JPH08221585A - System for plotting circle - Google Patents

Abstract

PURPOSE: To accelerate the plotting speed at the time of plotting a small circle by performing reduction arithmetic to respective apex coordinate values based on the size of the circle to be plotted, calculating the coordinates of respective apexes to form the plotted circle and displaying the plotted circle by connecting the coordinates of respective mutually adjacent apexes among those respective calculated apexes. CONSTITUTION: Based on the size of the circle to be plotted, the respective apex coordinate values are thinned and extracted from a basic circle coordinate memory 1 by a skip number memory 2 and a microprocessor 3 as apex coordinate thinning means. The reduction arithmetic is performed to those respective extracted apex coordinate values based on the size of the circle to be plotted by the microprocessor 3 as an apex coordinate calculating means and the coordinates of respective apexes to form the plotted circle are calculated. The plotted circle is displayed by connecting the coordinates of respective mutually adjacent apexes among those respective calculated apex coordinates while using a straight line plotting means 5, frame memory 6, display control part 7 and monitor 9 as plotted circle display means. Thus, plotting speed at the time of plotting the small circle can be accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circle drawing method using a graphic display device, and more particularly to a circle drawing method capable of improving a drawing speed when drawing a small circle.

[0002]

2. Description of the Related Art Generally, in a graphic display device capable of drawing a geometrical figure, when drawing a circle,
A circle drawing method in which a circle is drawn approximately by a polygon is widely used.

In this type of circle drawing method, a plurality of vertex coordinates forming a polygon are stored in advance, and each vertex coordinate is linearly connected to draw an approximate circle of the polygon. Here, in order to draw a beautiful circle even when the approximate circle is displayed on the full screen of the graphic display device, for example, a circle whose diameter is the vertical length of the screen is used as the basic circle, and this basic circle is It is possible to draw by a hundred and four quadrangles made up of 144 vertex coordinates.

Further, in the drawing process when the drawing circle to be drawn is smaller than the basic circle, each vertex coordinate of the basic circle is converted into each vertex coordinate of the drawing circle based on the reduction ratio of the drawing circle with respect to the basic circle. By doing so, the drawing circle is drawn.

[0005]

However, in the above-described circle drawing method, since the coordinates of the 144 vertices of the basic circle are converted into the coordinates of the vertices of the drawing circle, the drawing circle may be small. However, since it takes the same drawing time as the basic circle, there is a problem that the drawing speed is slow for a small circle. The present invention has been made in consideration of the above situation, and an object of the present invention is to provide a circle drawing method capable of improving the drawing speed when drawing a small circle.

[0006]

The invention according to claim 1 corresponds to a basic circle having the maximum size that can be drawn in a drawing method of a circle in which a drawing circle is approximately drawn with a polygon. A basic circle coordinate memory that stores a plurality of vertex coordinate values of a polygon, and a vertex coordinate thinning-out means that thins out and extracts each vertex coordinate value from the basic circle coordinate memory based on the size of the drawing circle. A vertex coordinate calculation means for reducing each vertex coordinate value extracted by the vertex coordinate thinning means based on the size of the drawing circle to calculate each vertex coordinate forming the drawing circle; Among the vertex coordinates calculated by the calculation means, the drawing circle display means for connecting the adjacent vertex coordinates to display the drawing circle is a circle drawing method.

The invention according to claim 2 is the circle drawing method according to claim 1, wherein the size of the drawing circle is the radius of the drawing circle. Furthermore, the invention corresponding to claim 3 is the circle drawing method according to claim 1, wherein the size of the drawing circle is the diameter of the drawing circle.

[0008]

Therefore, in the invention according to claim 1, the plurality of vertex coordinate values of the polygon corresponding to the basic circle having the maximum drawable size are stored by taking the above means. A basic circular coordinate memory is provided, and the vertex coordinate thinning means is
Based on the size of the drawing circle, each vertex coordinate value is thinned out and taken out from the basic circle coordinate memory, and the vertex coordinate calculation means extracts each vertex coordinate value taken out by this vertex coordinate thinning means as the size of the drawing circle. The drawing circle display means draws by connecting adjacent vertex coordinates among the vertex coordinates calculated by the vertex coordinate calculation means by performing a reduction calculation based on Since the circle is displayed, the drawing speed can be improved when drawing a small circle.

