DE2315674C2 - Apparatus for use in a simulator visual display system - Google Patents

Description

The invention relates generally to simulation and, more particularly, to apparatus for Generate sky, horizon and limited view area scenes in a simulator television display system.

One of the problems with a visual display system that uses a terrain model Generating an image to be presented to a student on a television screen consists of simulating of sky and horizon The terrain model is of limited size and cannot extend to the horizon extend. Various methods have been used to solve this problem, for example by providing painted mountain and sky scenes around the edges of the model for others Methods have been used in electronic devices that are somewhat of the present Invention are similar. However, none of these methods have been entirely satisfactory.

Another requirement that exists not only with camera model devices but with all visual display devices is the ability to have a simulate limited field of view. This has also been done in many ways, such as by means of Haze films, neutral density filters and electronic devices. Each of these systems has disadvantages.

The object of the invention is to create a system in which the F-generation of sky and horizon is effectively combined with the creation of limited field of view functions

According to the invention there is an apparatus for use in a simulator visual display system which includes a device for generating a Terrain video signal, a foreground area, television display means, and sync generator means for driving the scans

the video signal generating device and the display device, characterized by a Means for generating a cloud video signal that appears as white on a television screen, a Switching means having the terrain video signal as the first input and the cloud video signal as the second Receives input and responds to a control input to the first input as an output supply, when the control input is at a first level, the second input as an output when the control input is at a second level, and a proportional mixture to be supplied from the first and the second input when the control input is at a level between the first and the second level is located, and a device which shows the location of the simulated horizon detects and delivers a voltage with the second level when the simulated horizon is above the horizon and supplies a voltage which gradually changes from the second level to the first level when tier simulated horizon crosses the horizon downwards.

The invention is explained below with reference to the drawing, for example.

F i g. 1 is an overall block diagram of visual display equipment incorporating a preferred embodiment of apparatus in accordance with the invention;

F i g. Fig. 2 is a block diagram of the output control part of the embodiment of Fig. 1;

F i g. 3 is a block diagram of the horizon and function generator parts of the embodiment according to FIG

F i g. Fig. 4 shows waveforms for explaining Fig. 4. 3;

Figure 5 is a view of a typical grid that to understand the F i g. 3 is useful;

F i g. 6 is a waveform diagram. which shows the results of the multiplication with the runway visual area CA VR) divided by the height (h) :

Fig. 7 is a diagram showing the waveforms reproduces the generated by the function generator according to FIG. 3 are generated;

Figure 8 is a logic circuit diagram of the dividing and multiplying device of Figure 8. 3;

F i g. 9 is a logic diagram of the data buffer of FIG. 3.

In Fig. 1 shows the basic arrangement of the entire camera model system. A color television camera and probe 11 views a terrain model 13 and displays an image generator 12. The camera is controlled by means of a remote camera control device 15, from which the three color signals (red, green and blue). The entire system is synchronized by means of a synchronization generator 17. The color signals on lines 16 are fed to a special effects generator 19 which also has outputs from a computer 21 and a distraction reference generator 23 The computer 21 is a flight simulator computer in which the equations of motion of the Simulator are stored with which the visual display system is used, and he delivers on a Line 25 outputs, which with the place and the location of the simulated aircraft to be used are related in a manner as described below is described. It should be noted that the elements of the generator 12 also includes a television camera 11 viewing a film 13. The camera 11 may instead be a light spot scanner scanning a film. In general, the present apparatus can be used with any visual display system that utilizes television imaging.

The deflection reference generator 23 is a deflection generator operating with high accuracy and linearly, the horizontal and vertical deflection waveforms generated in the special effects generator 19 are used from the horizontal and vertical Developed drive signals which are supplied from the synchronizing generator 17, and the below Using techniques known in the television art. The outputs of the Generators 19 become display devices 27 fed, which are arranged to be of Trainee pilots can be viewed in the cockpit 29 of a simulated aircraft. In the cockpit 29 simulated controls are provided, the outputs of which are sent to the computer 21 via a line 31 Zugcfüiiri be who you used to süf the above to calculate the outputs obtained via a line 33 and in the cockpit 29 present instruments in a manner known in the art.

