JP2004030135A - Method and program for drawing part of circle in cad system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently draw part (circular arc) of an extremely expanded circle in a two-dimensional CAD system. <P>SOLUTION: The method for drawing part of the circle in the CAD system includes the steps for: determining the coordinates of four points indicating a rectangular display area for displaying a circle element which is part of the circle being a drawing target; operating the coordinates of intersections of the individual sides of the rectangle and the circle; and operating the coordinates of the part of the circle within the display area with angles formed of the coordinates of the intersections and the central coordinates of the circle as a starting angle and a final angle. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drawing method of a graphic in a CAD system.
[0002]
[Prior art]
2. Description of the Related Art Recently, CAD (Computer-Aided-Design) systems have become widespread in design work in various fields under the influence of high performance and low price of computers.
Along with the spread, drawings that initially use various shapes (circles, curves, etc.) from a set of simple line segments are increasing.
When drawing a circle element in the CAD system software, it is usually realized by using a circle drawing command provided in a compiler language for describing a program.
[0003]
However, since the drawing of a circle requires delicate smoothness as the display is enlarged, the amount of calculation required for drawing increases.
Therefore, these commands often do not correspond to a case where a part of a circle is extremely enlarged.
In this case, it is common to calculate circular coordinates by calculation using a trigonometric function, and draw the coordinates finely by line segments.
That is, a circle having a center coordinate (X0, Y0) radius r is
X = r × Cos θ + X0, Y = r × Sin θ + Y0 (θ = 0 to 2π)
, The coordinate group obtained is connected by a line segment and pseudo-drawn.
[0004]
As a method of drawing a part (arc) of a circle, a method described in Japanese Patent Application Laid-Open No. 2001-14357 is known.
This publication discloses the technique shown in FIGS. 7 to 10 using a part of a circle as a drawing method.
FIG. 7 is a diagram illustrating a graphic including a part of a circle to be drawn.
FIG. 8 is a diagram showing one stage for drawing the figure of FIG.
FIG. 9 is an enlarged view of a right angle portion of the figure of FIG.
FIG. 10 is a flowchart showing the procedure of the drawing method of the figure shown in FIG.
[0005]
In order to draw a figure including a part of a circle (arc) in the figure shown in FIG. 7, first, as shown in FIG. 8, a square 31a of FIG. .
First, the ruled lines 32 and 33 are designated by the cursor on the screen using the keyboard 2 and saved. (Step 11)
Next, the right angle portion 34 is identified and stored. (Step 12)
Next, the coordinates of the first end point 34a of the right angle portion 34 are calculated. (Step 13)
Next, the radius value of the first circular arc 35 is input to the coordinate center of the end point 34a. (Step 14)
Subsequently, the first circular arc 35 input to the right-angled portion 34 is drawn. (Step 15)
Next, each line segment is cut at the first and second contact points 36 and 37 between the arc 35 and the ruled lines 32 and 33, and the first and second straight lines 38 and 39 on the side of the first end point 34a are connected to the first and second straight lines 38 and 39. Is deleted. (Step 16)
In the technique disclosed in the above publication, even when a part of a circle is drawn, an arithmetic processing for drawing the entire circle is executed, and thereafter, a processing for deleting an unnecessary part is performed. The computational processing load required for was extremely large.
[0006]
[Problems to be solved by the invention]
However, since this method uses a lot of trigonometric functions, the amount of calculation of the drawing coordinates further increases, and a heavy load is imposed on the computer.
As a result, the drawing speed becomes slow, the work comfort is lost, and the operation is unstable due to extremely consuming memory resources.
Especially when drawing only a part of an extremely enlarged circle, the calculation of drawing the whole circle is performed as described above, and the unnecessary parts are deleted. I was even going.
