# Patent

## Title
Method and apparatus for adjusting a view of a scene being displayed according to tracked head motion

## Abstract

A method for controlling a view of a scene is provided. The method initiates with detecting an initial location of a control object. An initial view of the scene is displayed on a virtual window, the initial view defined by a view-frustum based on a projection of the initial location of the control object through outer edges of the virtual window. Movement of the control object to a new location is detected. An updated view of the scene is displayed on the virtual window, the updated view defined by an updated view-frustum based on a projection of the new location of the control object through the outer edges of the virtual window.

## Background
CLAIM OF PRIORITY
This application claims priority as a continuation of U.S. patent application Ser. No. 10/663,236, now U.S. Pat. No. 7,883,415, entitled “METHOD AND APPARATUS FOR ADJUSTING A VIEW OF A SCENE BEING DISPLAYED ACCORDING TO TRACKED HEAD MOTION,” filed on Sep. 15, 2003, which is herein incorporated by reference in its entirety for all purposes.


BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to video processing, and more particularly to an interface that enables controlling a virtual camera through a user's head motion in order to adjust the view being presented during an interactive entertainment application.
2. Description of the Related Art
The interactive entertainment industry strives to allow users a realistic as possible experience when playing an interactive video game. Currently, the scene views presented on screen during execution of the interactive application do not allow for the definition of a scene view according to actual tracked movement where the movement is captured without the use of markers. The requirement for a user to wear the sometimes awkward markers is a nuisance that has prevented the wide scale acceptance of the applications associated with the markers.
One attempt to provide a realistic experience is to provide a canned response to a detected movement. That is, a user may be monitored and if the user ducks or jumps a corresponding character of the application ducks or jumps. However, there is no correlation with the user's movement to the scene view being presented on display screen viewed by the user. Thus, in order to change a scene view being presented, the user is left with manipulating a joy stick to change the scene view. Moreover, a user is required to remember a number of abstract commands in order to access the various scene movement capabilities. For example, in order to peer around a corner within a scene, the user may have to key a button sequence in combination with manipulation of the joy stick in order to achieve the desired functionality. As can be appreciated, this manipulation is wholly unrelated to the physical movement, i.e., peering around a corner, tying to be emulated.
In view of the foregoing, there is a need for providing a method and apparatus configured to tie the actual movement of a user to modify a scene view being presented, without having the user wear markers, during an execution of an interactive entertainment application.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing a method and apparatus that tracks head motion of a user without markers in order to adjust a view-frustum associated with a scene being displayed. It should be appreciated that the present invention can be implemented in numerous ways, including as a method, a system, computer readable medium or a device. Several inventive embodiments of the present invention are described below.
In one embodiment, a method is provided for processing interactive user control for a view of a scene displayed on a virtual window. The method initiates with identifying a head of a user that is to interact with the scene. An initial view of the scene is displayed, comprising a view-frustum initially defined by a gaze projection of a location of the head through outer edges of the virtual window when the location of the head is substantially normal to about a center point of the virtual window. The identified head of the user is tracked during display of the scene, the tracking enabling detection of a change in location of the head of the user. The view-frustum is adjusted in accordance with the change in location of the head of the user, the adjusting of the view-frustum being in response to tracking a move in the location of the head away from normal relative to the center point of the virtual window. The adjusted view-frustum is defined by an updated gaze projection of the changed location of the head through the outer edges of the virtual window, such that the view-frustum moves in a direction opposite to the move in the location of the head. An updated view of the scene is displayed based on the adjusted view-frustum.
In one embodiment, a method is provided for controlling a view of a scene. The method initiates with detecting an initial location of a control object. An initial view of the scene is displayed on a virtual window, the initial view defined by a view-frustum based on a projection of the initial location of the control object through outer edges of the virtual window. Movement of the control object to a new location is detected. An updated view of the scene is displayed on the virtual window, the updated view defined by an updated view-frustum based on a projection of the new location of the control object through the outer edges of the virtual window.