2Ί The essence of the present invention is the special effects generator 19, which will be described in more detail below. However, before starting with this description, it seems appropriate first t ie types of scenes to consider that a

To be presented to pilots.

Under good visibility conditions, a terrain scene created by the camera 11 of the German model 13 must be will appear in the foreground with a horizon and sky or clouds. When the point of view

J5 parts of the site must be darkened or reduced can be blurred to simulate this limited view. If the simulated airplane climbs, it can enter in clouds, then at the top of the clouds exit and continue to rise. If that Airplane located in clouds is said to be a white scene to be available. When the aircraft is above clouds, it is in the cloud-modulating foreground white with blue skies of increasing intensity with increasing altitude required.

• * ⁵ The special effects generator 19 enables all of this, d. H. from this generator 19 will be any scenes other than those from camera 11 developed terrain scene generated synthetically

Deliver the basic block diagram of the special effects-

the generator 19 is shown in FIG. 2 reproduced.

A block 41 receives inputs of the values 10 sin Θ, cos θ sin Φ, cos Θ, cos Φ, RVR and h from the computer 21, where:

Φ RVR

Pitch angle of the simulated aircraft. Roll angle of the simulated aircraft Runway visibility area Height.

The horizontal and vertical reference deflections are also used as inputs to get on a line 43 to generate a horizon reference signal on a line-by-line basis. This signal is in a Function generator 45 processed in order to develop a control or gating signal, which to this used to switch between model video and special effects. The content of blocks 41 and 45 becomes explained in more detail below

When the camera is shown in FIG. I scans, it usually scans the sky area first (assuming there is one). During this period, the output obtained from c * em generator 45 on line 46 has the value zero. This forms a control or fade-in input for three controlled video amplifiers 47, 49 and 51. These amplifiers, which can be "Moloro ¹ ·: MC 1545 G" amplifiers, have two signal inputs, a signal output and a gate input. At zero volts at the gate input, the upper input (according to FIG. 2) is switched to the output. At two or more volts, the lower input is switched to the output. If the values are in between, the two input signals are mixed.

The upper inputs of the amplifiers 47, 49, 51 are each connected to the movable contact of a potentiometer tied together. That of the red amplifier 47 with a potentiometer 53, that of the green amplifier 49 with a potentiometer 55 and that of the blue amplifier m ·· a potentiometer 57 via an amplifier 59 summing the unity gain. The potentiometers are each on one Grounded side, and on the other side they are connected to a common voltage source. The potentiometers are each set so that the potentiometer 53 has an output that is 03 of his Input is, the potentiometer 55 has an output that is 0.59 of its input, and that Potentiometer 57 has an output that is 0.11 of its Input amounts. The amplifiers 47, 49 and 51 supply the red and green and via cell drivers 71, respectively the blue output to the display devices 27. If the potentiometers in the specified manner are set, the resulting color will be white. This is used to represent heaven to reproduce.

However, the sky changes during the different times of the day. To this change To reproduce, means are provided to change the color from light white for the day to gray for the Twilight and change to black for the night. This is done by having the input to the Potentiometers on a line 61 is controlled. The line 61 is with the common contact one of a relay 63 controlled relay pole 63/4 connected. In the position shown, it is above the normally closed contact with the common contact of one controlled by a relay 65 Relay pole 65/4. and thence through the normally closed contact of this relay with the movable one Contact of a potentiometer 67 connected. This potentiometer 67 is set so that there is one provides bright white video output that simulates the day

When the one relay 63 is actuated by a command received from the computer 21 indicating twilight, the line 61 is via the normally open contact of the relay pole 63.4. that is set so connected to the movable contact of a potentiometer 69 is that it provides a gray output If the other relay 65 is actuated by a command from the computer, the line is earthed 61 through the normally open contact of the Relaispols 65 A, giving a black output

