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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a figure displaying device such as the visual
scene display of the CGI (computer generated image) type.
2. Description of the Prior Art
During training for the control of an airplane, etc., a visual scene
display is used in order to simulate visual scenes which are seen out of
the window of a cockpit while following the movement of the airplane or
the like.
The visual scene display is such that edges representative of the contour
of a figure to be displayed are generated on the basis of data which is
transmitted from a computer which depends on the piloted status of the
airplane or the like; these edges are converted into a surface, and the
surface is displayed on a monitor device. With a prior-art display the
brightnesses of the respective figures displayed are uniform, so that the
picture tends to bring about visual fatigue and an inferior training
effect.
SUMMARY OF THE INVENTION
An object of this invention is to provide a figure displaying device which
can generate and display very real and natural pictures in accordance with
various circumstances and visibilities.
When the visual scene is generated and displayed as stated above, it is
necessary to generate and display on a monitor device figure which are as
real as possible in order to avoid visual fatigue and enhance the training
effect on a monitor device. To this end it becomes important to employ the
so-called gradation with which a figure more distant from a visual point
has a more blurred contour and to generate the peculiar visual scenes of a
cloudless sky, a mist, nighttime, twilight etc.
In view of the foregoing, this invention provides a figure displaying
device which generates a brightness signal corresponding to figure
information to be displayed and controls the modulation and frequency
characteristic of the brightness signal by the use of a brightness
modulation signal and a frequency characteristic control signal
respectively varying within a predetermined region.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fundamental block diagram of a visual scene display;
FIG. 2 is a diagram showing an example of a surface which is displayed;
FIG. 3 is a schematic block diagram of an embodiment of a figure displaying
device according to this invention;
FIG. 4 is a diagram showing an example of a brightness modulation region
according to this invention;
FIG. 5, including 5(a)-5(g), is a diagram showing examples of data which
are written into RAMs in FIG. 3;
FIG. 6 is a block diagram showing an example of the detailed arrangement of
a brightness modulation signal-generating circuit in FIG. 3;
FIG. 7 is a diagram showing an example of a surface which is displayed by
this invention;
FIG. 8 is a diagram of the operation timings of various parts in FIGS. 3
and 6;
FIG. 9 is a block diagram of an example of a circuit for generating various
signals for the circuit of FIG. 6;
FIGS. 10(a)-10(f) is a diagram of signal waveforms in various parts in FIG.
9;
FIG. 11 is a connection diagram showing an example of the detailed
arrangement of the D/A converters in FIG. 3; and
FIG. 12 is a connection diagram showing an example of the detailed
arrangement of a filter portion and an amplifier portion in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows the fundamental construction of a visual scene display system
of the type specified previously. Numeral 1 designates a computer, numeral
2 an interface, numeral 3 a vector generator, numeral 4 an edge-to-surface
converter, numeral 5 a coloring circuit, numeral 6 a color monitor device
such as color cathode-ray tube, and numeral 7 a synchronizing signal
generator.
In such construction, data which is transmitted from the computer 1 in
accordance with a piloted state is put into the vector generator 3 through
the interface 2. On the basis of the data, the vector generator 3
generates edges representative of the contour of a figure. The edge-to
surface converter 4 converts the edges from the vector generator 3 into a
surface and transmits the surface information to the coloring circuit 5.
Here the surface information is converted into color information, which is
displayed on the color monitor device 6. The operations of these circuits
are controlled by synchronizing signals from the synchronizing signal
generator 7.
Thus, a surface as shown in FIG. 2 can be indicated on the color monitor
device 6. In the figure, letters S, L, R, C and H denote the sky, a lawn,
a runway, a center line and the horizon.
Hereafter, embodiments of this invention will be described in detail with
reference to the drawings.
FIG. 3 shows a schematic block diagram of an embodiment of the figure
displaying device according to this invention, which corresponds to the
coloring circuit in FIG. 1. Shown in FIG. 3 is only the circuit which
corresponds to one of the three primary colors of red R, green G and blue
B. Letters C, B and F affixed to various numerals represent references to
the controls of the color information, brightness modulation and frequency
characteristics, respectively.