In another embodiment, a method is provided for displaying a view of a virtual environment on a display device. The method initiates with identifying a control object in front of the display device. An initial location of the control object is detected. The initial location of the control object is correlated to an initial virtual location of a virtual viewpoint in the virtual environment. An initial view of the virtual environment is displayed on the display device, the initial view of the virtual environment determined by a view frustum in the virtual environment defined by a projection of the virtual viewpoint through a virtual viewport in the virtual environment. A movement of the control object to a new location is tracked. The virtual viewpoint is moved to a new virtual location in accordance with the tracked movement of the control object, such that the movement of the virtual viewpoint relative to the virtual viewport is in a same relative direction as the movement of the control object relative to the display device. An updated view of the virtual environment is displayed on the display device, the updated view of the virtual environment determined by an updated view frustum in the virtual environment defined by an updated projection of the virtual viewpoint at the new virtual location through the virtual viewport.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.
FIG. 1 is a simplified schematic diagram illustrating a view-frustum.
FIG. 2 is a simplified schematic diagram illustrating a virtual space viewpoint which is capable of being set by an application developer in accordance with one embodiment of the invention.
FIG. 3 is a simplified schematic diagram illustrating a top view of a world space configuration where a user's relative position within a three-dimensional cube is used to effect a scene being presented during an interactive entertainment application in accordance with one embodiment of the invention.
FIG. 4 is a simplified schematic diagram illustrating alternative facial orientations generated for a system configured to adjust a point of view being displayed according to a user's head movement in accordance with one embodiment of the invention.
FIG. 5 is a simplified schematic diagram illustrating the generation of a template and the corresponding matching of the template to a region within a frame of video data in accordance with one embodiment of the invention.
FIG. 6A and FIG. 6B are simplified schematic diagrams illustrating a change in a view-frustum according to a change in a location of a control object relative to a view port in accordance with one embodiment of the invention
FIG. 6C is a simplified schematic diagram illustrating the translation of a view frustum with a control objects motion, thereby providing a parallax effect in accordance with one embodiment of the invention.
FIGS. 7A and 7B illustrate simplified schematic diagrams comparing virtual world views with real world views in accordance with one embodiment of the invention.
FIG. 8 is a simplified schematic diagram illustrating view-frustums configured to maintain an object location constant within a view port in accordance with one embodiment of the invention.
FIG. 9 is a simplified schematic diagram illustrating a view port rotation scheme where an object is viewed from different angles in accordance with one embodiment of the invention.
FIG. 10 is a simplified schematic diagram illustrating a scheme where a user's head stays in a fixed location but a view-frustum is rotated according to how the user's head moves I accordance with one embodiment of the invention.
FIG. 11 is a simplified schematic diagram illustrating the system configured to enable interactive user control to define a visible volume being displayed in accordance with one embodiment of the invention.
FIG. 12 is a flow chart diagram illustrating method operations for managing a visible volume display through a view port in accordance with one embodiment of the invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An invention is disclosed for adjusting a point of view for a scene being displayed during an interactive entertainment application according to the head movement of a user. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to obscure the present invention.
The embodiments of the present invention modify a point of view associated with a virtual camera during an interactive entertainment application through the marker-less tracking of a control object. Thus, the visible scene being presented on a display screen is effected to the actual movement of the control object. That is, the control object is tracked and the movement of the control object is translated to modify a view-frustum defining a visible scene presented on a display screen. For illustrative purposes, the embodiments described herein designate the control object as a user's head. Of course, certain features of a user's head may be tracked, e.g., the face or any other suitable facial feature. Accordingly, rather than using a joy stick controller to move a virtual camera that defines the point of view for the visible scene being presented, a change in the coordinates of a user's head, that is being tracked through an image capture device, results in defining a new view point and subsequently displaying the image data associated with the new view point. As mentioned above, the tracking of the control object is performed without markers affixed to the control object. Thus, the user is not required to wear a device for tracking purposes. One skilled in the art will appreciate that the image capture device may be any suitable camera, e.g., a web camera.