Hence, with a zero volt input is on the line 43 the combined vedeo output after passing the line driver 71 knows depending on the time of day,

gray or black. When the horizon is reached, the signal on line 43 gradually goes up from zero 2 volts above as described below. This causes amplifiers 47, 49 and 51 be switched to the terrain video signal, which via lines 73 and three controlled amplifiers 75,77 and 79 the lower inputs of amplifiers 47,49,51 is fed. This causes a gradual change from white to the model image, being the horizon is out of focus. As visibility diminishes, the function on line 46 changes to include more of that Obscure or blur model video information, d. H. that they have the effect of the horizon brings closer.

The amplifiers 75, 77 and 79 represent devices, the scenes lying above or below the clouds choose. When the simulator is under clouds, the terrain video signal will be in the above switched manner. However, the simulator can go through the clouds and out step out from their top. When the simulated airplane steps out of the clouds, one of the excites the computer 21 received signal a relay 81, which causes that on his Po! 81Λ a tension to the Amplifier 75, 77, 79 is applied causing them to approach their lower inputs switch.

Just like the upper inputs of amplifiers 47, 49, 51 are the lower inputs of amplifiers 75, 77, 79 connected to potentiometers 83 or 85 and 87, which are set so that they provide a white output. The input voltage to these potentiometers is obtained from a number of potentiometers 89 and 91, 93 supplied, depending on the operation of the relays 63 and 65 via relay poles 63ß and 65S to a Line 95 can be switched. The mode of operation is the same as for poles 63/4 and 65/4 with the exception that the night scene need not be completely black if the potentiometer 93 is able to produce a supply low voltage for dark gray.

As the aircraft emerges from the clouds, the amplifiers 47, 49, 51 switch, under the control of the signal on line 43, from a white sky to a white foreground (from amplifiers 75, 77, 79) as the horizon is passed. This is correct, since the sky looks white at this point. The relay 81, however, also actuates a second contact 81 β, which causes a part of a computer signal which represents the height above clouds to be transmitted via an amplifier 97, the relay pole 81 B and a resistor 99 is fed to the amplifier 59. This causes additional blue to be added to the output, with the amount of blue increasing as the altitude increases to produce the desired result, namely a sky that turns a darker blue color with increasing altitude

The way of working can be summarized as follows:

a) Under clouds, the sky is from the upper inputs of amplifiers 47, 49, 51 and the The foreground created by the lower entrances, the camera above the upper entrances the amplifier 75,77,79 can be delivered.

b) in clouds, the control signal on line 46 are held at zero so that circuits to the ground scene never occur.

c) Above clouds, the sky is created from the upper entrances to the amplifiers 47, 49, 51, and blue is added to amplifier 51 as a function of altitude above the clouds, while the foreground (now clouds) is created by the lower entrances, which are now via the Ve amplifiers 75, 77, 79 come from their lower inputs, which are set so that they deliver a white color.

d) In any case, the time of day and the brightness are controlled by means of relays 63 and 65, which regulate the equivalent voltages to all amplifiers.

FIG. 3 shows the horizon generator 41 and the function generator 45 of FIG. 2, which supply the circuit waveforms. Two data buffers 101 and 103 receive from the computer 21 as inputs the values cos Θ, sin Φ and rnc ft rrtc <ß Oip Anea'anae * anc Hipcpn Pnffprn wt * rA <* n RVR causes the horizon to fall further, like this in Fig. 5 by a line 129 and in FIG. 4 is illustrated by a zero reference line 131.