Referring to FIG. 3, symbols 11C, 11B, and 11F designate priority encoders;
symbols 12C, 12B, 12F, 13B, 13F, 14B and 14F random access memories
(hereinbelow, termed "RAMs"); numeral 15 an edge detector; numeral 16 a
latch register; symbols 17C, 17B and 17F high-speed digital/analog (D/A)
converters of the multiplication type; numeral 18 a low-pass filter
constructed of field effect transistors (FETs); numeral 19 an amplifier;
symbols 20B and 20F counters; symbols 21B and 21F rate multipliers;
symbols 22B and 22F high-speed D/A converters; symbols 23C, 23B and 23F
input terminals which receive as addresses of the RAMs 12-14 surface data
read out from a line memory (a memory for storing edge information
corresponding to one horizontal scanning line) of the edge-to-surface
converter 4 in FIG. 1; numeral 24 an output terminal which delivers an
output to the color monitor device 6 in FIG. 1; and symbols 25B and 25F
full adders. Symbol 10B indicates a circuit for generating a brightness
modulation signal, and symbol 10F a circuit for generating a control
signal for the frequency charcteristic.
FIG. 4 illustrates the relationship among various data in the brightness
modulation according to this invention, in which T indicates a vertical
scanning direction and Y a horizontal scanning direction. In the figure,
oblique lines B indicate a brightness modulation region, .phi. an angle
defined between the gradient of the brightness modulation region B and a
raster r, N.sub.o the width of the brightness modulation region B,
N.sub..phi. the number of horizontal scanning lines passing through the
brightness modulation region B, B.sub.o the initial value of the
brightness modulation, B.sub.N the final value of the brightness
modulation, .DELTA.B.sub.T the varying width of the brightness modulation
per horizontal scanning line, and .DELTA.B.sub.Y the varying width of the
brightness modulation per picture element.
The angle .phi. corresponds to, for example, the rolling angle of an
airplane to be piloted. It is expressed with the gradient
.DELTA.T/.DELTA.Y of the brightness modulation region B with respect to
the horizontal scanning direction, as the following equation (1):
.phi.=tan.sup.-1 (.DELTA.T/.DELTA.Y) (1)
The number N.phi. of the horizontal scanning lines passing through the
brightness modulation region B becomes as indicated by the following
equation (2):
N.phi.=N.sub.o /cos .phi. (2)
Subsequently, the varying width .DELTA.B.sub.T of the brightness modulation
per horizontal scanning line within the region B is expressed as the
following equation (3):
.DELTA.B.sub.T =(B.sub.N -B.sub.o)/N.phi. (3)
Letting N.sub.e denote the number of picture elements within one raster
passing through the brightness modulation region B, the varying width
.DELTA.B.sub.Y of the brightness modulation per picture element in the
region B has the relations of the following equations (4) and (5):
.DELTA.B.sub.Y =(B.sub.N -B.sub.o)/N.sub.e (4)
N.sub.e =N.sub.o /sin .phi. (5)
Although not illustrated in the drawing, similar relations to the foregoing
are also held for a control region F for the frequency characteristic.
FIG. 5 shows examples of the bit constructions per word of data which are
stored in the RAMs 12-14 in FIG. 3. (a) illustrates the bit construction
for the RAM 12C, (b) for the RAM 12B, (c) for the RAM 13B, (d) for the RAM
14B, (e) for the RAM 12F, (f) for the RAM 13F, and (g) for the RAM 14F.
Now, the data which is stored in the respective RAMs will be described in
detail.
(1) RAM 12C:
This RAM 12C stores the brightness levels of each kind of figure and the
presence of the brightness modulation as well as the frequency
characteristic control in the corresponding primary color, and has one
word assigned to a figure having a certain kind of color. Accordingly,
assuming that there is a figure having 32 kinds of colors, the RAM 12C is
constructed of 32 words.
