GB2470754A

GB2470754A - Generating and displaying images dependent on detected viewpoint

Info

Publication number: GB2470754A
Application number: GB0909580A
Authority: GB
Inventors: Anthony William Godar
Original assignee: Sony Computer Entertainment Europe Ltd
Current assignee: Sony Interactive Entertainment Europe Ltd
Priority date: 2009-06-03
Filing date: 2009-06-03
Publication date: 2010-12-08
Also published as: GB0909580D0

Abstract

An entertainment device 100 comprises a display 102, a video camera 180 positioned in a known physical relation to the display and operable to capture images of a user of the entertainment device, and a processing means (101, figure 1b) operable to analyse one or more images captured by the video camera 180 and estimate a position of the user relative to a reference position, and the entertainment device 100 is operable to generate for the display 102 an image having a selected viewpoint that deviates from a reference viewpoint in correspondence with a deviation of the estimated position of the user from the reference position. Video camera 180 is employed to track a user's head to estimate viewer position. Pre-recorded image pairs representing different predetermined viewpoints of the same scene are used for generating monoscopic images of stereoscopic content for display on monoscopic display 102, wherein the reproduced monoscopic image view point is based on the detected viewpoint position of the user.

Description

DISPLAY SYSTEM AND METHOD

The present invention relates to a display system and method.

It is anticipated that stereoscopic display systems and accompanying sources of content to display on them will be widely adopted in the future.

However, there will be a transition period during which not all users have stereoscopic display technologies, and for small and portable devices in particular this transition period may be significant; a delay between the introduction of home and portable equipment is common for new technologies, as was seen with tape, CD, DVD and currently Blu-Ray � systems.

Similarly there will be a small but important proportion of the population who find stereoscopic displays unsuitable; for example those with monocular vision, or who find stereoscopic displays uncomfortable to watch.

Given this transition period and the needs of a proportion of the population, it is therefore desirable to provide a satisfactory mode of monoscopic reproduction for stereoscopic content.

The present invention seeks to address or mitigate the above need.

In a first aspect, an entertainment device comprises a display, a video camera positioned in a known physical relation to the display and operable to capture images of a user of the entertainment device, and a processing means operable to analyse one or more images captured by the video camera and estimate a position of the user relative to a reference position, and the entertainment device is operable to generate for the display an image having a selected viewpoint that deviates from a reference viewpoint in correspondence with a deviation of the estimated position of the user from the reference position.

In another aspect, a method of image display for an entertainment device comprises capturing an image of a user of the entertainment device, analysing the captured image to estimate a position of the user in relation to a reference position, and generating for display an image having a selected viewpoint that deviates from a reference viewpoint in correspondence with a deviation of the estimated position of the user from the reference position.

Advantageously, by constructing an image that mimics the viewpoint of the user rather than retaining a fixed or default viewpoint, a 3D effect can be achieved as the displayed images appear to change in a manner that is consistent with looking at a real object in three dimensions. Typically this 3D effect is limited to a range of possible viewpoints that the user can adopt, and this is discussed in more detail herein. Notably, the 3D effect does not rely on wearing special glasses or using a so-called 3D television'.

Further respective aspects and features of the invention are defined in the appended claims.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 A and lB are schematic diagrams of an entertainment device in accordance with an embodiment of the present invention.

Figures 2A to 2C are schematic diagrams of prior art rendered displays.

Figures 3A to 3 C are schematic diagrams of rendered displays responsive to a user's viewpoint in accordance with an embodiment of the present invention.

Figure 4A is a schematic diagram of a stereoscopic camera and the respective images of a scene that it captures.

Figure 4B is a schematic diagram of the captured images of Figure 4A when overlaid.

Figures 5A to 5C are schematic diagrams of generated displays responsive to a user's viewpoint in accordance with an embodiment of the present invention.

Figure 6 is a flow diagram of a method of image display in accordance with an embodiment of the present invention.

A display system and method are disclosed. In the following description, a number of specific details are presented in order to provide a thorough understanding of the embodiments of the present invention. It will be apparent, however, to a person skilled in the art that these specific details need not be employed to practise the present invention.

Conversely, specific details known to the person skilled in the art are omitted for the purposes of clarity where appropriate.

