JPS6026986A - Graphic display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a graphic display device including a vector generation circuit for displaying a straight line connecting two points in a two-dimensional image enhancement using a rask scan method.

A conventional graphic display device has a vector generation circuit including a discriminator that calculates the slope of a line segment from the coordinates of the start point and end point of the line segment and determines coordinate points to be sequentially displayed.

Figure m1 shows a display example of vector drawing, where the coordinates of the starting point A of vector 11 are (XAIYA) and the coordinates of the ending point B are (XB
IYB). The unit displacement in the X direction is dX, the corresponding unit displacement in the Y direction is dY, and 1ΔX 1
If = IXB dX-1 (unit length), and if X is displaced by n unit length, the displacement y of Y from the starting point A at that time,
Similarly, . (2) That is, when D=-1ΔXI+21ΔY1≧0, the Y coordinate of the display dot ¥1 is set to YA+1.

1) When <O, set Y,=YA.

First, D+1)2≧0 (however, D2=21Δy1-2
1ΔXl), set the Y coordinate Y2 of the display dot to Yl+1
shall be.

When D, +D≧0 (however, Dt=21ΔYl),
Let Y2 be YA+1.

n=3, --- For n, C is determined in the same way as when n=2.

Therefore, an address for generating a vector can be calculated using the algorithm shown in (Step 1) to (Step 5) below.

The addresses in the X direction and Y direction are sequentially determined and plotted by the following steps.

(Step 1) ΔX=XB-XA, Δ"y=yB-yAD--1ΔXl
+21ΔYl, D1=21ΔYID2=21ΔYl
-21ΔX1 is calculated by H], set in each register, and set XA to X counter.
, sets YA in the X counter. Also, the number of drawing points in the 1ΔxBx direction is set in the dot counter.

(Step 2) Write the value (0 or 1) indicated by the line type register at the refresh memory address indicated by (X counter, X counter) (to display the line segments of each building, such as solid lines and broken lines).

(Step 3) If ΔX>0, count up the X counter by +1.

If ΔX<0, count down the X counter by 1.

(Step 4) Count down the dot counter by 1 until the count value is O.
When this happens, vector drawing ends.

(Step 5) (1) If D≧0, set D+D2, and when ΔX>O, count up the X counter by 1, and when ΔX<0, count down the X counter by 1, and go to step 2.

(II) If D > O, set D+D1, keep the count value of the X counter as it is, and go to step 2.

FIG. 2 is a block diagram of a vector generation circuit using the above algorithm. When starting point A and ending point B of a vector are given, XA of starting point A is set to X counter 11, and %YA is
The counter 12 is set to 5-. Furthermore, the adder 4 adds ΔX, ΔY, and D.

Calculate Dl and D2 and store the results in ΔX register 3. ΔY register 4. D register 8. Dl register6.
Set in D2 register 7.

Next, the polarity bit a of the output data of ΔX register 3 is positive/
The count up/down of the X counter 11 is
The count up/down of the X counter 12 is determined by the positive/negative of the polarity bit d of the output data of the ΔY register 5. The countable state of the X counter 12 is the D register 8.
is determined by the polarity bit b of b=v″0″(D>0
), the X counter 12 is enabled, and when b=ゝゝ1''(D<O), it is inhibited. The selection of the output of the register 6.7 by the selector 9 is also performed by the polarity hit b, and b= When the value is "0", the contents of the D2 register 7 are selected, and when b = "1", the output of the Dl register 6 is selected and inputted to the adder 10, and the result of addition with the output of the D register 8 is sent to the D register 8 again. Set to .

The above process is repeated until the borrow signal C of the ΔX counter 2 reaches ``6-0'' (the content of the ΔX register - 0). The bus drivers 13, 14, and 15 are active while the borrow signal C is "1" and are inhibited at C-0.

A vector can be drawn by specifying the start and end points using the method described above, but if you want to superimpose the character side and the class side, or when displaying two graph images on one screen so that they do not overlap each other, or When it is desired to display only a portion of one graph image, a function is required to display a valid portion of a vector only in a limited rectangular area (clip area) of the displayable area, that is, a clip function. As shown in Figure 3, the clip area is (XMIN + XMAX) and (YMIN
+YMAX), conventionally, before giving the start point and end point to the vector generation circuit, it is determined by the program whether the vector lI, which is determined by the start point A and the end point B, is within the clip area. It becomes necessary. As a result of the determination, if part of the vector 11 is outside the clipping area, find the intersection between the vector ll and the line segment that makes up the clipping area, and use that intersection as a new starting point or ending point.
Parameters must be set. Also, if it is completely outside the clipping area, vector drawing is not necessary.