In the eight bits of each word, the least significant six bits denote data
DI1C of the brightness level of the corresponding figure. The seventh bit
from the least significant bit LSB contains therein a control information
BMON indicating if the figure is subjected to the brightness modulation,
and the eighth bit contains therein a control information FMON indicating
if the frequency characteristic of the figure is controlled. Assuming by
way of example that the control information BMON and FMON are "1" and that
the operation lies within the brightness modulation region and the
frequency characteristic control region as stated hereinafter, the
corresponding figure information is subjected to brightness modulation and
frequency characteristic control respectively.
(2) RAM 12B:
This RAM 12B stores the initial value B.sub.o of the brightness modulation
in each brightness modulation region and has one word assigned to one
brightness modulation region, one word being made up of data DI2B of eight
bits. Supposing by way of example that if four brightness modulation
regions can be set then the RAM 12B is constructed of four words.
The initial value B.sub.o needs to be corrected because a point a of the
brightness modulation region B shown in FIG. 4 becomes below T=-1 in some
flight postures of the piloted airplane. More specifically, letting
N.sub..phi. ' denote the number of rasters within the region B as included
below T=-1 at the left end (r=1) of the brightness modulation region B,
the corrected value B.sub.o ' becomes as given by the following equation
(6):
B.sub.o '=B.sub.o +.DELTA.B.sub.T .multidot.N.sub..phi. ' (6)
The content of the RAM 12B is rewritten to a result accumulated by
.DELTA.B.sub.T every horizontal scanning line if the operation lies within
the brightness modulation region at the time of initiation of the
horizontal scanning.
For example, in a range of -1.ltoreq.T.ltoreq.a in FIG. 4, the content of
the RAM 12B is B.sub.o, and in the range of a <T.ltoreq.b, the result
accumulated by .DELTA.B.sub.T every horizontal scanning line is written
into the RAM 12B. At T=b, the content of the RAM 12B becomes as in the
following equation (7):
B.sub.o +.DELTA.B.sub.T .multidot.N.sub..phi. =B.sub.N (7)
In a range of b<T.ltoreq.1, the content of the RAM 12B becomes B.sub.N.
(3) RAM 13B:
This RAM 13B stores the varying width .DELTA.B.sub.T of the brightness
modulation per horizontal scanning line corresponding to each brightness
modulation region and has one word assigned to one brightness modulation
region, one word being made up of data DI3B of eight bits. If the
brightness modulation regions are four in number as in the case of (2),
the RAM 13B is constructed of four words.
As indicated in Equations (2) and (3), the varying width .DELTA.B.sub.T of
the brightness modulation is determined by the initial value B.sub.o,
final value B.sub.N, gradient .phi. and width N.sub.o of the brightness
modulation region. Among these values, .phi. is determined in accordance
with the piloted state of the airplane, and B.sub.o, B.sub.N and N.sub.o
are determined in advance in accordance with flight circumstances such as
flight under a cloudless sky and flight in a mist.
(4) RAM 14B:
Assuming the number of brightness modulation regions to be four, this RAM
14B is constructed of four words, each of which is made up of eleven bits.
In each word, bits from the LSB to the tenth bit store therein data which
represent the varying width .DELTA.B.sub.Y of the brightness modulation
per picture element in the corresponding brightness modulation region.
The data DI4B stored in the fifth-tenth bits counted from the LSB
correspond to the varying width .DELTA.B.sub.Y of the brightness
modulation indicated by Equations (4) and (5), while the data DI5B stored
in the LSB-fourth bit serves to compensate for insufficiency in the
varying rate of the brightness modulation with the data D14B. More
specifically, with the data DI4B, only .DELTA.B.sub.Y =1 can be increased
or decreased at the maximum per picture element. Therefore, when .phi.
becomes as large as .phi.=80.degree., the actual varying width per picture
element cannot be followed so that the insufficiency is compensated for
with the data DI5B.
