FR3147034A1 - System and method for reducing cyber-discomfort - Google Patents

Abstract

A system and method for reducing cyber-sickness (12) for navigation in an immersive virtual environment (2) is provided, comprising a control unit (7), a virtual environment (2) displayed on a display system (3), a position sensing system (6) of the user's physical viewpoint (4), and a navigation system (9) moving the user's virtual viewpoint in the virtual environment, The movements of the user's virtual viewpoint relative to the virtual environment, generated by the navigation system (9) and the actual rotations of the user's physical viewpoint relative to the real world (11) are monitored. Incentives for rotations of the user's physical viewpoint relative to the real world (11) are determined. Rotation prompts relate to at least partial corrections of discrepancies and/or mismatches between movements from the virtual viewpoint and actual rotations from the user's physical viewpoint. A visual reference (10) prepositioned in the virtual visual environment is modified in real time based on the rotation prompts. Abstract figure: Figure 4b

Description

System and method for reducing cyber-discomfort

The present disclosure relates to a cyber-sickness reduction system, a corresponding method, a computer program and a storage medium. The present invention aims to induce a physical head movement of the user, so as to reduce or eliminate the visuo-vestibular conflict, by the real-time use of a deformation-driven indicator object.

One of the essential tasks that a user can perform in a virtual environment is movement, also called navigation. Since the physical environment in which the user finds himself is generally more restricted than the virtual environment, the user must then use one or more navigation processes.

Navigation is subject to the phenomenon called cyber-sickness or simulator sickness, which manifests itself by symptoms of discomfort, headaches or dizziness, sometimes even vomiting. This movement can be done for example by using controllers from an immersive room, called CAVE, or by being equipped with a video headset, or in a driving or flight simulator. Whether navigation is carried out in a CAVE, in a simulator, using a 3D television or a 3D projection system, or equipped with a Virtual Reality (VR), Augmented Reality (AR) or Mixed Reality (MR) video headset, and whether for training, research, industrial design or in the field of gaming, the phenomenon of cyber-sickness is encountered by a large number of users, making the experiment difficult, unrepresentative or sometimes interrupting the exercise.

In the case where the display system used to view the virtual environment occupies a small visual field in a real environment, for example in the case of AR, the player or user's field of vision is small enough not to immerse him or her completely, keeping his or her external visual cues. The said user is therefore less subject to said nausea.

Conversely, a user navigating in an immersive virtual environment, such as in a CAVE or with a virtual or augmented reality headset, is frequently subject to cyber-sickness, or simulator sickness in the case of a simulator. One of the main reasons is that the movement perceived visually during virtual movement conflicts with the movement perceived by the vestibular system. The movement most likely to cause simulator sickness is rotation (for example during a maneuver in a turn – yaw and/or roll, but also during braking – pitching). Indeed, the brain of the user accustomed to moving in the real world expects to receive acceleration and speed measurements from his vestibular system of the inner ear, more precisely from the semicircular canals, consistent with those estimated by the visual system. In the absence of restitution of these physical effects by an adequate system, such as a dynamic driving or flight simulator, the brain triggers symptoms resembling those of motion sickness. In the real world, when moving, visual and vestibular information is generally consistent, but inconsistent information can also be perceived. This is the case of motion sickness, not for the driver, but for a passenger, who cannot anticipate movements, especially if he or she is not looking outside. This case is similar to that of a virtual environment. If the passenger is looking outside, the probability of motion sickness is reduced. In an immersive virtual environment, particularly in a CAVE or equipped with a head-mounted display, the modification of the visual environment during navigation is dissociated from the physical movement of the user and can therefore generate simulator sickness.

Simulator sickness is well known in the field of virtual environments. To reduce simulator sickness, it is known to reassociate visual perception with physical movement.

There are two main categories of means for moving around in a virtual environment.

Motion compensation devices allow the user to move naturally without having to trigger commands. The omnidirectional Cyberwalk treadmill or the Cybersphere are examples, and there are many other systems (hemispherical ball mat, moving tile network, active shoes, robot arms attached to the feet, etc.). Most of these devices have the disadvantage of being bulky or intrusive, and poorly suited to general public use. In addition, most are only suitable for natural movements of the observer, without being able to use navigation systems, for example a vehicle or any simulated artificial system.

