JP2597102B2 - Screen clipping method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a video game machine or the like that requires real-time high-speed processing in computer graphics. The present invention relates to a clipping method and an apparatus for cutting off a protruding image when it comes out.

[Prior art] The clipping technique is to consider a window in the screen and display only the figure inside the window, and display the figure in the window after performing processing to cut off the part that protrudes outside the window. Is what you do. In other words, when the inside of the window is a visible part, each element of the figure is divided into a visible part and an invisible part, and the efficiency of image processing is improved by an operation of eliminating the latter.

Three-dimensional computer graphics (Eihachiro Nakamae, Tomoyuki Nishida,
Shokodo, published 61.5.20) on page 103. In addition, the technology of aircraft simulator video is pixel No. 36
(Graphic Processing Center published 60.9.1).

In video games, image processing including clipping processing must be performed at high speed in real time, and all object figures are simplified as square matrix shapes and stored in ROM, and stored as necessary. Call object data as appropriate
It is displayed at any location in RAM. If this processing is performed by software, a burden is placed on the central processing unit,
The processing speed is reduced accordingly. As a technique for solving this problem, hardware processing is being attempted.

In this method, the entire monitor screen is regarded as a window and is not included in the field of view. Here, clipping is performed only on the right and lower portions of the screen.
Assuming that the object graphic straddles the right frame of the window as shown in the figure, assuming that the upper left corner of the graphic is point A, the H position counter is increased to the right from point A, and H
When the blanking area is reached, the transfer after that is stopped and the transfer to the transfer of the next line is repeated, whereby only the inside of the window is transferred. Considering the case of the lower frame of the window, assuming that the upper left corner of the figure is point B, the dots forming the figure are transferred horizontally from point B, and the V position counter is sequentially increased to enter the V blanking area. When it reaches, the subsequent transfer is canceled (that is, the transfer of the window frame figure is not performed). This method can save the transfer time compared to the method of transferring all the object graphics regardless of whether the window is inside or outside the frame.

[Problems to be Solved by the Invention] As described above, in the conventional clipping method using hardware, the positions where clipping is possible are performed because the reading direction and the writing direction of the object graphic are fixed. Is limited to the right frame and lower frame of the window, which is incomplete as clipping processing. In this case, clipping processing is not performed on the left and upper sides of the screen window frame, and the object figure is In the case of the left and upper sides, the image data is transferred regardless of the inside and outside of the window frame. Therefore, there is a problem in further eliminating wasteful image transfer and performing high-speed image processing in real time.

Accordingly, it is an object of the present invention to provide a screen clipping method and apparatus that enables the above-described conventional clipping processing to be performed on the upper side and the left side of the display frame.

[Means for Solving the Problems] In order to achieve the above object, a screen clipping method according to the present invention reads out matrix graphic information from a character generator and stores it in an arbitrary display section of a display memory in a first direction. Scanning and a second perpendicular to the first direction
In a display device for writing dots while sub-scanning in the direction, when writing the read graphic information into a display memory, if the graphic information protrudes from a display frame in a direction opposite to the first direction, a matrix of the graphic information is used. While reading the dots of each line, sequentially writing the read dots in the display section on the display memory in a direction opposite to the first direction,
At the time of protruding from the display frame, the reading / writing of the remaining dots of the line is stopped, and the read / write of the next line is started, and the graphic information protrudes from the display frame in the direction opposite to the second direction. In this case, while reading each line of the matrix of the graphic information, the read lines are sequentially written in the display section on the display memory in a direction opposite to the second direction, and when the lines protrude from the display frame, the remaining lines are read out. Reading / writing is stopped.

When reading the dots of each line of the matrix of the graphic information, for example, depending on the clipping position and the display form of the graphic information, the matrix can be read from the left end to the right end, or can be read from the right end to the left end, When reading each line of the matrix of graphic information, it is possible to read from the lower end to the upper end or from the upper end to the lower end of the matrix.

Further, the display device according to the present invention is a display device for reading matrix graphic information from a character generator and writing it at an arbitrary position in a display memory, wherein the read mode of the character generator and the read data are written to the display memory. Read / write mode control means for controlling the mode; character read mode for reading data from the character generator in a mode specified by the read / write mode control mode; In an aspect,
Writing means for writing the read data from the character generator; and protruding detecting means for detecting that the dots and lines to be written protrude from the display frame, a protruding portion according to the output of the protruding detecting means. Is stopped.

The display frame may be the entire effective display area, or may be a window frame of an arbitrary size at an arbitrary position in the effective display area.

[Operation] In the present invention, the conventional technique of clipping by hardware is based on the fact that the reading direction and the writing direction of the object graphic are fixed. The focus was on the fact that clipping was not possible. That is, the clipping process is performed by starting to write the character data read from the character generator from the lower side or the right side of the display section. that time,
The reading start position and reading direction of the character generator are also controlled so that the target object graphic is displayed correctly. As a result, clipping processing can be performed by hardware on the left side and the upper side of the display frame, and the waste of transferring the object graphic to the outside of the screen frame can be eliminated, and high-speed image processing suitable for a video game or the like can be performed. Can be realized.

[Embodiment] FIG. 2 is a diagram for explaining a definition of a display area and an explanation of clipping. In this embodiment, the window frame is an effective screen. The left frame is HLB (HOLIZONTAL LEFT BLANKING), the left side shows the left horizontal scanning retrace period, and the right frame is HRB (HOLIZONTAL
RIGHT BLANKING), and the right side thereof indicates a right horizontal scanning retrace period. The upper frame is VTB (VERTICAL TOP BLANKING), the upper frame of which is the vertical scanning retrace period, and the lower frame is VBB (VERTICAL
CAL BOTTOM BLANKING), and the lower side shows a vertical scanning retrace period.

Image data for displaying an image of a specific object displayed on a display device in a video game or the like is such that the entire image is rectangular as shown in FIG.
For example, it is divided into blocks of image data corresponding to pixels arranged in a matrix of 8.times.8, and end marks are inserted on the right and left sides as a square so that the way of combination as a figure can be understood. Each block is given a block address and stored in the memory of the character generator, read as object data as needed, restored to the original image, and displayed.

<Clipping Method> The clipping method of the present invention will be described with reference to FIG.

Now, assuming that there is an F-shaped object graphic inside the window frame and this object graphic moves to the upper side of the window frame and hangs on the VTB, the display position of this object graphic is V Position position and VT
In this case, if the clipping process is required, the display (writing) start position (object start address) of the object graphic, which has been conventionally performed, is determined from the calculation of the positional relationship of B if the clipping processing is required.
Instead of the upper left corner of the rectangle, transfer from the lower left corner of the rectangle and end the line when the end mark comes,
The V position counter is decremented (meaning that it rises up in the figure), the next line is transferred, and this operation is repeated sequentially. When the VTB is reached, the transfer is terminated.

Next, assuming that the object figure is on the left side of the window frame, the calculation of the positional relationship between the H start position of the object and the HLB also determines whether or not clipping is necessary. If done, the H position counter is decreased from the end mark on the right end of the object figure and the object data is transferred (meaning that it moves to the left side of the figure). If the H position reaches HLB, The transfer of the line is completed, and the transfer from the end mark of the next line is started, and the object data only in the window frame of the object graphic is transferred. When the object graphic covers the right side and the lower side of the window frame, the same clipping processing as in the related art can be performed.

As described above, in the clipping method according to the present invention, the clipping process can be executed also on the upper side and the left side of the window frame by starting to write the dot data read from the character generator from the lower side or the right side of the display section. At that time, as described later, the reading start position and the reading direction of the character generator are also controlled so that the target object graphic is displayed correctly. By changing the reading start position and the reading direction, the display form of the object can be changed.

<Clipping Apparatus> FIG. 1 shows a schematic block diagram of an apparatus for carrying out the clipping method of the present invention.

This device includes a control circuit 2, a character read address circuit 3 (character read means), a character generator 4, an up / down / left / right control register (write / read mode control means).
5, a screen protruding detection circuit (protruding detecting means) 7, a memory write address circuit (writing means) 6, and a bit map memory (display memory) 8. Control circuit 2
Has a CPU and a parameter table.

The control circuit 2 determines which object is displayed on the screen and where, selects a required object address from the operation result and a parameter table provided inside, and reads a character start address set signal of the object as a character. When the object is displayed on the screen, the state of the object to be displayed on the screen is indicated in the up / down / left / right control register 5, and the position on the screen where the object is to be displayed is stored as a position set signal as a position set signal. Output to the write address circuit 6.

The up / down / left / right control register 5 is configured as shown in FIG. 5 by a signal from the control circuit 2 (the hatched portion is actually written).
It is determined in advance whether or not the object needs to be inverted, and a read up / down / left / right inversion control signal and a write up / down / left / right inversion control signal are output according to the display state at the time of clipping of the object in FIG. The read up / down / right / left inversion control signal indicates the state of the object when sent to the character read address circuit 3, and the write up / down / left / right inversion control signal is sent to the memory write address circuit 6 and the off-screen detection circuit 7 to output the object. Indicates the write state.

Although not shown, the bit map memory 8 is read periodically and the written contents are displayed on a raster scanning display.

FIG. 7 shows a manner of reading an object in character generator 4 and a manner of writing the read data to bit map memory 8.

