JPH07182400A - Method for plotting solid figure - Google Patents

Abstract

PURPOSE:To decrease input manhours for data and reduce storage capacity, and to improve the efficiency of plotting. CONSTITUTION:When the solid figure is displayed on the screen of a display 13, projection angle data regarding a tilt angle and ellipticity are specified on a keyboard and stored in the memory of a system device 10, and data regarding segments displayed on the screen of the display are inputted as three- dimensional data on the keyboard 11, and, the three-dimensional data regarding the inputted segments are transformed to a two-dimensional coordinate system on the basis of the projection angle data to generate point and line data, which are stored in the memory. Then, data of ellipses and corner R ellipses of the two-dimensional coordinate system are generated on the basis of the three- dimensional data regarding the inputted segments and stored in the memory, and those data stored in the memory are displayed on the screen of the display.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stereoscopic drawing method for coexisting two-dimensional data and three-dimensional data to create a stereoscopic drawing.

[0002]

2. Description of the Related Art Conventionally, in this type of drawing method, in order to eliminate the complexity of drawing a three-dimensional drawing by hand, a three-dimensional drawing is created by a computer aided design (CAD) system using computer graphics technology. There was something to create. In the CAD system, the isometric projection method is used to draw and store the three views of the plan view and the side views, and the three-dimensional view is created based on the two-dimensional data of the three views.

[0003]

However, in the above-mentioned drawing method, the data input becomes complicated, the work content becomes complicated and the drawing takes time, and the two-dimensional data of the drawn three-view drawing is stored. However, there is a problem that the storage capacity becomes large. The present invention has been made in view of the above problems, and an object of the present invention is to provide a three-dimensional drawing method capable of reducing the number of data input steps to reduce the storage capacity and improving the drawing efficiency. .

[0004]

In order to achieve the above object, the present invention, when displaying a stereoscopic view on the screen of a display which is a display means, for example, an inclination angle and a tilt angle in each basic axis direction which is a display reference. Ellipticity reference data (projection angle data) is specified by a keyboard as an input unit and stored in a memory of a system unit as a storage unit, and data regarding a line segment displayed on the screen of the display is tertiary Original data is input from the keyboard, three-dimensional data regarding the input line segment is converted into a two-dimensional coordinate system based on projection angle data to create point and line data that are line segment display data, and Data of the ellipse and the corner R ellipse, which are data for displaying an elliptic curve in a two-dimensional coordinate system, are created based on the three-dimensional data relating to the input line segment stored in the memory. The memory stores, drawing method of the three-dimensional view of a segment display data and the elliptic curve display data stored in said memory to display on the screen of the display is provided with.

[0005]

[Function] Coexistence of two-dimensional data and three-dimensional data, two-dimensional input data is displayed on the screen as two-dimensional coordinates by the processing by the hand creation method, and all three-dimensional input data are coordinated by the basic axis. Convert and display on the screen as two-dimensional coordinates. Therefore, labor saving of data input, determination of ellipticity, and reduction ratio calculation can be easily performed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings of FIGS. FIG. 1 is a configuration diagram showing a basic configuration of a drawing system using a method for drawing a three-dimensional drawing according to the present invention.
In the figure, the system includes a system unit 10, a keyboard 11, a mouse 12, a display 13,
The plotter 14 is included. System unit 10
Is a program data for executing the drawing method according to the present invention, a memory (not shown) for storing two-dimensionally or three-dimensionally input data, operation data, and the like, and controls each of the above devices based on the data. It is composed of a CPU (not shown) that executes drawing of a three-dimensional drawing. Keyboard 11
It is used to operate the system and inputs data. The mouse 12 designates various functions such as position designation and copying / enlarging upon drawing. Further, the display 13 displays the points, lines, etc. designated at the time of drawing, and the plotter 14 prints out the created three-dimensional drawing.

Next, the principle of the drawing method according to the present invention will be described with reference to the flowchart of FIG. It should be noted that the projection method includes an isometric projection method, an isometric projection method, and an unequal projection method, and the drawing method according to the present invention can be applied to any of the projection methods. Since the isometric projection method is often used because it is easy to work, an example in which the drawing method according to the present invention is applied to the isometric projection method will be described.