In the invention according to claim 2, since the size of the drawing circle is the radius of the drawing circle, the same operation as the operation corresponding to claim 1 can be achieved. Further, in the invention according to claim 3, since the size of the drawing circle is the diameter of the drawing circle, the same operation as the operation corresponding to claim 1 can be achieved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a graphic display device to which a circle drawing method according to an embodiment of the present invention is applied. This graphic display device has a basic circular coordinate memory 1, an interlace number memory 2,
A common bus 8 for the microprocessor 3, the work memory 4, the line drawing unit 5, the frame memory 6, and the display control unit 7.
The display control unit 7 is connected to the monitor 8.

Here, the basic circle coordinate memory 1 is a memory in which 144 vertex coordinate values (x, y) corresponding to the basic circle are stored. Specifically, as shown in FIG. (X1
, Y1) = (cos 360 degrees / 144, sin 360
Degree / 144), (x2, y2) = (cos 360 degree × 2
/ 144, sin 360 degrees x 2/144), ..., (x14
4, y144) = (cos 360 degrees × 144/144, s
in 360 degrees × 144/144) is stored.

The jump number memory 2 is, as shown in FIG.
Based on the ratio n of the size of the drawing circle to the basic circle, the number m of jumps for thinning out the vertex coordinate values in the basic circle coordinate memory 1 and the vertex coordinate values of the basic circle after thinning are drawn in the drawing circle. And the angle number a indicating the number of times of calculation for converting each vertex coordinate value.

The microprocessor 3 controls the entire apparatus in accordance with the procedure shown in FIG. 4. Specifically, the basic circle coordinate memory is based on the ratio n of the size of the drawing circle to the basic circle. While referring to 1 and the jump number memory 2, each vertex coordinate value in the basic circle coordinate memory 1 is thinned out, and each vertex coordinate value of the basic circle after thinning is converted into each vertex coordinate value of the drawing circle. It has a function of giving each vertex coordinate value of the drawing circle to the straight line drawing unit 5.

The work memory 4 is the microprocessor 3
Is a storage unit used for calculation such as coordinate conversion. The straight line drawing unit 5 has a function of drawing a drawing circle in the frame memory 6 by connecting adjacent vertex coordinate values of the drawing circles given by the microprocessor 3 with a straight line.

The frame memory 6 stores data representing a drawing circle drawn by the straight line drawing section 5 in dot units as a screen image. The display control unit 7 sequentially fetches data for each line from the frame memory 6 and outputs the data to the monitor 9 as a video signal.

The monitor 9 displays the video signal received from the display controller 7 on the screen. Next, a drawing method of a circle by the graphic display device configured as described above will be described with reference to the flowchart of FIG.

Now, in the microprocessor 3, it is assumed that the radius of the drawing circle is input by the operation of the operator (ST
1). The microprocessor 3 divides the radius of the basic circle by the radius of the drawing circle to obtain the ratio n of the drawing circle to the basic circle, and obtains the ratio n as a result of the division (ST
2).

Subsequently, the microprocessor 3 determines the ratio n.
Accordingly, the number of jumps m and the number of corners a are fetched from the jump number memory 2 (ST3), and the vertex coordinates (xi, yi) are fetched from the basic circle coordinate memory 1 (ST4).

The microprocessor 3 also converts the vertex coordinates (xi, yi) into the vertex coordinates (Xi, Yi) {= (xi / n, yi / n)} of the drawing circle based on the ratio n. (ST5), the obtained vertex coordinates (Xi, Yi)
Is given to the straight line drawing unit 5 (ST6).

The straight line drawing section 5 uses the vertex coordinates (Xi, Y
i) and the vertex coordinates given last time are connected by a straight line, and the data of this straight line is updated in the frame memory 6.
The data in the frame memory 6 is given to the monitor 9 via the display controller 7. That is, a straight line connecting the respective vertex coordinates of the drawing circle is sequentially displayed on the monitor 9.

On the other hand, the microprocessor 3 adds the jump number m and "+1" to the address of the vertex coordinate (xi, yi) in the basic circular coordinate memory 1 to add the next vertex coordinate (xi + 1).
, Yi + 1) of the basic circular coordinate memory 1 is obtained (ST7). For example, when the ratio n = 2, the number of jumps is m = 1, so that the addresses of the basic circular coordinate memory 1 are skipped one by one, as shown in FIG. Is required. At this time, the angle number a = 144 / (m + 1) = 1
44/2 = 72.

Further, the microprocessor 3 subtracts 1 from the thus obtained angle a to obtain an undrawn angle, and determines whether or not this angle is zero (ST8).
When the number of undrawn corners is not zero, steps ST4 to ST
Repeat steps 7 to 7 again. As a result, the coordinates of the vertices forming the drawing circle are sequentially connected by a straight line.