By supplying an angle of inclination to the amplifier 113 via the 10 sin Θ input, the horizon 121 is similarly displaced by shifting the zero point 1! 9. The result of a small roll angle is illustrated in FIG. 5 by a grid 133 and in FIG. 4 by a waveform 135 . The horizontal waveform 137 is shown plotting only four lines for a vertical deflection 117 for the sake of simplicity. In practice, of course, 250 or more horizontal lines will be plotted for each vertical deflection. In the case of a roll angle, the expression cos θ sin Φ no longer has the value zero and the expression cos θ cos Φ no longer has the value one. If the vertical waveform is multiplied in the converters 105,117, the result is a waveform 139, and when the hori- \ A / f »ll *» * rm nfr

in ripm I Imfnrmpr 1Ω7

multiplying digital-to-analog converters 105 and 107, where they multiply the horizontal and vertical deflections from the generator 23. The outputs from the multiplier converters 105, 107 are then fed to the sign changing circuits 109 and 111 , which receive a bit as inputs from the computer 21, which indicates the sign of the values cos θ sin Φ and cos θ cos Φ. the working amplifier and electronic switches which are able to convert the signal for a minus sign at the input and not convert the signal for a plus sign. The outputs from circuits 109 and 111 are summed in amplifier 113 with part of RVR (field of view) and h (altitude) and with 10 sin θ from computer 21 and a trim voltage from potentiometer 115. Summing resistors are provided in the usual way at the amplification input in order to create the required division.

It is to be remembered that this part of the circuit is used to increase the horizon locate. To show how this is done, the test of FIG. 4 and 5 together with FIG. 3 useful.

Let us first assume the case in which the roll angle and the pitch angle both have the value zero. Both sin θ and sin Φ then have the value zero, while cos θ and cos Φ have the value one. Hence the only inputs to amplifier 113 are the vertical deflection, h, RVR and the trim voltage. The vertical waveform 117 is shown in FIG. When A is zero and RVR is infinite, the trim voltage potentiometer 115 is adjusted so that the line 119 representing zero volts is on the horizon 121 (Fig. 5) The upper part 123 of the waveform 117 is used to: the control or fade-in input, which in connection with F i g. 2 in the manner explained below.

As the altitude increases, the horizon falls. Therefore, the value h is used to create a DC offset under these conditions. This is in FIG. 5 by a line 125 and in FIG. 4 illustrated by a new zero line 127. As the field of view RVR decreases, the point where land becomes visible moves to the foreground. If this point is defined as the horizon, then it can be seen that adding an offset for is multiplied, the result is waveform 141. When this waveform is added in amplifier 113 , the end result is waveform 135.

The first horizontal scan, as it appears in waveform 135, just crosses line 143, the zero line representing the horizon. This corresponds to line 145 in FIG. The next scan crosses approximately the center, which is the line 147 in FIG. 5 corresponds. The next scan, corresponding to line 149 , only crosses at the beginning, and the last scan, corresponding to line 151 , does not cross at all. It should be noted that grid 133 (Fig. 5) represents the camera grid whatever the lower one Part of it forms the sky as a result of the inversion by the lens and the upper part forms the ground, the line 153 representing the horizon

In essence, the multiplication serves the horizontal scanning and the vertical scanning with cos θ sin Φ or with cos θ cos Φ in addition, the now inclined scanning axis system on a horizontal axis system to transform, and it gives the coordinate in the horizon axis system right-angled to the horizon

From the foregoing, it can be seen that subzero voltages , ie, minus voltages, occur on waveform 135 during the scan of the sky and that positive voltages occur during the scan of the terrain. It therefore follows that the controlled amplifiers described in connection with FIG. 2 must be switched at the points at which the waveform 135 crosses the zero line.

According to FIG. 3 becomes the output of amplifier 113, ie waveform 135 of FIG. 4 is fed via a gain-adjusting potentiometer 155 to a multiplier 157 , where it is multiplied by the value RVR / h generated in block 158 in the manner described below. This is necessary because, as will be apparent, the slant distance to points on the ground decreases as the altitude increases. Therefore, as the altitude increases, it is less visible from the ground. At a height of 1.8 km and a field of view of 1.8 km, nothing from the ground would be seen. It has been found that the multiplication by RVR / h comes close to the function considered here

The multiplier 157 has a diode 159 at its output in order to allow only negative outputs. If a slope angle of zero and a