In this way, when the clipping function is requested, the number of processing items in the program becomes extremely large, and the overall vector drawing speed decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a graphic display device that, when a clipping function is required in vector drawing, can process the function using hardware to reduce the load on the program and shorten the vector drawing time.

The graphic display device of the present invention includes a refresh memory, a means for storing data indicating the lengths in the X direction and the Y direction of a vector to be displayed on a two-dimensional screen using a rask scan method, and a means for storing the length in the X direction. The dot counter that is subtracted for each display command and the coordinates of the starting point and ending point of the vector are used to calculate the slope of the line segment, and it is determined whether or not the Y-direction coordinate should be moved in accordance with the movement of the X-direction coordinate. a discriminator that determines the coordinates of a point to be displayed; an X-Y counter that stores the coordinates of a point to be displayed; It is partially shown in the comparison diagram that only the vector drawing address within the clip area is transmitted to the refresh memory compared with the output of the Y counter. FIG. 4 corresponds to the part surrounded by a broken line in FIG. 2. Xλ (AX register 16 sets the maximum value of X in the clip area, XMIN register 17id sets the minimum value of X in the clip area, s YMA
X register 8 sets the maximum value of Y in the clip area as YMr.
N register 9 is a register that stores the minimum value of Y. The comparators 20, 21, 22, 23 have a function of comparing the address of the refresh memory at the time of drawing with the Tsukuda of the clip area, and the output signal e+f+g+h has the following meaning.

e=l: X counter value ≦X MAX value (e=Q: X counter value > X MAX value - ″9′:′
Near f-1; X counter value ≧ X M r N value [ f = o: X counter value < Y counter value ≧ Y MIN value ( h = Q : Y counter value < Y MIN value 5 The output signal i of the manual AND gate 24 is A of the number C2e + f + g + h
It is an ND output and is input to bus drivers 3.14.15, and when i=Q, each bus driver output is inhibited. In other words, if the lip area and the vectors of the starting point A and the ending point B are specified as shown in FIG.
Access to the fresh memory is prohibited from A to cl on llt, and vectors are drawn only from C to B, satisfying the C clip condition.

According to the present invention, even if a clip function is requested,
The program only needs to first set the clip area in the register, and then repeats the same process as when no clip is specified to support the vector clip function. That is, the intervention of program 10-pgrams is reduced, and vector drawing can be performed at high speed even when a clip is specified.

[Brief explanation of drawings]

Figure 1 is a display diagram showing the vector drawing state when there is no clip designation, Figure 2 is a block diagram showing a vector generation circuit in a conventional example, and Figure 3 is a display diagram showing the vector drawing state when a clip designation is made. 4 are block diagrams partially showing a vector generation circuit in an embodiment of the present invention. ■・・・Line type register, 2・・・Dot counter, 3・・・ΔX register, 4・・・・・・
Adder, 5...ΔY register, 6...
D register, 7...D2 register, 8...
...D register, 9...Multiplexer, 10
°°゛°゛Adder, 11...X counter, 12
...X counter, 13, 14.15...
・Bus driver, 16...XMAX register,
17...XMIN register, 18...
YMAX register, 19° old “YMIN register, 20
, 21, 22. 23...Comparator, 24.
...AND gate, A...Specified start point, B...Specified end point, C...Drawing start point, 11... Vector s XMAX...
...Maximum value of X in clip area, XMIN...
...Minimum value of X of clip area, Y MAX...
・Maximum value of Y in the clip area s YMIN・・・・・・
Minimum Y value of the clip area.

Claims (1)

[Claims] a refresh memory, a means for storing data indicating the length in the X direction and the Y direction of a vector to be displayed on a two-dimensional screen using the Rusk scan method, and a means for storing data indicating the length in the X direction and subtracting it for each display command. a dot counter; a determining unit that calculates the inclination of the line segment from the coordinates of the starting point and the ending point of the vector and determines whether or not the coordinate in the Y direction should be moved in accordance with the movement of the coordinate in the X direction; An X-Y counter that stores the coordinates of the power point and 2 that is clipped.
Comparing means for comparing the maximum and minimum values in the X direction and the maximum and minimum values in the Y direction of the dimensional display surface with the output of the X-Y counter and transmitting only the vector drawing address within the clip area to the refresh memory; A graphic display device comprising: