JPH06149333A - Surface model generation method based on three-dimensional coordinate data - Google Patents

Abstract

(57) [Abstract] [Purpose] A curved surface based on three-dimensional coordinate data that enables efficient optimization expression that matches the shape of the object to be measured at high speed without impairing the data volume reduction effect. The purpose is to provide a model generation method. A virtual data curved surface P constituted by a plurality of polygonal surfaces obtained by connecting a dividing line L that divides a coordinate data group representing a three-dimensional shape into a plurality of regions and connecting the coordinate data groups representing the three-dimensional shape. And a cutting plane M for cutting the three-dimensional shape in an arbitrary direction, and a curved surface having a quadrilateral region surrounded by the dividing line L as a unit region is generated to generate the three-dimensional shape. Generate a curved surface model of.

Description

Detailed Description of the Invention

[0001]

The present invention relates to three-dimensional coordinate data which is a shape processing method for converting a three-dimensional coordinate data group representing a three-dimensional shape of an object measured by a three-dimensional digitizer into CAD data. Based on the curved surface model generation method,
For example, the present invention relates to a curved surface model generation method based on three-dimensional coordinate data used to read shape data of an arbitrary die or shape model and generate design drawings or the like of them.

[0002]

2. Description of the Related Art A three-dimensional coordinate data group representing a three-dimensional shape of an object measured by a three-dimensional digitizer generally has a large capacity and also has a definition for relating the coordinates forming the three-dimensional coordinate data group. Since it is not done, it is difficult to handle as CAD data. Therefore, it is necessary to define the relationship between the coordinates by complementing the coordinates with a surface to generate a curved surface model. Conventionally, as a curved surface model generation method based on this type of three-dimensional coordinate data, a three-dimensional coordinate data group other than unnecessary points such as error reading points,
A spline curve that passes through all points along the measurement direction of the data by the three-dimensional digitizer is generated, and a Coons blending (Coons b) curve is generated for the curve network formed by the plurality of generated spline curves.
There is a method of generating an interpolated curved surface by a method such as lending). Here, in order to express a tens of thousands of three-dimensional coordinate data group with a curved surface with a small data capacity, the flat surface of the measured object is roughly divided, that is, divided into rough quadrilateral regions. Efficient optimization such as expressing the curved surface with reduced capacity, and detailing where the surface of the DUT is highly undulating, that is, dividing it into fine quadrilateral regions and expressing the curved surface with sufficient capacity data. Need to express.

[0003]

However, in the above-mentioned conventional technique, in order to avoid lengthening the processing time for generating the spline curve along an arbitrary direction, the measured data in the coordinate data group is to be measured. Since the spline curve is generated along the data measurement direction by the 3D digitizer regardless of the shape of the object, the degree of freedom of division into the quadrilateral region is limited, making efficient optimization expression difficult. There was a drawback. Furthermore, since the spline curve that passes all designated points is generated, the data capacity of the spline curve itself is not reduced, and it is difficult to reduce the data capacity as a whole. An object of the present invention is to eliminate the above-mentioned conventional drawbacks.

[0004]

To achieve this object, a first characteristic configuration of a curved surface model generation method based on three-dimensional coordinate data according to the present invention is a coordinate data group representing a three-dimensional shape in a three-dimensional Euclidean space. Is divided into a plurality of areas, and a virtual data curved surface composed of a plurality of polygonal surfaces obtained by connecting coordinate data groups representing the three-dimensional shape and the three-dimensional shape are cut in an arbitrary direction. It is defined as a line of intersection with the cutting plane, and a curved surface having a quadrilateral region surrounded by the dividing line as a unit region is generated. The second characteristic configuration is mesh data obtained by connecting coordinate data groups representing a three-dimensional shape in a three-dimensional Euclidean space, and two-dimensional coordinates data obtained by arbitrarily selecting from the coordinate data group. In the three-dimensional Euclidean space corresponding to the point sequence formed by obtaining the mapping to the Euclidean space, finding the intersection of the spline curve passing through the mapping data for the selected coordinate data and the mapping data for the mesh data, By defining a polygonal line connecting point sequences as a dividing line that divides a coordinate data group representing a three-dimensional shape into a plurality of regions, and generating a curved surface having a quadrilateral region surrounded by the dividing lines as a unit region. The point is that the curved surface model of the three-dimensional shape is generated.

[0005]

According to the first characteristic configuration, a plurality of polygon surfaces obtained by connecting coordinate data groups representing a three-dimensional shape, for example, as shown in FIG. 1, are represented by triangles having three adjacent points as vertices. By forming a virtual data curved surface of the measured object on a flat surface, etc., the surface of the measured object is roughly flat, and the surface of the measured object is rough. The line of intersection with the cutting plane that cuts in any direction is defined as the dividing line. A unit area is a quadrilateral area surrounded by the above dividing lines, and, for example, NURBS (Non
Uniform Rational B-Splin
e) A curved surface or the like is generated, and a plurality of generated curved surface groups are connected to generate a three-dimensional curved surface model.