Navigation processes are laws of commands of often already existing devices (joysticks, virtual reality gloves, etc.) that modify the movement process used in real life, allowing rapid learning and easy use. There are several, for example walking on the spot, which consists of mimicking walking to move forward. Redirected walking on the spot is a solution to the immersion problems due to the missing faces of the CAVE, it turns the environment imperceptibly so that the user never has to orient themselves towards the missing face. The virtual companion is a virtual animal controlled by reins, it pulls the user and allows rotations.

For example, "Grabbing the Air" is a navigation method in which the user can grab the air with his hand, pull it back towards him to scroll through the scenery, and make a lateral movement to make it rotate around him. A disadvantage of this system is that it does not reduce simulator sickness because the user's brain does not receive information from his vestibular system that is consistent with that estimated by the visual system.

Publication US-A1 2004/0102676 thus discloses a system for coupling the visual environment and navigation in order to reduce motion sickness. Said system requires several hardware devices such as a gyroscope, accelerometers, a positioning system known as GPS or "Global Positioning System" in English, optical sensors and vibration sensors and several software programs to reduce said motion sickness.

A disadvantage of the disclosed system is the need to use many hardware devices, which leads to high costs as well as sophisticated control of all devices.

Patent publication No. FR3025645 – 1458421 makes it possible to break down a rotational movement into two movements, each of which is natural, and thus avoids generating motion sickness or cyber-sickness by proposing to first perform a movement that is both visual and physical in the virtual world and then a movement of the operator that is also both visual and physical. However, since this process is not natural, it cannot be used to perform rotations in a way that is natural and understandable to the operator.

Apart from the patent cited above, the use of a navigation method generates a movement rendered only visually, and therefore generates a visuo-vestibular conflict potentially causing simulator sickness. For example, for a rotation to the right, a navigation method will generally use a rotation of the virtual environment to the left to render it.

Summary

One aim of the invention is to remedy the effects of cyber-sickness by supplementing or modifying a rotational navigation method in an immersive virtual environment.

The subject of the invention relates to the reduction of cyber-discomfort for any virtual movement of the observer piloted by a navigation system which generates cyber-discomfort effects to the extent that it generates a visuo-vestibular conflict. Said movement can be broken down into a linear movement and a rotational movement to which the invention relates.

The object of the invention is the reduction of cyber-sickness and simulator sickness for rotational movement, regardless of the axis of said rotation.

The object of the invention is therefore to provide a means of performing a rotational movement in an immersive virtual environment efficiently, comfortably and without visual-vestibular discomfort (cyber-sickness or simulator sickness).

The subject of the invention relates to the display and modification in real time of a visual reference during navigation in a virtual environment. Such a modification is designed to fulfill a visual incentive function making it possible to generate an involuntary rotation of the user's head, according to the commonly accepted hypothesis of stationarity of the surrounding world. During navigation in a virtual environment, this movement of the user's head, and possibly of the body, induced by the real-time modification according to the invention makes it possible to reduce or even eliminate the visuo-vestibular conflict and thus to reduce or even eliminate simulator sickness or "cybersickness" in English, or cyber-malaise.

Definitions are now provided for various terms used throughout this document.

The real world (or physical world) is the reference point of the room in which the user is physically located.

The user's physical viewpoint includes the spatial coordinates of a point representative of the user's vision in the physical world, this point can be for example a midpoint arranged between the user's eyes.

The user's virtual environment (or virtual world) includes all the virtual elements that can be viewed by the user.

The user's virtual viewpoint comprises the spatial coordinates, in a virtual spatial reference frame, of a point representative of the user's vision in the virtual world. Translation and/or rotation operations may be implemented, for example at the user's initiative, in order to modify the spatial coordinates of the virtual viewpoint.

The user's virtual visual environment is the portion of the virtual environment displayed on the display system, corresponding to the user's virtual point of view deemed to be located at the origin of the virtual spatial reference.

