JPS61175778A - Formation of form model - Google Patents

Abstract

PURPOSE:To attain the automatic production of an inside shell by forming an external form model as the gathering of faces and obtaining a face with the offset of desired thickness on a normal line which defines each face. CONSTITUTION:The position vector P2 of the face A is obtained from a position vector P1 which defines the face A, a normal line unit vector N1 and the thickness t1. Then ridgelines A' and B' are obtained from equations I and II of shell faces A' and B'. An equation III is obtained to obtain the equation IV of a face D'. Then the XYZ coordinates of apexes A', B' and D' are obtained as the intersecting points between the face D' (equation IV) and ridgelines A' and B' (equation III). Such operations are carried out with all faces to obtain the existing ridgelines and apexes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for creating a shape model in a computer-aided design system.

In recent years, computer-aided design systems (hereinafter referred to as CAD) have become popular, but CAD, which expresses three-dimensional shapes, is particularly capable of: ■ Displaying 3D images in the mind on graphics.

■ Acting on behalf of experiments and prototyping.

■ Confirmation of processes and operations of production equipment such as tools.

It is widely applied from the conceptual stage of design to production simulation.

The graphical representation of 3D images in the 3D shape CAD described above is the basis of creating a shape model of a product, but the means to easily develop it into an actual product than a completed model is still in its infancy. There is a demand for a simple method of automatically creating a hollow shape model having a predetermined wall thickness, for example, to move from the shape model to the next step.

[Conventional technology]

Although many methods for creating three-dimensional shape models have been studied and become popular, a model with a predetermined thickness from a completed model is created using a method similar to the above-mentioned external shape model.

In other words, 1. For example, when creating a shape model of a molded part such as a telephone, while interacting with the CRT display screen, (1) complete a shape model of the external shape of the telephone with the inside filled, and (3) create the external shape so that it has a predetermined wall thickness. Create the shape of the part to be hollowed out (cutter) in the same way as the external shape above, and
A hollow shape model was created by subtracting the cutter from the external shape.

The above cutter shape and hollow model are used for creating injection molding molds and simulating the placement of internal structural parts, etc., but the dimensions are based on the cutter creation method described in (■) using the same method as the external shape. The burden on the designer is extremely heavy, such as how to achieve alignment accuracy.

The method for creating a shape model will be explained below with reference to FIGS. 2(a) (bl(c)).

FIG. 2(a) is a diagram showing the basic functions of shape modeling.

(1) is a function that generates basic solids such as a rectangular parallelepiped, 9 cones, and 1 sphere, and can be made to any size by direct instruction with a light pen, etc. on one display screen, or by manually specifying coordinates, diameter, basic solids, etc. It is possible to create and display basic solids.

(2) is a function for creating free curves and free curved surfaces.

It can be expressed by specifying multiple coordinate points.9 For example, in the case of a free-form surface, Bezier+C
Equations such as oons and B-spline are well known.

(3) is a set calculation function, which allows a plurality of three-dimensional models to be arbitrarily set by giving coordinates to each model.

(4) is a local shape change function, which is a function to partially change the shape as shown in FIG.

(5) is a movement/rotation function, which is a function to arbitrarily move/rotate the three-dimensional model created in 9.

In addition to the basic modeling functions mentioned above, calculation functions such as coordinate values of vertices, length of edges, distance between solids, etc.

It is equipped with display functions such as hidden line removal and wire frame display.

The flow for digitizing the external shape model created by the basic modeling function described above will be explained using FIG. 2(b) (C1).

In FIG. 2+al, 1 indicates an example of a created external shape model, which is a cube. This model is defined by six surfaces, and each surface is defined by the position vector and normal of a point on two surfaces. For example, each coefficient of the equation % of the surface 3 can be obtained from the position vector P of the surface 3 and the normal vector N.

Furthermore, the edge Ia5 is determined as the intersection line between the surface 3 and the surface 4, and the apex 7 is determined as the intersection between the edge line 5 and the surface 6.

Therefore, as shown in FIG. 2(C), all the surfaces constituting the external shape model 1 can be converted into numerical values by performing the above calculation.

In FIG. 2(b), 2 is the cutter of the external shape model 1 (hereinafter referred to as the inner shell, and the external shape model is referred to as the outer shell). A shape model with the wall thickness subtracted (hereinafter referred to as offset) is created using the shape modeling function described above.

[Problem that the invention seeks to solve]

As explained above, when creating an inner shell or hollow model, it is necessary to create a shape model with a predetermined wall thickness while referring to the outer shell.

There was a problem in that it placed a heavy burden on the operator.

Therefore, the present invention aims to provide an automatic generation method for creating an inner shell or hollow model by giving a wall thickness to the external shape model.

[Means for solving the problem] The problem with the above conventional method is that firstly, a point having a predetermined wall thickness length is set on the normal line from the surface, and secondly, the position vector of the set point and the This problem can be solved by the shape model creation method of the present invention, which creates a surface having the normal line and thirdly synthesizes each of the created surfaces to create a shape model having a predetermined thickness.

[Effect]

The gist of the present invention will be explained using FIG. 1).

In Figure 1), surface 2 A is located at point Ao on that surface.
is expressed by a position vector PL and a normal unit vector N1, then a point Ao'' on the normal vector Nl is
To obtain a roadside shell with a predetermined wall thickness t1 from point AO, +
Nl side) Surface A, which is the inner shell of surface A with a predetermined thickness, by determining the position vector P2 of the above point A O+.

In the case of a plane, the surface equation is ax+by+cz=A Position vector P2゜However, a, b, c, A are P2. It will be expressed as a value determined from Nl.

Each face of the inner shell of each face is determined by the above procedure.