The character data is stored in the ROM constituting the character generator 4 by a conventional method. The character data, that is, the object reading mode is as follows.
Conventionally, it is fixed and read out by sub-scanning in the vertical direction while performing main scanning in the horizontal direction from the upper left corner of the matrix.
In the present invention, four types of object reading modes a, b, c, and d are provided depending on the difference in the reading start position. This 4
Four writing modes were prepared for each of the reading modes depending on the difference in the writing start position.

For the clipping at the left frame of the display window, the read / write mode a2, a3, b2, b3, c2, c3, d2, d3 whose writing start position is on the right side of the matrix (upper right corner or lower right corner) is used. Is done. Which of the read / write modes is used depends on the display mode of the object. In addition, in the clipping at the upper frame of the display window, the read / write mode a1, a2, b1, b2, c1, c in which the write start position is on the lower side of the matrix (lower left corner or lower right corner).
2, d1, d2 are used. As in the case of clipping at the left frame of the display window, which read / write mode is to be used depends on the display mode of the object.

There are four types of object display modes depending on the combination of left-right inversion / non-inversion and up / down inversion / non-inversion, and there are four read / write modes for each of the clipping positions. For example, read / write modes a4, b3, c1, and d2 are prepared for the object “F” that is non-inverted left and right and non-inverted vertically, and is used depending on the clipping position.

A screen up / down / left / right inversion control signal and a write address signal, which will be described later, are input to the screen protrusion detection circuit 7, and based on both input information, it is determined whether or not the corresponding object data covers the window frame of the screen. The line jump control signal for jumping the dots constituting the subsequent lines on the same line of the object data and moving to the next line is read out by the character when the judgment is made for each dot of the object data and the object data overlaps the window frame. It is given to the address circuit 3 and the memory write address circuit 6 as slipping information.

Here, the write top / bottom / left / right inversion control signal is a signal for designating the writing mode of the object. By this writing mode, the clipping limit of H and V is set from one of the address values of the four window frame lines of the effective screen. Is determined.

The character read address circuit 3 receives a character start address set signal, a read vertical inversion control signal, and a line jump control signal, and specifies the address of the corresponding object data that has been clipped to the character generator via an address bus.

The memory write address circuit 6 receives the position set signal of the object, the write up / down / left / right inversion control signal and the line jump control signal from the control circuit 2, and detects the clipped write address signal outside the screen via the address bus. It is sent to the circuit 7 and the bit map memory 8.

The bitmap memory 8 obtains the corresponding object data from the character generator via the data bus,
Further, the writing and display of the object subjected to the clipping process is performed by the write address signal from the memory write address circuit 6.

FIG. 5 shows a situation where the object is clipped by the window frame of the effective screen, and FIG. 6 is a view for explaining the progress of an example of the object clipping process on the left side of the effective screen.

In FIG. 6, if an example is shown in which a left-right inverted object of “F” is displayed on the left window frame of the effective screen, there are three possible situations depending on the position of the object on the frame line. One is when the object is only on the left frame, the second is when the object is on the upper frame, and the third is when the object is on the lower frame.

Here, in the first example of the upper left corner of the display frame, the write / read mode
Adopt c2. That is, in the character read address circuit 3, the data is inverted upside down at the time of reading (reading starts from the lower left corner of the object), and at the time of writing by the memory write address circuit 6, it is inverted upside down, left and right and written (to a matrix-shaped object). The writing is started from the lower right corner of the corresponding display section) and only the objects in the effective screen are written.

In the third example of the lower left corner of the screen, the writing mode a3 is adopted. That is, the data is read normally at the time of reading (the reading is started from the upper left corner of the object), and at the time of writing, it is horizontally inverted (the writing is started at the upper right corner of the display section).

In the case of the second object in which the object extends only on the left frame line, any one of the writing and reading modes c2 and a3 can be adopted.

A table in which two buildings separated by a certain distance from side to side in a left-right inverted and non-inverted display form for a building object as shown in FIG. 8A move from right to left on the screen as shown in FIG. 8B. Consider the example shown.

In screen 81 and the state, the building on the left is completely contained in the screen, and the building on the right is completely off the screen. In this state, no clipping processing is required. Next, in the state of the screen 82 to which the image has been moved, the building on the left side protrudes from the left frame of the screen, and the building on the right side protrudes from the right frame of the screen. In this state, clipping processing is required.
Further, in the state of the screen 83 to which the image has been moved, the building on the right is completely protruded from the screen, and the building on the left is completely included in the screen. In this state, no clipping processing is required.

