Driving a car in a virtual environment

Abstract

The system (100) includes a headset configured to be worn on the head of a driver (120) of a vehicle (105), the headset including a camera (130) providing a first view (205) of the interior space of the vehicle (105) and an optical display for the driver (120), a model (170) for providing a view of a virtual environment of the vehicle (105) for a predetermined position and orientation, a device for identifying the position and orientation of the head of the driver (120) with respect to the real environment of the vehicle (105), and a processing unit (110), wherein the processing unit (110) is configured to superimpose a second view (210) of the virtual environment for the identified position and orientation on the first view (205) of the interior space and provide the second view (210) of the virtual environment to the driver (120).

Description

[Technical Field]

[0001] A vehicle may be operated by a driver in a predetermined environment. For example, a vehicle may be driven on a test track isolated from public road traffic to train the driver operating the vehicle. This test track may have several features to dynamically expose the driver to predetermined driving situations, allowing the driver to better master them. In this way, the driver can be trained without exposing the driver or others to undue danger. [Background technology]

[0002] Training facilities on test tracks are typically designed to minimize damage if a driver fails to complete a task or even loses control of the car. For example, there may be a bank of vertical water fountains that a car can drive into. After a certain distance, some of the water fountains can be shut off, creating a gap that the driver can use to steer the car through. If the driver misses the gap, the car will be hit by the water fountains, but will not hit a solid object.

[0003] Such training facilities are cumbersome to set up and operate. It is not possible to train all possible driving maneuvers in a car at a single training facility. For example, the fountain trains mentioned above are usually permanently installed and cannot be modified to separate any set curves.

[0004] Conversely, test tracks can also be used to check the function of a vehicle in defined driving situations, for example, to test key aspects of the chassis, braking system, or steering system. Here again, even the most well-equipped test tracks offer limited flexibility and do not allow an unlimited number of different tests to be carried out in a given, limited area.

[0005] It has been proposed to simulate the behavior of a vehicle in a given driving situation. The driver can be seated in a simulator that mimics the interior space of the vehicle. The exterior area of ​​the vehicle can be conveyed by a corresponding display device, for example, a projector system. The simulator can be tilted to simulate longitudinal or lateral forces acting on the driver.

[0006] Simulators can, in principle, recreate an unlimited number of different driving situations. However, simulators can only convey to the driver some aspects of real driving. For example, they cannot simulate accelerations greater than the force of gravity. Vehicle cornering, acceleration, and deceleration at the vehicle's limits cannot always be realistically represented. Driver training using simulators can therefore be incomplete. Simulators can only be used to a limited extent for vehicle testing, since the actual driving behavior of a vehicle is often not known accurately enough and, therefore, in some cases, cannot be properly simulated. Summary of the Invention [Problem to be solved by the invention]

[0007] The problem of the present invention is to provide a technique for more realistic driving of a car in a virtual environment. The invention solves this problem by the subject matter of the independent claims. The subclaims present preferred embodiments. [Means for solving the problem]

[0008] The system according to the present invention includes a headset configured to be worn by a driver of a vehicle. The headset includes a camera providing a first view of the interior space of the vehicle and an optical display for the driver. The system also includes a model for providing a view of a virtual environment of the vehicle for a given pose, a device for determining the pose of the driver's head relative to the real environment of the vehicle, and a processing device. The processing device is configured to overlay a second view of the virtual environment for the determined pose on the first view of the interior space and provide it to the driver.

[0009] It has been shown that the realistic driving sensation of a car is best conveyed by driving an actual car in a real-world environment, while the conditions characteristic of a given driving situation are best reproduced by creating a virtual environment.

[0010] We propose that views of the real and virtual environments be presented to the driver in an interwoven manner, whereby the driver can still perceive elements in the interior space of the car, while views of elements outside the car are replaced by corresponding views of the virtual environment. In this way, the driver can drive the car in a real environment, while at the same time having the impression that he is driving through a virtual environment.

[0011] The interweaving of real and virtual content creates a convincing and consistent sensory impression for the driver. The driver has full control of the vehicle and can use all of the vehicle's systems. Such systems may include, for example, driver assistance, entertainment or comfort systems. The virtual environment can be controlled in a way that allows the driver to experience predetermined driving situations and learn to operate the vehicle within those situations.