The visual reference is a modifiable visual element such as a wireframe representation of a CAVE-type room, an arrow on the ground or any other type of visual reference or artifact that can be displayed as an overlay on the virtual visual environment. It is possible to define, for the visual reference, a reference appearance, shape and orientation in the virtual world. The modification of the visual reference can be, for example, a modification of appearance, shape and/or orientation relative to this reference appearance, shape and/or orientation.

The modifiable virtual nose is a particular example of a visual reference that is attached to the embodiment of the user's head in the virtual world. The virtual nose may be displayed in a CAVE-type room, or through a virtual reality headset, or in any other virtual visual environment. Optionally, the virtual nose may have the following general structure: a base fixed relative to the user's virtual viewpoint and a body extending from the base and ending in an end. The base may be displayed towards the bottom of the field of view in a region that corresponds, for example, in the physical world, to that of the user's nose. The virtual nose may be deformable, i.e. visual parameters of the virtual nose in the virtual environment, such as the position of the end, the shape of the body and/or the orientation of the body, may be made modifiable. The virtual nose may for example have a reference shape according to which the body is rectilinear associated with a reference orientation according to which the position of the extremity is such that the base-extremity vector points towards a central direction of the virtual visual environment. In particular, the virtual nose may be configured to indicate the direction of movement, such that its realignment towards a reference direction (for example forward) indicates to the user that he does not need to turn his head. When the shape of the visual reference is modifiable, it may be provided, for example, to curve the body. When the orientation of the visual reference is modifiable, it may be provided to modify the position of the extremity. When the appearance of the visual reference is modifiable, it may be provided to modify a degree of transparency and/or a color of the visual reference, or to display an emphasis mark at the edge of the visual reference.

The navigation process (or navigation system) is the means used by the user to trigger the modification of his virtual point of view in the virtual environment, whether by means of a physical device, a voice command or any action or movement of all or part of his body.

The present technique provides, through a system, a method and a computer program, different aspects of a visual procedure in the virtual world to induce voluntary movement of the user in the physical world by the use of an interactively modifiable element.

A system for reducing cyber-discomfort is thus proposed for navigation in an immersive virtual environment, comprising a control unit, a virtual visual environment, corresponding to a virtual point of view of the user, displayed on a display system, a system for capturing the position of the physical point of view of the user, and a navigation system moving the virtual point of view of the user in the virtual environment, said system being capable of:
monitoring the user's virtual viewpoint movements relative to the virtual environment generated by the navigation system;
monitor actual rotations from the user's physical perspective relative to the real world;
determining rotation incentives from the user's physical point of view relative to the real world, the rotation incentives relating to at least partial corrections of deviations and/or discrepancies between the movements from the virtual point of view and the actual rotations from the user's physical point of view; and
based on rotation prompts, modify in real time a pre-positioned visual reference in the virtual visual environment.

It is understood that “movements from the user’s virtual point of view relative to the virtual environment” are likely to designate translational movements and/or rotational movements.

It is understood that a “rotation incentive” refers to a correction of a currently observed discrepancy between movements from the virtual point of view and actual rotations from the user’s physical point of view. The rotation incentive includes at least one visual component which, when perceived by the user, is such as to induce an additional actual rotation from the user’s physical point of view, this additional actual rotation correcting, entirely or partially, the currently observed discrepancy.

It is understood that a “discordance” refers to a qualitative difference. For example, a translational displacement of the virtual point of view to the left that is not accompanied by any rotation of the physical point of view represents a discordance, because the user visually perceives a displacement without simultaneously performing a physical rotation of the head or body. This discordance is thus the source of a visuo-vestibular conflict.

It is understood that a “deviation” designates a quantitative difference. For example, a rotation of the virtual point of view of 90° to the left which is accompanied by a rotation of the physical point of view of 10° to the left represents a significant discrepancy between the displacement visually perceived by the user and the actual rotation of his head or body. This discrepancy can be expressed here in the form of an angular difference equal to 80° and is also a source of visuo-vestibular conflict.