In one embodiment, the physical movement in the real world, that is associated with the control object being tracked, is transformed to a virtual movement of a virtual camera defining a visible scene. The visible scene in the virtual world is then displayed through a virtual window, then rendered onto a rectangular area with screen coordinates, referred to as the view port. As used herein, the view port may any suitable display screen, e.g., a television monitor, a computer monitor, etc. While the embodiments described herein refer to a video game application, the embodiments may be applied to any suitable interactive entertainment application. Accordingly, with respect to a video game application any suitable video game console, such as the “PLAYSTATION 2”® manufactured by Sony Computer Entertainment Inc. may be incorporated with the embodiments described below. However, the embodiments including a video game console may also include any suitable computing device in place of the video game console. For example, with reference to on-line gaming applications, the computing device may be a server.
In one embodiment, a video camera is set proximate to a graphical display and pointed at the user to detect user movements. In particular, a change in location associated with the user's head or face is detected by the video camera. Each frame of video is processed to locate the position of the user's head in the image, by matching a portion of the video frame with a face template captured from a specific user, or a canonical face template. The face template is initially captured by the user placing his face within a capture region defined on a display screen. Once the user's face is within the capture region the system is signaled so that an image of the user's face may be stored as gray scale image data or some other suitable image data for storage in memory. The virtual viewpoint and view frustum used for displaying the scene are modified to correspond to the user's tracked head or face location during execution of an interactive entertainment application. In addition, distance of the user's head from the camera may be determined from the scale of their face/head features in the video image. The mapping from the head location to the virtual view is dependent on the application. For example, a game developer may decide on the factors defining the mapping of the head location to the virtual view.
FIG. 1 is a simplified schematic diagram illustrating a view-frustum. As is generally known, the view-frustum is used to define viewable objects for presentation. Thus, from viewpoint 100 a pyramid is defined. View-frustum 106 is bounded by the four sides of the pyramid having an apex at viewpoint 100. View-frustum 106 may be thought of as a truncated pyramid where near plane 102 clips the pyramid defined from viewpoint 100 at a front end, i.e., closer to the viewpoint. Far plane 104 clips the pyramid at a far end. Thus, view-frustum 106 defines a truncated pyramid volume, wherein the visible volume for display through a view port is defined within the truncated pyramid volume of view frustum 106. One skilled in the art will appreciate that the view-frustum enables objects defined in three-dimensional space to be culled in order to present the visible objects on a two-dimensional screen. Consequently, plane 102 may be considered a virtual display screen, i.e., a view port, in which objects defined within view-frustum 106 are presented.
FIG. 2 is a simplified schematic diagram illustrating a virtual space viewpoint which is capable of being set by an application developer in accordance with one embodiment of the invention. Viewpoint 110 is associated with a particular distance to virtual window 108. As a result of that distance, the scene being presented through virtual window 108 may be modified. In other words, distance 111 may be used to define a scale of a scene being displayed in virtual window 108. As can be seen, viewpoint 110 may be moved closer to or farther from virtual window 108 in order to manipulate the scene being presented. With reference to video game applications, distance 111 is set by a game developer or programmer as desired. Thus, distance 111 may be manipulated to provide the effect of being right up against virtual window 108, a significant distance away from virtual window 108, or any distance in between. For example, with respect to a video game application, a character running may be associated with a distance being relatively close to virtual window 108 in order to see the ground directly in front of the character. Alternatively, an application displaying a view from an airplane in flight, may be associated with a large distance to provide the effect of a global view.
FIG. 3 is a simplified schematic diagram illustrating a top view of a world space configuration where a user's relative position within a three-dimensional cube is used to effect a scene being presented during an interactive entertainment application in accordance with one embodiment of the invention. Here, image capture device 116 is configured to track control object 112, e.g., a user's head or face region, within a capture zone defined by three-dimensional cube 114. As will be explained in more detail below, image capture device 116 is in communication with a computing device controlling the image data, i.e., the scenes, being presented on display screen 118. Thus, as control object 112 moves within the capture zone the change in location captured by image capture device 116 is translated in order to effect a corresponding change to a view-frustum defining the visible scene being presented on display screen 118. For example, the pyramid discussed with reference to FIG. 1 having an apex associated with control object 112 defines a view-frustum. As will be described in more detail below, the movement of control object 112 causes a scene view being presented to change relative to the movement of the control object. In one embodiment, image capture device 116 is configured to zoom-in on various quadrants of three-dimensional cube 114 in order to locate where head 112 is relative to the three-dimensional volume. It should be appreciated that image capture device 116 may be any suitable camera capable of tracking a user's head within a capture zone. It should be further appreciated that the tracking is performed through a marker-less scheme.
Still referring to FIG. 3, in one embodiment, image capture device 116 is a depth camera. For example, the depth camera discussed in U.S. application Ser. No. 10/365,120 entitled “Method and Apparatus for Real Time Motion Capture,” is an exemplary depth camera capable of determining a distance of control object 112 to display screen 118. This application is herein incorporated by reference in its entirety for all purposes. Thus, the view being displayed on display screen 118 may be modified in response to movement within capture zone 114 of control object 112. Additionally, the scale associated with the image data being displayed may be manipulated according to a change in the distance of the user's head to the display screen. In another embodiment, an image capture device without depth capability may be used, where control object 112 is a user's head or facial region, and where the size of a face associated with the user's head is compared in successive video frames in order to translate a change in the distance from the user's head to the display screen. For example, a change in size of the user's head, or another suitable control object, within a range of about 15% in the successive video frames may be used to manipulate the scale of a scene being presented on display screen 118. One skilled in the art will appreciate that the use of an image capture device 116 where the image capture device does not have depth capability will require a more powerful processor as compared to the use of a depth camera.
FIG. 4 is a simplified schematic diagram illustrating alternative facial orientations generated for a system configured to adjust a point of view being displayed according to a user's head movement in accordance with one embodiment of the invention. Here, image 120a is initially captured as the template of a user's head. Upon the capture of image 120a, associated images 120b and 120c are generated where the facial orientation is rotated relative to axis 122. That is, image 120b is created by tilting the face of image 120a in one direction, while image 120c is created by tilting the face of image 120a in a different direction, thereby identifying additional three dimensional positions of the head. One skilled in the art will appreciate that numerous other templates may be generated where the orientation or size of the face is modified from the original template. Additionally, any suitable orientation change or size change from the original captured image may be generated. In one embodiment, a degree of change in the orientation or size is determined for use in modifying a scene view.
FIG. 5 is a simplified schematic diagram illustrating the generation of a template and the corresponding matching of the template to a region within a frame of video data in accordance with one embodiment of the invention. Here, template 124a is created upon initialization as described above. In one embodiment, template 124a is a 12×16 pixel size region. Region 130 represents a frame of video data. Within the frame of video data search region 126 is defined. In one embodiment, a size associated with search region 126 is determined by how far, in terms of pixels, a user can move between frames. For example, if a user moves eight pixels in between frames, the size of search region 126 is configured to accommodate this movement so that the movement may be captured. Thus, in one embodiment, each frame of video data is searched within the search region in order to locate a match between the template defined in search region 126 and stored template 124a, thereby enabling computation of a change in movement of a user. In another embodiment, a match is found for template 124a, which is stored in memory as described above, and a corresponding region 124b within search region 126 through a sum of absolute differences scheme also referred to as an L1 norm calculation. That is, values associated with each pixel of template 124a are subtracted from corresponding pixels within an area defined in search region 126 in order to locate an area within the search region