Roilapt are assumed to be Mull, the input to multiplier 137 is similar to waveform 117 of FIG. The multiplier inverts so that the output, when passed by diode 159, will be similar to waveform 161 shown in Figure 6 when multiplied by one (ie, RVR-h). In FIG. 6, two examples are also shown when it is multiplied by a value other than one. Waveform! 65 corresponds to a multiplication by 10 (ie /? VT? = 5 and Z) = ¹ A), and waveform 167 corresponds to a multiplication by i / <(ie, RVR = Ui and / i = 2). These waveforms are designed to be used to control the controllable amplifiers described above. As noted above, voltages of zero or below will cause the sky to turn on and voltages above 2 volts will cause the foreground to turn on, while voltages in between will cause a mixture to turn on.

5 volts, it can be seen that waveform 165 switches rapidly from sky to terrain, while waveform 167 only blends a small portion of the terrain with the white sky causing the whole scene to appear blurred, which is correct because in this case R VR is less than h .

The final processing of waveform 135 (now 161 or 165 or 167) is done in shaping circuits connected to the output of the multiplier 157 are connected (Fig. 3). There are two circuits 171 and 173 provided, the first of which gives the correct transition from sky to terrain, if under clouds, while the second circuit results in the transition from sky to white clouds, when above the clouds. These circuits are common diode function generators, with the ones shown Diodes and potentiometers are set so that they result in the required switching points.

F i g. 7 illustrates the nature of the output functions generated. The waveforms 175 has the Shape for the transition from sky to terrain corresponding to circuit 171 and waveform 177 has the shape for the transition from sky to clouds, which corresponds to circuit 173 Der the latter transition is said to be a sharper transition, as is the case in the real environment

Which of the two circuits is to be used is determined by a relay 179. When the relay is in the deenergized state, the relay pole 179Λ grounds the circuit 173 at its output to an amplifier 181. The relay pole 179ß is open, and the output of the circuit 171 is the Amplifier 181 is supplied. When the relay 179 is energized by a command received from the computer 21 indicating a condition over clouds, the relay head closes and grounds! 179ß the circuit 171 and the relay pole 179/4 opens to allow the circuit 173 to feed its output to the amplifier 181. When in the clouds, a relay 183 (Fig. 3) is energized causing a positive voltage is applied to the input of the amplifier is applied 181, thereby resulting in a negative output results, which prevents a switch from sky to ground, so that a completely white image is created, if the waveforms are selected 175 and 177, and ⁵ are they 181 at the output of the amplifier inverted to provide the required zero-to-positive inputs on line 43 to the controllable amplifiers according to FIG. 2 to generate.

F i g. 8 gives in detail the circuit of blocks 157 and 158 according to FIG. 3 again. The altitude signal h is introduced into a multiplier 182 in analog form. A plurality of resistors 183 form the input here.

These resistors have wide resistances 185 connected in series and provide inputs to a summing amplifier 187. From each series resistor junction a line goes to a block 191 which consists essentially of a plurality of electronic There are switches to earth that are individually controlled by corresponding inputs on lines 193 will.

The values of resistors 183 and 185, together with that of a feedback resistor 189, are selected in such a way that a gain is obtained which is dependent on the state of the switches in block 191. This enables h with a DigiiälwOi iciiigdjig düi ucii lines! 33 iiiuiiipimei i . Such devices for multiplying an analog voltage by a digital word are known in the art and need not be further described here. The output of amplifier 187 is summed at 192 with the output of an amplifier 194, which has the value RVR as an input, via summing resistors 195 and 197. The sum is fed to two comparison devices 199 and 201, specifically at the upper input of the comparison device 199 and at the lower input of the comparison device 201. The other inputs of the comparison devices 199 and 201 are grounded. The multiplied h is an inverted value and R VR is a non-inverted value. Therefore one value (7? VV? ^ Is positive and the other value ^ negative.