The same situation can be described as both a discrepancy and a gap. For example, a rotation of the virtual viewpoint of 50° to the left which is accompanied by a rotation of the physical viewpoint of 10° to the right represents both a qualitative difference because the directions of rotation are opposite, and a quantitative angular difference equal to 60°.

Advantageously, the system is also capable of:
performing a comparison between several predefined modification modes of the visual reference by means of a supervised learning model, on the basis of a respective evaluation of the user's tracking of the rotation recommendations when the visual reference is respectively modified according to each of the predefined modification modes, and
choose, from the predefined editing modes, a custom editing mode for the user based on the comparison result.

Thus, it is possible, for example, to display the visual reference in its reference appearance, shape and orientation when the user's physical viewpoint and virtual viewpoint are aligned, within a predefined threshold of angular deviation, but to modify the visual reference when this deviation exceeds the predefined threshold. The modification may include a change in appearance, for example in color, and/or in shape and/or in orientation. This change may be progressive and a function of the amplitude of the angular deviation. Modifications of a different nature may be provided depending on the situation encountered.

For example, in a situation where the user's physical viewpoint remains unchanged during and/or following a translation of the virtual viewpoint forwards or backwards, it may be intended to modify the length of the visual reference and/or to make a slight change in orientation of the visual reference upwards or downwards, in the direction of a point located slightly above the horizon in the virtual environment.

Considering a situation where the user's physical viewpoint remains unchanged during and/or following a rotation of the user's virtual viewpoint to the right, it may be intended to distort the visual reference to the right, thereby causing a stimulus for the user. If the user reacts to the stimulus by rotating his or her head or body to the right, then it may be intended to modify the visual reference again so as to restore its reference appearance, shape and/or orientation.

Advantageously, monitoring the actual rotations from the user's physical point of view relative to the real world comprises collecting, by means of the position capture system from the user's physical point of view, time series indicative of angular parameters relating to the orientation of the user's head, the angular parameters including positions, speeds, accelerations and/or jerks.

Advantageously, the visual reference is modified according to a command linked to the navigation system and to the rotational movement of the user's head, so the user's brain perceives information from his vestibular system consistent with that estimated by the visual system, which significantly reduces, or even eliminates, the risks of simulator sickness depending on the response time of the system.

The human brain has a plasticity that allows it to tolerate certain inconsistencies, in amplitudes and temporality. It is therefore not necessarily a question of coordinating and synchronizing rotations precisely (although we try to stick to it as closely as possible). The idea is to induce a "sufficient" head movement to allow the user to maintain visual-vestibular coherence. Artificial intelligence methods are mentioned in this document for various reasons, and in particular for the purpose of helping to stick as closely as possible to the user's perception and their perceptual characteristics.

Advantageously, at the start of the user's navigation in the virtual environment by means of the navigation system, the visual reference is preferably oriented aligned with respect to the user's physical point of view. Said visual reference may optionally not be displayed when the navigation system is not in use.

Advantageously, the visual reference is generated virtually and displayed with the virtual environment by the display system when the user uses the navigation system.

Advantageously, modifying the visual reference includes modifying the shape, orientation and/or appearance of the visual reference.

Advantageously, during rotational navigation, the visual reference rotates in the desired direction so that the physical viewpoint also rotates in the same direction.

At the same time, the virtual world rotates in the opposite direction to the real world, reduced by all or part of the rotational movement from the physical point of view of the observer, due to the impact of the rotation of the visual reference.

The rotation speeds relative to the real world of the visual reference and the virtual world are advantageously controlled depending on perceptual thresholds, elapsed time, as well as the rotation speed from the physical point of view relative to the real world.

The rotation perceived by the user is that of his head relative to the virtual world, that is to say the accumulation of the rotation of the virtual world relative to the real world and the rotation of his head relative to the real world.

When the user stops using the navigation system, the visual reference stops and may no longer be displayed. The virtual world also stops relative to the real world. The rotation performed during navigation is the sum of the rotation of the virtual world relative to the real world and the rotation of the head relative to the real world.