that generates the lowest score when compared to template 124a. For example, corresponding pixel values from template 124a and region 124b are subtracted from each other. The absolute value of each of the differences is then taken and summed in order to obtain a score associated with the comparison of template 124a and region 124b. The corresponding region within search area 126 having the lowest score when compared to template 124a is the most likely candidate for a match. In one embodiment, a threshold score must be obtained in order for the region within search area 126 to be considered a match to template 124a. In one embodiment, if no match is found, then the location of the control object defaults to a location determined within a previous frame. One skilled in the art will appreciate that the comparison through the sum of absolute differences is provided for exemplary purposes only and is not meant to be limiting. That is, other suitable techniques such as taking the square of the differences may also be used in order to calculate the score. In essence, any technique which generates a positive value from each of the differences may be used to calculate the score.
Still referring to FIG. 5, in one embodiment, the image data to determine a match are gray scale luminance values associated with each of the pixels of the corresponding image data. It will be apparent to one skilled in the art that other suitable values associated with the pixels may also be used for the calculation to determine a match to template 124a. It should be appreciated that search region 126 may be set to a new default location within display region 130 during the execution of the interactive entertainment application. In addition, the image data used for the template may be dynamic in order to enhance the tracking of the user's facial features. Thus, when tracking the facial region of a user's head, should the user turn his face from the capture device, the image data captured when the facial region was lost may be tracked in substitution of the initial facial region.
FIG. 6A and FIG. 6B are simplified schematic diagrams illustrating a change in a view-frustum according to a change in a location of a control object relative to a view port in accordance with one embodiment of the invention. In FIG. 6A, the user's head 134a is tracked at an initial position, thereby defining a view-frustum defining visible volume 136 which is behind view port 132 and between side boundaries 136a and 136b. Should the user's head move closer to view port 132, as illustrated by location 134b of the user's head, the associated view-frustum is modified. That is, view-frustum 138, which is defined behind view port 132 and between side boundaries 138a and 138b, provides a wider angle of view behind relative to view-frustum 136. It should be appreciated that this effect may be analogized to looking out a window. That is, the farther a person is from the actual window the view angle will be more limited.
FIG. 6B illustrates the movement of a view-frustum from side to side in an asymmetric manner in accordance with one embodiment of the invention. Here, the user's head is initially in location 133a, thereby defining view-frustum 142 behind view port 132 and between side boundaries 142a and 142b. As the location of the user's head moves to location 133b, the boundaries of view-frustum 140 are modified as compared to view-frustum 142. That is, the user in location 134b has a wider angle of sight through the right-hand side of view port 132 as defined by side boundary 140b. However, a more limited angle of sight through the left-hand side of view port 132 is associated with view frustum 140 through side boundary 140a. It should be appreciated that with reference to FIG. 6B, view-frustum 142 defines a symmetrical view-frustum. That is, the line of sight from a user's head at location 133a is normal to a center point 135 of the plane defined by view port 132. However, as the user's location is moved to location 133b the view-frustum is adjusted as described above and becomes asymmetrical. As such, the eye-gaze direction from location 134b is not normal relative to a center of view port 132. In other words, the view plane is no longer perpendicular to the gaze direction, which is atypical for views provided through video games. The display may be considered as a virtual window into a scene, wherein the embodiments described above adjust the view-frustum to show what a user can see through this window as his head moves. It should be appreciated that this provides a parallax effect but also a change in viewing angle.
FIG. 6C is a simplified schematic diagram illustrating the translation of a view frustum with a control objects motion, thereby providing a parallax effect in accordance with one embodiment of the invention. Here, as a user's head, or a facial feature of the user's head, moves from location 135a to 135b, the perpendicular angle of gaze direction to a center point of the corresponding view port is maintained. Thus, it appears as viewpoint 132 is translated along with the change in location of the user's head, which may be referred to as strafing. It should be appreciated that visible volume captured through the corresponding view frustums of locations 135a and 135b changes as the boundaries of the corresponding view frustums move. In one embodiment, a user's head moving up and down is tracked to cause the game's view frustum to provide a different viewpoint while maintaining a symmetrical view-frustum. One skilled in the art will appreciate that it is important to maintain the virtual camera direction as described in the embodiment of FIG. 6c for peering around a corner such as in a stealth or first person shooter game. One skilled in the art will appreciate that a TV screen acting as view port 132 may be viewed much larger than it actually is relative to the entire visual field of the user in order to provide a bigger window for the user so that a user does not feel they are looking through a tiny window.