Thereafter, when the result of the determination in step ST8 shows that the number of undrawn corners is zero, it is considered that the drawing of the drawing circle has been completed, and the drawing process of the circle is ended. As described above, according to this embodiment, the basic circle coordinate memory 1 in which the plural vertex coordinate values of the polygon corresponding to the basic circle having the largest drawable size are stored is provided, and the microprocessor 3 is provided.
Based on the size of the drawing circle, the vertex coordinate values are thinned out from the basic circle coordinate memory 1 and the vertex coordinate values are reduced based on the size of the drawing circle to form the drawing circle. By calculating the respective vertex coordinates and giving them to the straight line drawing unit 5, the straight line drawing unit 5 draws in the frame memory 6 by connecting the respective adjacent vertex coordinates of these vertex coordinates, and the display control unit 7 A drawing circle is displayed on the monitor 9 via the monitor. That is, since the number of vertex coordinates used for drawing is reduced according to the size of the drawing circle, the drawing speed can be improved when drawing a small circle.

In the above embodiment, the ratio n = radius of the basic circle / radius of the drawing circle is described, but the present invention is not limited to this, and the ratio n = radius of the drawing circle / basic circle of step ST2. Meanwhile, in step ST5, the coordinates of the vertices of the drawing circle (Xi, Yi) {= (xi * n, yi *)
n)}, the same effects can be obtained by implementing the present invention in the same manner.

Further, in the above embodiment, the case where the ratio n is obtained based on the radius of the basic circle and the radius of the drawing circle has been described, but the present invention is not limited to this, and it is based on the diameter of the basic circle and the diameter of the drawing circle. Even if the ratio n is obtained by the above, the same effects can be obtained by implementing the present invention in the same manner.

In the above embodiment, the case where the number of vertex coordinates of the basic circle is 144 has been described, but the present invention is not limited to this, and the number of vertex coordinates of the basic circle may be any other number. The invention can be implemented in the same manner and similar effects can be obtained. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0027]

As described above, according to the invention of claim 1, a basic circle coordinate memory storing a plurality of vertex coordinate values of a polygon corresponding to a basic circle having the maximum drawable size is provided. The vertex coordinate thinning-out means thins out and extracts each vertex coordinate value from the basic circle coordinate memory based on the size of the drawing circle, and the vertex coordinate calculating means extracts each vertex coordinate thinning-out means. Reduce the vertex coordinate value based on the size of the drawing circle to calculate the coordinates of each vertex forming the drawing circle,
Since the drawing circle display means displays the drawing circle by connecting the adjacent vertex coordinates among the vertex coordinates calculated by the vertex coordinate calculating means, it is possible to improve the drawing speed when drawing a small circle. Can be provided.

According to the second aspect of the invention, since the size of the drawing circle is the radius of the drawing circle, it is possible to provide a circle drawing system which can achieve the same effect as in the first aspect. Further, according to the invention of claim 3, since the size of the drawing circle is the diameter of the drawing circle, it is possible to provide a circle drawing method which can achieve the same effect as in the first aspect.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a graphic display device to which a circle drawing method according to an embodiment of the present invention is applied;

FIG. 2 is a configuration diagram of a basic circular coordinate memory in the embodiment,

FIG. 3 is a configuration diagram of an interlace number memory in the embodiment,

FIG. 4 is a flow chart for explaining the operation of the embodiment.

FIG. 5 is a schematic diagram for explaining the operation in the embodiment.

[Explanation of symbols]

1 ... Basic circular coordinate memory, 2 ... Jump number memory, 3 ... Microprocessor, 4 ... Work memory, 5 ... Straight line drawing section,
6 ... Frame memory, 7 ... Display control unit, 8 ... Bus, 9 ...
monitor.

Claims (3)

[Claims] 1. A circle drawing method for drawing a drawing circle approximately by a polygon, in which a plurality of vertex coordinate values of a polygon corresponding to a basic circle having the largest drawable size are stored. A circle coordinate memory, a vertex coordinate thinning-out means for thinning out and extracting each vertex coordinate value from the basic circle coordinate memory based on the size of the drawing circle, and each vertex extracted by the vertex coordinate thinning means. Among the vertex coordinates calculated by the vertex coordinate calculation means for reducing the coordinate value based on the size of the drawing circle and calculating the vertex coordinates forming the drawing circle, A drawing circle display means for connecting the coordinates of adjacent vertices to display the drawing circle. 2. The circle drawing method according to claim 1, wherein the size of the drawing circle is a radius of the drawing circle. 3. The circle drawing method according to claim 1, wherein the size of the drawing circle is a diameter of the drawing circle.