According to the second characteristic configuration, as shown in FIG. 7, coordinate data P obtained by arbitrarily selecting from a coordinate data group representing a three-dimensional shape in the three-dimensional Euclidean space (x, y, z). _i (x, y, z), (i = 0, 1, ...,
n) is specified to obtain mapping data Q _i (u, v), (i = 0,1, ..., N) in the two-dimensional Euclidean space (u, v), and mapping data Q _i (u, v) , (I = 0, 1, ...,
n) is derived and a spline curve C is derived,
As shown in FIG. 8, the three-dimensional Euclidean space (x, y,
The mapping data to the two-dimensional Euclidean space (u, v) for the mesh data obtained by connecting the coordinate data groups representing the three-dimensional shape in z) is obtained. Next, the intersection points Q ′ _j (u ′, v ′), (of the mesh data and the spline curve C in the two-dimensional Euclidean space (u, v),
_j = 0, 1, ..., N ′), and the inverse mapping P ′ of the intersection Q ′ to the three-dimensional Euclidean space (x, y, z)
Define _j (x, y, z), (j = 0, 1, ..., N ′) as a spline type dividing line. Similarly to the above, for example, NURBS (Non Uniform R
relational B-Spline) curved surface etc. are generated,
The three-dimensional curved surface model is generated by connecting the generated plural curved surface groups.

[0007]

As described above, according to the present invention, it is possible to generate a dividing line in an arbitrary direction in a short time. Therefore, an efficient optimization expression that matches the shape of the object to be measured can be obtained with a reduced data capacity. It has become possible to provide a curved surface model generation method based on three-dimensional coordinate data that can be performed at high speed without impairing the effect.

[0008]

EXAMPLES Examples will be described below. As shown in FIG. 2, a data processing device relating to a curved surface model generation method based on three-dimensional coordinate data includes a three-dimensional digitizer 2 for reading the shape data of a shape model 1 as an object to be measured and a storage medium 3 such as a floppy disk. Via the curved surface model generation device 4 for converting the coordinate data group represented by the surface shape xyz rectangular coordinate system of the geometric model 1 read by the three-dimensional digitizer 2 into data suitable for the CAD system, and the curved surface model generation. The data conversion processing device 5 converts the output data of the device 4 into a general-purpose IGES file as an intermediate file.

The curved surface model generation device 4 is composed of a graphics computer having a high resolution CRT as a display device, and is input via the storage medium 2 and displayed on the CRT as shown in FIG. With respect to the coordinate data group thus created, a portion of the shape model 1 whose surface is flat is roughly divided, and a portion of the shape model 1 where the surface is highly undulated is divided into details, so that a pointing device such as a mouse (not shown) is used. Using the device, the cutting plane P representing the boundary of the region to be divided is input. The curved surface model generation device 4 configures the virtual data curved surface M of the shape model 1 with a plurality of polygon surfaces obtained by connecting each coordinate point to the coordinate data group representing the three-dimensional shape. For example, as shown in FIG. 1, the virtual data curved surface M of the shape model 1 is formed by a plane represented by a triangle having three adjacent points as vertices in the coordinate data group representing the three-dimensional shape. The intersection line between the cutting plane P and the virtual data curved surface M is defined as a division line L, and the division line L
A formula that represents is calculated and derived. That is, the dividing line L is a curve that strictly lies on the virtual data curved surface M. As shown in FIG. 4, a plurality of dividing lines L are defined by the above-described procedure, and the region surrounded by the dividing lines L is divided into quadrilaterals, and the quadrilateral region surrounded by each dividing line is divided. Is used as a unit area for subsequent processing.

Generally, a spline curved surface such as NURBS is a "piecewise polynomial surface", which is a surface obtained by smoothly connecting polynomial expressions. When the spline curved surface is composed of m × m patches, “m” is called the number of basic patches, and the part represented by the polynomial expression is called a “patch”. Upon generation, first, the number of basic patches and the allowable error are designated, and the following processing is performed for each area. Here, the tolerance is the same for all patches. First, the curved surface S is generated by the least square method with the fineness of the number of basic patches, and the distance between each generated curved surface S and the virtual data curved surface M is calculated. The distance d between the curved surface S and the virtual data curved surface M is the maximum distance between the points forming each surface, and the distance d between the points.
_i is calculated by the following formula. d _i = dis (F (u _i , v _i ), S (u _i , v _i )) where F (u _i , v _i ), S (u _i , v _i ) are the curved surface S and the virtual data. It is mapping data of the curved surface M to the two-dimensional Euclidean space (u, v). The distance S between the curved surface S and the virtual data curved surface M deviates from the allowable error range.
Then, the number of patches is doubled vertically and horizontally, and the curved surface is recalculated. By repeating the above calculation until it is within the allowable error range, all the curved surfaces S are within the allowable error. Therefore, a flat portion is a surface that is roughly expressed without the need for the recalculation, and a highly undulating portion is finely recalculated.