Data BUPDN in the most significant bit within each word indicates the
varying direction of the varying width .DELTA.B.sub.Y of the brightness
modulation, that is, whether the brightness modulation is in the
increasing direction or the decreasing direction with respect to the
horizontal scanning. For example, if the data BUPDN is "1", the brightness
modulation is in the increasing direction.
The RAM 12F stores therein the initial value of the frequency
characteristic in each frequency characteristic control region, while the
RAM 13F stores the varying width of the frequency characteristic per
horizontal scanning line in each frequency characteristic control region,
and the RAM 14F stores therein the varying width of the frequency
characteristic per picture element in each frequency characteristic
control region.
The bit constructions of each word for the contents of these RAMs 12F, 13F
and 14F are as shown in (e), (f) and (g) in FIG. 5, respectively. The
details are essentially the same as those of the bit constructions of the
RAMs 12B, 13B and 14B stated in the above items (2), (3) and (4)
respectively, and the explanation is therefore omitted here.
The respective data above stated is written into the foregoing RAMs 12, 13
and 14 by proper write means during the vertical blanking of the color
monitor device 6 in FIG. 1.
If the raster lies within the brightness modulation region or the frequency
characteristic control region, the content of the RAM 12B and the varying
width .DELTA.B.sub.T of the brightness modulation of every raster are
added during the horizontal blanking of the monitor device 6, and the
content of the RAM 12B is rewritten to the operated result.
FIG. 6 shows an example of a more detailed arrangement of the brightness
modulation signal-generating circuit 10B in FIG. 3. Numeral 31 designates
a priority encoder, numerals 32-35 selectors, numeral 36 a counter,
numerals 37-39 RAMs, numeral 40 a full adder, numerals 41 and 42 latch
registers, numerals 43 and 44 up- and down-counters respectively, numeral
45 a rate multiplier, numeral 46 a high-speed D/A converter of the
multiplication type, numeral 47 a high-speed D/A converter, numeral 48 an
edge detector, numeral 49 an OR gate, and numeral 50 an AND gate. Among
these components, the priority encoder 31 corresponds to 11B in FIG. 3;
the RAMs 37, 38 and 39 correspond to 13B, 12B and 14B in FIG. 3
respectively; the adder 40 corresponds to 25B in FIG. 3; the counters 43
and 44 correspond to 20B in FIG. 3; the rate multiplier 45 corresponds to
21B in FIG. 3; and the D/A converters 46 and 47 correspond to 17B and 22B
in FIG. 3 respectively.
FIG. 7 shows an example of the visual scene which is displayed on the
monitor device in accordance with this invention. The example has two
brightness modulation regions B1 and B2 and two frequency characteristic
control regions F1 and F2.
FIG. 8 shows a time chart of the operations of various parts in FIGS. 3 and
6 during the scanning of the raster r in the display of FIG. 7. HSYNC
designates a horizontal scanning period; CP2 a clock of 20 MHz for the
rate multiplier 45; LINC.sub.S, C.sub.L, C.sub.R and C.sub.C outputs from
the line memory (inputs to the input terminal 23C) representing the sky, a
lawn, a runway, and a center line, respectively; RAMCADR a readout address
of the RAM 12C; LATCCK a clock for latch to be applied to the latch
register 16 (output of the edge detector 15); LINB1 and B2 outputs of the
line memory (inputs of the input terminal 23B) representing brightness
modulation regions; RAMBADR a readout address of the RAM 12B; CNTBLD a set
timing of the counter 20B (corresponding to the counters 43 and 44 in FIG.
6); LINF1 and F2 outputs of the line memory (inputs of the input terminal
23F) representing frequency characteristic control regions; RAMFADR a
readout address of the RAM 12F; and CNTFLD a set timing of the counter
20F.
Hereafter, the operations of the circuits in FIGS. 3 and 6 will be
described in detail with reference to FIGS. 7 and 8.