In an example embodiment of the present invention, a hand-held entertainment device comprises a traditional display, such as a standard LCD display. In addition the hand-held device comprises a video camera, which may be monoscopic (i.e. only have one lens), or monoscopic with a distance measuring function (a so-called z-cam'), or stereoscopic (i.e. having two lenses separated by some lateral distance). The video camera is mounted in a fixed relationship to the display, for example by being clipped into a USB port of the device or by being integrated with it.

In a videogame application, a traditional device renders a viewpoint normal (i.e. perpendicular) to the screen of the device, so that the user always appears to be looking directly into the game world regardless of their actual position with respect to the device.

This is illustrated in figures 2A-2C, where a virtual object 200 is rendered on a display 102 independently of the relative position of the viewer with respect to the display.

By contrast, in an embodiment of the present invention, the relative deviation of the user's eyes, face or head from the perpendicular centreline of the display (as determined using video images from the camera) is used to modify the rendered viewpoint on the screen.

This is illustrated in figures 3A-3C, where a virtual object 200 is rendered on a display 102 responsive to the relative position of the viewer with respect to the display.

The result is an illusion that the display has depth, and that the object is being displayed in 3D. Typically the changes in relative deviation will be small and caused by unconscious, small continuous movements of the user's hands and head, though of course the user may also intentionally choose to adopt a different viewpoint.

In addition to images rendered directly from a virtual environment, it is also possible to generate a similar effect from stereoscopic video sources. Using a first of the two source images as a reference, the deviation of each element of the first image in the second image, optionally together with parallax information from previous frames, provides sufficient depth information about picture elements in the stereo image pair to synthesise a new image having small deviations in the placement of the picture elements that are consistent with small deviations in the relative position of the user with respect to the display, thus again generating an illusion that the display is a 3D display.

Referring now to Figure 1A, in an embodiment of the present invention a Sony � PlayStation Portable � (PSP) entertainment device acts as the hand-held entertainment device 100. The PSP body 104 comprises, inter alia, a left joypad 106 and a right joypad 108. These are used to interface with software running on the PSP. In addition, the PSP comprises an integral display 102 and a speaker 103. In addition, a video camera 180 (depicted, as a non-limiting example, as a stereoscopic camera with two lenses 182 and 184) is plugged into a USB connector 125 mounted in the top of the PSP body.

Referring now also to Figure 1B, a summary schematic diagram of a PSP acting as the entertainment device 100 according to an embodiment of the invention is provided. The PSP comprises a central processing unit (CPU) 101, a graphics processing unit (GPU) 110 for polygon rendering and the like, a media engine 131 and an audio/video processor (AVC) 132 for image rendering, video and audio playback and the like, and a direct memory access controller (DMAC) 140, linked by a common bus 160. The DMAC 140 also links to an external bus 170 through which inputs and outputs are communicated, including with a wireless communication means (TxfRx) 120, a USB connector 125, a flash memory stick interface 135 that can act as a storage means for the device, and to the integral display 102.

Steps carried out under software control then cause the entertainment device to operate as described below.

The relative position of a user's head, face andlor eyes with respect to the display 102 may be determined by analysis of video images captured from the video camera 180, itself positioned in fixed relationship to the display. Thus, for example, if the user's eyes are perfectly aligned with a centreline perpendicular to the centre of the display, then their head will appear slightly offset in the captured video image by a known amount accounted for by the distance between the camera and the centreline and potentially also the distance of the user from the camera. Generally the user may be deemed to be perfectly aligned with the centreline of the display when their eyes are vertically aligned with it and equidistant on either side. Alternatively such alignment may be inferred from coarser recognition such as of head and/or face position.

With respect to this default offset in the captured video image, differences in the position of the user's head / face / eyes can be measured to evaluate their deviation from the centreline. This deviation can then be used to alter the point of view displayed by the device, as described herein.

in one embodiment of the present invention it will be appreciated that a monoscopic camera can determine differences in the user's position in an X-Y image plane, but if the distance (or Z direction) of the user from the display is also desired (for example to more accurately adjust the relative parallax of 3D objects in the display) then the distance of the user can be estimated from the relative size of their head. This may be done by generating an average head size during use, on the assumption that the user's head movements will vary about a central position, or head size may be measured during a calibration stage. It will be appreciated that head size' encompasses the evaluation of any suitable head or facial features; for example, the relative size of the triangle formed by the user's eyes and mouth may be used instead.