Also provided is a method for reducing cyber-sickness for navigation in an immersive virtual environment, the method being implemented by a system for reducing cyber-sickness comprising a control unit, a virtual visual environment, corresponding to a virtual point of view of the user, displayed on a display system, a system for capturing the position of the physical point of view of the user, and a navigation system moving the virtual point of view of the user in the virtual environment, said method comprising:
monitoring the movements of the user's virtual point of view relative to the virtual environment generated by the navigation system;
monitor actual rotations from the user's physical perspective relative to the real world;
determining rotation incentives from the user's physical point of view relative to the real world, the rotation incentives relating to at least partial corrections of deviations and/or discrepancies between the movements from the virtual point of view and the actual rotations from the user's physical point of view; and
based on rotation prompts, modify in real time a pre-positioned visual reference in the virtual visual environment.

Advantageously, the proposed method comprises:
a step of displaying a visual reference,
a rotation step of the visual reference linked to the navigation system, and to the orientation of the user's physical point of view in relation to the real world,
a step of disabling the display of the visual reference.

Depending on the proposed technique, the display system can be stationary relative to the real world, as in most CAVE or immersive room type installations, or linked to the user's head, as in the case of a virtual or augmented reality headset.

Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the attached drawings, in which:

Fig. 1

is a schematic view of an immersive room with a user navigating a virtual environment.

Fig. 2

is a schematic top view illustrating an example of use of the invention with a CAVE type environment.

Fig. 3

is a schematic top view illustrating the use of the invention with a virtual or augmented reality headset. And illustrate references used for the description of the invention.

Fig. 4a, 4b, 4c and 4d

, , And are schematic views of rotating the virtual environment and changing the visual reference from the user's physical viewpoint.

In the following description, like reference numbers designate identical parts or parts having similar functions.

According to the which presents an embodiment of the invention, a user (1) can navigate virtually in a virtual environment (2) broadcast on a display system (3). This display system (3) can comprise for example a screen for a "powerwall" type system, two screens for a "workbench" type system, from three to 6 screens for a "CAVE" type system, or more generally one or more screens of any shape(s) for an immersive room. The display system (3) can also be an extended reality headset, namely virtual, augmented or mixed/fused reality.

The representation of the virtual environment (2) depends on the physical point of view (4) of the user (1) in relation to the real world (11), on the vision pyramid (5) according to which he views said representation, as well as on the position of the virtual point of view of the user. The physical point of view (4) of the user (1) is measured continuously, directly or indirectly, by a position capture system (6), such as for example cameras or an inertial unit.

The images broadcast on the display system (3) are generated by a control unit (7) connected to said display system as well as to the position capture system (6).

The user (1) may or may not be equipped with a pair of specific glasses (8) to allow him a stereoscopic perception of the virtual environment (2) on the display system (3), or any other 3D visualization system.

A navigation system (9) allows the user (1) to move around in the virtual environment (2). This system can be activated by an external participant (not shown) or by the user (1) himself, by means of movements of all or part of his body and/or physical interfaces such as a controller, a joystick, a treadmill, a steering wheel or pedals for example.

Optionally, a system may be provided to control the generation and display of an avatar of the user. The avatar is displayed superimposed on the virtual environment (2) and is prepositioned relative to the user's physical point of view. The avatar is a representation of all or part of the user's body and may take the form of a character, an articulated skeleton, a head, a hand, or more generally any form, articulated or not, that the user could assimilate to a representation of his person in the virtual environment. The main function of the avatar is to transcribe in real time movements or gestures that the user makes in the physical world. There are many known avatar generation technologies for this purpose. These technologies may rely, for example, on position data such as that from the position capture system (6). Some known avatar generation and display technologies also rely on data from a device manipulated by the user. This may then be data from the user's interaction with a physical interface of such a device and/or position data from position sensors integrated into such a device. This data is then used to generate a representation of the hand manipulating the device.

Finally, the invention provides a system for reducing cyber-malaise, cybersickness or simulator sickness (12), which controls the display and modification of a visual reference (10), displayed superimposed on the virtual environment (2). Like the avatar described above, this visual reference (10) is prepositioned relative to the physical point of view of the user and can take for example the form of a vertical grid as in the , an arrow on the ground, or any other shape, artifact, or object, whether articulated or not. A virtual nose attached to the user's avatar, a complete or partial car cockpit, or an object held in a hand of the user's avatar, such as a gun, sword, staff, etc. in a game, are all particular examples of visual reference.