FIGS. 7A and 7B illustrate simplified schematic diagrams comparing virtual world views with real world views in accordance with one embodiment of the invention. In FIG. 7A, a virtual world view defined by view-frustums originating from locations 144a and 144b through virtual view port 142a. In FIG. 7B, real world views are defined by view-frustums associated with location 144a′ and 144b′ through view port 142b. It should be appreciated that location 144a in the virtual world corresponds to location 144a′ in the real world. Likewise, location 144b corresponds to location 144b′. Furthermore, with respect to video game applications or any other interactive entertainment applications, view port 142b may be considered a television screen or any other suitable type of display screen. For FIG. 7A, a virtual camera is associated with locations 144a and 144b. In real world configuration of FIG. 7B, a tracking device such as a camera tracks movement of the user's head from initial location 144a′ to a next location 144b′. This movement is interpreted in the real world as set by code developers for that scene. A physical movement in the real world of FIG. 7B is then transformed or mapped into virtual movement in the virtual world of FIG. 7A in order to move the virtual camera to define a scene to be displayed on view port 142b in the real world. It should be appreciated that the scale of movement does not necessarily match between the real world and the virtual world. However, the user is provided with the impression of control over the view movement during execution of the interactive entertainment application.
FIG. 8 is a simplified schematic diagram illustrating view-frustums configured to maintain an object location constant within a view port in accordance with one embodiment of the invention. Here, object 150 defines a center of interest point. That is, the view-frustums associated with various locations, such as locations 144a′ and 144b′ relative to view port 142 center around object 150. Thus, object 150 appears at a constant position in the scene from the different locations 144a′ and 144b′. For example, in a game, if there is a statue that is important for some reason, then the configuration described above enables the statue to be maintained at the center point or point of interest of the scene. Therefore, the user's attention is drawn to the statue even though the scene presentation may not be physically correct. As illustrated in FIG. 8, in order to maintain the relative position of object 150, the size of view port 142 is adjusted.
FIG. 9 is a simplified schematic diagram illustrating a view port rotation scheme where an object is viewed from different angles in accordance with one embodiment of the invention. Here, the virtual camera orbits around path 152 in order to define the plurality of view-frustums 154-1 to 154-n, which provide views of object 156 at various angles. Thus, this embodiment may be used when looking over a person's shoulder, or as a person moves around path 152 relative to object 156, i.e., directing an orbiting camera in a 3rd person game. FIG. 10 is a simplified schematic diagram illustrating a scheme where a user's head stays in a fixed location but a view-frustum is rotated according to how the user's head moves. For example, the user's head may tilt or twist within a location thereby defining different view-frustums. Here, view-frustums 162-1 through 162-n are defined around location 160 which corresponds to a user's head. In this embodiment, a user provided with the capability of looking around a cockpit for flight simulation applications or out of side windows of a vehicle during driving simulation applications.
FIG. 11 is a simplified schematic diagram illustrating the system configured to enable interactive user control to define a visible volume being displayed in accordance with one embodiment of the invention. Here, display device 164 is in communication with computing device 168 which includes a controller 170. Camera 116 is configured to monitor user 172. That is, as user 172 moves, camera 166 tracks a location of the movement of the facial region 174 of the user as described above. A position of virtual camera 176 capturing a scene being presented is adjusted in response to the movement of the facial region, thereby modifying the scene presented through display device 164. For example, camera 116 may be configured to track a user's head located through comparison with a template which is stored in memory of computing device 168. Computing device 168 compares the template to video frame data captured through camera 116 as described with reference to FIG. 5. For example, if user 172 moves his head to peer around a corner, virtual camera 176 is adjusted to provide a view on display device 164 providing a scene of what is around the corner.