First of all, there will be explained a color displaying method in the case
where neither the brightness modulation nor the control of the frequency
characteristic are carried out (outside the brightness modulation region
or BMON=0 and outside the frequency characteristic control region or
FMON=0). The raster r is taken as an example in FIG. 7. The output
LINC.sub.S of the line memory storing the figure range of the sky is
generated at a horizontal scanning point y=y.sub.o, and enters the
priority encoder 11C from the input terminal 23C. Thus, the priority
encoder 11C assigns the address RAMCADR of the RAM 12C, to read out the
brightness level of the corresponding primary color from the RAM 12C (the
output LINC.sub.n of the line memory and the content of the address n of
the RAM 12C are brought into correspondence in advance). On the other
hand, the edge of the output LINC.sub.S is caught by the edge detector 15,
the latch register 16 having the clock LATCCK impressed thereon, and the
data DI.sub.1 read out from the RAM 12C is loaded into the latch register
16. This data is applied to the multiplication type D/A converter 17C and
is converted into an analog voltage V.sub.D. The converted voltage V.sub.D
is passed through the FET low-pass filter portion 18 as well as the
amplifier portion 19 and is applied to an R, G or B terminal as the
brightness signal of the monitor device 6 in FIG. 1. Now, the select
signal S of the selectors 34 and 35 is "0". Therefore, when the selectors
select set values SA and SB in the case of executing no brightness
modulation, the multiplication input voltage V.sub.S of the D/A converter
17C becomes constant, and the brightness does not vary with time. In this
case, e.g. "10000000" being a binary signal is set as the set value SA and
e.g. "0000" is set as the set value SB. The same applies to the control of
the frequency characteristic, and the FET gate voltage V.sub.G of the
low-pass filter portion 18 becomes constant so that the frequency
characteristic does not vary.
Subsequently, the output LINC.sub.L of the line memory indicative of the
figure of the lawn is generated at a scanning point y.sub.1. When it is
received from the input terminal 23C, the address RAMCADR of the RAM 12C
becomes "L", and the color of the lawn is displayed through the same
procedure as described above. At a scanning point y.sub.2, the output
LINC.sub.R of the line memory indicative of the figure of the runway is
developed, and the content of the address RAMCADR of the RAM 12C is
displayed. Here, LINC.sub.L is connected to a priority input terminal
higher in the priority level than that of LINC.sub.S, and LINC.sub.R is
connected to one higher than that of LINC.sub.L. Thus, even superposed
figures are displayed in the order of the priority level. The same applies
to the output of LINC.sub.C representative of the figure of the center
line of a runway, etc.
Now, a brightness modulating method will be explained. When the signal LINB
representative of the brightness modulation region B is "1" and the signal
BMON is "1", the brightness of the figure gradually varies from the
above-stated brightness (the content of the RAM 12C) in accordance with
the contents of the RAMs 12B, 13B and 14B.
The explanation will be made along the timing of the raster r in FIG. 7.
At the scanning initiation point y.sub.o of the raster r, the ranges of the
brightness modulation regions B1, B2 and the frequency characteristic
control regions F1, F2 are not involved. In rasters for which the
horizontal scanning-initiating points lie within the regions, the varying
width .DELTA.B.sub.T of the RAM 37B is added to the content of the RAM 38
by means of the adder 40 during the horizontal blanking, and the content
of the RAM 38 is rewritten by the use of the result. More specifically, at
the same time that a clock signal CP (at, for example, 2.5 MHz), generated
during the horizontal blanking begins to be counted by the counter 36, the
content of the counter 36 is selected and applied as addresses to the RAMs
37 and 38 by the selector 32 with the horizontal synchronizing signal
HSYNC. The contents thus read out from the RAMs 37 and 38 are added by the
adder 40, and the result of such addition is stored into the latch
register 41 with the clock signal CP.sub.1. When a write control signal WE
is applied to the RAM 38, the content of the latch register 41 is written
into the RAM 38 to rewrite this RAM 38. The addition by the adder 40 is
executed for every address assigned by the counter 36. However, the
rewrite of the RAM 38 is actually executed at only the address
corresponding to the specified brightness modulation region in which the
initiation point of the present scanning line lies.