Next, the edges and further the intersections (vertices) of the edges can be determined.

In the case of free-form surfaces, etc., the curved surface is defined by multiple points, but in this case, one position vector and normal are found for all points to find a point with a predetermined wall thickness, and from those points a new free-form surface is defined. Define a surface.

As described above, an inner shell or hollow model can be easily created simply by specifying a predetermined wall thickness based on an external shape model.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1(a) is a block diagram showing the configuration of a computer system implementing the present invention, and FIG. 1(C) is a flowchart of an example of operation.

In FIG. 1(a), 10 is a central processing unit CPU.

Reference numeral 11 denotes a main storage unit, and 12 a shape model generation unit, which generates a shape model according to input instructions as described above.
2b, set calculation unit 12c9, local shape change unit 12d, movement/rotation control unit 12e.

It is composed of a graphic characteristic calculation section 12f.

13 is a shell calculation unit according to the present invention; 14 is a display control unit that controls display on the CRT display unit 15 and input of the light pen 16; 1; creation of display data; 9; display management; element extraction; and 17; 18 is a file device, and 19 is an output section.

In the above system configuration, the operator uses the light pen 1
6. A shape model is created while interacting with the CRT display section 15 using the key input section 17 and the like.

When the above outer shell is completed and an inner shell is generated, specify the thickness of each surface. At this time, the shell calculating section 13 operates and calculates the inner shell of each surface. Subsequently, the calculation results are sent to the shape model generation unit 12, where the coordinates of each part are calculated, the inner shell is completed, and the CRT display unit 1
5 is displayed.

An example of the operation of the shell calculation unit 13 will be described below using a rectangular parallelepiped as an example, with reference to FIG. 1(C).

(1) First, for surface A, find surface A1 of the inner shell.

That is, the position vector P1 that defines the two planes A. P2 obtained from the unit vector Nl of the normal line and the rank expression of the surface A'' from the wall thickness t1
From the normal line N1, the equation for the surface A'' is determined. That is, the equation for the first surface is set as alx+bly+clz=, Al...■, and its coefficients are determined.

(2) For plane B, find the equation of plane B' of its inner shell using the above procedure. The result is a2x+b2y+
Let c2z=A2...■.

(3) Obtain the ridgeline A'B' from formulas ■ and ■.

a3x+b3y+c3z=o...■(4) Regarding the surface, the equation of the surface D9 of the inner shell is determined by the above procedure. The result is a4x+b4y+c4z=A
4...■.

(5) Find the XYZ coordinates of the vertex A'B'D" as the intersection of the surface D" (■formula) and the ridgeline A'B' (■formula).

(6) Perform the above calculations on all faces to find existing edges and vertices.

The inner shell is obtained through the above steps, and the shape model generation unit 1
2 completes the three-dimensional model including the inner shell.

In the above example, we explained a plane, but in the case of a free-form surface, as mentioned above, calculate the two-position vector and normal vector for multiple points that define the free-form surface, and then perform the above calculation to find each point. Define a new free-form surface.

Figure 1 (dl - (1
1 to (4). In the figure, St is the original surface, S
2 represents the offset surface, P (R in the case of plurality), Ro and ro represent the radius of the original surface, and R and r represent the radius of the offset surface, respectively.

When calculating the inner shell of these surfaces, conventionally, the radii R and r that define the cross sections of the two surfaces are specified, but the radii R and r are offset by the thickness of the outer shell in the radial direction. If this value is used, the present invention can be applied as is by using the place value as it is for processing.

Note that torus surfaces [such as those shown in Figure 1(d)-(41) in which the central axis of the surface is further defined by a second axis (ring diameter Rr) are also processed by offsetting only the normal direction in the same manner as above. can.

With the generation method explained above, an inner shell (cutter) can be automatically generated by specifying the wall thickness in the external shape model, but the reference model is the inner shell and the outer shell with a predetermined wall thickness is also offset in the normal direction. It can be generated in the same way.

〔Effect of the invention〕

As explained above, according to the present invention, the exterior shape model is a set of surfaces, and the inner shell is defined by finding a surface offset by the required wall thickness on the normal line that defines each surface. A shell can be automatically generated.

[Brief explanation of the drawing]

FIG. 1(a) is a block diagram of an example computer system implementing the present invention. FIG. 1(b) is a diagram illustrating the generation of a three-dimensional inner shell. FIG. 1(C) is a flowchart showing an example of the inner shell generation operation. Figure 1 (dl is a diagram showing how to define a basic solid. Figure 2 (a) is a diagram explaining the basic function of shape model generation. Figure 2 (b) is a diagram of shape generation by shape model calculation. Figure (C) is a flowchart of shape model calculation. In the figure. 10 is the central processing unit CPU. 11 is the main memory section. 12 is the shape model generation section. 12a is the basic three-dimensional generation section. 12b is free curve surface generation 12c is a set calculation unit. 12d is a local shape conversion unit. 12e is a movement/rotation control unit. 12f is a figure characteristic calculation unit. 13 is a shell calculation unit, 14 is a display control unit. 15 is a CRT display unit. 16 is a Light pen section, 17 is key human power section. 18 is file device, 19 is output section. ((C) Dormitory 1m (a) '#2 Closed

Claims (1)

[Claims] A shape model creation method for creating a shape model having a predetermined wall thickness from an appearance shape model composed of a plurality of surfaces defined by a surface equation, a position vector representing the position of the surface, and a normal representing the direction. (1) Setting a point on the normal line of each surface having a length of a predetermined thickness from the surface,
(2) creating a surface having the position vector of the point set above and the normal line; and (3) combining each of the created surfaces to create a shape model having a predetermined wall thickness. How to create a model.