JPH0145639B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device, particularly a vector scan type graphic display device, and relates to a method for displaying an arbitrary circular arc by approximating a regular polygon.

A vector scan type graphic display device generally has a function of displaying a straight line connecting the starting point coordinates and the ending point coordinates on the storage type cathode ray tube surface. Therefore, in a computer, a figure to be displayed can be broken down into a plurality of line segments, and the starting point/end point coordinates of the lines can be sent as a set to the display device in sequence. In addition, non-linear, irregular figures are either approximately decomposed into a large number of minute line segments and displayed in the same manner as above, or they are decomposed into dots and all dot coordinates are sent and displayed as dots. Therefore, when displaying such irregular shapes,
This method has drawbacks such as the time required for fine line segment decomposition or dot decomposition in a computer, and the amount of data transmitted between the computer and the display device increases.

For this reason, conventionally, only when displaying circles or arcs, images are automatically created on the display device side by giving the center coordinates and radius (and starting point/end point coordinates for circular arcs) from the computer side. Some display devices are equipped with a display function, but in conventional display devices, the radius of a circle is calculated based on the center point on the screen, and each coordinate on the circumference of the circle is determined. , it was difficult to display arcs whose center point was not on the screen.

The present invention aims to solve the above problems and will be explained in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram of a display form according to the present invention, where 1 is a display screen, and as shown in the figure, when drawing an arc (abcdef) with a center point O and a radius R that is not on the screen, a large number of vectors V1 to It is disassembled into V5 and displayed. The instruction information from the computer includes the coordinate S of the starting point a, the initial vector V1 (that is, θo and r), the increment angle Δθ, and the number of repetitions n (5 times in the example shown).

FIG. 2 is a block diagram of an embodiment of the present invention.
2 to 6 are registers for temporarily storing each of the above instruction information, 7 is an adder, 8 is an end point coordinate calculation means, 9 is an end point coordinate register, 10 is a minus 1 circuit, and 11 is a control circuit for each of these means 2 to 10. , 12 is a conventional vector display which, when given the start point/end point coordinates, displays a straight line vector connecting them.

The operation shown in FIG. 2 will be explained. From the computer n, s,
When each value of r, θo, and Δθ is received, first, the coordinates of the end point b of the initial vector V1 are calculated by the calculation means 8 based on θo and r, and set in the register 9.

Note that the method of calculating each end point coordinate in the end point coordinate calculating means 8 is performed using a known mathematical means. For example, the coordinates of the end point b at the starting point a are as follows: Coordinates of b = (X ₀ + r cos θ, Y ₀ + r sin θ ₀ ) Note that the coordinates of a are (X ₀ , Y ₀ ).

Register 3 and register 9 are provided to display means 12 to display line segment ab. Further, the contents of register 2 are incremented by 1, and θo+Δθ is set in register 5 by adder 7. Furthermore, the end point coordinates of register 9 are set in register 3 and used as the starting point coordinates of the second vector V2.

In the same way as in this state, the end point coordinates of the second vector V2 are calculated by the calculation means 8 and set in the register 9, and steps .about. are repeated in the same manner until the contents of the register 2 become zero.

The arc (abcdef) can be displayed with the above steps. Note that r and Δθ are determined by the radius R of the circle, but a sufficiently small value may be applied as a constant for r.

As another example, instead of specifying the number of repetitions n, the coordinates of the final point f are specified, and the coordinates of the final point f, which are calculated sequentially, are compared each time, and it is determined that the two match or match within a predetermined tolerance. You can also end the process.

In any case, according to the present invention, any arc can be drawn regardless of whether the center point is on the screen or not, and only a small amount of instruction information from the computer is required.

Note that by setting Δθ and r as functions of n, it is possible to display any line figure other than a circular arc.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of arc drawing according to the present invention, and FIG.
The figure is a block diagram of one embodiment of the present invention. In the figure, 2 to 6 and 9 are registers, 7 is an adder,
8 is the end point coordinate calculation means, 10 is the minus 1 circuit,
11 is a control circuit, and 12 is a vector display means.

Claims (1)

[Scope of Claims] 1. In a display device having display means for displaying a straight line connecting the two points on the screen given starting point coordinates and ending point coordinates, the starting point coordinates, the initial vector, the incremental angle given from an external device, and means for temporarily storing either the number of repetitions or the final point coordinates; and a calculating means for sequentially calculating the next end point coordinates by using the previous end point coordinates as new starting point coordinates based on the temporarily stored information. means for repeating the calculation operation up to the temporarily stored number of repetitions or until the calculated end point coordinates match the temporarily stored final point coordinates, and based on the start point/end point coordinate set sequentially given from the calculation means A display device characterized in that the display means displays images sequentially.