A curved surface model corresponding to the shape model 1 is formed by connecting the curved surfaces stretched for each unit area by the above-described procedure so as to obtain tangential plane continuity or curvature continuity between the plurality of unit curved surfaces. To generate.

Another embodiment of the present invention will be described below. In the above method, the data read by the three-dimensional digitizer is not only the direct-motion type data obtained by reading the DUT from one direction, but also the data obtained by combining the data read from a plurality of directions. It can be applied to dynamic rotation type data, rotation type data obtained by rotation, and the like.

In the above embodiment, the virtual data curved surface was described as a plane represented by a triangle having three adjacent points as vertices. However, other virtual data curved surfaces such as a quadrangle can be used. It may be a polygonal shape or a spline curved surface.

The method of generating a curved surface for each quadrilateral region is not limited to a unique one, but NURBS (Non
Uniform Rational B-Splin
e) A known curved surface generation method such as a curved surface generation method can be appropriately used.

In the above embodiment, a plurality of dividing lines L for dividing the coordinate data group representing the three-dimensional shape in the three-dimensional Euclidean space into a plurality of regions are obtained by connecting the coordinate data groups representing the three-dimensional shape. Although the virtual data curved surface P formed by the polygon surface and the cutting plane M for cutting the three-dimensional shape in any direction have been described, the dividing line L is generated by the following method. In addition, for mesh data (contour data of the polygon surface) obtained by connecting coordinate data groups representing a three-dimensional shape in a three-dimensional Euclidean space, and coordinate data obtained by arbitrarily selecting from the coordinate data group A mapping to the two-dimensional Euclidean space is obtained, and a spline curve passing through the mapping data for the selected coordinate data and a mapping data for the mesh data are obtained. L _1, L ₂ in broken line (e.g. FIG. 5 the calculated intersection point, formed by connecting point sequences in a three-dimensional Euclidean space corresponding to the sequence of points consisting of the intersection of the,
It is also possible to adopt the method of expressing by L ₃ , L ₄ ).

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a curved surface model generation method.

FIG. 2 is a block diagram of the system.

FIG. 3 is a configuration diagram of a main part

FIG. 4 is a conceptual diagram showing a display state of a coordinate data group representing a three-dimensional shape on a CRT.

FIG. 5 is a conceptual diagram showing a state in which coordinate data groups representing a three-dimensional shape are divided by dividing lines.

FIG. 6 is a conceptual diagram of the completed curved surface model.

FIG. 7 is an explanatory diagram of a curved surface model generation method according to another embodiment.

FIG. 8 is an explanatory diagram of a curved surface model generation method according to another embodiment.

[Explanation of symbols]

 L division line M cut surface P virtual data curved surface

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 12, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Claims (2)

[Claims] 1. A plurality of polygons obtained by connecting a dividing line (L) that divides a coordinate data group representing a three-dimensional shape in a three-dimensional Euclidean space into a plurality of regions by connecting the coordinate data group representing the three-dimensional shape. A quadrilateral region defined by a line of intersection of a virtual data curved surface (P) configured by a surface and a cutting surface (M) that cuts the three-dimensional shape in an arbitrary direction, and is surrounded by the dividing line (L). A method of generating a curved surface model based on three-dimensional coordinate data for generating a curved surface having a unit area as a unit area and generating a curved surface model of the three-dimensional shape. 2. A mesh data obtained by connecting coordinate data groups representing a three-dimensional shape in a three-dimensional Euclidean space, and a two-dimensional Euclidean space for coordinate data obtained by arbitrarily selecting from the coordinate data group. The map is obtained, the intersection of the spline curve (C) passing through the mapping data for the selected coordinate data and the mapping data for the mesh data is obtained, and the point in the three-dimensional Euclidean space corresponding to the point sequence formed by the intersection is obtained. A polygonal line connecting the columns is defined as a dividing line (L) that divides a coordinate data group representing a three-dimensional shape into a plurality of regions, and a quadrilateral region surrounded by the dividing line (L) is a unit region. A curved surface model generation method based on three-dimensional coordinate data for generating a curved surface and generating a curved surface model of the three-dimensional shape.