Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
The present invention is directed to apparatus for
generating a plurality of moving objects on a video display
screen and more specifically to apparatus used in the context of
a video amusement game.
One example of a system for causing images of objects
to move about on a screen of a video display tube under the
control-of an operator is U.S. patent 3~793r483 issued February
19, 1974, in the name of Nolan Bushnell entitled "Video Image
Control System For Amusement Device" and assigned to the present
assignee. This patent shows a separate motion counting or com-
parator circuit for each moving object to be displayed.
Another system is disclosed in U. S. Patent No.
4,116,444 issued September 26, 1978, in the names of the present
inventors and assigned to the present assignee and entitled
"Method For Generating A Plurality of Moving Objects On A video
Display Screen". The video game which uses this Patent is a tank
battle game designed for as many as eight players where each play-
; er is assigned a unique tank. Because of the large number of
objects and the relatively complex movement of the tanks, the
Patent discloses a system which includes a horizontal memory whichmay contain an object identification code in any one of 256 hori-
zontal memory locations. The actual video image is generated by
an associated graphics generator and picture memory which responds
to the object code.
The above U. S. Patent 4,116,444 also discusses the
disadvantage of other approaches.
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Objects and Summary of the Invention
It is a general object of the present invention to
provide an improved apparatus for generating a plurality of
moving objects on a video display screen.
It is another object of the invention to provide
apparatus as above which provides an optimum approach for
display of between four to eight objects on a screen.
In accordance with the above objects there is
provided apparatus for generating a plurality of moving
10 objects on a video display screen which is scanned in
successive frames by an image forming beam traversing the
screen along a plurality of horizontal lines in response to
horizontal and vertical synchronizing signals. Manual
control inputs are provided for a plurality of game players.
15 The control inputs determine the movement of the objects.
Graphics generator means associated with each object are
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provided for supplying video data~to the image forming beam.
A plurality of horizontal and vertical line memories cor-
respond to each of the objects. Each horizontal memory has
a number of bit memory locations corresponding to each
resolution element of the horizontal line and each vertical
memory has a number of memory locations corresponding to the
total number of horizontal scan lines. Means connect each
of the horizontal and vertical memories to the graphics
generator means associated with a single object and are
responsive to a coincidence of bits from both of the memories
to activate the graphics generator means to form an image.
Brief Description of the Drawings
Figure 1 is a schemmatic representation from a
player's point of view of the video game utilizing the
present invention;
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Figure 2 is a cross-sectional view substantially
taken along line 2-2 of Figure 1 showing one set of player
controls; and
Figure 3 is a block circuit diagram embodying the
present invention.
Detailed Description of the Preferred Embodiment
Figure 1 illustrates the front of a display
cabinet in somewhat schematic form of a video game called
COPS N' ROBBERS (Trademark of Atari, Inc.). Each player has
a pair of controls lla through lld which control an as-
sociated car 12a through 12d which are placed on video
display screen 10 on a simulated city street. As shown in
Figure 2 each player has a foot pedal 13 to control the
speed of his car along the street and a pistol grip 14
` 15 movable to seven different positions to control the angular
orientation of a gun 15 sticking out of the window of the
car. Push-button (Figure 2) 16 at the top of the pistol
' handle fires the gun and simulated bullets 16a-d are shown
on the screen. When an opposing car is hit it crashes to the
bottom of the "street" out of sight. By pressing the foot
' pedal 13 again, it reappears ready for another pass at
; "blowing away" the other car. Cars 12a and 12b at the left
; side of the screen belong to the "cops" and cars 12c and 12d
to the "robbers". A beer truck 18 driving up and down the
middle of the street between opposing sides provides cover
and challenges timing and accuracy.
The overall circuit block diagram shown in Figure
3lincludes the video display screen 10 which is controlled
by a computer or microprocessor 21 having player control
inputs 11. Typically the game format would be ~tored in a
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read-only memory associated with computer 21. A sync gen-
erator 22 associated with computer 21 (or in many cases an
integral part of it) provides for horizontal and vertical
address or synchronization pulses and also an indication of
the vertical retrace period. It is connected by control
line 23 to computer 21 and also to a switching unit 24.
