JPH0113114B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to window-viewport conversion, that is, displaying a display portion (display segment) in a first window (window) on a display device in a second window (viewport). The present invention relates to a display conversion method.

[Background of the invention]

A computer display device displays graphics, characters, etc. on a display device based on data from a host computer, an input device, etc., and is used in graphic processing systems and the like. An example of such a display device is shown in FIG. This device includes a central processing unit (CPU) 10, a read-only memory (ROM) 12, a random access memory (RAM) 14, an input device 16, an input/output interface (I/O) 18, and a display control Circuits 20 are commonly connected via a bus 22. The CPU 10 is, for example, a Z8001 type microprocessor,
RAM by the program stored in ROM12
14 is used as a temporary storage circuit to perform various control and data processing. The input device 16 is a keyboard or a tablet, and inputs character information, graphic information, various commands, etc. I/O 18 provides communication with external devices such as a host computer. The display control circuit 20 has a conventional configuration, although its structure differs depending on whether the display 24 is a raster scanning type or a vector scanning type, and displays display data inputted via the input device 16 or I/O 18 and processed by the CPU 10. is displayed on the display 24. 2 and 3 show the display screen of display 24. FIG. For example, as shown in FIG. 2, to draw a triangle as a display portion (display segment) by vector scanning, display data is input via the input device 16 or I/O 18 and stored in the RAM 14. A part of the memory contents of this RAM 14 is shown in FIG. This stored content is converted into a format suitable for display, and the display control circuit 20 sequentially reads out the converted data and displays a triangle on the display 24 as shown in FIG. That is, first, set the starting point to the pivot point (reference point) coordinates XOA,
Move (MOVE) to YOA, and then move to the first vertices of the triangle, XIA and YIA. Next, draw a straight line from this first vertex to the second vertex X2A, Y2A (DRAW), and from the second vertex to the third vertex X3A, Y3
Draw a straight line at A, and then draw a straight line from the third vertex to the first vertex. These operations can be realized, for example, by controlling the beam deflection and brightness of the CRT serving as the display 24 using a vector generator and a brightness control circuit in the display control circuit 20.

By the way, in a graphic processing system, the first rectangular window set by the input device 16
One of the important functions is the so-called window/viewboard conversion function, in which the display portion displayed in the display screen 26 is displayed in a separately set rectangular second window (viewboard) 28. To perform this function, first the first window 26 is
and the second window 28 is set. In FIG. 2, the first window 26 has coordinates XmW, YmW and XMW,
It can be set by YMW, and the second window 2 in Figure 3
8 is set by the coordinates XmV, YmV and XMV, YMV. These setting values are stored as parameters in the RAM 14 as shown in FIG. next
The CPU 10 is the length data XW of the first window 26 in the X direction.
(=XMW-XmW) and Y-direction length YW data (=YMW-YmW), as well as X-direction length data XV (=XMV-XmV) and Y-direction length data YV (= Find YMV−YmV).
The display portion displayed within the first window 26 is then detected using, for example, a conventional clipping method. This clipping method was published by Ivan E. Sutherland in 1968 as the clipping divider. Next, regarding the coordinates of each vertex of the detected display part, for example, a triangle, point XmW,
Find the relative coordinates based on YmW. Here, let the relative coordinates of each vertex of the triangle in the first window 26 be representatively XA, YA, and the 3
Let XC and YC be the relative coordinates of each vertex of the rectangle with reference to XmV and YmV, as follows.

XW:XV=XA:XC Therefore, XC=XV・
XA/XW Also, YW:YV=YA:YC YC=YV・YA/YW This calculation is performed by the CPU 10 for each vertex,
The obtained coordinates are pivot points XOC, YOC
Convert to coordinates based on . Based on these final coordinates, the display control circuit 20 displays a display as shown in FIG. 3 on the display 24. Note that the coordinates of each vertex within the second window 28 may be relative coordinates based on the immediately previous coordinates according to the order in which vectors are drawn.

As mentioned above, in order to change the display, it is necessary to multiply and divide the coordinate data (XV・
XA/XW and YV/YA/YW). The first method of performing this operation is to first multiply XV and XA or YV and YA, and then divide the resulting value by XW or YW. This method requires multiplication and division for each X or Y coordinate of each vertex, and requires a long time for display conversion. This becomes more noticeable as the number of coordinate points to be calculated increases. In the second method, XV/
Find XW or YV/YW and multiply this found value by XA or YA. According to this second method,
Since XV/XW or YV/YW is a value common to each coordinate point, this value only needs to be calculated once, which is faster than the first method.

By the way, the calculation methods by the CPU 10 include an integer calculation method and a floating point calculation method. Integer arithmetic is fast, but decimals are rounded down. Also, although floating point arithmetic is slow, it can also obtain values below the decimal point. In the second method described above,
When dividing XV/XW or YV/YW, in the integer arithmetic method, the decimal part of the result is rounded down, so
Must be floating point arithmetic. Furthermore, since there is a very high possibility that the division result contains a decimal point, the floating-point arithmetic method must be used to multiply the division result by XA or YA. Therefore, the second method is also inappropriate for performing faster display conversion, that is, faster window-to-view conversion.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a display conversion method that allows faster processing.

[Summary of the invention]

According to the present invention, the length of each side of the first and second windows in the X and Y directions is determined, and N digits (N is a positive Add "0" for the integer). Note that adding "0" is the same as shifting the length data of each side of the second window to the left (in the direction of the upper digits) in a shift register or the like, and can be processed at high speed. Here, N is determined by the number of digits of the coordinate data of the first and second windows; for example, when the coordinate data is 16 binary digits (16 bits), N=16. Next, the data with 0 added is divided by the length data of each side of the first window using integer operations, and the data obtained by this division is multiplied by each coordinate data of the display part in the first window using integer operations. . Furthermore, the data obtained by this multiplication and N are used to newly display the display portion within the second window. Therefore, since the present invention uses an integer arithmetic method, it is fast, and since N digits of "0" are added below the least significant digit of the length data of each side of the second window, the calculated data without sacrificing accuracy.

[Embodiments of the invention]

Examples of the present invention will be described below. First, as described above, display data is input via the input device 16 or I/O 18 and is stored in the RAM 14.
Since the data stored in the RAM 14 is as shown in FIG. 4, a display as shown in FIG. 2 is performed. Next, in order to set the first window 26 and the second window 28, parameters XmW, YmW and XMW,
YMW and parameters XmV, YmV and XMV,
YMV is input through the input device 16 and stored in the RAM 14 as shown in FIG. 5 along with data (not shown) representing the types of these parameters. CPU10
is determined from the parameters related to the first window 26.
A display portion existing within window 26 is detected. In this example, the detected display portion is a triangle. The processing up to this point is the same as that described in the above-mentioned "Background of the Invention".

Next, embodiments of the present invention will be further explained with reference to flowcharts, but these processing methods will be explained as programs.
Note that it is stored in the ROM 12 and executed by the CPU 10. First, the preprocessing of the X coordinate will be explained with reference to FIG. In step 30, the length data XV of the second window 28 in the X direction is obtained from the parameters XMV and XmV. In this embodiment, the coordinate data is 16 bits, and the data XV is "0011 0000 0010 1011" (302B in hexadecimal notation). This value is stored in register A in CPU10.
The information is accumulated as shown in Figure A. Similarly, step 32
, the length data XW of the first window 26 in the X direction
is determined from the parameters XMW and XmW, and the value is stored in register C of the CPU 10 as shown in FIG. 7C. Note that the data XW is, for example, "0101 1010 0110
0000" (5A60 in hexadecimal). Although the data in this embodiment is 16 bits, the most significant bit MSB is a sign bit and indicates whether the data is positive (0) or negative (1). Therefore, the data address area is 2 ¹⁵ × 2 ¹⁵ , or 32768 × 32768.

In step 34, data XV in register A of the CPU 10 is shifted by a predetermined bit, for example 16 bits, to the left, that is, to the higher bit side. This means that N bits (N=16) of "0" are added next to the least significant bit LSB of data XV. In particular, if this processing is performed as a data shift within a register, high-speed processing becomes possible. The new data XVS with “0” added is “0011 0000 0010 1011
0000 0000 0000 0000” (302B in hexadecimal format)
0000), and the new contents stored in register A are shown in FIG. 7B. At step 36, data XVS is divided by data XW using integer arithmetic to obtain result D. This result R is “0000 0000 0000
0000 1000 1000 0111 0001” (0000 in hexadecimal
8871), and the seventh register is stored in register D in CPU10.
It is accumulated as shown in Figure D. Next, in step 38, each bit of the data D in the register D is checked sequentially starting from the MSB, starting with the bit that becomes "1" first.
Extract only 15 bits on the LSB side. Note that if the first bit that becomes ``1'' is within the 14th bit from LSB, it is assumed that ``0'' continues below LGB, and 15 bits are extracted. Extracted
Add a sign bit (for example, "0" indicating positive) to the MSB upper bit of the 15-bit data,
Let it be a 16-bit factor F. This factor F
"0100 0100 0011 1000" (4438 in hexadecimal)
The data is accumulated in the register F of the CPU 10 as shown in FIG. In addition, in this factor F, the decimal point is at the 15th bit from the LSB, so "1111" (15 in decimal notation, F in hexadecimal notation) is stored in register E of CPU 10 as shown in Figure 7E as shift count SC. Accumulate as if The value of this shift count SC is data indicating which bit from the LSB side of the 16-bit factor F the decimal point is located, and is the number of bits to shift data XV to the higher bit side.
16 and the position of the bit that first becomes "1" from the MSB of data D. Therefore, the value obtained by dividing data XV by data XW is represented by the values of both factor F and shift count SC. When step 38 is completed, the preprocessing of the X coordinate is completed. Note that steps 30 to 38
requires only integer operations and shift operations, resulting in high-speed processing. Perform the same processing as steps 30 to 38.
This is also done for the coordinates, but the XW and YW of the first window 26
If the ratio of is equal to the ratio of XV and YV of the second window 28,
No preprocessing regarding the Y coordinate is required.

Next, with reference to the flowchart of FIG. 8, changing of display data following preprocessing will be described. first,
The CPU 10 reads display data (see FIG. 4) from the RAM 14 in step 40, and determines in step 42 whether or not the read data is coordinate data. If the read data is coordinate data (if affirmative), the process proceeds to step 44, where this coordinate data is multiplied by the factor F obtained in the preprocessing by integer arithmetic. Note that the coordinate data is from the first window 2.
If the relative coordinates are not within 6, that is, XmW, YmW
If it is not relative data based on , it is necessary to convert it into relative data before performing multiplication using factor F. It should also be noted that the corresponding factor F is used depending on whether the data is X coordinate data or Y coordinate data. Up to this point, the shift count SC
However, due to multiplication, the result (the result of multiplying 16-bit data by 16-bit data is also 16
The decimal point position for bit data) is still the position indicated by shift count SC. Therefore, in step 44, the multiplication result is further converted into 16-bit data representing coordinates with the decimal point taken into account, based on the shift count SC. Step 4
Returning to step 2, if the read data is not coordinate data (if negative), that is, if the read data is a command such as "MOVE" or "DRAW", proceed to step 46 and save the read data as is. . Therefore, steps 44 and 46
The data passed through can be virtually represented as shown in FIG. 9, which corresponds to FIG.

By the way, since the coordinate data obtained in step 44 are relative coordinates with respect to the coordinates XmV, YmV of the second window 28, in step 48 they are converted into coordinate data XC, YC suitable for display. For example, in this embodiment, the precision in the data area is 16 bits, but the address space of display 24 is 12 bits by 12 bits. So in this case XmV,
Since YmV, XMV, and YMV are also 12-bit coordinate data, the data obtained in step 44 is also 12-bit. By adding instructions, etc. to the remaining 4 bits, the capacity of the RAM 14 can be saved. Further, the coordinate data is converted into relative coordinates convenient for vector scanning. In this case, the coordinates of the reference point XOC,
You can move the displayed part just by transforming the YOC.
However, this step 48 may be performed as appropriate for the display system in use. Step 5
If the value is 0, it is determined whether all data has been processed, and if all data has not been processed yet (in the case of negative), the process returns to step 40 and the next data is read from the RAM 14. In addition, if all data has been processed (if affirmative), the display data change is completed and the RAM 14
The changed data is stored as shown in FIG. In the case of FIG. 10, each data includes coordinate data and commands.

The display control circuit 20 sequentially reads out the data shown in FIG. 10 from the RAM 14, and displays the data shown in FIG. 3 on the display 24. Furthermore, XOC and YOC are
Compatible with XOA, YOA, XIC, YIC is XIA, YIA
, X2C, Y2C corresponds to X2A, Y2A,
X3C and Y3C correspond to X3A and Y3A. Then,
The display conversion, ie, window viewport conversion, is completed.

It should be noted that although the above description describes one preferred embodiment of the present invention, those skilled in the art will understand that various changes can be made without departing from the gist of the present invention. For example, the number of digits (number of bits) of the coordinate data can be arbitrary, and the number of digits (number of bits) of "0" added after the least significant digit LSB of the length data of each side of the second window can also be set as desired. Any number may be used in consideration of calculation accuracy.
Furthermore, when the first window and the second window are rotated with respect to the coordinate axes, the same processing as described above may be performed while taking the rotation angle into consideration.

〔Effect of the invention〕

As described above, according to the present invention, shift operations and integer operations are performed instead of floating point operations, so display conversion can be performed at high speed. In particular, the more coordinate points there are to convert within the first window, that is, the more complex the figure, the more
The effect of the present invention becomes remarkable.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a display device for implementing the present invention, FIGS. 2 and 3 are diagrams showing display examples for explaining the present invention, and FIGS. 4 and 5 are for explaining the present invention. 6 is a flowchart for explaining the present invention, FIG. 7 is a diagram showing the stored contents of a register for explaining the present invention, and FIG. 8 is a diagram for explaining the present invention. FIGS. 9 and 10 are flowcharts showing the contents stored in the memory for explaining the present invention. 26: 1st window, 28: 2nd window.

Claims (1)

[Claims] 1. Displaying a display portion on a display according to X and Y coordinate data, setting rectangular first and second windows on the display, and displaying the display in the first window. In the display conversion method for newly displaying a part in the second window, the length of each side in the X and Y directions of the first window and the second window is determined, and the length data of each side of the second window is calculated. Next to the least significant digit of , N digits (N is a positive integer) of ``0'' are added and carried, and the data with the ``0'' added is calculated by integer operation to calculate the length of each side of the first window. Divide by each data, and extract data of M digits (M is a positive integer) from the most significant digit of the data obtained by the division to the least significant digit from the first digit that becomes other than "0", Find the data of the digit corresponding to the decimal point, and use integer arithmetic to combine the data of the M digits above and the 1st digit above.
It is characterized by multiplying each coordinate data of the display part in the window, and newly displaying the display part in the second window using the data obtained by the multiplication and the data of the digit corresponding to the decimal point. Display conversion method.