[0012] For example, driving techniques such as drifting around a given curve can be taught in this way without risk. The boundaries of the curve exist only in the virtual environment, while there are no boundaries or obstacles in the real environment. If the car were to deviate from the virtual curve, this would not cause any real damage to the car. In this way, any curve or series of curves can be created in the virtual environment, and the driver can realistically negotiate the curves with the car. Curves can be prepared in a relatively small area, saving space and avoiding delays. There is no need to build or maintain real infrastructure in the real environment. The car can be better observed in the given driving situations that the driver may cause in the virtual environment. This allows for more accurate vehicle inspections.

[0013] The interior space of the vehicle may be defined by a window. Preferably, an overlay is provided so that the virtual environment is visible to the driver only in the area of ​​the window. The rest of the interior space may include, for example, the vehicle roof liner, vehicle pillars, dashboard, steering wheel, vehicle seats, operating elements, side doors, vehicle floor or center console, and is preferably displayed to the driver from the perspective of the driver's head relative to the vehicle.

[0014] There may be multiple windows that can be treated in the same way, for example a windshield in front of the driver and side windows to the right and left of the driver, or a skylight with additional windows may be integrated into the ceiling. The car windows are transparent, allowing car occupants not wearing headsets to view the real car environment.

[0015] The window may be fitted with a predetermined optical symbology, and the processing device may be configured to determine the orientation and position of the window in the first view of the interior space based on the symbology.

[0016] Optical symbols can be more easily automatically recognized than window boundaries when scanning the interior space. This prevents the portion of the virtual environment the driver sees in the window area from being sized or oriented incorrectly relative to the view of the interior space. Furthermore, it is more reliably possible to prevent the recognized window position from shifting in the first view, for example, while dynamically maneuvering the vehicle. Otherwise, the views may shift from one another, creating an unrealistic impression for the driver, which could result in side effects such as disorientation or nausea.

[0017] The symbol may be associated with a window shape. For example, the symbol may comprise an optical, two-dimensional binary code, such as a QR code, and the shape may be associated with the code. Additionally, the symbol or the code represented by the symbol may be associated with a size, orientation, and position. The system may be tailored for use with various vehicles, and vehicles with different window shapes may have different symbols. Based on the recognized symbol, the system can more reliably determine what type of vehicle the system is installed in or what window shape is correct.

[0018] The device may include a first sensor for determining the position and orientation of the vehicle in the real environment and a second sensor for determining the position and orientation of the driver's head in the vehicle. Thus, for example, a processing device can determine the position and orientation of the driver's head relative to the real environment based on the positions and orientations determined using both sensors. It has been found that a realistic driving sensation can only be achieved if the real environment and the virtual environment are aligned with each other with high quality. Using both sensors, the position and orientation of the driver's head relative to the real environment can be determined more reliably. As a result, the first view and the second view can be aligned with each other with higher accuracy.

[0019] Furthermore, to more reliably determine the position and orientation of the vehicle or the driver's head in the virtual environment, it is preferable to also use one or more other sensors or information sources mounted on the vehicle, which may be configured to determine the position, direction, or orientation, or both.

[0020] The device may have an absolute positioning device, which may in particular be formed by a receiver for a satellite-aided navigation system (GNSS), and which may additionally be configured to determine and provide a direction of movement and a speed of movement.

[0021] Furthermore, the device may comprise a relative positioning device, which may in particular be formed by an odometer. The odometer may operate based on rotation sensors attached to the wheels of the vehicle. The vehicle's speed or steering angle may also be used to determine the relative position of the vehicle. In another embodiment, a camera-based odometer may be provided, in which case the position of the vehicle is determined based on the apparent positions of landmarks in the vehicle's real environment and the known absolute positions associated with these landmarks.

[0022] The device may include an acceleration sensor, which is preferably configured to determine acceleration along or around a longitudinal, lateral or vertical axis of the vehicle, thereby taking into account, among other things, pitching, rolling or yaw of the vehicle. The acceleration sensor can also be used to determine vibrations of the vehicle.

[0023] The system may also include a device that restricts the vehicle's location to a predetermined area in the real environment. This technology is known as geofencing. If the vehicle exceeds or is about to exceed the predetermined area, the vehicle can be controlled longitudinally and / or laterally to resist this. The area can be selected so that obstacles and vulnerable objects are located outside this area. In this way, safety inside and outside the vehicle can be more reliably guaranteed.

