JPH0589249A - Sector generating device - Google Patents

Abstract

PURPOSE:To generate a sectoral figure, whose inside is painted out, by hardware or software having a simple configuration. CONSTITUTION:An arc digital differential analyzing(DDA) operation part 12 receives parameters such as coordinates of both end points and the radius of an arc from a parameter setting part 10 and scans and converts the arc by DDA of a circle based on the Bresenham circle drawing algorithm to obtain raster lattice points Pi on the arc from the start point to the end point one by one. A segment DDA operation part 14 receives not only coordinate data of the point of the pivot of a sector to be drawn from the parameter setting part 10 but also coordinate data of raster lattice points on the arc obtained by the arc DDA operation part 12 and discriminates all picture elements which segments connecting respective points on the arc and the point of the pivot of the sector pass. An output part 16 outputs coordinate data of picture elements passing respective segments, which are obtained by the segment DDA operation part 14 with respect to raster lattice points on the arc, as data of raster coordinates of segments connecting raster lattice points and the pivot point of the sector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to computer graphics technology, and more particularly, to an apparatus for generating a fan-shaped interior.

[0002]

2. Description of the Related Art Conventionally, as a technique for generating a fan shape whose interior is filled, as shown in FIG. 9, a fan-shaped outline (fan shape that does not fill the interior) S to be drawn is generated, and a scan line Ri and a fan shape are focused. There is a method of obtaining intersection points Pi and Qi with the contour S and connecting these two intersection points Pi and Qi with a straight line. The fan-shaped contour S is composed of two line segments OA and OB that connect the point O of the fan-shaped point and the end points A and B, and an arc AB that connects the end points A and B. A region in which both Pi and Qi are located on the arc AB, one intersection point Pi is located on the line segment OA, and the other intersection point Q is
i is a region located on the arc AB, one intersection point Pi is located on the line segment OA, and the other intersection point Q is
The area is divided into three areas, i is an area located on the line segment OB, and the area is filled.

[0003]

As described above, in the conventional fan-shaped generating device, the areas inside the fan-shaped contour S are filled by dividing the areas into three areas, and the intersection points Pi and Qi for each area. Since it has to be performed, the calculation becomes complicated, and the hardware or software of the calculation device becomes complicated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a device capable of generating a fan-shaped figure whose interior is filled with hardware or software having a simple structure.

[0005]

In order to achieve the above-mentioned object, a fan-shaped generator of the present invention is provided in a fan-shaped generator for drawing a fan-shaped figure whose interior is filled on a grid point coordinate system. Arc generating means for scan-converting an arc defining a fan-shaped contour to be drawn from the parameters,
Line segment generating means for outputting, as raster coordinates, the coordinates of all pixels through which a straight line connecting each point on the arc determined by the arc generating means and the point of the fan shape to be drawn passes. It was composed.

[0006]

When the raster grid points on the circular arc are obtained by the scan conversion of the circular arc generating means, the straight line (Li) connecting the raster grid points and the required points can be defined from the coordinates of both points.

When this straight line (Li) is defined, a straight line DD using, for example, the Bresenham straight line drawing algorithm
By calculating A, the raster pixel between the raster grid point and the fan-shaped essential point can be obtained. But,
According to such a method, adjacent straight lines (Li), (Li +
Pixels that are not selected as raster pixels (non-raster pixels) may occur between 1), and those pixel portions become non-filled portions.

In the present invention, an arithmetic operation is performed so that all pixels passing through each straight line (Li) are selected as raster pixels.
As a result, the space between adjacent arbitrary straight lines (Li) and (Li + 1) is always filled with raster pixels, and a non-filled portion does not occur.

As described above, according to the present invention, a line segment is defined between each point on a circular arc of a fan shape to be drawn and a point of interest, and each line segment and adjacent line segments are filled with no space. Since this is done, it is not necessary to perform case classification for each area as in the conventional case, and it is possible to generate a fan-shaped figure whose interior is filled by a uniform calculation from the start point to the end point.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows the configuration of a fan-shaped generator according to an embodiment of the present invention. This fan-shaped generator includes a parameter setting unit 10, an arc DDA calculation unit 12, and a line segment DDA calculation unit 1.
4 and the output unit 16.