First, when a three-dimensional drawing is created, it is necessary to determine the three-dimensional basic axis direction (projection angle) in advance (step 101). When the projection angle is set by the setting data input from the keyboard 11, the drawing data is next input (step 102). The input data is selected for each element (point, line) (step 103), and the dimension is determined, that is, whether the input data is two-dimensional data or three-dimensional data is determined (step 104).

If the input data is three-dimensional data, the three-dimensional processing is performed. Here, the system device 10 is based on the set projection angle data,
The coordinates of the three-dimensional data are converted (step 10
5) It is stored in the memory and displayed on the screen of the display 13 as a two-dimensional coordinate system (step 10).
7). If the input three-dimensional data is a point or line, along with the coordinate-converted two-dimensional data,
The three-dimensional data is also stored in the memory as a system database, and only the two-dimensional data of other elements such as arc and free curve data is stored in the memory as the system database. That is, in this embodiment, in order to reduce the amount of data stored in the memory, the storage is basically two-dimensional data. The reason why the points and lines have three-dimensional data is that three-dimensional data of points and lines is required when creating an ellipse described later.

If the input data is two-dimensional data, a two-dimensional process is performed. Here, the system device 10 stores the input two-dimensional data in the memory (step 106) and displays it as two-dimensional coordinates on the screen of the display 13 (step 107). By the way, the basic axis set in step 101 is
The X, Y, and Z axes shown in FIG. 3 are settable values in the basic axis direction, as shown in FIG. 3, are the ellipticity α of the Z plane and the angle θ formed by the horizontal line and the X axis. The ellipticity of the X and Y planes and the angle between the Y axis and the horizon are naturally determined by the principle of the isometric projection method. Further, the inclination of the Z axis is vertical and cannot be changed.

The projection angle data set by the above setting method is stored in the memory of the system unit 10 as a projection angle data table having the contents shown in Table 1 below.

[0012]

[Table 1] Since the tilt angle of the Z axis is vertical and invariant, it is not registered in the data table.

In the drawing system of the present embodiment, the three-dimensional data is coordinate-converted by the CPU of the system unit 10 based on the values in the projection angle data table and displayed on the screen of the display 13 as two-dimensional coordinates. The formula for this coordinate conversion is as follows. That is,

[0014]

## EQU00001 ## Two-dimensional X coordinate = {three-dimensional X coordinate value × cos (X-plane ellipticity) × cos (X-axis tilt angle)}-{three-dimensional Y coordinate value × cos (Y-plane ellipticity) × cos ( Y-axis tilt angle)} Two-dimensional Y coordinate = {three-dimensional Z coordinate value x cos (Z-plane ellipticity)} + {three-dimensional X coordinate value x cos (X-plane ellipticity) x sin (X-axis tilt angle)} + {Three-dimensional Y coordinate value x cos (Y plane ellipticity) x sin (Y axis tilt angle)} (1)

[0015] In step 105, the calculation function of the personal computer or the like takes time to calculate the coordinate conversion, so that the display screen cannot be enlarged or reduced smoothly. For this reason, in this embodiment, the data (two-dimensional coordinate data) once subjected to coordinate conversion is stored in the memory as a database of each element, and in the case of screen display, the stored two-dimensional data is used. To do. This improves the responsiveness of data display. When the coordinate value is moved or rotated using the stored two-dimensional data, the CPU performs the coordinate conversion calculation again and re-registers the two-dimensional coordinate data in the database.

In the present embodiment, the three-dimensional data is stored only in the point and line data as described above, and the other elements do not have the three-dimensional data. In addition, the point and line data may be stored only in two-dimensional data. For this reason, the memory is provided with a dimension division, and the CPU makes a determination at the time of processing based on the dimension division. The data structure of the points and lines is shown in Table 2 below.

[0017]

[Table 2] In Table 2 above, the two-dimensional / three-dimensional division indicates whether the data is only two-dimensional data or three-dimensional data, and the group number indicates the number of each element. , The color number indicates the color designation displayed on the screen, and the coordinate values (1) and (2) of the line data indicate the coordinate values at both ends of the line.

