SU807366A1 - Device for shaping cicumference on crt screen - Google Patents

Description

The invention relates to computer technology and can be used in devices for displaying information.

A device for forming circles containing a control unit, a counter, a register, a memory unit, and AND, and OR elements [1]. ⁵

The closest in technical essence is a device for forming circles on the screen of a cathode ray tube, containing series-connected adders, code-voltage converters 10, a backlight unit connected to a CRT, a control unit, the first output of which is connected to one inputs of the adders and other inputs of the code converters -voltage, the second output of the control unit is connected to the register [2]. ^fifteen

The main disadvantage of the known devices is their complexity due to the need for storage, amendments on each line of the television raster.

The purpose of the invention is to simplify the device.

This goal is achieved in that the device comprises a comparison unit and a counter connected to the third output of the control unit and the first input of the comparison unit, the second input of which is connected to the fourth output of the control unit, the input of the control unit is connected to the output of the comparison unit, the third input of which connected to the output of the register .;

The drawing shows a block diagram of the proposed device.

The device comprises a register 1, a control unit 2, a comparison unit 3, a counter 4, adders 5 and 6, code-voltage converters 7 and 8, a backlight unit 9, and a cathode ray tube 10.

The device operates as follows.

A circle radius code R is sent to register 1 of the circle radius code, for example, from a computer, and codes of coordinates of the starting point of the circle X _о and Yo — R are received on adders 5 and 6 for calculating the current coordinates of the semicircles and where X _о and Υ _ο - codes of coordinates of the center of the circle relative to the starting point of the screen, located at the upper left.

The coordinate Υ ₀ —R can be calculated directly in the device.

. 807366

At the beginning of the formation of the raster? according to the .vinal from the control unit 2, the circle radius code from register 1 enters the comparison unit .3.

If the current coordinates X _t and Υ _τ coincide with the coordinates Xo and Υ _β —R, the control unit 2 generates a signal according to which the converters 7 and 8 work out the specified coordinates.

After the initial point of the circle is highlighted, the coordinates of the points of the left and right semicircles are formed for the next line of the television raster on the CRT screen 10. For this, a signal decreasing the vertical coordinate by one is received from input control unit 2 to input comparing unit 3, and therefore the equation circumference

U ² + V ² = R ² , (1) expressed by the horizontal U and vertical V axes intersecting at its center for the starting point of the circle, which in this system has coordinates U о = 0 and V _o = R is written

U * + (Vo-1) ² = R ² ₊ E _Vi = R ² , (2) where Εν, - -2V ₀ + 1 is the first increment of the square V. Therefore, the radius R ₁ will correspond to the new value of the vertical coordinate V <R, and the sign of the value of the mismatch equal to E _l = E _V will have a negative value, which will ensure the signal from the block 3 comparison in block 2. control.

In order to eliminate the inconsistency that has arisen, i.e., to fall back on a circle of radius R, a signal is received from the control unit 2 to the input a of the comparison unit 3 and the input of the counter 4 for forming horizontal increments, increasing the coordinate U о and the contents of the counter by one. Moreover, the equation (2) of the circle takes the form (Uo + I) ² + (Vo-l) ² = R ² + EU (= R | (3) where E _u = 2U o + I is the first increment of the square U. *

In this regard, the value of the mismatch will become equal

E _d = E <+ £ _ν _ ⁽⁴⁾ If Li <0, i.e., the sign of the mismatch has not changed, then the coordinate U _o is given the following unit increment. This is repeated until the mismatch sign becomes positive. At the same time, in the counter 4 of the formation of increments horizontally, an increment will be formed, which is entered in the adder 5 and 6, where it is added up and, accordingly, subtracted for the right and left semicircles with the coordinate X _{about there} . The described processes end at the beginning of the next line, after which the transducers 7 and 8 work out the coordinates of the circle, and the backlight unit 9 highlights the current sections of the circle. The horizontal incrementing counter 4 is set to zero at the beginning of each previous television line in order to form an increment for the next line. If decreasing the coordinate of Vo by one does not change the sign of the radius mismatch to negative, then the increment for the next line will be zero, and the coordinates of the circle will be processed based on the information in adders 5 and 6, which was used for the previous line.

When the number of pulses received from the control unit 2 to the comparison unit 3 by input b is compared with the circle radius code contained in register 1 of the radius code * *, the display of the upper half of the circle will end and the control unit will switch to the formation mode of the lower half of the circle, consisting in decreasing the coordinate of Uo by one and increasing the coordinate of Vo at each measure, so that the mismatch signs are reversed. '

The process of displaying the circle ends when the number of pulses received from the control unit 2 at input b is equal to 2R.

When plotting an arc of a circle (in the case Y <R), the device starts in the previous frame by the signal Υ _τ = — _ο —R, but only that part of the circle is displayed for which the condition Y _T 'D.

The introduction into the device of block 3 of comparison and counter 4 of the formation of horizontal increments allows to simplify the maintenance of the device and ensures the formation on a television raster also of parabolas and other figures with good image quality.

Claims (2)

1. USSR author's certificate number 610144, cl. G 06 K 15/20, 1977. 2. USSR author's certificate No. 538832, cl. G 06 K 15/20, 1977 (prototype). S -