Computer 21 determines from the player control
inputs a change of location of all of the four objects which
in this case are the cars 12a through 12d and also the
bullets 16a-d. This "data" information of the horizontal
(H) and vertical (V) positions of the objects is connected
to switches 24 where it is used to address vertical storage
units or memories 261 N~ and horizontal storage units or
memories 271 N Markers ("ones") are written into the
memories at locations corresponding to the H and V positions
of each object. By setting the appropriate number of
adjacent markers, the size of the`coincidence window (e.g.,
the roughly rectangular outline of cars 12a-b) can be varied;
in other words, the size of the object. The H and V memories
26, 27 are later read in time coincidence under the control
of synchronizing generator 22 to decode the H and V coin-
cidence windows in time with the electron beam of display
10.
One pair of H and V memories are required to each
independent object. These memories as indicated are typical-
ly random access or shift registers. They are line memories
and contain the same number of bit memory locations cor-
responding to the desired number of resolution elements.
For example, each horizontal memory 27 breaks down the
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horizontal line into 512 resolution elements and each ver-
tical memory 26 of 256 bit memory locations which, of course,
correspond to the total number of horizontal scan lines
outside of vertical sync. The 256 is, of course, a typical
number of lines for a frame of a video picture.
To summarize thus far, computer 21 on a time share
basis for each object 1,2...N decides, in response to a
player control, where an object to be located in the next
frame and outputs a "1" data bit in the horizontal and
vertical memories to cause the display of the data at the
corresponding location. Specifically, this is illustrated
by the point 28 on the video display screen 10 which cor-
responds to the binary 1 in memories 261 and 271. This
showing is simplified. In actual practice if a car 12a were
being displayed a sufficient number of markers would be
stored in a memory 26 to indicate the length of the car and
thus provide the vertical portion of the coincidence window.
Movement of the car in a vertical direction is accomplished
by a simple shift of the vertical markers. In the case of
the horizontal memories since the cars 12 at least do not
change position the capability of the horizontal memories is
j not fully utilized.
The pictorial content of the object is provided by
the use of graphics generators 29 and their associated
picture memories 301 N. These are coupled to the associated
vertical and horizontal memories 26 and 27 by AND gates 31.
For example, AND gate 311 responds to the 1 bits in vertical
and horizontal memories 261 and 271 to activate its as-
sociated graphics generator 291 to produce on the video line
321 the actual video data. The output line of the AND gates
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actually provides the H and V coincidence window in which is
placed the object by the graphics generator means 29, 30.
In practice graphics generator 29 consists of horizontal and
vertical counters, the 14 MHz and HSync clock inputs, re-
spectively. These counters are enabled by AND gate 31 andaccess the video data from picture memory 30 under the
overall control of computer 21. It is apparent that since
the H and V memories 26, 27 determine the horizontal and
vertical size of the object to be displayed the graphics
generator logic is very simplified.
Operation
Now referencing the block diagram o-f Figure 3 to
the video game shown in Figure 1 typically objects 1 through
4 provide the car objects 12a-d and objects 5 through 8
would be the bullets from the associated guns on the car.
; The car object includes the gun 15 in any one of its seven
angular orientations. Each orientation is stored in the
associated picture memory 30 and the proper angular orien-
tation is retrieved from this picture memory by appropriate
command from the computer~or microprocessor 21. In one mode
of operation the binary one or marker data of the vertical
and horizontal memories will provide the coincidence window
of the object to be displayed such as a car.
However in the case of forming the bullet objects
which may consist of only single bits (or one resolution
element) the actual binary ones in the horizontal and verti-
cal storage memories can be utilized for this purpose without
the use of graphics generator or picture memory.
Vertical and horizontal memories 26 and 27 are
updated during vertical retrace. In general, the random
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access memories 26 and 27 are organized N by S where N is
the number of objects on the screen and S is the sum of the
number of resolution elements of the sync generator for the
respective axes. For a game with four moving objects, 512
horizontal resolution elements, and 256 vertical elements,
only 3,072 memory locations are needed. This compares with
524,288 locations using a conventional memory approach and
assuming separate decoded outputs for each object to be
displayed (512 x 256 x 4).
The present approach is optimum for display of
generally between four and eight objects on the screen
assuming each object has horizontal and vertical size
greater than unity. Thus for certain types of games the
present invention provides for optimum and economical memory
costs. In addition, separate horiæontal and vertical
memory structure for each object makes programming of the
computer or microprocessor much simpler. Since each object
has an independent graphics generator means, objects can
overlap, have separate colors or intensities, and can be
checked foL overlap with minimum hardware or software.
Because of this simplicity added features are possible
where, for example, a slave object can be provided merely by
repeating the binary 1 in a horizontal or vertical memory
without any change in the other memory. Also for relatively
simple objects such as bullets, etc. size can be easily
varied.