[0007]
An object (object) of the present invention is to efficiently draw a part (arc) of an extremely enlarged circle in a two-dimensional CAD system.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a method of drawing a part of a circle in a CAD system,
Determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a drawing target circle; calculating intersection coordinates of each side of the rectangle and the circle; Calculating the coordinates of a part of the circle in the display area, using the angle formed by the coordinates and the center coordinate of the circle as a start angle and an end angle, to render the part of the circle. (Claim 1)
[0009]
Also, in the CAD system, a method of drawing a part of a circle,
A step of determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a circle to be drawn; and a step of determining whether or not the coordinates of the four points are within the circle. Calculating the intersection coordinates of each side of the rectangle and the circle only when it is determined that the coordinates of the first to third points among the coordinates of the four points are present in the circle; And calculating the coordinates of a part of the circle in the display area, using the angle formed by the coordinates of the circle and the center coordinates of the circle as a start angle and an end angle. (Claim 2)
[0010]
Also, in the CAD system, a method of drawing a part of a circle,
A step of determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a circle to be drawn; and a step of determining whether or not the coordinates of the four points are within the circle. If it is determined that one of the coordinates of the four points is within the circle, the coordinates of the intersection of the circle with two sides sandwiching the point within the circle are calculated, and the intersection coordinates are calculated. And calculating the coordinates of a part of the circle in the display area with the two angles formed by the center of the circle as the start angle and the end angle, thereby rendering the part of the circle. (Claim 3)
[0011]
Also, in the CAD system, a method of drawing a part of a circle,
A step of determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a circle to be drawn; and a step of determining whether or not the coordinates of the four points are within the circle. If it is determined that the coordinates of two of the coordinates of the four points are within the circle, the intersection coordinates of two parallel lines passing through the points existing in the circle and the circle are calculated. Calculating the coordinates of a part of the circle in the display area with the two angles formed by the coordinates and the center of the circle as the start angle and the end angle, and rendering the part of the circle. (Claim 4)
[0012]
Also, in the CAD system, a method of drawing a part of a circle,
A step of determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a circle to be drawn; and a step of determining whether or not the coordinates of the four points are within the circle. If it is determined that the coordinates of three of the four coordinates are within the circle, the coordinates of the intersection of the circle and two sides sandwiching one point that is outside the circle are calculated. Calculating the coordinates of a part of the circle in the display area with the two angles formed by the coordinates and the center of the circle as the start angle and the end angle, and rendering the part of the circle. (Claim 5)
[0013]
In a CAD system, a program for drawing a part of a circle,
A process of determining coordinates of four points indicating a rectangular display area for displaying a circle element which is a part of a circle to be drawn; a process of calculating coordinates of intersections of each side of the rectangle with the circle; A part of the circle that causes a computer of a CAD system to execute a process of calculating a coordinate of a part of the circle in the display area with an angle formed by the coordinates and the center coordinate of the circle as a start angle and an end angle. The program to draw. (Claim 6)
[0014]
In a CAD system, a program for drawing a part of a circle,
A process of determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a circle to be drawn; and a process of determining whether or not the coordinates of the four points are present in the circle A process of calculating intersection coordinates between each side of the rectangle and the circle only when it is determined that one to three coordinates of the four coordinates are present in the circle; Drawing a part of the circle that causes a computer of a CAD system to execute a process of calculating coordinates of a part of the circle in the display area, with the angle formed by the center coordinate of the circle as a start angle and an end angle. Program to do. (Claim 7)
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
In the CAD system, when the circle 1 is extremely enlarged and a part is displayed, a part (arc) of the displayed circle is in a display area 2 determined by four points (P !, P2, P3, P4). The drawing is performed such that a part of the circumference of any of the two or three sides of the four sides.
At this time, the relationship between the four-point coordinates (P1 to P4) indicating the display area 2 and the circle 1 can be classified as follows.
Among the four coordinates (P1, P2, P3, P4) indicating the display area 2,
(A) As shown in FIG. 1, only one point exists inside the circle 1.
(B) Two points exist inside the circle 1 as shown in FIG.
(C) Three points exist inside the circle 1 as shown in FIG.
(D) All four points are inside the circle 1 as shown in FIG.
(E) As shown in FIG. 5, all four points exist outside the circle 1, and the circle 1 exists inside the display area 2.
(F) As shown in FIG. 6, all four points exist outside the circle 1, and the circle 1 exists outside the display area 2.