The cyber-sickness reduction system (12) is connected to the position sensing system (6) and the navigation system (9), which enables it to collect and monitor temporal developments from the physical and virtual viewpoints of the user. Depending on these temporal developments, the cyber-sickness reduction system can determine (quantitative) deviations and/or (qualitative) discrepancies between the movements from the virtual viewpoint on the one hand and the rotations from the physical viewpoint on the other hand. The cyber-sickness reduction system controls the changes in the visual reference in real time depending on these deviations and/or discrepancies.

Different modifications of the visual reference can be implemented. These can be shape modifications, i.e. deformations, orientation modifications, size modifications, color modifications, appearance modifications, transparency modifications, sharpness modifications, etc. Several types of modifications of the visual reference can be implemented simultaneously, for example a deformation can be combined with a color change.

The successive application in real time of such modifications has the effect of animating the visual reference by slaving, for example, its appearance or its current form to the discrepancies between the rotations from the physical point of view and the movements from the virtual point of view of the user.

There illustrates in a top view a use of the invention with a CAVE type system. The virtual world (2) is represented by the hatched surface. The CAVE display system (3) is symbolized by the 3 solid lines, and the visual reference (10) is symbolized by the 3 dotted lines.

There illustrates in top view a use of the invention with a virtual or augmented reality headset. Similarly for the , the virtual world (2) is represented by the hatched surface, and the visual reference (10) is represented by the dotted lines.

According to Figures 2 and 3, several reference points can be used to describe and understand the operation of the invention.

“R real world” is the real world reference point (11), that is, the reference point of the physical room in which the user is located.

“R virtual world” is the reference point of the virtual environment (2) displayed by the display system (3).

“R head” is the reference point from the user’s physical point of view (1).

“R visual reference” is the reference linked to the visual reference (10) to which the invention relates in particular.

Finally, “R display system” is the reference of the display system (3) on which the representation of the virtual environment is broadcast.

In most CAVE or immersive room type installations, the display system (3) is stationary relative to the real world (11). In this case, “R display system” and “R real world” are stationary relative to each other. When using a virtual or augmented reality headset, the display system (3) is linked to the user’s head (1), and therefore in this case it is “R display system” and “R head” that are stationary relative to each other. For the sake of clarity, “R display system” is therefore not shown on the , being almost confused with “R head”.

Figures 4a, 4b, 4c and 4d show examples of rotations in an extended reality headset type environment, using the navigation system (9) and the cyber-discomfort reduction system (12) according to one embodiment of the invention (12).

There represents the user's virtual visual environment in an initial state before the right rotation. In the initial state, the user's head and the visual reference (10) are aligned, i.e., "R head" and "R visual reference" are aligned. In this initial state, the visual reference (10) may optionally not be displayed. On the , the visual reference (10) is an elongated virtual nose having a base located towards the origin of the “R visual reference” mark, a straight body and a rounded end.

There represents the user's virtual visual environment in a current state, during the right rotation of the virtual viewpoint by means of the navigation system (9).

The speed of this rotation to the right is noted "ω virtual point of view". The virtual visual environment represented on the simultaneously underwent a rotation of the same speed in the opposite direction (to the left in this example) relative to the real world.

The rotation perceived by the user (1) is that of his head relative to the virtual world (2), i.e. the cumulative rotation of the virtual world (2) relative to the real world (11) and the rotation of his head relative to the real world (11). It has been shown that the brain reacts mainly to the acceleration felt, and to a lesser extent to the speed of movement, as well as to the derivative of the acceleration or "jerk".

To avoid or at least limit the visuo-vestibular conflict, it is necessary that the movements of the virtual point of view correspond substantially to the movements of the physical point of view. In other words, it is necessary that, while the navigation system operates the rotation movement of the virtual point of view, the user performs a synchronized rotation movement of the physical point of view, in the same direction (here to the right).