In the parameter setting unit 10, parameters for defining a fan shape to be drawn, such as coordinates of each point O and both end points A and B, a central angle of a circular arc, and a radius are set. These parameters may be set and input by a user's key operation or pointing operation under an input routine.

The circular arc DDA calculation unit 12 receives parameters such as the coordinates of both end points A and B and the radius of the circular arc from the parameter setting unit 10 and receives a DDA (digital digit) of a circle based on the Bresenham circle drawing algorithm. The circular arc AB is scan-converted by the differential analysis), and as shown in FIG. 8, each raster grid point Pi on the circular arc AB is obtained from the starting point A to the ending point B one by one.

The line segment DDA calculation unit 14 receives from the parameter setting unit 10 the coordinate data of the required point O of the fan shape to be drawn, and each raster grid point Pi on the arc AB determined by the arc DDA calculation unit 12. All the pixels through which the line segment Li connecting each point Pi on the arc AB and the point O of the fan shape passes, and the coordinate data of those pixels is output.

The output unit 16 converts the coordinate data of the pixels around each line segment Li obtained by the line segment DDA calculation unit 14 for each raster grid point Pi on the arc AB into the raster lattice point Pi on the arc AB. It is output as raster coordinate data of a line segment connecting the point O of the fan shape. The raster coordinate data from the output unit 16 is sent to a display device (not shown) for drawing on a CRT display, or is sent to a printing device (not shown) for drawing on recording paper. Alternatively, it may be sent to an image memory (not shown) for storage.

Next, the operation of the line segment DDA calculation unit 14 will be described with reference to FIGS. 2 and 3,
Fi, j is a grid point, and Gi, j is a pixel. In this example, F
0,0 is a point O of the ellipse to be drawn, F8,5 is one raster grid point Pi on the arc AB defining the contour of the ellipse to be drawn, and the straight line Li is the raster grid on the arc AB. Point Pi
Is a straight line connecting the point O of the fan shape.

FIG. 2 shows the raster coordinates of pixels obtained when the DDA of the straight line Li is calculated using the Bresenham straight line drawing algorithm as it is. According to Bresenham's straight line drawing algorithm, x or y is increased by one unit (grid point distance) according to the inclination of a given straight line, and the distance between the actual straight line position and the closest grid point position is investigated. Determines the increment (0 or 1) of the other variable y or x.

In the illustrated example, since the inclination θ of the straight line Li with respect to the X axis is 0 <θ <45 °, it is decided to determine the increment of y when the grid point coordinate is increased by one unit in the x direction. Become. For example, when the distance from the starting point F0,0 is increased by one unit in the x direction by one unit, the distance (error) from the intersection J1 between the straight line x = 1 and the straight line Li to the grid point F1,1 is greater for the grid point F1,1.
Since it is shorter (closer), the grid point F1,1 is selected, and thus the pixel G1,1 is selected as a raster pixel (pixel to be filled). In this way, the starting point F0,0
Between (O) and the end point F8,5 (Pi), the grid points F1,1, F
2,1, F3,2, F4,3, F5,3, F6,4 and F7,4 are selected as raster grid points, and pixels G1,1 and G2,1 are selected.
, G3,2, G4,3, G5,3, G6,4, G7,4 are raster pixels.

If the Bresenham straight line drawing algorithm is applied as it is as described above, the pixel G1,0 which is not selected as a raster pixel although the straight line Li passes through is selected.
, G3,1, G4,2, G6,3 exist. Because of this
There may be a pixel that is not a raster pixel between the adjacent line segments Li and Li + 1 connecting the adjacent raster coordinate points Pi and Pi + 1 on the arc AB and the point O, respectively. Areas may result in not being filled.

In this embodiment, the error evaluation method of Bresenham's straight line drawing algorithm is changed so that such non-filled portions do not occur. That is, in the line segment DDA calculation unit 14 of the present embodiment, the DDA of the straight line Li is calculated based on the Bresenham straight line drawing algorithm, and the original raster pixels G0.0, G1,1, G2,1, G3, 2, G4,3
, G5,3, G6,4, G7,4 are determined, and pixels G1,0, G3,1, other than those pixels through which the straight line Li passes,
G4,2 and G6,3 are also added to the raster pixels. As a method of discriminating these additional raster pixels, for example, there is a method of discriminating from the coordinates of the intersection JN of the straight line x = N and the straight line Li when they are increased by one unit in the x direction.