FIG. 12 is a flow chart diagram illustrating method operations for managing a visible volume display through a view port in accordance with one embodiment of the invention. The method initiates with method operation 180 where a head of the user is identified. For example, the head of the user may be initialized as described above in order for a template to be generated of the head of the user for use as described below. In one embodiment, the initialization of the head of the user captures a gray scale image of the head of the user and stores that image in memory. The visible volume may be a portion of a view-frustum that defines a scene for presentation as described with reference to FIG. 1. The method then advances to operation 182 where a location of the head of the user is tracked relative to a view port. For example, as a user tilts, rotates or moves their head from one location to another, the new location or orientation is tracked relative to a view port. As described above, a view port may be a television screen or any other suitable display screen. Additionally, the movement of the head of the user is captured through a camera that may or may not have depth capturing capability. The method then advances to operation 184 where a view-frustum is translated in accordance with a change in location of the head. Any number of translations of the view-frustum may be used as described above with reference to FIGS. 7 through 10. Additionally, while a template of a head is used for tracking purposes, one skilled in the art will appreciate that numerous other schemes may be incorporated in place of the template of the head. For example, any suitable marker-less scheme that determines where a user's head may be utilized. In one embodiment, the relative distance of the user's head to a view port is also tracked to adjust a scale associated with scene being presented.
In summary, the above described embodiments enable the tracking of a user's head in order to move a point of view to correlate to the head movement. The tracking is performed without markers, thereby freeing previous restrictions on a user, especially with reference to virtual reality applications. While exemplary applications have been provided for viewing control applications, it should be appreciated that numerous other suitable applications may use the embodiments described herein. For example, additional specific uses include: directing the view change in a 3D cut-scene, movie or replay; judging distances using the depth-cue provided by head-motion parallax, e.g., what distance to jump in a platformer game; a scary effect of restricting the normal field of view, e.g., showing the small area visible with a flashlight, and requiring the user to move their head to see more; and using head motion as a trigger for events related to the user's view, such as, triggering a warping effect when a user looks over a precipice to indicate vertigo, and triggering a game character's reaction when you look at something. In another embodiment, a sniper mode may be provided where the virtual camera is finely moved according to fine movements of the user's head, similar to peering through the crosshairs of a rifle when aiming the rifle.
It should be appreciated that the embodiments described herein may also apply to on-line gaming applications. That is, the embodiments described above may occur at a server that sends a video signal to multiple users over a distributed network, such as the Internet, to enable players at remote noisy locations to communicate with each other. It should be further appreciated that the embodiments described herein may be implemented through either a hardware or a software implementation. That is, the functional descriptions discussed above may be synthesized to define a microchip configured to perform the functional tasks for locating and tracking a user's head or facial region and translating the tracked movement to define a scene for presentation.
With the above embodiments in mind, it should be understood that the invention may employ various computer-implemented operations involving data stored in computer systems. These operations include operations requiring physical manipulation of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. Further, the manipulations performed are often referred to in terms, such as producing, identifying, determining, or comparing.
The above described invention may be practiced with other computer system configurations including hand-held devices, microprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers and the like. The invention may also be practiced in distributing computing environments where tasks are performed by remote processing devices that are linked through a communications network.
The invention can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable medium include hard drives, network attached storage (NAS), read-only memory, random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and other optical and non-optical data storage devices. The computer readable medium can also be distributed over a network coupled computer system so that the computer readable code is stored and executed in a distributed fashion.
Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims. In the claims, elements and/or steps do not imply any particular order of operation, unless explicitly stated in the claims.