Next, the point drawing method will be described with reference to FIGS.
Will be described with reference to the drawings. First, in the case of drawing points, as shown in the schematic diagram of FIG. 4, the front-back direction from the origin O with respect to the X-axis, the left-right direction from the origin O with respect to the Y-axis, and the Z-axis with respect to the Z-axis. It is necessary to determine the vertical direction.
Therefore, in the flowchart of FIG. 5, when inputting numerical data from the keyboard 11, in order to clarify the vector in each of the X, Y, and Z axis directions, when there are vectors in the front, left, and bottom directions, , Input the data with a minus (step 201). For example, when the input data is three-dimensional data, as in the example shown in FIG.
Actual lengths in the X, Y, and Z axis directions "10", "15",
Separate “20” in order with commas and enter “-10,15,
Enter as "-20" and start a new line.

The system unit 10 determines the number of data of the input data (step 202). here,
For example, the number of data is determined by the number of commas. If the number of commas is “0”, that is, the number of data is “1”, the process ends without determining the data input, and the number of commas is “1”. That is, if the number of data is “2”, it is determined that the two-dimensional data is input. If the number of commas is “2”, that is, the number of the data is “3”, it is determined that the three-dimensional data is input. To do.

In the above judgment, if the input data is two-dimensional data, the two-dimensional point data is registered as a database in the memory in the system unit 10 without performing coordinate conversion (step 204). If the input data is three-dimensional data, the coordinates are converted into two-dimensional data based on the equation (1) (step 203), and the two-dimensional and three-dimensional point data (see Table 2) is used as a database. It is registered in the memory of the device 10 (step 204).

Then, the registered data is output to the display 13 so that the operator can recognize it, and points are displayed on the screen (step 205).
Returning to step 201, the next data input is awaited. Next, a line drawing method will be described based on the flowchart of FIG. The line drawing is performed by inputting data at both ends of the line, but basically it is the same as the point drawing. However, if either of the data at both ends of the line is input as two-dimensional data,
In this embodiment, the characteristic of this line is two-dimensional.

First, when data is input as a line from the keyboard 11 (step 301), the number of data is judged as in the case of drawing points (step 302). In the case of three-dimensional data, equation (1) is used. The coordinate conversion into two-dimensional data is performed based on the above (step 303), and the two-dimensional and three-dimensional data are temporarily stored in the memory in the system device 10 (step 304). If the input data is two-dimensional data, it is temporarily stored in the memory without performing the coordinate conversion (step 304).

The system unit determines the number of temporarily stored data (hereinafter referred to as "temporary storage number") (step 305). Here, when the temporary storage number is "1", the process returns to step 301 and waits for data input at the other end. If the number of temporary storage is "2", the input data is registered (step 306), and the temporary storage is 2
Line data (see Table 2) is created from the point data (step 307), and the line data is registered as a database (step 306).

Then, the temporarily stored old data is deleted to set the number of data to "1" (step 308), and the registered line data is output to the display 13 to display a line on the screen. (Step 309) Then, the process returns to step 301 and waits for the next data input. next,
A method of calculating data in ellipse drawing will be described with reference to the schematic diagram of FIG. The ellipticity of a circular arc in a three-dimensional view is the three-dimensional cosine (vector) in which the ellipse faces
It is calculated by the arc cosine value for the reduction value of. That is,

[0025]

## EQU00002 ## Reduction rate = (distance on coordinate-converted plane) / (distance of three-dimensional direction cosine) Ellipticity = cos ^-1 (reduction rate) (2)

[0026] In this equation (2), the distance of the three-dimensional direction cosine is the actual length, which is obtained from the three-dimensional data of the line.

The tilt angle of the ellipse is the angle of the vector on the plane obtained by coordinate-converting the three-dimensional direction cosine, that is, the angle between the short axis of the ellipse and the horizontal line shown in FIG. In the present embodiment, the data structure of the ellipse is as shown in Table 3 below, which is registered and managed in the memory.

[0028]

[Table 3] In the present embodiment, the data division in the above data structure is only two-dimensional, but the present invention is not limited to this,
It is also possible to include 3D data for future system construction. Further, the elliptic arc start angle and the elliptic arc end angle are the angles shown in FIG. 9.

Next, an ellipse drawing method will be described with reference to the flowchart of FIG. First, when data as an ellipse, for example, a numerical value for the diameter of the ellipse is input from the keyboard 11 (step 401), line data (two-dimensional or three-dimensional element) having the same vector as the central axis of the ellipse to be drawn, or the same ellipse. An ellipse having a degree / tilt angle is selected (step 402). Then, the point at the center position is selected (step 403).