[0016]
In the case of FIG. 5E of FIG. 5, all four points are outside the circle 1, but since the center of the circle 1 is inside the display area 2, all the circles are drawn. Draw using commands.
In FIG. 6F, all four points are outside the circle 1, but since the center of the circle 1 is outside the display area 2, the circle 1 is outside the display area 2. , Circle 1 need not be drawn.
Also, in the case of FIG. 4 (d) and in the case where all four points are inside the circle 1, there is no need to draw since the display area 2 does not include a circle.
[0017]
Therefore, a part of a circle is drawn in the display area 2 in the cases (a), (b), and (c) shown in FIGS.
Hereinafter, for each of the above three cases, the necessary arithmetic processing and drawing method will be described in detail.
[0018]
-When only one point exists inside the circle 1. (Fig. 1)
Two points of intersection between the two sides of the point existing inside the circle 1 and the circle 1 are calculated.
The two angles formed by the two points and the center of the circle 1 are defined as a start angle and an end angle, and coordinates are calculated only in that range to draw an arc.
[0019]
-When two points exist inside the circle 1. (Fig. 2)
Two points of intersection between the two parallel lines passing through the points inside the circle 1 and the circle 1 are calculated.
The two angles formed by the two points and the center of the circle 1 are defined as a start angle and an end angle, and coordinates are calculated only in that range to draw an arc.
[0020]
-When three points exist inside the circle 1. (Fig. 2)
Calculate two intersections between two sides of one point existing outside the circle 1 and the circle 1.
The two angles formed by the two points and the center of the circle 1 are defined as a start angle and an end angle, and coordinates are calculated only in that range to draw an arc.
[0021]
By performing the above-described sorting, when drawing a part (arc) of the enlarged circle 1, only the part actually displayed is calculated and drawn, thereby reducing the total amount of calculation necessary for drawing. Thus, the drawing can be efficiently performed.
[0022]
【The invention's effect】
The invention according to claim 1 is a method for drawing a part of a circle in a CAD system,
Determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a drawing target circle; calculating intersection coordinates of each side of the rectangle and the circle; Calculating the coordinates of a part of the circle in the display area, with the angle formed by the coordinates and the center coordinates of the circle as the start angle and the end angle, the part of the circle is drawn. By calculating and drawing only the displayed portion, the total amount of calculation required for drawing can be reduced, and drawing can be performed efficiently.
[0023]
In the invention according to claim 2, a method of drawing a part of a circle in a CAD system,
A step of determining coordinates of four points indicating a rectangular display area that displays a circle element that is a part of a circle to be drawn; and a step of determining whether or not the coordinates of the four points are within the circle. Calculating the intersection coordinates of each side of the rectangle and the circle only when it is determined that the coordinates of one to three of the coordinates of the four points are within the circle; And calculating the coordinates of a part of the circle in the display area, with the angle formed by the angle formed by the center coordinates of the circle as the start angle and the end angle. And the case where there is no need to draw a circle.
[0024]
According to the third to fifth aspects of the present invention, it is possible to perform a process according to the determination result of the step of determining the coordinates of four points indicating a rectangular display area that displays a circle element that is a part of the circle to be drawn.
[0025]
According to the sixth and seventh aspects of the present invention, by calculating and drawing only the part that is actually displayed, the total amount of calculation required for drawing can be reduced, and a program for efficiently executing drawing can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a state in which only one of four coordinates of a display area exists inside a circle 1;
FIG. 2 is a diagram illustrating a state in which two of four coordinates of a display area exist inside a circle;
FIG. 3 is a diagram showing a state where three points out of four coordinates of a display area exist inside a circle;
FIG. 4 is a diagram showing a state in which all four points of four-point coordinates in a display area are present inside a circle;
FIG. 5 is a diagram showing a state in which all four points of the four-point coordinates of the display area exist outside the circle, and the circle exists inside the display area.
FIG. 6 is a diagram showing a state in which all four points of the four-point coordinates of the display area exist outside the circle, and the circle exists outside the display area.
FIG. 7 is a diagram illustrating a graphic including a part of a circle to be drawn.
