving method characterized by performing these. A CAD data transmission method for transmitting CAD data from a first CAD system to a second CAD system,
Computer
A representative point selection process for selecting a plurality of representative points from a group of points consisting of three-dimensional coordinate information representing the curved surface of the object;
A main curvature calculation process for calculating a principal curvature at each representative point based on a positional relationship between each representative point and a plurality of points in a point group existing around the representative point; and
A curvature line creation process for creating a curvature line based on the principal curvature at each representative point;
Adjacent curvature line lattice compression process for calculating a first basic quantity and a second basic quantity between a curvature line intersection where the curvature lines intersect each other and an adjacent curvature line intersection adjacent to the curvature line intersection;
A CAD data transmission process of transmitting the first basic quantity and the second basic quantity at each curvature line intersection and the coordinate value of each curvature line intersection as CAD data;
Run
The CAD data transmission method, wherein the adjacent curvature line intersection is a point that is not necessarily included in the CAD data. The CAD data receiving method for receiving the CAD data created by the CAD data transmitting method according to claim 3, wherein the second CAD system is from the first CAD system,
Computer
A curved surface reproduction process of generating a curvature line grid based on each intersection of the curvature lines included in the CAD data and reproducing a curved surface;
Based on the first basic quantity and the second basic quantity at the intersection of each curvature line, an adjacent curvature line intersection restoring process for restoring the coordinate value of the adjacent curvature line intersection;
The CAD data receiving method characterized by performing these. A data structure for causing a computer to send and receive CAD data between a first CAD system and a second CAD system,
The data structure is
The coordinate value of a point in the point cloud consisting of three-dimensional coordinate information representing the curved surface of the object or a point on the curved surface of the object near the point;
One or more first basic quantities and second values associated with the coordinate values of a point in a point group composed of three-dimensional coordinate information representing the curved surface of the object or a point on the curved surface of the object near the point A basic quantity dataset,
Including
Curvature line intersections where the curvature lines calculated from the principal curvatures at the respective representative points selected from within the point group are the first basic quantity and the second basic quantity, and a representative point near the curvature line intersection or A parameter representing a positional relationship with an adjacent curvature line intersection adjacent to the curvature line intersection;
The coordinate value and the data set of the first basic quantity and the second basic quantity are used by the computer for the process of restoring the curvature line in the second CAD system, and on the curved surface estimated from the curvature line. A data structure used in the process of restoring points. A CAD data transmitting apparatus for transmitting CAD data from a first CAD system to a second CAD system,
Computer
Representative point selection means for selecting a plurality of representative points from a point group consisting of three-dimensional coordinate information representing the curved surface of the object;
Based on the positional relationship between each representative point and a plurality of points in a point group existing around the representative point, main curvature calculating means for calculating a principal curvature at each representative point,
Curvature line creating means for creating a curvature line based on the main curvature at each representative point;
A basic quantity calculating means for calculating a first basic quantity and a second basic quantity that are associated between a curvature line intersection where the curvature lines intersect each other and the representative point in the vicinity of the curvature line intersection;
CAD data transmitting means for generating the first basic quantity and the second basic quantity at each curvature line intersection and the first basic quantity and the second basic quantity as CAD data and transmitting the CAD data;
Run
The CAD data transmitting apparatus, wherein the representative point in the vicinity of the intersection of the curvature lines is a point that is not necessarily included in the CAD data. The CAD data receiving device for receiving the CAD data created by the CAD data transmitting device according to claim 6, wherein the second CAD system is from the first CAD system,
Computer
A curved surface reproducing means for generating a curvature line grid composed of a curvature line and a curvature line from each curvature line intersection included in the CAD data, and reproducing a curved surface from the curvature line grid;
The coordinate value of the representative point is restored based on the first basic quantity and the second basic quantity that are positional parameters representing the relationship between the intersection of each curvature line included in the CAD data and the representative point. Representative point restoration means,
The CAD data receiving apparatus characterized by performing these. A CAD data transmitting apparatus for transmitting CAD data from a first CAD system to a second CAD system,
Computer
Representative point selection means for selecting a plurality of representative points from a point group consisting of three-dimensional coordinate information representing the curved surface of the object;
Based on the positional relationship between each representative point and a plurality of points in a point group existing around the representative point, main curvature calculating means for calculating a principal curvature at each representative point,
Curvature line creating means for creating a curvature line based on the main curvature at each representative point;
Adjacent curvature line lattice compressing means for calculating a first basic quantity and a second basic quantity between a curvature line intersection where the curvature lines intersect each other and an adjacent curvature line intersection adjacent to the curvature line intersection;
CAD data transmitting means for transmitting the first basic quantity and the second basic quantity at each curvature line intersection and the coordinate value of each curvature line intersection as CAD data;
Run
The CAD data transmitting device, wherein the adjacent curvature line intersection point is not necessarily included in the CAD data. The second CAD system is a CAD data receiving device for receiving the CAD data created by the CAD data transmitting device according to claim 8 from the first CAD system,
Computer
Curved surface reproducing means for generating a curved line lattice based on each intersection of the curved lines included in the CAD data and reproducing a curved surface;
Based on the first basic quantity and the second basic quantity at the intersection of each curvature line, an adjacent curvature line intersection restoring means for restoring the coordinate value of the adjacent curvature line intersection;
The CAD data receiving apparatus characterized by performing these. A CAD data transmission program for transmitting CAD data from a first CAD system to a second CAD system,
Computer
A representative point selection step of selecting a plurality of representative points from a point group consisting of three-dimensional coordinate information representing the curved surface of the object;
A main curvature calculating step for calculating a principal curvature at each representative point based on a positional relationship between each representative point and a plurality of points in a point group existing around the representative point; and
A curvature line creating step for creating a curvature line based on the principal curvature at each representative point;
A basic quantity calculating step for calculating a first basic quantity and a second basic quantity that are associated between a curvature line intersection where the curvature lines intersect each other and the representative point in the vicinity of the curvature line intersection;
A CAD data transmission step of creating the coordinate value of each curvature line intersection and the first basic quantity and the second basic quantity at each curvature line intersection as CAD data, and transmitting the CAD data;
Run
The CAD data transmission program, wherein the representative point in the vicinity of the intersection of the curvature lines is not necessarily included in the CAD data. The CAD data receiving program for receiving the CAD data created by the CAD data transmitting program according to claim 10, wherein the second CAD system is from the first CAD system,
Computer
A curved surface reproduction step of generating a curvature line grid composed of a curvature line and a curvature line from each curvature line intersection included in the CAD data, and reproducing a curved surface from the curvature line grid;
The coordinate value of the representative point is restored based on the first basic quantity and the second basic quantity that are positional parameters representing the relationship between the intersection of each curvature line included in the CAD data and the representative point. A representative point restoration step;
A CAD data receiving program characterized by executing A CAD data transmission program for transmitting CAD data from a first CAD system to a second CAD system,
Computer
A representative point selection step of selecting a plurality of representative points from a point group consisting of three-dimensional coordinate information representing the curved surface of the object;
A main curvature calculating step for calculating a principal curvature at each representative point based on a positional relationship between each representative point and a plurality of points in a point group existing around the representative point; and
A curvature line creating step for creating a curvature line based on the principal curvature at each representative point;
Adjacent curvature line lattice compression step for calculating a first basic quantity and a second basic quantity between a curvature line intersection where the curvature lines intersect each other and an adjacent curvature line intersection adjacent to the curvature line intersection;
A CAD data transmission step of transmitting the first basic quantity and the second basic quantity at each curvature line intersection and the coordinate value of each curvature line intersection as CAD data;
Run
The CAD data transmission program characterized in that the intersection of adjacent curvature lines is not necessarily included in the CAD data. The second CAD system is a CAD data receiving program for receiving the CAD data created by the CAD data transmitting program according to claim 12 from the first CAD system,
Computer
A curved surface reproduction program for generating a curvature line grid based on each intersection of the curvature lines included in the CAD data and reproducing a curved surface;
Based on the first basic quantity and the second basic quantity at the intersection of each curvature line, an adjacent curvature line intersection restoration program that restores the coordinate value of the adjacent curvature line intersection;
A CAD data receiving program characterized by executing

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