JPH04352291A - Circle drawing system of graphic display system - Google Patents

Abstract

PURPOSE:To draw a circle at a high speed. CONSTITUTION:A circumference registering process means 2a is actuated from an input means 1a and circle information on radii which are high in use frequency are registered. A circle drawing control means 3a checks whether or not circumference information is registered in a circumference address storage means 7a. When the information is registered, a circumference drawing process means 6a is actuated to calculate the address of a circumference by adding the address of the center position of a specified circle on a frame buffer 8a to a relative address registered in the circumference address storage means 7a, thereby writing pixel data in the address. When the information is not registered, on the other hand, a segment developing process means 4a is actuated to approximate the circumference with a polygon and develop it into a segment sequence; and a segment drawing process means 5a is actuated to generate addresses of respective dots on the segments in the segment sequence, thereby writing the pixel data. Thus, the circle with the specified radius is drawn at the indicated position on the frame buffer 8a and displayed on a display device 9a.

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 for a graphic display system.

0002

2. Description of the Related Art In the circle drawing method of a conventional graphic display system, a circle is drawn by approximating the circumference of a circle to a polygon every time it is drawn, expanding it into a series of line segments, and drawing the line segments.

0003

[Problems to be Solved by the Invention] The circle drawing method of the conventional graphic display system described above requires polygonal approximation of all circumferences, line segment series expansion, and even when circles with the same radius are frequently used.
Since it is necessary to draw line segments, there is a problem that the processing time becomes long.

0004

[Means for Solving the Problems] The circle drawing method of the graphic display system of the present invention includes a frame buffer in which a drawing is drawn, an input means for inputting a circle registration instruction, circle information, and a circle drawing instruction, and a center of the circle. Line segment expansion processing means for approximating a circle as a polygon based on a position and radius and developing the circumference into a line segment sequence; and a line segment drawing process that is activated by the line segment expansion processing means and draws a straight line in the frame buffer. means, a circumference address storage means for storing a plurality of sets of circumference address data strings, activated by the circle registration instruction, approximating the circumference with a polygon from the circle information and developing it into a line segment sequence; a circumference registration processing means for registering in the circumference address storage means a relative address string from the center position of the circle to the circumference when drawn in a frame buffer; and a circumference registration processing means for registering a relative address string of the circumference from the circumference address storage means a circumferential drawing processing means for reading and writing pixel data into the frame buffer; and, if a circle having the same radius as the radius of the circle instructed to be drawn by the drawing instruction exists in the circumferential address storage means, the circumferential drawing processing; and circle drawing control means for starting the line segment expansion processing means in the case of a circle having a radius different from the radius of the circle instructed to be drawn.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of a first embodiment of the present invention, FIG. 2 is a block diagram of a second embodiment of the present invention, and FIG. 3 is a diagram showing registered data in the circumferential address storage means of FIGS. 1 and 2. It is. In the registration data in Figure 3, Rn is the radius, and Ln is the circumference length (dot number).
, An(Ln) represents a relative address string obtained by converting the address of each dot on the circumference into a relative address from the center position of the circle.

Next, the operation of the first embodiment of the present invention will be explained with reference to FIGS. 1 and 3. The operator uses input means 1
A circle registration instruction is input from step a to start the circumference registration processing means 2a, and register information on circles with frequently used radii. The circumference registration processing unit 2a uses a polygon approximation processing unit 21a to approximate the circumference with a polygon based on the size of the radius and develop it into a line segment sequence. After development, the circumferential address registration unit 22a registers each dot on the line segment array in the circumferential address storage means 7a in the form of a relative address from the center position of the circle.

Next, the operator issues a circle drawing instruction from the input means 1a and starts the circle drawing control means 3a. The circle drawing control means 3a checks whether the circumference information of the circle to be drawn by the radius determination section 31a is registered in the circumference address storage means 7a. If it is registered, the circumference drawing processing means 6a is activated by the circumference drawing processing means starting section 32a.
Start. The circumference drawing processing unit 6a stores the address on the frame buffer 8a of the center position of the circle specified by the circumference address calculation processing unit 61a in the circumference address storage unit 7.
Add to the relative address registered in a. After calculating the circumference address, the circumference drawing processing unit 62a writes pixel data to the address. As a result, a circle with the specified radius is drawn at the specified position on the frame buffer 8a.

Furthermore, the radius determining section 3 of the circle drawing control means 3a
If it is determined that the circle with the radius specified by 1a is not registered, the line segment expansion processing means activating section 33a activates the line segment expansion processing means 4a. Line segment expansion processing means 4
a, the polygon approximation processing unit 41a approximates the circumference with a polygon based on the size of the radius, develops it into a line segment sequence, and the line segment drawing processing unit activating unit 42a starts the line segment drawing processing unit 5a. do. The line segment drawing processing unit 5a generates an address for each dot on the line segment of each line segment column using the line segment drawing processing unit 51a, and writes pixel data therein. As a result, frame buffer 8
A circle with the specified radius is drawn at the specified position on a and displayed on the display device 9a such as a CRT.

