JPS63240682A - Clipping processing system for graphic display - Google Patents

Abstract

PURPOSE:To simplify the composition of a display device and to accelerate display speed by providing a means which judges whether a picture element is written in a frame memory or not according to the value of the picture element previously formed on a mask plane memory. CONSTITUTION:A mask plane having a pattern which only the part where the range of an overlapped window which has more priority of display than a window drawing a graphic, is eliminated from the range of the window drawing the graphic is '1' is formed on the mask plane memory 4. Then a segment is generated one by one while approximating a dot (a picture element) by a segment generator 6 and the generated picture element is written in the frame memory 8. At that time, the picture element 8a to be written and the picture element 4a of the mask plane memory 4 being at the same position as the element 8a are read out at the same time and the result of the AND operation of them is written in the frame memory 8. As the result, clipping processing is executed.

Description

[Detailed Description of the Invention] [Summary] For example, a graphic display, etc., which includes at least a frame memory, a mask plane memory, and a line segment generator, and displays graphics by writing graphic data into the frame memory. , in the clipping process when drawing a figure in a specific window, when the figure data is written to the frame memory, the pixel value of the mask plane for the specific window, which has been generated in advance, is used to draw the figure. By providing means for writing the graphic data while determining whether to write it into the frame memory, the graphic clipping process for the specific window is performed.

[Industrial application field]

The present invention includes at least a frame memory, a mask plane memory, and a line segment generator, and displays graphic data by writing graphic data to the frame memory. This invention relates to a clipping processing method when drawing figures.

With the recent improvement in the processing power of computer systems, data processing such as computer-aided design (CAD) and computer-aided manufacturing (CAM) can now be performed even on relatively small computer systems called engineering workstations (EWS). However, in this field,
Data processing for design and manufacturing is often performed while displaying multiple figures in a so-called multi-window format.

In this case, it is necessary to perform a process of not displaying figures that protrude from the frame of the window (viewport set within the screen), and this process is called clipping.

The clipping process is often performed in units of line segments (vectors), and generally the clipping process itself takes time, placing a large burden on the display speed, and is difficult to perform on a relatively small workstation. In computer systems, there is a need for a clipping processing method that can display graphics at high speed while minimizing the load caused by this clipping processing.

[Prior art and problems to be solved by the invention] FIG. 4 is a diagram illustrating a conventional clipping processing method.

As is clear from the flowchart in this figure (in conventional clipping processing, it is necessary to judge whether there is a possibility that the line segment to be drawn intersects with the frame of a specific window), If there is a problem, the general method is to calculate the intersection with the frame of the window, replace it with the coordinate values of both end points of the line segment (see step 22), and draw only the part included within the frame. It was a target. (See step 23) This method has the advantage that the area to be actually drawn is reduced, but has the disadvantage that calculations for this purpose take a considerable amount of time.

In particular, in the aforementioned multi-window overlapping display, which has become more common recently, the frame is not just a rectangle, but a polygon formed by a combination of multiple rectangles. Since the processing is performed in rectangular units, there is a problem in that the calculation time further increases.

Furthermore, when performing clipping processing by dividing the polygon into multiple rectangles, for example, the end points of continuous line segments generated within adjacent rectangles may not connect, and in that case, the coordinates of the end points are correction had to be made, requiring complex control.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the conventional art, it is an object of the present invention to provide a method that simplifies the control of the clipping process necessary for graphic display in a multi-window format and speeds up the display speed. .

[Means for solving problems]

FIG. 1 is a diagram showing an example of the configuration of a clipping processing method according to the present invention.

The present invention provides a bitmap type display device which includes at least a frame memory 8, a mask plane memory 4, and a line segment generator 6, and which displays a graphic by writing graphic data to the frame memory 8. To perform clipping processing when displaying data in a specific window, the graphic data is transferred to a specific pixel 8 of the frame memory 8.
At the time of writing to the frame memory 1, a means 7 for controlling whether or not to write to the frame memory 10 is controlled by the value of the corresponding pixel 4a of the mask plane for the specific window, which has been generated on the preset mask plane memory 4. Based on the write control means 7, graphic data is written to each pixel of the frame memory 8, thereby performing clipping processing on a specific window.

[Effect]

That is, according to the present invention, for example, a graphic display is provided with at least a frame memory, a mask plane memory, and a line segment generator, and performs graphic display by writing graphic data to the frame memory.
In the clipping process when drawing a figure in a specific window, when writing the figure data to the frame memory, the pixel values of the mask plane for the above-mentioned specific window, which were generated on the front side, are used to write the figure data into the frame memory. By providing a means to write the graphic data while determining whether or not to write it, the graphic clipping process for the specific window is performed, which eliminates the need for complicated control regarding the clipping process and the time-consuming process. There is no need to calculate coordinates,
This has great effects in simplifying the configuration of the display device and improving the display speed.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The above-mentioned FIG. 1 is a diagram showing a configuration example of the clipping processing method of the present invention, FIG. 2 is a flowchart of the clipping processing according to the present invention, and FIG. 3 is a conceptual diagram of the clipping processing according to the present invention. The mask plane memory 4 and the write circuit 7 in FIG. and steps 30 and 32 in FIG. 2 are the means necessary to carry out the invention. Note that the same reference numerals indicate the same objects throughout the figures.

Hereinafter, the clipping processing method of the present invention will be explained with reference to FIGS. 1 to 3.

First, in the present invention, a mask plane as shown in FIG. 3(a) is created in the mask plane memory 4.

The mask pattern is an overlap window (■) that has a higher display priority than that window (■) from the range of the window (6) in which a figure is currently being drawn.

This is a pattern in which only the part excluding the range (2) is 1°. , Incidentally, the size of the mask plane memory 4 is the same size as the frame memory 8.

(See step 30 in FIG. 2) Next, as shown in FIG. While approximating, 1 tree brother is generated (
* indicates the starting point pixel of the line segment, and the mouth indicates the ending point pixel of the line segment).

At this time, the pixels generated one after another are written into the frame memory 8. At this time, the pixel 4a of the mask plane memory 4 at the same position (address) as the pixel 8a to be written is simultaneously read out, and the pixel 4a to be written is read out at the same time. The value of the mask plane, the pixel value read from the mask plane, and the result of performing a logical AND operation are written into the frame memory 8. Alternatively, writing to the frame memory may be gated using the pixel value read from the mask plane memory 4. (See step 32 in FIG. 2.) In this way, among the pixels to be written, only those pixels (figures) that are within the relevant window and that are not hidden by other windows are stored in the frame memory 8.
As a result, the above-mentioned clipping was performed.

In the flowchart of Fig. 2, line segments that completely protrude from the window ■ are checked and excluded in step 31, but this process can be performed using, for example, the well-known ``Cohen-Sutherland algorithm ”
(For example, rW, M.

Newman, R.F., Sproul, "Interactive Computer Graphics (I), 2nd Edition", pp. 74-77, published by McGraw-Hill, Inc., September 10, 1981), it can be easily realized and processing efficiency can be improved. effective in improving

The above is the concept of clipping processing according to the present invention.

Next, specific operations in the clipping process of the present invention will be explained with reference to FIG.

In this example, the activation of the creation of a mask plane.

Starting the occurrence of each line segment, and checking whether it is completely outside the frame of the window in which you are trying to draw the shape,
Although it is assumed that the control is performed by a program executed by the central processing unit (CPU) 1, it goes without saying that it may be realized by hardware.

Line segment generation is performed by a line segment generator 6 typified by a digital differential analyzer (DDA), and rectangular area filling circuit 3 clears the rectangular area with "0" or 1' in the mask plane memory 4. Writing control to the frame memory 8 is performed by hardware using the write circuit 7.

First, the central processing unit (CPtl) 1 executes a specific program to activate the rectangular area filling circuit 3 as many times as necessary to generate a mask plane in the mask plane memory 4. Rectangle filling circuit 3
moves within the rectangular area specified by area specification register 2 at °0
It has a function to fill in with ゛ or ``1''.