[0024] Other safety measures may include additional controls for longitudinal or lateral steering of the vehicle for additional passengers, such as an additional brake pedal for a passenger, preferably without a headset, who can take over control of the vehicle if it is about to deviate from a predetermined, controllable driving state.

[0025] Furthermore, the system preferably projects the display correctly onto the interior or exterior mirror. If the interior space of the vehicle is defined by windows and a rearview mirror is mounted on the outside of the windows, a further view of the virtual environment for the rearview mirror may be identified and superimposed on the first view so that the view is visible to the driver in the rearview mirror. In a similar manner, a further view of the virtual environment for a rearview mirror mounted in the interior space may be identified and superimposed on the first view in a corresponding position. This allows the driver to better and more easily perceive the area of ​​the virtual environment behind them.

[0026] According to another aspect, a vehicle includes a system as described herein, which can be used to train a driver to operate the vehicle or to guide a driver through predetermined driving situations with the vehicle, for example to study driving characteristics.

[0027] The method according to the present invention comprises the steps of determining the position and orientation of the head of a driver of a vehicle relative to the real environment of the vehicle, determining a first view of the interior space of the vehicle as seen from the driver's head, determining a second view of a virtual environment of the vehicle for the determined position and orientation, superimposing the second view of the virtual environment on the first view of the interior space, and providing the superposition to the driver.

[0028] The method may be performed in part or in whole by the system described herein. In particular, at least part of the method may be performed by a processing device comprised by the system. This may in particular be implemented electronically, for example by incorporating a programmable microcomputer or microcontroller. The method may also be present in the form of a computer program product comprising program code means. The computer program product may be stored on a computer-readable data carrier. Features or advantages of the system may also be applied to the method, and vice versa.

[0029] The virtual environment can adjust according to the car's movements. This allows the driver to be coached to steer the car in a specific way dynamically, i.e. according to the steering movements made by the driver. For example, hints can be given on how to change the steering angle or an ideal line along which the driver must keep the vehicle. This allows for playful learning of specific driving techniques, such as drifting, or for the car to be put into specific driving positions. This can accelerate driver training and the execution of specific tests of the car.

[0030] In a further development, the method can be applied to two systems installed in two vehicles. More vehicles can be involved in the method, each equipped with the system described herein. The vehicles are then in a real environment but in separate environments, where the virtual environments for the systems or vehicles correspond to each other. In this way, interactions between the vehicles can be reproduced in a more realistic yet non-hazardous way.

[0031] The model may have one avatar for each vehicle, and the avatars can be updated according to the movement of each vehicle. This allows, for example, collisions between avatars to be identified without the vehicles colliding. Optionally, visual attention symbols for the avatars of the other vehicles can be displayed inside the vehicle. This gives a driver in one of the vehicles the impression that he or she sees the other vehicle within his or her vehicle's environment. A collision between two vehicles can also be displayed correspondingly inside the other vehicle.

[0032] This development can be used to create complex scenarios or to pit drivers against each other on a set task. Driving situations requiring more than one vehicle can be triggered by multiple vehicle drivers operating closely together.

[0033] The invention will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 is a diagram showing a system installed in a vehicle. [Figure 2] FIG. 10 is a diagram illustrating scene superposition. [Figure 3] 1 illustrates a driver in a car. [Figure 4] FIG. 1 shows a flowchart of a method. DETAILED DESCRIPTION OF THE INVENTION

[0035] 1 illustrates a system 100 installed in a vehicle 105. The illustrated system 100 includes a processing unit 110 connected to a headset 115. The headset 115 is configured to be worn on the head of a driver 120 of the vehicle 105. The driver 120 is in the interior space of the vehicle 105 and can control the longitudinal or lateral movement of the vehicle 105. Additionally, the driver may use additional systems or devices installed in the vehicle 105.

[0036] The headset 115 includes at least one optical display 125 for the driver 120. The headset 115 is preferably implemented so that the display 125 is all that the driver 120 sees, i.e., the driver only sees the content provided to the driver by the display 125. In the illustrated embodiment, a display 125 is provided for each eye of the driver 120. Additionally, the headset 115 is equipped with a camera 130 configured to provide a view of at least the interior space of the vehicle 105.