The cyber-sickness reduction system simultaneously monitors the movements of the virtual point of view operated by the navigation system and the rotations of the physical point of view simultaneously operated by the user.

Based on this monitoring, the cyber-sickness reduction system is able to determine at any time one or more values relating to a felt movement, such as the felt movement speed, the felt acceleration and/or the felt “jerk”, and to apply a pre-established strategy of limitation or suppression of the visuo-vestibular conflict in order to:

choose, based on the value(s) relating to the felt movement, a target value for the rotation speed from a physical point of view and

change the visual reference according to the difference between the target value and the currently recorded value of the rotation speed from a physical point of view.

In the example of the that the value recorded at a current instant of the rotation speed from the physical point of view, noted “ω physical point of view”, is lower than the target value determined by the cyber-discomfort reduction system, noted “ω target physical point of view”.

On the , the change in visual reference is a deformation: the body of the deformable nose becomes curved, which shifts the end to the right without the position of the base being significantly modified.

This distortion is perceived by the user, consciously or not, as an incentive to increase the speed of rotation of his head to the right to get closer to the target speed. The visuo-vestibular conflict is reduced, as is cyber-discomfort.

In general, the modification of the visual reference must be considered as being subject to a shift observed between a movement from the virtual point of view and a corresponding rotation from the physical point of view. This shift can be defined qualitatively and/or quantitatively.

This point can be illustrated by comparing three situations all three beginning with the initial state associated with the and ending with three distinct current states respectively associated with the examples in Figures 4b, 4c and 4d.

The first situation is associated with the and concerns a rotation movement of the virtual viewpoint to the right associated with an insufficiently rapid rotation of the physical viewpoint to the right. In this first situation, the visual reference is slightly distorted, in real time during navigation in the virtual world, due to the gap between "ω physical viewpoint" and "ω target physical viewpoint". This slight distortion is represented on the .

The second situation is associated with the and concerns a rotation of the virtual viewpoint to the right associated with a sufficiently rapid rotation of the physical viewpoint to the right. In this second situation, the cyber-discomfort reduction system determines that the gap between "ω physical viewpoint" and "ω target physical viewpoint" is substantially zero or less than a predetermined threshold and does not implement any modification of the visual reference. On the , the visual reference is thus not distorted.

The third situation is associated with the and concerns a significant discrepancy or gap between the movement of the virtual viewpoint (to the left) and the rotation of the physical viewpoint. Such a situation is likely to occur when

the movement of the virtual viewpoint is particularly fast compared to the rotation of the physical viewpoint (significant deviation), or

the movement of the virtual point of view is not accompanied by any rotation of the physical point of view (discordance), or

the rotation of the physical viewpoint is performed in the opposite direction to that of the virtual viewpoint movement (discordance).

A significant deviation is then obtained between "ω physical viewpoint" and "ω target physical viewpoint", leading to a large amplitude modification of the visual reference. Thus, for example, the visual reference is distorted more significantly on the that on the : the curvature of the body is more marked.

Figures 4a to 4d illustrate an application of a particular example of a pre-established strategy for limiting or eliminating visuo-vestibular conflict.

It should be noted that this strategy can be scalable and in particular personalized according to the user's particular sensitivity to the visuo-vestibular conflict and/or according to the user's receptivity to the modification of the visual reference.

For this purpose of customization, it is possible to offer the user a set of available modification modes and to request a selection by the user of a modification mode to be favored. Optionally, the modification mode thus selected can then be saved as user profile data.

The proposed modification methods may differ from each other by the nature (shape and/or size and/or color, etc.) of the modification(s) made and/or by the value of one or more parameters influencing the amplitude of this or these modifications.

The amplitude of a modification made can be characterized by an amplitude parameter whose real-time determination depends not only on the target value, but also on the mathematical function for calculating the amplitude parameter as a function of the difference between the target value and the recorded value of the rotation speed from the user's physical point of view. In general, the modifications of the visual reference can be controlled according to different criteria, alone or combined with each other, these criteria being able to relate for example to perceptual thresholds, to the elapsed time, as well as to the rotation speed of the user's head relative to the real world and/or to other measured or inferred parameters.