Therefore, the procedure for creating a mask brain is: fl) clearing all areas of the mask plane memory 4, (2) clearing ``1'' in the window ■, (3) clearing multiple files with higher display priority than the window ■. ■ Windows.

■°0” is cleared.

Next, the program executed by the central processing unit (CPU) 1 retrieves the line segment data to be drawn from the main memory (MS), not shown, and uses the above-mentioned "Cohen-Sutherland algorithm" etc. to completely complete the drawing. Check whether it is outside the frame of the window to be drawn. If it is outside the frame, ignore it. If not, set the starting point coordinate value and increment value in the line segment specification register 5, and send it to the line segment generation circuit 6. Start.

The line segment generation circuit 6 generates one pixel that approximates the line segment based on the centered line segment information. Upon receiving this pixel address and one pixel value, the write circuit 7 for the frame memory 8 writes the value of the pixel in the mask plane memory 4 corresponding to the writing position outputted from the read circuit 9 of the mask plane memory 4 to 1′ or “
0'' determines whether to write the pixels generated by the line segment generator into the frame memory 8, and if the value from the mask plane memory 4 is, for example, 1'', the writing operation is performed. In order to perform such control, the addresses of the write circuit 7 for the frame memory 8 and the read circuit 9 for the mask plane memory 4 are, of course, the same.

By controlling the writing to the frame memory 8 in this manner, the clipping process for the window (2) to be drawn can be realized without calculating the coordinates of the intersection between the drawing line segment and the frame of the window (2) as in the conventional art.

Note that in the above example, the drawing target window is cleared ``1'' to control the write circuit 7 for the frame memory 8, but the drawing target window is cleared ``1''. Needless to say, there is no need to limit it.

As described above, the present invention provides a bitmap type display device having at least a line segment generator, a frame memory, and a mask plane memory, in which clipping processing is performed on a specific window. For example, for a mask plane memory that
The mask plane memory corresponding to the pixel position is cleared when writing the pixel generated from the line segment generator to the frame memory. The feature is that whether or not to write is controlled based on the pixel value of .

〔Effect of the invention〕

As described above in detail, the clipping processing method for graphic display of the present invention includes at least a frame memory, a mask plane memory, a line segment generator,
Graphic display is performed by writing graphic data to the frame memory. For example, in a clipping process when drawing a graphic in a specific window on a graphic display, etc., the pre-preparation process is performed at the time the graphic data is written to the frame memory. By providing means for writing the graphic data while determining whether to write it to the frame memory based on the generated pixel value of the mask plane for the specific window, clipping of the graphic for the specific window is performed. This eliminates the need for complicated control related to clipping processing and calculation for determining intersection point coordinates, which takes 9 hours, and has a great effect on simplifying the configuration of the display device and improving the display speed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a configuration example of the clipping processing method 2 of the present invention. FIG. 2 is a flow chart of clipping processing according to the present invention. FIG. 3 is a conceptual diagram of the clipping process of the present invention. FIG. 4 is a diagram explaining a conventional clipping processing method. It is. In the drawing, 1 is a central processing unit (CPIJ), and 2 is an area specification register. 3 is a rectangular area filling circuit. 4 is masked brain memory. 5 is a line segment specification register, and 6 is a line segment generator. 7 is a write circuit, 8 is a frame memory. 9 is a readout circuit + 8a, 4a is a pixel. ■～■ are windows. 20-23. 30 to 32 are processing steps. are shown respectively. [This method] The main investigation's cry 0) Good place 3! 2
ward's

Claims (1)

[Claims] Comprising at least a frame memory (8), a mask plane memory (4), and a line segment generator (6), graphic display is performed by writing graphic data to the frame memory (8). In a bitmap type display device that performs clipping processing when displaying the graphic data in a specific window, at the time the graphic data is written to a specific pixel (8a) of the frame memory (8), Means (7) for controlling whether or not to write to the frame memory (8) according to the value of the corresponding pixel (4a) of the mask plane for the specific window, which has been generated on the mask plane memory (4) in advance. ), and based on the write control means (7), graphic data is written to each pixel of the frame memory (8), thereby performing clipping processing for a specific window. .