Alternatively, in another embodiment distance can be directly determined by a monoscopic camera equipped with depth measurement means, such as an ultrasound or an optical (e.g. infra-red) emitter operable to measure distances. A known example of such a camera is the so-called z-cam provided by 3DV Systems (http://www.3dvsystems.com). Such a camera can thus provide information enabling the estimation of differences in the user's position in the X, Y and Z planes directly.

Similarly, in a further embodiment a stereoscopic cariera having two lenses can be used to determine the distance of a user by the relative difference in position of the user with respect to the two images captured by the camera. In this case the closer the user is to the stereoscopic camera, the greater the divergence between the positions of the user in the two images, based upon a function of the user's distance and the known separation of the two lenses. Optionally the lenses may be mounted tilted slightly towards each other in order to is amplify this effect.

In any event, using one of the above embodiments the entertainment device can thus derive the relative deviation of the user in the X-Y plane from the centreline of the display, and optionally also the distance of the user along the centreline from the display.

Referring now to figures 2A to 2C, in a conventional entertainment device displaying, for example, a videogame, a viewpoint is rendered that is consistent with the user being in perfect alignment with the centreline of the display, as seen in Figure 2A. This viewpoint is still rendered whether or not the user is indeed in perfect alignment with the centreline of the display, as illustrated in the bottom part of figures 2B and 2C, showing the same actual output on the display.

By contrast, referring now to Figures 3A to 3C, in an embodiment of the present invention the device renders a viewpoint that is consistent with the user's estimated position with respect to the centreline of the display. Thus when the user is perfectly aligned with the centreline, the rendered viewpoint coincides with that seen in the conventional device, as shown in Figure 3A. However, when the user deviates from this alignment, the entertainment device computes an alternative viewpoint consistent with the user's deviation in position, and displays this alternative viewpoint instead.

Using Figure 3B as an example, one may imagine the display 102 to be a window onto the virtual object 200. In this case, if the user were to move slightly to their right, they would expect to be able to see the right-hand side of the object.

Using the X, Y and optionally Z position information of the user obtained by analysis of the video camera output, the correct apparent view of the object can be calculated and then displayed, giving the illusion that the display really is a window into the virtual world containing the object. This is seen in the bottom part of Figure 3B, showing the actual output of the display.

Similarly, in Figure 3C the user has moved slightly to the left, and the estimated change in the user position is used to calculate (or recalculate) the view of the object that would be apparent in the display was a window through which the object was being viewed.

This view is then rendered and displayed on the display to give the illusion that the display really is a window into the virtual world containing the object. This is again seen in the bottom part of Figure 3C, showing the actual output of the display.

It will be appreciated that whilst a viewpoint can be computed based on measurements on both the vertical and horizontal axis, optionally the viewpoint may be only computed based on deviations on the horizontal axis (X-axis).

It will also be appreciated that in practice a user may not view a display perfectly centred face on by default. Therefore optionally an angular offset for the centreline may be used so as to point to the user's natural viewing position. This position may be determined during a calibration phase and/or by a long-term average of the user's viewing position. Thus, for example, if the user typically holds the display so that they view it horizontally centrally but from 15 degrees below perpendicular vertically, then optionally the notional centreline can be set to follow this line of sight so that an image based on a viewpoint perpendicular to the display will in fact be shown when the user is at this offset position.

The computation of new viewpoints within a videogame is well known for conventional purposes, such as for example the relative movement of a virtual camera following a user's avatar in a third-person perspective game. Consequently such computation is not discussed in detail herein.

Alternatively or in addition, however, the above principles can also be applied to recorded media.

In a first instance, a stereoscopic media source is available. Stereoscopic media typically comprises a sequence of pairs of pre-recorded images, in which each pair of pre-recorded images represents a respective different predetermined viewpoint; e.g. that of the left and right lens of the stereoscopic movie camera in which the images were originally captured.

A first option is simply to switch between left and right images depending on whether the user's viewpoint is to the left or the right of the centreline, but this may cause unpleasant uttering effects.

However, as noted above in relation to the stereoscopic camera of the entertainment device, it is possible to compute the relative distance of an image element in a stereoscopic pair of images according to the size of the displacement between the respective instances of the image element in the pair of images.