Next, the element selected in step 402 is checked (step 404). That is, here, it is determined whether a line or an ellipse is selected as an element. If a line is selected and its element is two-dimensional, the end position data of the line, that is, the two-dimensional X and Y coordinate values (1) and the two-dimensional X and Y coordinate values in Table 2 are used. From (2) and the horizontal line, the plane angle of the line (see FIG. 9) is calculated to calculate the inclination angle of the ellipse (step 405). When the above line is selected and its element is three-dimensional, both end position data of the line, that is, the coordinate values (1) of the three-dimensional X, Y and Z in Table 2 and the three-dimensional X, Y and Z The ellipticity is calculated by calculating the reduction ratio of the vector from the coordinate values (2) and (2) (step 406).
If an ellipse is selected in step 404, the ellipse tilt angle and ellipticity are extracted from the ellipse data in Table 3 (steps 407 and 408). Then, ellipse data is created based on the input elliptic diameter and the tilt angle / ellipticity calculated or extracted in steps 405 to 408 (step 409).

Next, it is checked whether or not the ellipticity is input next to the diameter of the ellipse when the data is input in step 401 (step 409). That is, when drawing an ellipse, for example, it may be desired to draw by designating a predetermined ellipticity. In such a case, in this embodiment, the ellipticity can be input as the second parameter. In addition,
As an input method in this case, the system device 10 can recognize the ellipticity by, for example, entering a comma next to the diameter of the ellipse and then an ellipticity from the keyboard 11.

Here, when the ellipticity is input,
The ellipticity in the elliptic data is forcibly replaced with the ellipticity input / designated from the keyboard 11 (step 410), and the elliptic data is registered in the memory of the system device 10 as a database (step 411). If there is no ellipticity input, step 409.
The ellipse data created in step 3 is registered in the memory of the system device 10 as a database (step 411).

The registered ellipse data is output to the display 13 so that an ellipse is displayed on the screen centering on the designated point (step 413) and the process returns to step 401 to wait for the next data input. . Next, a method of calculating data in corner R drawing will be described based on the schematic diagram of FIG.

For example, when a corner R is drawn on two intersecting lines, if the figure is a plane figure, the arc of R is a perfect circle. Therefore, the corner R is simply calculated by calculating the arc of the two lines. However, when the figure is a three-dimensional figure, the created arc becomes an ellipse, which makes it difficult to create the corner R. Therefore, in this embodiment, the ellipticity and the inclination angle of the arc of the corner R are obtained by the following method,
The above corner R is created.

In FIG. 11, in order to obtain the ellipticity of the corner R, the data of the two intersecting lines 20 and 21 are
It must be stored as the three-dimensional line data shown in Table 2. That is, when either one or both of the line data are two-dimensional data, ellipticity cannot be calculated by calculation, and therefore the ellipticity and the inclination angle of the ellipse must be input separately from the keyboard 11.

When the above-mentioned two intersecting lines 20 and 21 are three-dimensional, a plane provided by both lines, that is, a vertical vector 23 at the intersection with respect to a plane 22 determined by the end points (3 points) of both lines. To calculate. Then, the reduction ratio of the obtained vector is calculated, and the ellipticity and the tilt angle are calculated by the same method as the calculation in the ellipse drawing (equation (2) and FIG. 8).
reference).

Next, the plane coordinate positions of the two lines when the arc is a perfect circle are calculated from the calculated ellipticity and tilt angle. That is, in order to return the above-obtained ellipse to a perfect circle, the coordinates in the minor axis direction of the ellipse are set as shown in FIG.
This is possible by moving by a factor of {1 / sin (ellipticity)}. Based on this method, the coordinate of the line is adjusted to the ellipse to perform the coordinate conversion, and the lines 24 and 25 after the coordinate conversion shown in FIG. 13 are obtained. And the coordinate-converted line 2
Arcs in contact with 4, 25 are calculated, and the center coordinates of the arc 26 shown in FIG. Further, a process reverse to the process of the coordinate conversion in which the line coordinates are adjusted to the ellipse is performed to obtain the center coordinates and the contact point of the elliptic arc, and the coordinate conversion process is performed to make the R elliptic arc 27 as shown in FIG. To create.