In the screens 81 and 83, for the building on the left side, any of the read / write modes a3, b4, c2, and d1 in FIG. 7 can be selected.
Similarly, for the building on the right side, read / write modes a4, b3, c
Either of 1 and d2 can be selected.

On the screen 82 requiring the clipping process, for the building on the left side that protrudes on the left side, the writing mode in which the writing start position is on the right side is selected. At this time, since the object is displayed in a horizontally inverted display mode, the read / write mode a3 or c2 is selected. Conversely, for the right building that protrudes from the right, the writing mode in which the writing start position is on the left is selected. At this time, since the object is in a non-left-right inverted display mode, the read / write mode a4 or c1 is selected.

FIG. 9 shows a more specific block diagram of an embodiment for performing object inversion and screen clipping. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals.

The memory write address circuit 6 includes a write horizontal (H) address generation circuit 6a, a write vertical (V) address generation circuit 6b, and a one-line transfer end detection circuit 6c. Both address generating circuits 6a and 6b can be constituted by up-down counters, for example. The write H address generation circuit 6a
In response to the write left / right inversion signal and the one-line transfer end signal from the circuit 6c, an H address is given to the bit map memory 8 and the overflow detector 7a. Write V address generation circuit
6b receives the write upside down signal and the one-line transfer end signal, and supplies the V address to the bit map memory 8 and the off-screen detection circuit 7. Screen overflow detection circuit 7
Consists of a protruding detector 7a and a state determiner 7b. The protruding detector 7a detects the protruding dot or line from the display frame on the basis of both write addresses, and supplies an upper / lower / left / right protruding detection signal to the state determiner 7b. The state determiner 7b receives the write up / down inversion signal and the write left / right inversion signal together with these protruding detection signals, and outputs a forced one-line transfer end signal or a forced one-object transfer end signal. The one-line transfer end detection circuit 6c
Upon receiving the write character data and the forced one-line transfer end signal, it outputs a one-line transfer end signal. After receiving the transfer start signal from the control circuit 2, the one-object end detection circuit 9 receives the one-line transfer end signal or the forced one-object transfer end signal, and returns a transfer end signal to the control circuit 2. The character reading circuit 3 reads object data from the character generator 4 based on the H address and the V address according to the read up / down inverted signal and the read left / right inverted signal of the up / down / left / right control register 5 and sends the data to the bit map memory 8. Read circuit 3 receives the one-line transfer end signal as a line jump signal. Unlike the embodiment of FIG. 1, in this case, the read character data is once taken into the read circuit 3, so that the object can be enlarged. In addition, a display mode such as horizontal inversion and vertical inversion of the object graphic can be selected as a secondary function.

[Effects of the Invention] As described above, according to the present invention, the object of the clipping process can be expanded to the upper side and the left side of the display frame, thereby achieving high-speed image processing suitable for a video game or the like. Can be realized. In addition, a display mode such as horizontal inversion and vertical inversion of the object graphic can be selected as a secondary function.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a display area and clipping, FIG. 3 is an explanatory diagram for explaining a clipping method, and FIG. FIG. 5 is an explanatory diagram showing an example, FIG. 5 is an explanatory diagram showing a state of clipping of an object to a display frame,
FIG. 6 is an explanatory diagram showing a mode of clipping at the left end of the display frame, FIG. 7 is an explanatory diagram showing a read / write mode, and FIGS. 8A and 8B are specific display examples in which clipping is required. FIG. 9 is a specific block diagram of an embodiment of the present invention. 2 ... Control circuit 3 ... Character read address circuit 4 ... Character generator 5 ... Up / down / left / right control register 6 ... Memory write address circuit 7 ... Screen out-of-screen detection circuit 8 ... Bit map memory

Claims (2)

(57) [Claims] 1. A matrix-like graphic information is read from a graphic information storage means, and main scanning is performed in an arbitrary display section on a display memory in a first direction while sub-scanning is performed in a second direction perpendicular to the first direction. A display device for writing dot information, wherein the vertices of the arbitrary display section are vertices in an area included in a display area displayed on display means on the display memory, and vertices adjacent to the vertices in the display area. When there is a vertex outside the area located outside, while reading the dot information of each line of the matrix of the graphic information from the address corresponding to the vertex inside the area toward the address corresponding to the vertex outside the area, The read dot information is sequentially written on the display section on the display memory along a direction from the inside vertex to the outside vertex, and at least the After the dot information to be written in the display area is written, the reading / writing of the remaining dot information of the line is stopped, and the process shifts to the reading / writing of the next line. . 2. A method for reading / writing the next line, comprising: when writing dot information in an arbitrary writing section having only one vertex in the area, from the vertex including the vertex in the area to the line including the vertex outside the area. 2. The screen clipping method according to claim 1, wherein lines for reading dot information are sequentially changed.