Parameters affecting the magnitude of a change made may include parameters of such a mathematical function, such as expected maximum and minimum values for the magnitude parameter, a slope in the particular case of a linear function, etc.

Furthermore, as already indicated, the target value is calculated based on the movements recorded from the physical and virtual points of view, according to a pre-established calculation method. The pre-established calculation method may itself result from a choice among several available calculation methods. Thus, the parameters influencing the amplitude of a modification made may relate to the choice of the calculation method to determine the target value and/or to the adjustment of coefficients involved in this calculation method.

It is also possible to implement supervised machine learning methods to determine which modification mode to favor among the set of available modification modes.

Such means may be based, for example, on an analysis of the movements made by the user in response to different tested modes of modification of the visual reference and/or on the user's responses to requests relating, for example, to his comfort during an immersion session in the virtual environment where different types of modifications are successively tested.

Claims (11)

Cyber-sickness reduction system (12) for navigation in an immersive virtual environment (2), comprising a control unit (7), a virtual visual environment (2), corresponding to a virtual point of view of the user, displayed on a display system (3), a position capture system (6) of the physical point of view of the user (4), and a navigation system (9) moving the virtual point of view of the user in the virtual environment, said system (12) being capable of:
monitoring movements from the user's virtual point of view relative to the virtual environment generated by the navigation system (9);
monitoring actual rotations from the user's physical point of view relative to the real world (11);
determining rotation incentives from the user's physical point of view relative to the real world (11), the rotation incentives relating to at least partial corrections of deviations and/or discrepancies between the movements from the virtual point of view and the actual rotations from the user's physical point of view; and
depending on the rotation incentives, modify in real time a visual reference (10) prepositioned in the virtual visual environment. The system of claim 1, wherein the visual reference (10) is generated virtually and displayed with the virtual environment (2) by the display system (3). The system of claim 1 or 2, wherein modifying the visual reference (10) comprises modifying the shape, orientation and/or appearance of the visual reference. The system of claim 3, wherein the visual reference (10) comprises:
a base positioned in a fixed manner relative to the user's physical point of view,
one end, and
a body extending from the base to the end. The system of claim 4, wherein modifying, in real time, the shape of the visual reference comprises, at least, curving the body of the visual reference. The system of claim 4 or 5, wherein modifying, in real time, the orientation of the visual reference comprises, at least, modifying the orientation of the end of the visual reference. System according to one of claims 1 to 6, in which the system is further capable of:
performing a comparison between several predefined modification modes of the visual reference by means of a supervised learning model, on the basis of a respective evaluation of the user's tracking of the rotation recommendations when the visual reference is respectively modified according to each of the predefined modification modes, and
choose, from the predefined editing modes, a custom editing mode for the user based on the comparison result. System according to one of claims 1 to 7, in which monitoring the actual rotations from the physical point of view of the user relative to the real world comprises collecting, by means of the position capture system (6) from the physical point of view of the user (4), time series indicative of angular parameters relating to the orientation of the user's head, the angular parameters including positions, speeds, accelerations and/or jerks. A method for reducing cyber-sickness for navigation in an immersive virtual environment (2), the method being implemented by a cyber-sickness reduction system (12) comprising a control unit (7), a virtual visual environment (2), corresponding to a virtual point of view of the user, displayed on a display system (3), a position capture system (6) of the physical point of view of the user (4), and a navigation system (9) moving the virtual point of view of the user in the virtual environment, said method comprising:
monitoring movements from the user's virtual point of view relative to the virtual environment generated by the navigation system (9);
monitoring actual rotations from the user's physical point of view relative to the real world (11);
determining rotation incentives from the user's physical point of view relative to the real world (11), the rotation incentives relating to at least partial corrections of deviations and/or discrepancies between the movements from the virtual point of view and the actual rotations from the user's physical point of view; and
depending on the rotation incentives, modify in real time a visual reference (10) prepositioned in the virtual visual environment. Computer program comprising instructions for implementing the method according to claim 9 when this program is executed by a processor. Non-transitory recording medium readable by a computer on which is recorded a program for implementing the method according to claim 9 when this program is executed by a processor.