## Claims

1. A method for processing interactive user control for a view of a scene displayed on a display device configured as a virtual window into the scene, comprising:
identifying a head of a user that is to interact with the scene;
displaying an initial view of the scene on the display device configured as the virtual window into the scene, the initial view of the scene comprising a view-frustum initially defined by a gaze projection of a location of the head through outer edges of the virtual window when the location of the head is substantially normal to about a center point of the virtual window;
tracking the identified head of the user during display of the scene, the tracking enabling detection of a change in location of the head of the user;
adjusting the view-frustum in accordance with the change in location of the head of the user, the adjusting of the view-frustum being in response to tracking a move in the location of the head away from normal relative to the center point of the virtual window, the adjusted view-frustum defined by an updated gaze projection of the changed location of the head through the outer edges of the virtual window, such that the view-frustum moves in a direction opposite to the move in the location of the head; and
displaying an updated view of the scene on the display device based on the adjusted view-frustum.

2. The method of claim 1, further comprising,
adjusting a scale of the scene according to a change in a distance of the head of the user from a depth capture device.

3. The method of claim 1, wherein the interaction with the scene by tracking movement of the head of the user is independent of user hand-held controls for interacting with the scene.

4. The method of claim 1, wherein the tracking includes,
identifying a search region within a frame of the user image data; and
comparing values within the search region to template values of a stored initial frame of image data.

5. The method of claim 1, wherein the method operation of tracking the identified head of the user during display of the scene includes,
tracking a facial portion of the head; and
matching image data associated with the facial portion to image data associated with a template of the facial portion.

6. The method of claim 1, wherein the adjusted view-frustum is such that a move in the location of the head towards a side of the virtual window provides for a wider angle of view through an opposite side of the virtual window.

7. A method for controlling a view of a scene, comprising:
detecting an initial location of a control object;
displaying an initial view of the scene on a display device configured as a virtual window into the scene, the initial view defined by a view-frustum based on a projection of the initial location of the control object through outer edges of the virtual window;
detecting movement of the control object to a new location;
displaying an updated view of the scene on the display device, the updated view defined by an updated view-frustum based on a projection of the new location of the control object through the outer edges of the virtual window.

8. The method of claim 7, wherein lateral movement of the control object in a given direction relative to the virtual window causes lateral movement of the updated view-frustum in the opposite direction.

9. The method of claim 7, wherein a change in distance of the control object from the virtual window causes a change in scale in the updated view.

10. The method of claim 7, wherein the updated view-frustum is such that a move in the location of the head towards a side of the virtual window provides for a wider angle of view through an opposite side of the virtual window.

11. The method of claim 7, wherein the control object is a head of a user.

12. The method of claim 11, wherein detecting the initial location includes detecting a facial region of the head of the user.

13. A method for displaying a view of a virtual environment on a display device, the method comprising:
identifying a control object in front of the display device;
detecting an initial location of the control object;
correlating the initial location of the control object to an initial virtual location of a virtual viewpoint in the virtual environment;
displaying an initial view of the virtual environment on the display device, the initial view of the virtual environment determined by a view frustum in the virtual environment defined by a projection of the virtual viewpoint through a virtual viewport in the virtual environment;
tracking a movement of the control object to a new location;
moving the virtual viewpoint to a new virtual location in accordance with the tracked movement of the control object, such that the movement of the virtual viewpoint relative to the virtual viewport is in a same relative direction as the movement of the control object relative to the display device;
displaying an updated view of the virtual environment on the display device, the updated view of the virtual environment determined by an updated view frustum in the virtual environment defined by an updated projection of the virtual viewpoint at the new virtual location through the virtual viewport.

14. The method of claim 13, wherein identifying the control object includes capturing an initial frame of image data including the control object, and identifying the control object within the initial frame of image data.

15. The method of claim 14, wherein detecting the initial location of the control object includes,
generating a template of the control object based on the captured initial frame of image data,
capturing successive frames of image data,
determining a search region within the successive frames of image data, and
searching within the search region for a match to the template of the control object.

16. The method of claim 15, wherein tracking the movement of the control object includes,
repeating the capturing successive frames of image data, determining a search region, and searching within the search region.

17. The method of claim 13, wherein the moving the virtual viewpoint in accordance with the tracked movement of the control object is such that the movement of the virtual viewpoint relative to the virtual viewport has a greater scale of movement in the virtual environment compared to the movement of the control object relative to the display device.

18. The method of claim 13, wherein the control object is a head of a user.