[0037] Preferably, the imaging characteristics of camera 130 are matched to the optical characteristics of the driver's 120 visual system so that the view provided by camera 130 can be output to display 125 and the driver's 120 perceives the view as close as possible to the visual impression the driver would receive without headset 115. If necessary, the processing unit 110 can adjust the view to do so. It should be noted that multiple cameras 130 may be provided on or attached to headset 115.

[0038] The headset 115 may be equipped with markers 135 that can be used as optical reference patterns. The markers 135 are preferably shaped and attached to the headset 115 so that the markers optically indicate the position and / or orientation of the headset 115. For example, a further camera 130 may be attached to a structural member of the vehicle 105 and configured to optically scan the headset 115. The markers 135 are easily recognizable during scanning, allowing the position and orientation of the headset 115 to be determined.

[0039] Similarly, markers 135 may be attached to structural members of the automobile 105, and the position and orientation of the headset 115 can be determined based on optical scanning of the markers 135 by a camera 130 attached to the headset 115.

[0040] 1, the frame 140 of a window 145 that defines the interior space of the automobile 105 is selected as the structural member. The marker 135 may be attached to the upper edge of the frame 140, for example, near the rearview mirror 150. The camera 130 is illustratively attached to the lower edge of the frame 140.

[0041] Optionally, window 145 is fitted with an optical symbol 155, preferably a one- or two-dimensional structure. This symbol 155 may be binary coded, having light and dark areas, the location and extent of which can be automatically processed to decode the coded information. The information may indicate the geometry of window 145. The geometry may relate specifically to the size and shape of window 145. In yet another embodiment, information 155 includes a designation of an entry in a data memory, and information regarding the geometry of window 145 is associated with that entry. The data memory may contain multiple entries and associated geometric shapes.

[0042] System 100 preferably further includes a receiver 160 for Global Navigation Satellite System (GNSS) signals, which is capable of determining the geographic location of vehicle 105 and, optionally, the direction and speed of travel of vehicle 105 based on the received signals.

[0043] Acceleration sensors 165 may be provided to determine the rotational acceleration or acceleration of the vehicle 105 around multiple spatial axes. The acceleration sensors 165 are preferably configured to determine the longitudinal, vertical and lateral axes of the vehicle 105. The acceleration along one of these axes (translational) or the acceleration around one of these axes (rotational) may then be determined. A corresponding acceleration sensor 165 may also be attached to the headset 115 and connected to the processing unit 110.

[0044] The system 100 further comprises a model 170 configured to reproduce the virtual environment. The virtual environment is adjusted to the real environment of the vehicle 105. To this end, the orientation and position of the virtual environment relative to the real environment are pre-specified. As the vehicle 105 moves in the real environment, it also moves in the virtual environment. As the vehicle 105 follows a predetermined trajectory, the vehicle will assume a series of poses, for each of which a view of the virtual environment can be specified by the model 170. The series of views provided corresponds to the impression of driving along that trajectory through the virtual environment.

[0045] The ground surface progression of the real environment of the vehicle 105 is preferably mirrored in the virtual environment, thus in particular slopes, roads, objects or landmarks of the real environment may be reflected in the virtual environment.

[0046] Further preferably, an interface 175 is provided for connecting to devices on board the vehicle 105. Via this interface 175, parameters of the position, orientation or movement of the vehicle 105 can be obtained, among others. Exemplary devices on board the vehicle 105 that can provide such information can include an ABS system, an electronic chassis control, a prime mover control as a driving motor or a navigation system. Optionally, sensors on board the vehicle 105 can also be used in the system 100. For example, an existing interior camera 130 can be used to scan the headset 115.

[0047] Optionally, a wireless communication device 180 is provided, which may be configured to communicate with a central station or with other systems 100 installed on further vehicles 105 .

[0048] 2 illustrates an overlay 200 that may appear to a driver 120 in a vehicle 105 while looking through a headset 115. The overlay 200 includes a portion of a first view 205 and a portion of a second view 210. The first view 205 is provided by a camera 130 attached to the headset 115 of the driver 120. The second view 210 is determined based on a view of the virtual environment of the vehicle 105 for a particular head pose of the driver 120.