When, upon gradual variation of the brightness modulation, the initiation
point of the raster has reached the boundary point of the brightness
modulation region, the content of the RAM 38 becomes the final value BN of
the brightness modulation. Accordingly, at the scanning initiation point
y.sub.o lying outside the brightnes modulation region B.sub.1, the output
of the RAM 38 is the final value BN.sub.1 of the brightness modulation
region B.sub.1. When the scanning point has reached y.sub.3, it falls
within the brightness modulation region B.sub.1, the output LINB.sub.1 of
the line memory enters the priority encoder 31, and the content of the
address corresponding to LINB.sub.1 (for example, address 1), that is,
BN.sub.1 is loaded into the up- and down-counters 43 and 44 by the use of
the edge signal CNTBLD detected by the edge detector 48. Here, the counter
43 is a binary counter for count-up, while the counter 44 is a binary
counter for count-down.
On the other hand, the content of the same address of the RAM 39 is loaded
into the latch register 42 by the same timing signal CNTBLD. The data D15B
of the first-fourth bits counted from the LSB is applied to the data input
terminal B of the selector 35, the data DI4B of the fifth-tenth bits
counted from the LSB is applied to the data input terminal DI of the rate
multiplier 45, and the data BUPDN of the eleventh bit is applied to the
selector terminal S of the selector 33. Here, if the data BMON of the
seventh bit from the LSB in the output of the latch register 16 in FIG. 3
is "1", a signal is applied to the selector terminals S of the selectors
34 and 35 through the AND gate 50, and if the data BUPDN of the eleventh
bit from the LSB in the output of the latch register 42 is "1", a signal
"1" is applied to the selector terminal S of the selector 33, so that the
selectors 33-35 select the inputs of the data input terminals B
respectively.
In the rate multiplier 45, the data DI4 of the fifth-tenth bits counted
from the LSB of the RAM 39 is applied to an input terminal DI thereof, and
a clock CP.sub.2 at, for example, 20 MHz is applied to an input terminal
f.sub.in thereof. Also the rate multiplier 45 delivers from its output
terminal f.sub.out a clock of a rate determined by the input data DI4B
relative to the clock CP.sub.2, and applies it to the counters 43 and 44.
In the respective counters 43 and 44, the count-up and the count-down are
executed with the output clock from the rate multiplier 45. At this time,
the selectors 33 and 34 select the data of the input terminals B, that is,
the output of the counter 43, so that the output is applied to the
multiplication type D/A converter 46. Further, the data DI5B from the LSB
to the fourth bit of the RAM 39 is applied to the D/A converter 47 through
the selector 35, and the output after the analog conversion is applied to
the D/A converter 46. In the D/A converter 46, the data corresponding to
the multiplication value between the data applied to its data input
terminal DI from the selector 34 and the data applied to its control
terminal V.sub.S from the D/A converter 47 is converted into an analog
signal, which is applied to the multiplication type D/A converter 17C in
FIG. 3.
Accordingly, as the scanning point of the raster r moves from y.sub.3 to
y.sub.1, the brightness level in the corresponding primary color rises,
and at the scanning point y.sub.1, that is, the point of intersection with
the horizon H, approximately the initial value B.sub.01 of the brightness
modulation region B.sub.1 is reached.
Subsequently, the output LINB.sub.2 of the line memory is generated at the
scanning point y.sub.1, the contents of an address corresponding thereto,
for example, address 2 are read out from the RAMs 38 and 39, and the
brightness modulation in the brightness modulation region B.sub.2 is
executed in the same way as described above. Accordingly, at the scanning
point y.sub.4, the proportion of the modulation becomes substantially
equal to the initial value B.sub.02 of the region B.sub.2, and when the
scanning point y.sub.4 is exceeded, the brightness is not modulated.
In the case where the raster r has entered the frequency characteristic
control region F.sub.1 or F.sub.2, a signal for the frequency
characteristic control is generated in a simil | | |