Next, the operation of the second embodiment of the present invention will be explained with reference to FIGS. 2 and 3. The operator uses input means 1
A circle drawing instruction is issued from b, and the circle drawing control means 3b is activated. The circle drawing control means 3b checks whether the circumference information of the circle to be drawn is registered in the circumference address storage means 7b by the radius determination section 31b. Radius determination section 31
If it is determined that the line segment expansion processing means 4b is not registered, the line segment expansion processing means activating section 33b activates the line segment expansion processing means 4b. The line segment expansion processing unit 4b uses a polygon approximation processing unit 41b to approximate the circumference with a polygon based on the size of the radius and expands it into a line segment sequence. Thereafter, the line segment drawing processing means 5b is activated by the line segment drawing processing means starting section 42b. The line segment drawing processing unit 5b generates a write address for each dot on the line segment using the line segment drawing processing unit 51b, and writes pixel data therein. As a result, a circle with the specified radius is drawn at the specified position on the frame buffer 8b. and,
The circumference registration processing means 2b is started by the circumference registration processing means starting section 52b. The circumference registration processing means 2b checks whether the circumference address storage means 7b is full or not using the registration management section 23b. If it is full, the circumference information of the radius least frequently used is deleted, and the circumference address registration unit 22b sets the write address of each dot on the generated line segment by the line segment drawing processing unit 5b from the center position of the circle. It is converted into a relative address and registered in the circumferential address storage means 7b.

If the radius determining unit 31b of the circle drawing control unit 3b determines that a circle with the specified radius is registered, the circumference drawing processing unit activating unit 32b starts the circumference drawing processing unit 6b. . The circumference drawing processing means 6b adds the address on the frame buffer 8b of the center position of the circle specified by the circumference address calculation processing section 61b to the relative address registered in the circumference address storage means 7b. The circumference address is calculated and pixel data is written to the address by the circumference drawing processing section 62b. As a result, a circle with the designated radius is drawn at the designated position on the frame buffer 8b and displayed on the display device 9b.

[0011]

Effects of the Invention As explained above, the present invention can draw circles at high speed by registering relative addresses from the center position to the circumference of frequently used circles drawn on the frame buffer or circles that have been drawn once. There is an effect that can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a first embodiment of the invention.

FIG. 2 is a block diagram of a second embodiment of the invention.

FIG. 3 is a diagram showing registration data in the circumferential address storage means of FIGS. 1 and 2;

[Explanation of symbols]

1a, 1b Input means 2a, 2b Circumference registration processing means 3a, 3b Circle drawing control means 4a, 4b Line segment expansion processing means 5a, 5b Line segment drawing processing means 6a, 6b Circumference drawing processing means 7a, 7b Circumference address Storage means 8a, 8b
Frame buffers 9a, 9b Display device 21a Polygon approximation processing units 22a, 22b Circumferential address registration unit 23b
Registration management section 31a, 31b Radius determination section

Claims (3)

[Claims] 1. A frame buffer in which a drawing is drawn, an input means for inputting a circle registration instruction, circle information, and a circle drawing instruction, and a polygonal approximation of a circle from the center position and radius of the circle,
a line segment expansion processing means for expanding a circumference into a line segment string; a line segment drawing processing means activated by the line segment expansion processing means to draw a straight line in the frame buffer; and a plurality of sets of circumference address data strings. from the center position of the circle when it is activated by the circle registration instruction, approximates the circumference with a polygon from the circle information, develops it into a line segment sequence, and draws it in the frame buffer. Circumference registration processing means for registering a relative address sequence up to the circumference in the circumference address storage means; and a circle for reading out the relative address sequence for the circumference from the circumference address storage means and writing pixel data into the frame buffer. If a circle having the same radius as the circle instructed to be drawn by the drawing instruction exists in the circumference address storage means, the circumference drawing processing means is started, and the radius of the circle instructed to be drawn is activated. and a circle drawing control means for activating the line segment expansion processing means in the case of a circle having a radius different from that of the circle drawing method for a graphic display system. 2. A circle drawing method for a graphic display system according to claim 1, wherein said circumference registration processing means is activated by said line segment drawing processing means. 3. The circumference registration processing means checks whether or not the circumference address storage means is full, and if it is full, deletes the circumference information of the radius least frequently used, and deletes the circumference information of the least frequently used radius, 3. The graphic display system according to claim 2, wherein the processing means converts the write address of each dot on the generated line segment into a relative address from the center position of the circle and registers the same in the circumferential address storage means. Circle drawing method.