FIG. 8 is a diagram showing one stage for drawing the graphic in FIG. 7;
FIG. 9 is an enlarged view of a right angle portion of the graphic in FIG. 7;
FIG. 10 is a flowchart illustrating a procedure of a drawing method of the graphic in FIG. 7;
[Explanation of symbols]
1 circle 2 rectangular display area P1 to P4 4 point coordinates

Claims (7)

A method of drawing a part of a circle in a CAD system,
Determining coordinates of four points indicating a rectangular display area for displaying a circle element that is a part of a circle to be drawn;
Calculating intersection coordinates of each side of the rectangle and the circle;
Calculating the coordinates of a part of the circle in the display area, with the angle formed by the intersection coordinates and the center coordinates of the circle as the start angle and the end angle;
A method of drawing a part of a circle, comprising: A method of drawing a part of a circle in a CAD system,
Determining coordinates of four points indicating a rectangular display area for displaying a circle element that is a part of a circle to be drawn;
Determining whether the coordinates of the four points are within the circle;
Calculating the intersection coordinates of each side of the rectangle and the circle only when it is determined that the coordinates of the first to third points among the coordinates of the four points are present in the circle;
Calculating the coordinates of a part of the circle in the display area, with the angle formed by the intersection coordinates and the center coordinates of the circle as the start angle and the end angle;
A method of drawing a part of a circle, comprising: A method of drawing a part of a circle in a CAD system,
Determining coordinates of four points indicating a rectangular display area for displaying a circle element that is a part of a circle to be drawn;
Determining whether the coordinates of the four points are within the circle;
When it is determined that one of the coordinates of the four points is present in the circle, the coordinates of the intersection of the circle and two sides sandwiching the point present in the circle are calculated, and the intersection coordinates are calculated. Calculating the coordinates of a part of the circle in the display area, with the two angles formed by the center of the circle as the start angle and the end angle;
A method of drawing a part of a circle, comprising: A method of drawing a part of a circle in a CAD system,
Determining coordinates of four points indicating a rectangular display area for displaying a circle element that is a part of a circle to be drawn;
Determining whether the coordinates of the four points are within the circle;
When it is determined that the coordinates of two of the coordinates of the four points are present in the circle, the coordinates of the intersection between the two parallel lines passing through the points existing in the circle and the circle are calculated. Calculating the coordinates of a part of the circle in the display area, using the two angles formed by the center of the circle as the start angle and the end angle;
A method of drawing a part of a circle, comprising: A method of drawing a part of a circle in a CAD system,
Determining coordinates of four points indicating a rectangular display area for displaying a circle element that is a part of a circle to be drawn;
Determining whether the coordinates of the four points are within the circle;
When it is determined that the coordinates of three of the four coordinates are within the circle, the coordinates of the intersection of the circle and two sides sandwiching one point outside the circle are calculated, and the intersection coordinates are calculated. Calculating the coordinates of a part of the circle in the display area, using the two angles formed by the center of the circle as the start angle and the end angle,
A method of drawing a part of a circle, comprising: A program for drawing a part of a circle in a CAD system,
A process of determining coordinates of four points indicating a rectangular display area for displaying a circle element which is a part of a circle to be drawn;
A process of calculating intersection coordinates of each side of the rectangle and the circle;
A process of calculating coordinates of a part of the circle in the display area, with an angle formed by the intersection coordinates and the center coordinates of the circle as a start angle and an end angle;
Which causes a computer of a CAD system to execute the program. A program for drawing a part of a circle in a CAD system,
A process of determining coordinates of four points indicating a rectangular display area for displaying a circle element which is a part of a circle to be drawn;
Processing for determining whether or not the coordinates of the four points are within the circle;
Only when it is determined that the coordinates of 1-3 points among the coordinates of the four points are present in the circle, a process of calculating intersection coordinates of each side of the rectangle and the circle;
A process of calculating coordinates of a part of the circle in the display area, with an angle formed by the intersection coordinates and the center coordinates of the circle as a start angle and an end angle;
Which causes a computer of a CAD system to execute the program.

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