Next, the method of drawing the corner R will be described with reference to the flowchart of FIG. First, when data as the corner R, for example, a numerical value of the radius of the corner R is input from the keyboard 11 (step 501), two lines to which the corner R is attached are selected (step 502). Then, the position to attach the corner R is designated (step 50).
3). The reason for specifying this position is that two intersecting lines have four corner angles, and therefore it is necessary to instruct which corner angle to select.

Next, the element of each line selected in step 502 is checked (step 504). That is, here, it is determined whether or not the data of the selected line are all three-dimensional data or two-dimensional data. Here, if all the data of the selected lines store three-dimensional data, it is confirmed whether or not the above two lines intersect in the three-dimensional space (step 505), and the intersection is performed. If not, end the operation,
If they intersect, the vertical vector at the intersection with respect to the plane provided by both lines is calculated (step 506). Then, the ellipticity and the tilt angle are calculated by the same method as the calculation in the ellipse drawing (step 507).

In step 504, if the data of the selected line includes line data composed of two-dimensional data, the ellipticity and the tilt angle cannot be calculated, so an ellipse equivalent to the corner R is obtained. An ellipse having a degree and a tilt angle is selected (step 508). Then, the ellipticity and the tilt angle are extracted from the selected ellipse (step 509). The selection of the ellipse is, for example, similar to the conventional CAD system, a message for instructing the selection of an ellipse having an ellipticity and an inclination angle equivalent to the corner R from the system device 10 is displayed on the display 13, and this message is displayed. Ask the operator to select the ellipse you want to draw accordingly.

When the ellipticity and the inclination angle of the ellipse are obtained, the selected line is subjected to coordinate conversion based on the coefficient obtained by the ellipticity and the inclination angle, and the arc center coordinate and the line on the perfect circle are calculated. Calculate contact coordinates (step 51)
0). Furthermore, the calculated arc center coordinates and contact coordinates are
Inverse calculation is performed based on the above coefficient, and the coordinates are converted into the positional relationship in the original ellipse (step 511).

Then, the start angle and the end angle of the corner R elliptic arc are obtained from the coordinate-converted arc center coordinates and contact coordinates (step 512), and the data of the elliptic arc is registered in the memory as a database (step 513). The data of the registered elliptic arc is output to the display 13 to display the corner R elliptic arc at the designated corner position on the screen (step 514), and returns to step 501 to wait for the next data input.

Therefore, in this embodiment, the two-dimensional data and the three-dimensional data are made to coexist, and the two-dimensional input data is displayed on the screen as the two-dimensional coordinates by the processing by the conventional hand creation method, and the three-dimensional input is performed. All data is coordinate-converted with the basic axes and displayed on the screen as two-dimensional coordinates, which saves labor for data input work.
The ellipticity and the reduction rate in the case of three-dimensional data can be automatically and easily calculated, thereby improving the efficiency of drawing.

In the present embodiment, the system database is managed basically on the basis of two-dimensional data and only points and lines are managed for two-dimensional data and three-dimensional data, thus reducing the memory capacity in the system unit. it can.
Further, in the present embodiment, when a stereoscopic view is created by adding arbitrary rotation, the rotation angle is set in advance, the input data including the above rotation is subjected to coordinate conversion, and displayed on the screen. Is also possible. The reason why such a method is adopted is that the drawing method of this embodiment manages data in a multidimensional manner.
This is to prevent the direction of the stereoscopic drawing from being changed by three-dimensional rotation after the stereoscopic drawing is created.

Next, the procedure for making a three-dimensional drawing from the drawing of the shaft holder consisting of the flange 30 and the cylindrical portion 31 shown in FIG. 16 using the drawing method of the above-described embodiment will be described based on the drawing procedure of FIG. explain. First, in this procedure, the vertical, horizontal, and height of the three-dimensional direction are set as the X, Y, and Z axes of FIG. 3, and the drawing direction is first defined, and the projection angle data is registered. Then, as shown in FIG. 17 (1), three-dimensional data (vertical, horizontal,
By inputting the height, the outline of the surface of the flange 30 and the center point (5 points) of the through hole 32 are provided. By inputting these data, line and point data are created by the line drawing and point drawing methods and registered in the memory, and the created outline and the center point of the through hole are displayed on the display 13 as two-dimensional coordinates. Displayed on the screen.