Referring now to Figures 4A and 4B, a stereoscopic movie camera 1010 generates a pair of images whose viewpoints are separated by a known distance. In Figure 4A, both lenses of the stereoscopic camera are looking at a sequence of objects P,Q, R, S and T, and two further objects N and 0 (assumed for the purposes of explanation to be positioned above the other objects). As can be seen in the resulting pair of images 1012 and 1014, the different image viewpoints result in a different image of the objects from each lens. In Figure 4B, an overlay image 1020 of the stereoscopic image pair illustrates that the displacement between the objects within the image pair 1012 and 1014 is inversely proportional to the distance of the object from the stereoscopic movie camera.

Notably, overlay image 1020 also indicates that the true position of the objects with respect to a perpendicular centreline equidistant between the lenses of the stereoscopic movie camera is simply the average of their apparent positions in the stereoscopic pair of images.

The correspondence between the image elements depicting the objects in images 1012 and 1014 may be determined using known analysis techniques, such as cross-correlation.

Using this information it is then possible to interpolate a new image using the image elements corresponding to objects P, Q, R, S and T for any angle of deviation from a perpendicular centreline equidistant between the lenses of the stereoscopic movie camera, out to the angle of the respective lenses.

Referring to Figures 5A to 5C, in a first instance shown in 5A, the default notional viewpoint perpendicular to a centreline equidistant between the lenses of the camera is shown.

Recall that the order of the objects is known from their relative distances, and their positions are known from the average of their positions in the image pair. The result is shown in interpolated image 1020A of Figure SA.

This single interpolated image may then be shown on the monoscopic (standard) display of the entertainment device 100 when it detects that the user is viewing the screen centrally, in the manner described previously herein.

However, as previously described, when the user's viewing position deviates slightly from the central (or an average) position, this deviation can be replicated in the displayed view.

Thus referring to Figure 5B, the user's viewpoint is at a position slightly to the left of the centreline of the display (and hence also the centreline of the stereoscopic movie camera) and so, using the information about the true distance and position of the image features derived from the stereoscopic images, a different interpolated image 1020B of Figure 5B may be generated that is consistent with the users relative viewpoint.

Similarly in Figure 5C, the user's viewpoint is slightly to the right of the centreline, and again an interpolated image 1 020C is generated.

It will be appreciated that the left and right images of the stereoscopic image pair contain complementary background details. For example, the region of background obscured by object P in image 1012 is visible in image 1014. In general, for interpolation of viewpoint angles lying between the lenses of the stereoscopic movie camera, enough of each image element (including the background) is available in at least one of the stereoscopic images to construct the interpolated image completely. In other words, the overlapping view points of the image pair provide image redundancy within the angle of overlap that may be used during construction of the interpolated image, and for any horizontal deviation up to the angle of the left or right lens, there will be image information available for more distant image elements revealed by looking to the left' or right' of the central viewpoint of the display.

However it will also be appreciated that for a traditional stereoscopic movie camera, such image redundancy and hence interpolation is only available in the horizontal axis. In other words, there is no image information for background image elements that may be revealed by looking above' or below' the central viewpoint of the stereoscopic movie camera and hence the display. Thus in this case typically the entertainment device will therefore only interpolate the image in response to the horizontal deviation of the user from the centreline. Clearly, if a stereoscopic' movie camera were to comprise 2 additional lenses horizontally centred but vertically spaced (i.e. rotated 90 degrees to the original cameras) then the resulting complementary stereoscopic pair of image can be used for vertical interpolation.

It will be appreciated that stereoscopic movie camera' encompasses any stereoscopic camera used to generate recorded stereoscopic media, potentially including stereoscopic camera 180 attached to the entertainment device, and that reference above to interpolating image pairs from the camera encompass interpolating image pairs from the recorded stereoscopic media.

Optionally, historical information about the video may also be used, for example where it is difficult to resolve an object's distance (for example where repeated instances of a pattern may cause a false estimate of distance between repeating instances, or where correlation between instances of an object in a stereoscopic image pair is difficult). In particular, the parallax movement of elements in a sequence of images may be used to resolve such ambiguities. For example, a wallpaper background with a repeating pattern will have a small parallax movement compared to objects in the foreground. Similarly a distant object will have the same parallax in the stereoscopic image pair even if correlation of the image elements corresponding to the object is difficult to achieve. Where observed parallax and an analysis of a single stereoscopic image pair disagree on the apparent distance of an object, in an embodiment of the present invention the observed parallax may be used in preference to compute the distance, or alternatively to limit the region in the corresponding image of an image pair in which the corresponding view of the image element may be sought.