If the multiplied h is less than RVR , the resulting voltage is positive and the comparator 201 has an output which makes a gate 203 effective. The gate 203 receives the drive signal at a further input via a gate 205, which is used to ensure that the gate 203 is not made ineffective by an output of a gate 207, and the pulse through the gate 203 passes to the down counting input of a '' counter 209. The counter output is reversed by an inverter 211 and fed to block 191 where it causes h to be multiplied by a larger number and therefore to be larger. When the absolute value of the multiplied h reaches that of RVR , the voltage at connection 192 becomes zero and the comparison device 201 switches off, as a result of which further counting pulses are rendered ineffective. The value of the output of the inverter 211 is R VR / h. This must be true, since one knows that Λ times x = Ä VR or x = R VR / h.

If the absolute value of the multiplied Λ is greater than R VR , the comparator 199 activates a gate 213 to cause an up-count value to be applied to the counter 209. If it is reversed by the inverter 211, this causes the multiplied h to decrease until, as before, an equality is reached at which point in time the comparator 199 renders the gate 213 ineffective

There are limits of RVR and h in the system, and for the correct operation of the system the value RVR / h is also limited. This is the purpose of gates 207 and 215. If the counts in counter 209 are all zero, do that Gate 207 the gate 203

ineffective, which prevents further down counting. Similarly, if the Values in the counter are all one, the outputs of inverter 211 are all zero, and gate 215 does the gate 213 ineffective.

The R VA / A output is then fed to a multiplier comprising a switch 217, resistors 219 and 221, and an amplifier 223 with feedback 225, in all respects the same as the h- multiplier described above. In this case the analog input is that from potentiometer 155 according to FIG. 3 modified scanning signal obtained. The feedback path of the amplifier 223 is more complicated due to the diode 159 provided at its output, which was described above in connection with FIG. For a negative voltage output, the feedback takes place via a resistor 227. In order to avoid a shut-off state, any positive voltages are fed back via a diode 229 and a resistor 231

As examples of the types above. Components that are in the Circuit can be used, the following can be mentioned:

Amplifier 187,193 Amplifier 223 Comparator 199,201 Switches 191,217 Toi e 203,213 Gates 207,215 Inverter 211 Counter 209

FairchildMa741 Harris 2605 National LM 306 Texas Inst SIV 7406 Motorola MC 862P Motorola MC 1802 Motorola MC 883P Motorola MC 8563

As mentioned in connection with Fig. 3, the Data supplied to the buffers 101 and 103 from the computer 21. The supplementary update speed of the computer is in the range of 10 to 20 per second. The television screen speed is 30 frames per second (US) or 25 frames per second (Europe), whereby the field velocities are double. Therefore must the buffers synchronize these two speeds in order to avoid undesirable effects in the display avoid. Furthermore, in some systems there is absolute electrical isolation between the computer 21 and the visual display system. In Fig. 9 is a data buffer reproduced, which all meets the requirements.

The insulation is effected by means of circuits 233, which each have a device that emits light, when a computer input is received, and a second device responsive to that light to provide an output. In this way a perfect electrical insulation is achieved

s One device that can be used with circuit 233 is what is labeled Texas Instruments TlXL-112. For reasons of simplification are in Fig. 9 only four outputs shown In practice, as many outputs are provided as there are for the

ι υ desired resolution are required, this being the case for any number of inputs will work.

The output lines of circuits 233 are all grounded through resistors 235 to ensure that the output is ground when no signal The outputs are then sent to a register 237, one side of a comparator 239 and a second 241. A high frequency timer 245 switches the output of the register 237 to other side of the comparator 239. When the computer

: n Data is updated and register 237 is not is set, there is no comparison. If the Data at the input and the output of register 237 are the same, which indicates a stable state, then the comparator 239 provides an output. It's closed

: j notice that this condition means that the data in the second register 241 are also stable at this point in time, the register 241 being a duplicate of register 237 and has the same inputs as this. The comparator output supplies one

vi Actuation input for an AND gate 243 (in actual practice two NAN D gates are used, one of which produces an inversion). The other input to gate 243 is the vertical return signal. The exit of gate 243

3i controls the data in register 241 to the Multiplier according to Fig. 3. In this way, data is only sent to the multiplier during the vertical rewind supplemented (updated) and only if the data input from the computer is not

■■ • o changes, which avoids problems with the display device.