Next, as shown in FIG. 17 (2), mouse 1
Select two intersecting lines with 2 and enter the radius. By this data input, corner R elliptic arc data is created by the corner R drawing method and registered in the memory,
Further, the created corner R elliptic arc is displayed at a predetermined position on the screen as two-dimensional coordinates. Furthermore, FIG.
As shown in (3), enter the diameter of the through hole, select an ellipse with the same ellipticity, and then select the center of the circle. By this data input, ellipse data is created by the ellipse drawing method and registered in the memory, and the created ellipse (through hole) is displayed on the screen corresponding to the center of the circle selected above as two-dimensional coordinates. Displayed in place.

Next, as shown in FIG. 17 (4), the outline of the displayed flange surface is copied and moved downward to draw the thickness of the flange on the screen. The copying of the outline is performed by the copy function of the present system, and the outline is normally displayed on the screen as two-dimensional coordinates. Then, as shown in FIG. 17 (5),
The corners R on both outlines of the flange surface are connected by a line to erase unnecessary lines.

Next, as shown in FIG. 17 (6), the cylindrical portion 3
Enter the data of 1 and set the center line. Then, the cylindrical portion 31 is drawn on the screen by using the pipe drawing function of this system. The pipe drawing function automatically creates a pipe shape by inputting the diameter of the ellipse and selecting the center line, and the created pipe is displayed as two-dimensional coordinates on the screen. .

Finally, by drawing a hole in the cylindrical portion and correcting the line, the three-dimensional drawing is completed.

[0050]

As described above, according to the present invention, when the stereoscopic view is displayed on the screen of the display means, the reference data for each direction which is the display reference is designated from the input means and stored in the storage means. Data regarding a line segment that is stored and displayed on the screen of the display means is input from the input means as three-dimensional data, and the three-dimensional data regarding the input line segment is
Conversion to a two-dimensional coordinate system based on the reference data to create line segment display data, which is stored in the storage means, and an elliptic curve display of a two-dimensional coordinate system based on the input three-dimensional data regarding the line segment. Data is created and stored in the storage means, and the line segment display data and the elliptic curve display data stored in the storage means are displayed on the screen of the display means, thus reducing the number of data input steps. The storage capacity can be reduced and the efficiency of drawing can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a basic configuration of a drawing system using a method for drawing a three-dimensional drawing according to the present invention.

FIG. 2 is a flowchart for explaining the principle of the drawing method according to the present invention.

FIG. 3 is an isometric projection diagram for explaining a method of setting projection angle data.

FIG. 4 is a schematic diagram for explaining a method of inputting point data.

FIG. 5 is a flowchart for explaining a point drawing method.

FIG. 6 is a diagram showing an example of inputting point data.

FIG. 7 is a flowchart for explaining a line drawing method.

FIG. 8 is a schematic diagram for explaining a data calculation method in ellipse drawing.

FIG. 9 is a diagram showing an elliptic arc start angle and an elliptic arc end angle included in ellipse data.

FIG. 10 is a flowchart for explaining an ellipse drawing method.

FIG. 11 is a schematic diagram for explaining one step of a data calculation method in corner R drawing.

FIG. 12 is a schematic diagram for explaining one step of a method of calculating data in corner R drawing.

FIG. 13 is a schematic diagram for explaining one step of a data calculation method in the corner R drawing.

FIG. 14 is a schematic diagram for explaining one step of a method of calculating data in corner R drawing.

FIG. 15 is a flowchart for explaining a corner R drawing method.

16A and 16B are a plan view and a side view of a shaft holder for which a three-dimensional drawing is to be created using the drawing method of the present embodiment.

FIG. 17 is a view for explaining the drawing procedure of the three-dimensional view of the shaft holder shown in FIG.

[Explanation of symbols]

 10 system unit 11 keyboard 12 mouse 13 display 14 plotter

Claims (1)

[Claims] 1. When displaying a stereoscopic view on the screen of the display means, reference data relating to each direction which is a display reference is designated from the input means and stored in the storage means, and is displayed on the screen of the display means. Data about the displayed line segment is input as three-dimensional data from the input means, and the three-dimensional data about the input line segment is converted into a two-dimensional coordinate system based on the reference data to display line segment data. And storing it in the storage means, creating elliptic curve display data of a two-dimensional coordinate system based on the input three-dimensional data relating to the line segment, storing it in the storage means, and storing it in the storage means. A method for drawing a three-dimensional diagram, characterized in that the displayed line segment display data and elliptic curve display data are displayed on the screen of the display means.