Similarly, historical information about the distance of an image element in one or more previous frames, optionally in combination with motion vector data, can provide a prediction of the distance of the image element in the present image pair. In this case a distance estimate that falls outside a threshold divergence from the predicted distance can be overridden and an extrapolated distance can be used instead. Similarly the distance of the image element in a preceding image pair together with motion vectors can help to identify an image element for which correlation within the current image pair proves difficult; for example when one object moves directly behind another, so that non-overlapping partial views of the object are seen in the stereoscopic image pair.

Thus more generally the relative movement of objects in a sequence of images, can provide distance information to supplement that obtained from a stereoscopic image pair.

Alternatively or in addition to the above embodiments for pre-recorded media, for devices where the computational load (or power requirements of such computation) involved in the above interpolation techniques are undesirable, such interpolated images may be generated in advance and stored as data supplementary to the original stereoscopic recorded media. For example, a total of eight images (the original pair and six interpolated angles) may be stored. Optionally an odd number of interpolations may be performed, giving a symmetrical set of angles including a single centreline viewpoint. The device then selects whichever interpolated image is closest to the user's current viewpoint. It will be appreciated that more or less than eight images may be chosen, depending on desired quality levels, storage capacity, etc., and that the angles chosen may not be regularly separated, for example being closer together near the centreline viewpoint.

Of course it will be appreciated that the above interpolation techniques may still be used where such supplementary data is available, and may either discard the supplementary data and only use the stereoscopic images, or alternatively may interpolate between the images that bound the desired viewpoint angle.

It will also be appreciated that the device need not be a hand-held device; for example a video billboard may use the above system, either interpolating in real time or accessing previously interpolated images to present to a potential viewer as they pass the billboard.

Referring now to Figure 6, a method of image display for an entertainment device comprises: in a first step (slO), capturing an image of a user of the entertainment device; in a second step (s20), analysing the captured image to determine a position of the user in relation to a reference position; and in a third step (s30), generating for display an image having a selected viewpoint that deviates from a reference viewpoint in correspondence with the deviation of the relative position of the user from the reference position.

It will be apparent to a person skilled in the art that variations in the above method corresponding to operation of the various embodiments of the apparatus as described and claimed herein are considered within the scope of the present invention, including but not limited to: -the reference viewpoint being one selected from a list consisting of a viewpoint perpendicular to the centre of the display, and a viewpoint corresponding to a time-averaged position of the user relative to the display; -the video camera being one selected from the list consisting of a monoscopic camera, a monoscopic camera comprising a distance measuring means, and a stereoscopic camera; -the apparent position of the user in the or each captured image being corrected by a factor dependent upon the known physical relationship between the video camera and the display; -the generated image being based upon a pair of pre-recorded images that each represents a respective different predetermined viewpoint, and the step of generating an image comprising the step of estimating the distance and position of image elements in the pair of pre-recorded images; -In particular, the distance may be estimated by one or more selected from the list consisting of: -analysing the first pair of pre-recorded images to identify the positions of corresponding instances of the image element in each image of the first pair of pre-recorded images, and estimating the distance of the image element in dependence upon the distance between the respective positions of the corresponding instances of the image element in each image of the first pair of pre-recorded images; -analysing images from a sequence of two or more pre-recorded image pairs including the first pair of pre-recorded images, to measure the parallax motion of the image element in the images of the first pair of pre-recorded images, and to estimate the distance of the image element in dependence upon its measured parallax motion; and -estimating the distance of the image element based upon the distance of the image element as estimated for one or more previous images in a sequence of two or more pairs of pre-recorded images including the first pair of pre-recorded images; -the step of generating an image comprises the step of calculating changes to the estimated positions of the image elements consistent with the selected viewpoint and arranging the image elements within the generated image according to their calculated position and relative distance from an image plane; and -the step of generating an image comprises the step of rendering a graphical representation of a virtual environment from a viewpoint deviating from the reference viewpoint in correspondence with the relative position of the user with respect to the reference position.

Finally, it will be appreciated that the methods disclosed herein may be carried out on conventional hardware suitably adapted as applicable by software instruction or by the inclusion or substitution of dedicated hardware.

Thus the required adaptation to existing parts of a conventional equivalent device may be implemented in the form of a computer program product or similar object of manufacture comprising processor implementable instructions stored on a data carrier such as a floppy disk, optical disk, hard disk, PROM, RAM, flash memory or any combination of these or other storage media, or transmitted via data signals on a network such as an Ethernet, a wireless network, the Internet, or any combination of these of other networks, or realised in hardware as an ASIC (application specific integrated circuit) or an FPGA (field programmable gate array) or other configurable circuit suitable to use in adapting the conventional equivalent device.