Apparatus has thus been shown which can capture both sky, clouds and limited viewing scenes The generated above as well as below the clouds Device can not only in camera model vision systems, but in any vision system in which a Television display is intended to be used. In the described and illustrated embodiment, different within the scope of the invention

so amendments are made.

In addition 7 sheets of drawings

Claims (18)

Patent claims: 1. Apparatus for use in a simulator visual display system with at least means for generating a terrain video signal of a foreground area, television display means and synchronizing means for driving the scans of the Terrain video signal generating device and the television display device, characterized by first devices (67, 69) for Generating a cloud video signal which appears white on a television screen (27), switching means (47, 49, 51) which the terrain video signal as receive a first input and the cloud video signal as a second input and which on address a control input to provide the first input as an output when the Control input is at a first level, to provide the second input as an output, when the control input is at a second level, and a proportional mixture off the first and the second input when the control input is at a level located between the first and the second level, and a detector device (41) which determines the location of the simulated horizon and what a voltage from the second level delivers if the simulated horizon above the horizon I> gt and delivers a voltage that gradually changes from the second level to the first level when the simulated horizon the Horizon crosses downwards 2. Device according to Claims 1, characterized by second devices (89, 91, 93) for generating a cloud video signal, second switching devices (75, 77, 79) which are arranged between the terrain video signal generating device and the first switching devices (47, 49, 51) * > and receive the terrain video signal as a first input and the second cloud video signal as a second input and which are responsive to a control signal to provide the first input as an output when the control signal is at a first level and the second input as to provide an output when the control signal is at a second level, and means (81, SiA) for supplying a control signal to the second switching means *> (75, 77, 79) at the first level to detect scenes under clouds to simulate, and at the second level to simulate scenes over clouds. 3. Apparatus according to claim 2, characterized in that the television display device (27) is a color display device, that each of the video signals contains a red, a green and a blue video signal, with separate devices of the first and the second switching devices (47, 49, 51 ί 75, 77, 79) are provided for each color, ^M and that a device (97, SiB) is provided which supplies additional blue video signals to the blue device (51) of the first switching devices when the control signal is at the second level is located. 4. Apparatus according to claim 3, characterized in that the additional blue video signal is created in that a voltage is supplied which is a function of the height above the clouds represents 5. Apparatus according to claim 2 or 3, characterized in that the first switching devices (47,49,51) and the second switching devices (75, 77,79) controlled video amplifiers. 6. Device according to one of claims 2 to 5, characterized by a signal strength control device (21, 63, 65, 67, 69, 89, 91, 93), wdche the Strength and thus the brightness of the first and second cloud video signals as a function of the Time of day controls 7. Apparatus according to claim 6, characterized in that the signal strength control device a plurality of adjustable voltage sources (67, 69, 89, 91, 93), one for each Time of day is provided for each of the first and second switching devices (47, 49, 51; 75, 77, 79), third switching devices (63, 65) which have the voltage sources as inputs and im Responding to a control signal one of these voltage sources to the inputs of the first and of the second switching devices can switch, and a control signal generating device (21) which a control signal ran, which the simulated Time of day 8. Device according to one of the preceding claims, characterized in that the visual display system (11-29) simulated scenes for a flight simulator supplies that the detector means (41) waveform generating means (101 to 113) which has the horizontal scanning, the vertical scanning and functions of the simulator's climb and roll are received as inputs and output as a waveform representing the resolved scanning movement represents perpendicular to the horizon with the waveform going from a negative to a positive Voltage goes and zero can cross at that point on the horizon, and that shaping circuits (171, 173) are provided which have the waveform as an input and cause the Waveform is transformed to create a voltage that goes from the first to the second Level goes over every time the zero volt point is crossed. 