[0049] The first view 205 is of the interior space of the automobile 105 and reflects what the driver 120 would also see if they were properly holding their head without the headset 115. This includes all of the equipment and functional components of the automobile 105, particularly the steering wheel and cockpit. The driver 120 also sees himself, as can be seen in FIG. 2 from, for example, the driver's 120's hands on the steering wheel.

[0050] A portion of the second view 210 is inserted into the first view 205 where the interior space of the vehicle 105 is defined by the window 145. The transition between the first view 205 and the second view 210 is highlighted in Figure 2 by a dashed line. This line is not normally part of the views 205, 210 and is not visible to the driver 120.

[0051] 2, a windshield and side windows are provided, through which an exterior mirror 215 can be seen. Optionally, for a certain position or orientation of the exterior mirror 215, a portion of a third view 220 specified by the model 170 in the virtual environment may be displayed on the surface of the exterior mirror 215. In a similar manner, the opposite exterior mirror or rearview mirror can also be handled.

[0052] To illustrate possible modes of operation of the system 100, FIG. 2 shows two gates 225 located adjacent to each other within the virtual environment of the vehicle 105.

[0053] The driver 120 may be tasked with passing through a gate 225 that is presented to the driver in a particular manner, for example with a predetermined color, and avoiding another gate that may be presented to the driver with another predetermined color. The colors of the gates 225 may, for example, alternate according to a predetermined pattern or by chance. In particular, the colors may only be inserted later depending on the driving speed and the distance of the vehicle 105 from the gate 225. In this way, the driver 120's reflexes and ability to drive the vehicle 105 through the correct gate 225 in a controlled manner, even at high speeds, may be trained.

[0054] 3 shows an exemplary view of a driver 120 in a vehicle 105 equipped with the system 100. The driver 120 wears a headset 115, which is preferably relatively small and light so as not to get in the way of the driver 120 or hinder head movement. Two cameras 130 are mounted approximately in front of the driver's 120's eyes. Marker elements 135 are distributed on the frame of the headset 115.

[0055] Part of the real environment of the car 105 can be perceived through the side and rear windows. The driver 120 cannot see the real environment, but can see part of the virtual environment of the car 105 in the area of ​​the window 145 via the headset 115.

[0056] 4 shows a flowchart of a method 400. The method 400 may be performed by the system 100, among others.

[0057] In step 405, the headset 115 can be detected from the vehicle 105. To do so, the headset 115 may be scanned by a fixedly mounted camera 130.

[0058] In step 410, the position and pose of the head of the driver 120 within the vehicle 105 can be determined, for example, by determining the position and pose of the headset 115 relative to the orientation and position of the markers 135 during the optical scan.

[0059] In step 415, the interior space of the vehicle 105 can be scanned from the headset 115. To this end, a camera 130 attached to the headset 115 can be used. Optionally, the position and pose of the head of the driver 120 can also be determined based on this scan. To this end, in particular, the orientation and position of markers 135 fixedly attached to the vehicle 105 can be determined in the scan.

[0060] To determine the position and orientation of the vehicle 105 in the real environment, in step 420 the absolute position of the vehicle 105 can be determined, for example, using a GNSS receiver 160 or a camera-based location recognition means, which can be connected to the system 100 via an interface 175.

[0061] In step 425, the acceleration of the vehicle 105 may be determined. The acceleration may be determined by the acceleration sensor 165 or based on systems installed on the vehicle 105, such as the drive system or the braking system.

[0062] The relative position of the vehicle 105 can be determined in step 430. The relative position can be determined in particular based on information about the movement or speed of the vehicle 105. To this end, in particular, the odometer signal of the vehicle 105, which can be obtained via the interface 175, can be analyzed.

[0063] Based on the information collected in steps 420-430, the position and pose of the vehicle 105 in the real environment can be determined in step 435.

[0064] In step 440, the head pose of the driver 120 in the real environment can be determined based on the head pose in the vehicle 105 and the position of the vehicle 105 in the real environment. For optimal results, the head pose should be determined in step 440 with as much accuracy as possible and, if dynamic, with as little time delay as possible. Intermediate results can be further improved based on other information.

[0065] In step 445, a view of the virtual environment can be determined based on the determined pose, which view is also referred to herein as a second view.