Claims

CLAIMS1. An entertainment device, comprising: a display; a video camera positioned in a known physical relation to the display and operable to capture images of a user of the entertainment device; and a processing means operable to analyse one or more images captured by the video camera, and estimate a position of the user relative to a reference position; and wherein the entertainment device is operable to generate for the display an image having a selected viewpoint that deviates from a reference viewpoint in correspondence with a deviation of the estimated position of the user from the reference position.
2. An entertainment device according to claim 1, in which the reference viewpoint is one selected from the list consisting of: i. a viewpoint perpendicular to the centre of the display; and ii. a viewpoint corresponding to a time-averaged position of the user relative to the display.
3. An entertainment device according to claim 1 or claim 2, in which the video camera is one selected from the list consisting of: i. a monoscopic camera; ii. a monoscopic camera comprising a distance measuring means; and iii. a stereoscopic camera.
4. An entertainment device according to any one of the preceding claims, in which the apparent position of the user in the or each captured image is corrected by a factor dependent upon the known physical relationship between the video camera and the display.
5. An entertainment device according to any one of the preceding claims, in which the entertainment device is operable to generate the image based upon a first pair of pre-recorded images that each represents a respective different predetermined viewpoint.
6. An entertainment device according to claim 5, in which the processor is arranged to estimate a position for an image element based upon an average of the apparent positions of the image element in the first pair of pre-recorded images.
7. An entertainment device according to claim 5 or claim 6, in which the processor is arranged to estimate the apparent distance of an image element by one or more selected from the list consisting of: i. analysing the first pair of pre-recorded images to identify the positions of corresponding instances of the image element in each image of the first pair of pre-recorded images, and estimating the distance of the image element in dependence upon the distance between the respective positions of the corresponding instances of the image element in each image of the first pair of pre-recorded images; ii. analysing images from a sequence of two or more pre-recorded image pairs including the first pair of pre-recorded images, to measure the parallax motion of the image element in the images of the first pair of pre-recorded images, and to estimate the distance of the image element in dependence upon its measured parallax motion; and iii. estimating the distance of the image element based upon the distance of the image element as estimated for one or more previous images in a sequence of two or more pairs of pre-recorded images including the first pair of pre-recorded images.
8. An entertainment device according to any one of claims 5 to 7, in which the entertainment device is arranged to generate an image having a selected viewpoint using the distance and position of image elements as estimated from one or more pairs of pre-recorded images.
9. An entertainment device according to claim 8 in which the entertainment device is arranged to generate the image by calculating changes to the estimated positions of the image elements consistent with the selected viewpoint and arranging the image elements within the generated image according to their calculated position and relative distance from an image plane.
10. An entertainment device according to claim 1, in which the generated image is a graphical representation of a virtual environment as rendered from a viewpoint deviating from the reference viewpoint in correspondence with the deviation of the estimated position of the user from the reference position.
11. A method of image display for an entertainment device, comprising the steps of: capturing an image of a user of the entertainment device; analysing the captured image to estimate a position of the user in relation to a reference position; and generating for display an image having a selected viewpoint that deviates from a reference viewpoint in correspondence with a deviation of the estimated position of the user from the reference position.
12. A method of image display for an entertainment device according to claim 11, in which the generated image is based upon a pair of pre-recorded images that each represents a respective different predetermined viewpoint, and the step of generating an image comprises the step of: estimating the distance and position of image elements from the pair of pre-recorded images.
13. A method of image display for an entertainment device according to claim 12, in which the step of generating an image comprises the step of: calculating changes to the estimated positions of the image elements consistent with the selected viewpoint and arranging the image elements within the generated image according to their calculated position and relative distance from an image plane.
14. A method of image display for an entertainment device according to claim 11, in which in which the step of generating an image comprises the step of: rendering a graphical representation of a virtual environment from a viewpoint deviating from the reference viewpoint in correspondence with the deviation of the estimated position of the user from the reference position.
15. A computer program for implementing the steps of any one of method claims 11 to 14.
16. An entertainment device substantially as described herein with reference to the accompanying drawings.
17. A method of image display for an entertainment device substantially as described herein with reference to the accompanying drawings.