9. Apparatus according to claim 8, characterized by means (h, RVR, 115) for imparting a DC offset to the waveform to ensure that the zero point occurs on the horizon 10. The device according to claim 8 or 9, characterized by an offset device (RVRX which supplies the waveform generating device with an offset input which represents the field of view 11. Device according to one of claims 8 to 10, characterized by rcine displacement device (h) which supplies a displacement voltage which represents the fall of the horizon due to an increase in height 12. Device according to one of claims 8 to 11, characterized by a multiplier (157, 158) which multiplies the waveform by the field of view (RVR) divided by the height (h) . 13. The apparatus according to claim 12, characterized in that the multiplying device (157, 158) has the following parts: a first multiplying digital-to-analog converter (182) which has a voltage representing the height (h) as its analog input, a first comparator (199) whose lower input is grounded and whose s upper input is connected to the output of the multiplying digital-to-analog converter (182) via a summing resistor (195), a second comparator (201), the upper input of which is grounded and the lower input of which is connected to a summing resistor (197) Receives and is directly connected to the upper input of the first comparator (199), an up and down counting counter (209), a first NAND gate (213), which at its first input the output of the first comparator (199 ) receives and at its second input receives a train of timing pulses and which supplies its output to the up-counting input of the counter (209), a second NAND gate (203), which a n receives the output of the second comparator (201) at its first input and receives the timing pulses at its second input and which feeds its output to the down-counting input of the counter (209), an inverter (211) which has the output of the counter (209) as an input receives and supplies its output to the first multiplying digital-to-analog converter (182) as a digital input, and a second multiplying digital-to-analog converter (157) receiving the waveform as its analog input and the output of the inverter (211) as its digital input 14. The apparatus according to claim 13, characterized by a third NAND gate (215) which the Receives outputs of the counter (211) as inputs and the first NAND gate (213) one him Ineffective input feeds, and a fourth NAND gate (207), which the outputs of the Counter (209) receives as inputs and the second NAND gate (203) one him ineffective making input 15. Device according to one of claims 8 to 14, characterized in that the waveform generating device (101-113) has the following parts: a first multiplier (105) which the horizontal scanning (H) as an input and the cosine of the slope angle times the sine of the roll angle (cos θ sin Φ) as the other input receives a second multiplier so (107), which receives the vertical sampling (V) as one input and the cosine of the pitch angle times the cosine of the roll angle (cos θ cos Φ ) as the other input and a summing amplifier (113) which receives the outputs of the first multiplier (105) and the second multiplier (107) as inputs and delivers the waveform at its output 16. Apparatus according to claim 15, characterized in that the simulator (11-29) a digital computer is controlled (21) by ^M and that the first multiplier (105) and said second multiplier (107) multiplying digital-to-analog converters are , the cosine of the pitch angle times the sine of the roll angle (cos θ sin Φ) and the cosine of the pitch angle times the cosine of the roll angle (cos θ cos Φ ) fed as digital outputs from the Sinvj'atorcomputer (21) will. 17. The device according to claim 16, characterized by each of the first at the digital inputs Multiplier (105) and the second multiplier (107) provided buffers (101, 103), each of which comprises: a first register (237) which has its inputs from the digital computer (21) receives a comparator (239), which as a set of inputs the outputs of the first Register (237) and receives the inputs of the first register (237) as the second set of inputs, a second register (241) which receives the inputs of the first register (237) as inputs and its outputs to one of the multipliers (105, 107), a high frequency timer (245), the Provides pulses which switch the inputs of the first register (237) to its outputs AND gate (243), which the outputs of the comparator (239) as an input and a vertical Receives return signal from the synchronizing generator (17) as a second input and delivers a signal which has the inputs of the second register (241) whose outputs switch 18. The device according to claim 7, characterized by insulating circuits (233) arranged between the buffers (101, 103) and the digital outputs of the computer (21).