[0066] Based on the scan of the interior space, a view of the interior space can be identified, also referred to herein as a first view, in step 415. In optional step 450, the orientation and position of window 145 can be determined in the first view. To do so, the boundaries of window 145 can be identified in the first view or geometric information about the shape and dimensions of window 145 can be used accordingly.

[0067] In step 455, the first view and the second view may be overlaid, preferably by replacing the portion of the first view that falls within the area of ​​window 145 with the corresponding portion of the second view.

[0068] In step 460, this overlay may be output to the driver 120 via at least one display 125 of the headset 115. [Explanation of symbols]

[0069] 100 systems 105 Automobiles 110 Processing equipment 115 Headset 120 Driver 125 display 130 Camera 135 Marker 140 frames 145 Window 150 Rearview mirror 155 symbols 160 GNSS receiver 165 Accelerometer 170 model 175 Interface 180 Communication Equipment 200 Overlays 205 First Sight 210 Second Sight 215 exterior mirror 220 The Third Sight Gate 225 400 ways 405 Headset detection from vehicle perspective 410 Identifying the Driver's Head Position in a Vehicle 415 Scanning the interior space of a vehicle from a headset 420 Absolute Positioning 425 Determining Acceleration 430 Relative Positioning 435 Determining Vehicle Position and Pose in Real Environments 440 Identifying Driver's Head Position in Real Environments 445 Identifying Scenes in Virtual Environments 450 Identifying Windows 455 Overlapping Scenes Output to 460 driver

Claims

1. A system (100), comprising: - a headset adapted to be worn on the head of a driver (120) of the motor vehicle (105), - the headset has a camera (130) providing a first view (205) of the interior space of the vehicle (105) and an optical display for the driver (120); a model (170) for providing a view of the virtual environment of said vehicle (105) for a given pose; a device for determining the position and pose of the head of the driver (120) with respect to the real environment of the vehicle (105); a processing unit (110) configured to superimpose on the first view (205) of the interior space a second view (210) of the virtual environment for the identified orientation and provide it to the driver (120); A system (100) having:

2. 2. The system (100) of claim 1, wherein the interior space of the automobile (105) is defined by a window, and an overlay is provided such that the virtual environment is visible to the driver (120) only in the area of ​​the window.

3. 3. The system (100) of claim 2, wherein an optical predetermined symbol is attached to the window, and the processing device (110) is configured to determine the orientation and position of the window in the first view (205) of the interior space based on the symbol.

4. The system (100) of claim 3, wherein the symbol is associated with a shape of the window.

5. The system (100) of any one of claims 1 to 4, wherein the device has a first sensor (160, 165, 175) for determining the position and orientation of the automobile (105) in the real environment, and a second sensor (130) for determining the position and orientation of the head of the driver (120) in the automobile (105).

6. The system (100) of claim 5, wherein the device comprises an absolute positioning device (160).

7. The system (100) according to claim 5 or 6, wherein the device comprises a relative positioning device (175).

8. The system (100) of any one of claims 5 to 7, wherein the device comprises an acceleration sensor (165).

9. The system (100) according to any of the preceding claims, further comprising a device for restricting the position of the vehicle (105) to a predetermined area of ​​the real environment.

10. 10. A system (100) as described in any one of claims 1 to 9, wherein the interior space of the automobile (105) is defined by a window (145) on the outside of which a rearview mirror (215) is mounted, and a further view (215) of the virtual environment is identified for the rearview mirror (215) and superimposed on the first view (205) so that the view is visible to the driver (120) within the rearview mirror (215).

11. A motor vehicle (105) comprising a system (100) according to any one of claims 1 to 10.

12. A method (400) comprising: - determining (440) the position and pose of the head of the driver (120) of the car (105) with respect to the real environment of the car (105); - identifying (415) a first view (205) of the interior space of the vehicle (105) from the head of the driver (120); - identifying (445) a second view (210) of the virtual environment of the vehicle (105) for the identified pose; - superimposing (455) the second view (210) of the virtual environment onto the first view (205) of the interior space; - Present the superposition to the driver (120) A method having the steps.

13. 13. The method (400) of claim 12, wherein the virtual environment is adjusted in response to movement of the vehicle (105).

14. 14. A method (400) according to claim 12 or 13, in which systems (100) are provided mounted on two vehicles (105) in two real environments that are separate from each other, and for these systems (100) only one common virtual environment is used.

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