Therefore, according to the line segment DDA calculation of the present embodiment, as shown in FIG.
All pixels G0,0, G1,0, G1,1, G2,1, G3,1, G3,2 through which a straight line Li connecting i and the point O of the sector shape passes
, G4,2, G4,3, G5,3, G6,3, G6,4, G7,4 are selected as raster pixels, and their respective grid points F0,0, F1,0, F1,1 are selected. , F2,1, F3,1, F3,
2, F4,2, F4,3, F5,3, F6,3, F6,4, F7,4
Is selected as the raster coordinate.

FIG. 4 shows how the line segment DDA operation of this embodiment fills. In the figure, the dotted line KAB is a part of a fan-shaped arc AB to be drawn, and the grid points Pi, Pi + 1, Pi + 2
Is a raster grid point on the arc AB determined by the arc DDA calculation unit 12, and O is a key point of a fan shape to be drawn.

Such three raster grid points Pi and Pi +
Line segments Li and Li + 1 connecting 1 and Pi + 2 to the point O of the fan shape
, Li + 2 are defined, but according to the line segment DDA calculation of the present embodiment, all the pixels through which each line segment Li, Li + 1, Li + 2 pass are selected as raster pixels, so As described above, the space between the line segments Li, Li + 1, and Li + 2 is always filled with raster pixels, and a non-filled portion does not occur.

5 to 7 show line segments Li, Li + 1, Li + 2.
The distribution of raster pixels obtained by the line segment DDA calculation unit 14 for each of the above. The filled area in FIG. 4 corresponds to a combination of these raster pixels around each line segment.

As described above, according to the present embodiment, as shown in FIG. 8, a line segment Li is provided between each raster grid point Pi on the arc AB of the fan shape to be drawn and the point O of the fan shape. Draw
At this time, the line segments Li-1, Li, Li + 1 adjacent to each other can be filled without any space. Therefore, it is not necessary to divide the case into a plurality of filled areas as in the conventional case, and the start point A
A completely filled fan-shaped figure can be generated by uniform calculation from the end point B to the end point B.

[0025]

As described above, according to the present invention,
Each point on the circular arc of the sector to be drawn is obtained by scan conversion, and the coordinates of all the pixels passing through the straight line connecting each point on the determined arc and the point of the sector are output as raster coordinates. As a result, a fan-shaped figure whose interior is filled is generated, so that the fan-shaped generator can be realized by hardware or software having a simple structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a fan-shaped generator according to an embodiment of the present invention.

FIG. 2 is a comparative diagram for explaining the operation of the line segment DDA calculation unit of the embodiment.

FIG. 3 is a diagram for explaining an operation of a line segment DDA calculation unit of the embodiment.

FIG. 4 is a diagram showing a state of filling in a fan shape according to an example.

5 is a diagram showing a distribution of raster pixels around a first straight line forming the filled area in FIG. 4;

FIG. 6 is a diagram showing a distribution of raster pixels around a second straight line forming the filled area in FIG. 4;

7 is a diagram showing a distribution of raster pixels around a third straight line forming the filled area in FIG. 4;

FIG. 8 is a diagram showing a process of generating a filled fan-shaped figure according to the embodiment.

FIG. 9 is a diagram showing a process of generating a filled fan-shaped figure by a conventional fan-shaped generator.

[Explanation of symbols]

 10 parameter setting unit 12 circular arc DDA calculation unit 14 line segment DDA calculation unit 16 output unit

Claims (1)

[Claims] 1. A fan generating device for drawing a fan-shaped figure whose interior is filled on a grid point coordinate system, and an arc generating means for scan-converting an arc defining a fan-shaped contour to be drawn from given parameters. A line segment generating means for outputting, as raster coordinates, the coordinates of all pixels through which a straight line connecting each point on the arc determined by the arc generating means and the point of the fan shape to be drawn passes. A fan-shaped generator comprising: