U.S. patent application number 11/225726 was filed with the patent office on 2006-01-12 for pointing device and cursor for use in intelligent computing environments.
This patent application is currently assigned to Microsoft Corporation. Invention is credited to Hubert Pham, Andrew Wilson.
Application Number | 20060007142 11/225726 |
Document ID | / |
Family ID | 33511298 |
Filed Date | 2006-01-12 |
United States Patent
Application |
20060007142 |
Kind Code |
A1 |
Wilson; Andrew ; et
al. |
January 12, 2006 |
Pointing device and cursor for use in intelligent computing
environments
Abstract
A system and process for directing a laser beam within a space
is presented. The system includes a pointing device which
periodically outputs orientation data indicative of the direction
it is pointing and a cursor device which projects a laser beam. The
orientation data is used to compute the direction the pointing
device is pointing in terms of yaw and pitch angles. The laser beam
is directed to locations in the space relative to the amount of
movement of the pointing device. In an absolute mode, the pointed
device and the laser beam of the cursor device are pointed at the
same location in the space, whereas in a relative mode, the
pointing device does not point at the same location as the laser
beam. The position of the laser can be used to select a variety of
hardware devices known to be in a room for future control
actions.
Inventors: |
Wilson; Andrew; (Seattle,
WA) ; Pham; Hubert; (Cupertino, CA) |
Correspondence
Address: |
MICROSOFT CORPORATION;C/O LYON & HARR, LLP
300 ESPLANADE DRIVE
SUITE 800
OXNARD
CA
93036
US
|
Assignee: |
Microsoft Corporation
Redmond
WA
|
Family ID: |
33511298 |
Appl. No.: |
11/225726 |
Filed: |
September 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10461646 |
Jun 13, 2003 |
|
|
|
11225726 |
Sep 13, 2005 |
|
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Current U.S.
Class: |
345/158 |
Current CPC
Class: |
G09G 5/08 20130101; G06F
3/0346 20130101 |
Class at
Publication: |
345/158 |
International
Class: |
G09G 5/08 20060101
G09G005/08 |
Claims
1. A system for directing a laser beam within a space to act as a
cursor, comprising: a pointing device which periodically outputs
orientation data indicative of the direction it is pointing; a
cursor device which projects a laser beam at a location in the
space determined by the direction the pointing device is pointing;
and a computing device which receives the orientation data output
by the pointing device and which is in communication with the
cursor device to control where the laser beam is projected, and
which computes the direction the pointing device is pointing from
the received orientation data and uses this orientation data to
direct the laser beam to a particular location in the space.
2. The system of claim 1, wherein a user by manipulating the
pointing device can shine the laser beam on any location desired in
the space that is within line of sight of the cursor device.
3. The system of claim 1, wherein the cursor device comprises: a
platform; a laser which when activated projects a laser beam into
the space; and a pair of servos connected between the platform and
the laser, wherein a first of the servos is configured so as to
move the laser in a manner that controls the yaw direction of the
laser beam and the other of the servos is configured so as to move
the laser in a manner that controls the pitch direction of the
laser beam.
4. The system of claim 3, wherein the pointing device is a
hand-held unit resembling a wand and said orientation data
represent the orientation of the wand, and wherein the computing
device uses the orientation data to direct the laser beam to a
particular location in the space by computing pitch and yaw angles
that the laser is to be moved to in view of the wand orientation
and providing these angle to the cursor device.
5. The system of claim 4, wherein the pitch and yaw angles are
provided as angle data to the cursor device which converts the data
to motor commands which are applied to the servos to move the laser
to the pitch and yaw angle specified in the angle data.
6. The system of claim 4, wherein the computing device converts the
pitch and yaw angles to motor commands and provides these commands
to the cursor device which applies them to the servos to move the
laser to the pitch and yaw angle specified.
7. The system of claim 3, wherein the cursor device is mounted in a
location within the space, and the servos have ranges of motion,
which allows shining the laser beam on a plurality of locations of
interest without interference.
8. The system of claim 7, wherein the space is a room, and the
cursor device is mounted on a ceiling of the room.
9. The system of claim 1, wherein the computing device is in
communication with the cursor device via a wired connection.
10. The system of claim 1, wherein the computing device is in
communication with the cursor device via a wireless connection.
11. The system of claim 1, wherein the computing device further
directs the laser beam to a prescribed home location whenever there
has been no change in the orientation data received for a
pre-established period of time.
12. The system of claim 1, wherein the computing device further
directs the laser beam to move in prescribed pattern whenever
receiving changed orientation data after a prescribed period of
time in which there had been no change in the orientation data
received, wherein said pattern is designed to attract a user's
attention to the location of the laser beam.
13. The system of claim 1, wherein the computing device further
accesses a model of the location of objects within the space and
directs the laser beam to move to shine on a modeled object in
response to a user-input command to point the laser beam at that
object.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of a prior application
entitled "A POINTING DEVICE AND CURSOR FOR USE IN INTELLIGENT
COMPUTING ENVIRONMENTS" which was assigned Ser. No. 10/461,646 and
filed Jun. 13, 2003."
BACKGROUND
[0002] 1. Technical Field
[0003] The invention is related to cursor devices, and more
particularly to a system and process for directing a laser beam
within a space to act as a cursor in an intelligent computing
environment.
[0004] 2. Background Art
[0005] Ubiquitous (i.e., intelligent) computing promises to blur
the boundaries between traditional desktop computing and the
everyday physical world. A popular vision of tomorrow's computing
pushes computational abilities into everyday objects, each
participating in a complex and powerful integrated intelligent
environment. Tomorrow's home and office environments, for example,
may include a variety of small and large networked displays and
smart controllable devices. For instance, the modern living room
typically features a television, amplifier, DVD player, lights,
computers, and so on. In the near future, these devices will become
more inter-connected, more numerous and more specialized as part of
an increasingly complex and powerful integrated intelligent
environment.
[0006] This migration away from the desktop and "into the walls"
presents several challenges for user interface design. For example,
how does the user of tomorrow's intelligent environment select one
of many devices? Today, this problem is most often addressed by
maintaining a separate interface, such as an IR remote control, for
each device.
[0007] Tomorrow's intelligent environment presents the opportunity
to present a single intelligent user interface (UI) to control many
such devices when they are networked. This UI device should provide
the user a natural interaction with intelligent environments. For
example, people have become quite accustomed to pointing at a piece
of electronic equipment that they want to control, owing to the
extensive use of IR remote controls. It has become almost second
nature for a person in a modern environment to point at the object
he or she wants to control, even when it is not necessary. Take the
small radio frequency (RF) key fobs that are used to lock and
unlock most automobiles in the past few years as an example.
Inevitably, a driver will point the free end of the key fob toward
the car while pressing the lock or unlock button. This is done even
though the driver could just have well pointed the fob away from
the car, or even pressed the button while still in his or her
pocket, owing to the RF nature of the device. Thus, a single UI
device, which is pointed at electronic components or some extension
thereof (e.g., a wall switch to control lighting in a room) to
control these components, would represent an example of the
aforementioned natural interaction that is desirable for such a
device.
[0008] There are some so-called "universal" remote controls on the
market that are preprogrammed with the known control protocols of a
litany of electronic components, or which are designed to learn the
command protocol of an electronic component. Typically, such
devices are limited to one transmission scheme, such as IR or RF,
and so can control only electronic components operating on that
scheme. However, it would be desirable if the electronic components
themselves were passive in that they do not have to receive and
process commands from the UI device directly, but would instead
rely solely on control inputs from the aforementioned network. In
this way, the UI device does not have to differentiate among
various electronic components, say by recognizing the component in
some manner and transmitting commands using some encoding scheme
applicable only to that component, as is the case with existing
universal remote controls.
[0009] Of course, a common control protocol could be implemented
such that all the controllable electronic components within an
environment use the same control protocol and transmission scheme.
However, this would require all the electronic components to be
customized to the protocol and transmission scheme, or to be
modified to recognize the protocol and scheme. This could add
considerably to the cost of a "single UI-controlled" environment.
It would be much more desirable if the UI device could be used to
control any networked group of new or existing electronic
components regardless of remote control protocols or transmission
schemes the components were intended to operate under.
[0010] It is noted that in the remainder of this specification, the
description refers to various individual publications identified by
a numeric designator contained within a pair of brackets. For
example, such a reference may be identified by reciting, "reference
[1]" or simply "[1]". A listing of references including the
publications corresponding to each designator can be found at the
end of the Detailed Description section.
SUMMARY
[0011] The present invention involves a system and process for
directing a laser beam within a space to act as a cursor. This
cursor device, which will be referred to as the WorldCursor, is
analogous to the mouse and cursor used in traditional graphic user
interfaces. Namely, a user may select and interact with a physical
device by positioning the cursor on the device and clicking.
However, the WorldCursor goes much further. It is a solution to
providing a natural, expressive interface for interaction in
ubiquitous computing environments, where it is often a requirement
to interact with devices beyond the desktop, and often in scenarios
in which the traditional mouse and keyboard are inappropriate or
unavailable. For example, the WorldCursor allows the user to point
at and select items within a room, much as a mouse allows a user to
point at objects on a computer display.
[0012] The WorldCursor device itself includes a small platform that
is typically installed on the ceiling. It has two small servo
motors of the kind used in radio-controlled airplanes, and a laser,
such as the red lasers used in laser pointing devices currently
employed to give presentations. The first of the servos is
configured so as to move the laser in a manner that controls the
yaw direction of the laser beam and the other servo is configured
so as to move the laser in a manner that controls the pitch
direction of the laser beam. Thus, under computer control, the
motors may be steered to point the laser almost anywhere in the
room.
[0013] One embodiment of the system employs control inputs from a
conventional device such as a computer mouse, trackball, gamepad,
or the like to dictate the movement of the WorldCursor laser. In
this embodiment the computer controlling the movement of the laser
receives movement control commands generated by one of the
aforementioned movement control devices which specifies the
direction the laser beam is to be pointed. The computer then
provides commands to the WorldCursor device that direct the laser
beam to move about the space as specified by the movement control
commands.
[0014] In another embodiment of the WorldCursor system, a pointing
device is included that periodically outputs orientation data
indicative of the direction it is pointing. In addition, the
WorldCursor and pointing devices are both in communication with the
aforementioned computer which runs a program that receives the
orientation data output by the pointing device and computes the
direction the pointing device is pointing from the received
orientation data in terms of yaw and pitch angles. The program then
directs the laser beam generated by the WorldCursor to a particular
location in the space as determined by the direction the pointing
device is pointing.
[0015] The present system can further be employed to implement a
process for selecting an object within a space. In general, this
involves a user causing the laser beam to shine on a selectable
object by manipulating the pointing device and then using the
device to select the object.
[0016] In tested versions of the WorldCursor system, the pointing
device took the form of a hardware device referred to as the XWand,
which is the subject of a co-pending U.S. patent application
entitled "A SYSTEM AND PROCESS FOR SELECTING OBJECTS IN A
UBIQUITOUS COMPUTING ENVIRONMENT" which was filed on May 31, 2002
and issued Ser. No. 10/160,692. The XWand is a hardware device and
software system which allows the user to point at and operate
various objects in the room. For example, the user may point the
XWand at a known light, push a button on the XWand, and the light
may turn on.
[0017] More particularly, the XWand device contains onboard sensors
to support the computation of orientation information and gesture
recognition. These sensors include a pair of accelerometers. When
motionless, these accelerometers sense the acceleration due to
gravity, and each can be used to sense either the pitch or roll
angle of the device. Another of the sensors is a 3-axis
magnetoresistive permalloy magnetometer. This senses the direction
of the Earth's magnetic field in 3 dimensions, and can be used to
compute the yaw angle of the device. The values from the
accelerometer and magnetometer are relayed to a host computer by
radio link. These values are combined to find the absolute
orientation of the device with respect to the room. This
orientation is updated in real time at a rate of about 50 Hz, and
is accurate to a few degrees in each of yaw, pitch and roll
axes.
[0018] The XWand system determines which device the user is
pointing at by combining the orientation and 3-D position of the
XWand with a 3-D model of the room and the devices within it.
Orientation of the XWand is determined as explained above from the
onboard sensors, while XWand position is determined with stereo
computer vision. The 3-D model of the room and devices is entered
into the system by pointing with the XWand itself in a special
training mode. With the orientation, position and model of the
room, it is easy to determine which if any object in the world
model the XWand is pointing at. Audio feedback is provided to
indicate to the user that the object is known to the system and can
be controlled by the XWand, but in general little feedback is
necessary since the pointing is absolute in nature.
[0019] The WorldCursor improves upon the XWand system by not
requiring an external position sensing technology. There are a
number of drawbacks to using the external computer vision system.
First, the system involves installing multiple cameras in the room.
Part of the installation requires a rather precise calibration of
the cameras against the geometry of the room. Secondly, the
acquisition of the geometric model of the room and its devices
requires a further calibration phase. Thirdly, computer vision
techniques rely on having a clear line of sight to the device.
Although this can be alleviated somewhat by installing more
cameras, this approach can be prohibitively expensive and complex
to install. Finally, installation of cameras inevitably raises
privacy objections. The combination of the WorldCursor with the
XWand eliminates the need for the external camera setup.
[0020] In a first mode of operation of the WorldCursor, the laser
beam is directed in an absolute pointing mode where the location
that the laser beam is pointed is substantially the same location
that the pointing device (e.g., the XWand) is pointing. The process
that accomplishes this absolute pointing mode involves first
computing a set of offset angles for the laser made up of
respective yaw and pitch angles that define the angular distance
between the origin of a spherical coordinate system associated with
the WorldCursor and a prescribed origin of the spherical coordinate
system for the space. Likewise, a set of offset angles for the
pointing device are computed that represent the respective yaw and
pitch angles defining the angular distance between the origin of a
spherical coordinate system associated with the pointing device and
the prescribed origin of the spherical coordinate system for the
space. Next, aligning pitch and yaw angles are computed that define
how far the laser must be moved in order to point the laser beam at
the approximately the same point in the space that the pointing
device is pointing. The aligning pitch angle is defined as the sum
of the offset pitch angle of the laser and the computed pitch angle
of the pointing device less its offset pitch angle, and the
aligning yaw angle is defined as the sum of the offset yaw angle of
the laser and the computed yaw angle of the pointing device less
its offset yaw angle. Once the aligning angles are computed, the
laser is moved to these angles so as to point the laser beam at
approximately the same location in the space that the pointing
device is pointing.
[0021] It is noted that the offset angles computed above are
initial angle values which are typically only valid for a part of
the space. If the pointing device and WorldCursor are very close to
each other, the angle values would remain valid no matter where the
pointing device is directed. However, this will not be the usual
case because the WorldCursor will typically be mounted on the
ceiling of the space. If the pointing device is pointed outside the
part of the space where the initial offset values are valid, the
correspondence between the location the pointing device is pointing
and the location the laser beam is shining is lost. Thus, the
correspondence must be maintained in order to continue operating in
the absolute pointing mode. If the user desires that the laser spot
appear where the pointing device is pointed, or if the user would
like to have the spot at least be in the field of the view of the
user as they use the pointing device, a "clutching" procedure can
be employed. To clutch the WorldCursor, the user momentarily
activates a switch on the pointing device (e.g., pushes its button)
whose state is included in each orientation data message sent by
the pointing device. When the switch is activated, the laser stops
moving with the pointing device and the user then reorients the
pointing device, lining it up so that it points directly at the
laser spot. When ready to resume WorldCursor control, the user
reactivates the switch and the laser spot beings moving again in
correspondence with the pointing device.
[0022] It is noted that the user could also orient the pointing
device during a clutching operation such that it does not point at
the laser spot. If so, this creates a relative pointing condition
where the laser mimics the movements of the pointing device (e.g.,
moving the XWand left or right produces the same direction of
movement in the laser beam), but not in correspondence with it. It
is not clear if users require even approximate correspondence for
successful use of the device. Experience with computer mice
suggests that this is not necessary. Thus, this relative pointing
mode may be of no consequence to the user, or even preferred.
[0023] One desirable feature of this system is that it does not
require the 3D position of the pointing device to be known, nor a
3D model of the room or of the devices within the room. Active
devices such as lights, displays, etc., need only be known to the
system by their spherical (yaw, pitch) coordinates which are used
to set the position of the two motors on the WorldCursor device.
This can be accomplished using outside methods or by using the
WorldCursor to generate a model of the space. In general, a model
of the space can be accomplished by pointing the laser beam at an
object in the space and recording the pitch and yaw angles of the
laser as its location. The user can then enter its extent in the
form of a radius defining a circle that is used represent the
object. Alternately, objects, such as walls, can be represented by
polygons. In this case, the laser beam is made to shine on each
vertex of the polygon representing an object and the spherical
coordinates of the laser are recorded for each point. In either the
circle or polygon cases, the user can also enter information about
the object, such as its identity that can be used to control the
object once it is selected.
[0024] Once the space has been modeled as described above, it is
possible to determine whether the laser beam is shining on a
modeled object so that it can be selected for future control
actions. In the case of a circle representing an object in the
space, the laser beam is considered to be on the object if the
WorldCursor's laser pitch and yaw angles are within the specified
radius of the circle. In the case of a polygon representing an
object, a conventional point-in-polygon technique can be use to
determine if the laser beam is on the object. Still further, it is
possible to determine the point on a polygon representing an object
in the space that the laser beam is shining on using a transform
that maps the pitch and yaw angle coordinates of the laser to
orthogonal coordinates of the polygon.
[0025] It is even possible to use the WorldCursor and the pointing
device to generate a 3D model of the space where objects are
modeled as 3D points with extents or as polygons. More
particularly, given the 3D location of the pointing device and its
orientation in combination with the 3D location of the WorldCursor
and the orientation of its laser (which is assumed to be directed
at the same point as the pointing device), then, it is possible to
solve for unknown 3D point coordinates for any location the laser
is shining on.
[0026] A procedure that can be employed to establish and maintain a
reasonable correspondence between the pointing device and
WorldCursor without clutching involves exploiting the geometry of
the space in which the WorldCursor system is operating. If the
geometry of the room is known in terms of a 3D coordinate system,
whether obtained from an outside source or generated as described
above, as well as the 3D positions of the WorldCursor, and the
pointing device, then the WorldCursor may be controlled such that
the pointing device always points directly at the laser spot. It is
noted that a reasonable correspondence between the laser beam and
the pointing device can be maintained even if the 3D location of
the pointing device is not known absolutely but is assumed to be at
a location that it generally can be found.
[0027] However, if the approximate 3D geometry of the space is
known or generated as described above, then there is also a
technique to compute the precise 3D position of the pointing device
(assuming it is unknown to the system) by exploiting the above
mentioned clutching operation. In this way a more precise
correspondence can be maintained as explained above. If the user is
clutching so that the pointing device points at the laser spot,
each of these clutching operations provide information that can be
related mathematically to the 3D position of the pointing device.
After a few such clutching operations, it is possible to compute
the 3D position of the device. The advantage in doing so is that no
more clutching operations are necessary to maintain pointing
device-WorldCursor correspondence, so long as the actual position
of the pointing device does not change dramatically. It is noted
that this online calibration requires no more clutching operations
than the system which does not exploit the approximate room
geometry. Further in the long run it requires fewer clutching
operations if the user does not move about the room often.
[0028] In addition to the just described benefits, other advantages
of the present invention will become apparent from the detailed
description which follows hereinafter when taken in conjunction
with the drawing figures which accompany it.
DESCRIPTION OF THE DRAWINGS
[0029] The specific features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying drawings
where:
[0030] FIG. 1 is a diagram depicting a general purpose computing
device constituting an exemplary system for implementing the
present invention.
[0031] FIG. 2 is a diagram depicting a system for directing a laser
beam within a space to act as a cursor according to the present
invention.
[0032] FIG. 3 is an image depicting one prototype version of the
WorldCursor device employed in the system of FIG. 2.
[0033] FIGS. 4A and B are a flow chart diagramming a process for
modeling objects in a space using the WorldCursor system of FIG. 2,
wherein the objects are modeled as circles using spherical
coordinates.
[0034] FIGS. 5A and B are a flow chart diagramming a process for
modeling objects in a space using the WorldCursor system of FIG. 2,
wherein the objects are modeled as polygons using spherical
coordinates.
[0035] FIG. 6 is a flow chart diagramming a process for
automatically switching between slow and fast filters to adjust the
relative cursor movement-to-pointing device movement speed.
[0036] FIGS. 7A and B are a flow chart diagramming a clutching
process for aligning the WorldCursor laser beam and XWand by making
the laser beam shine on approximately the same location in the
space that the XWand is pointed.
[0037] FIG. 8 is a flow chart diagramming one version of a process
for establishing and maintain a reasonable alignment between the
pointing device and WorldCursor involving computing the 3D location
of the pointing device and using this along with a knowledge of the
rest of the geometry of the space to compute the pitch and yaw
angles that when applied to the WorldCursor laser will make it
point at approximately the same location as the pointing
device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] In the following description of the preferred embodiments of
the present invention, reference is made to the accompanying
drawings which form a part hereof, and in which is shown by way of
illustration specific embodiments in which the invention may be
practiced. It is understood that other embodiments may be utilized
and structural changes may be made without departing from the scope
of the present invention.
1.0 The Computing Environment
[0039] Before providing a description of the preferred embodiments
of the present invention, a brief, general description of a
suitable computing environment in which the invention may be
implemented will be described. FIG. 1 illustrates an example of a
suitable computing system environment 100. The computing system
environment 100 is only one example of a suitable computing
environment and is not intended to suggest any limitation as to the
scope of use or functionality of the invention. Neither should the
computing environment 100 be interpreted as having any dependency
or requirement relating to any one or combination of components
illustrated in the exemplary operating environment 100.
[0040] The invention is operational with numerous other general
purpose or special purpose computing system environments or
configurations. Examples of well known computing systems,
environments, and/or configurations that may be suitable for use
with the invention include, but are not limited to, personal
computers, server computers, hand-held or laptop devices,
multiprocessor systems, microprocessor-based systems, set top
boxes, programmable consumer electronics, network PCs,
minicomputers, mainframe computers, distributed computing
environments that include any of the above systems or devices, and
the like.
[0041] The invention may be described in the general context of
computer-executable instructions, such as program modules, being
executed by a computer. Generally, program modules include
routines, programs, objects, components, data structures, etc. that
perform particular tasks or implement particular abstract data
types. The invention may also be practiced in distributed computing
environments where tasks are performed by remote processing devices
that are linked through a communications network. In a distributed
computing environment, program modules may be located in both local
and remote computer storage media including memory storage
devices.
[0042] With reference to FIG. 1, an exemplary system for
implementing the invention includes a general purpose computing
device in the form of a computer 110. Components of computer 110
may include, but are not limited to, a processing unit 120, a
system memory 130, and a system bus 121 that couples various system
components including the system memory to the processing unit 120.
The system bus 121 may be any of several types of bus structures
including a memory bus or memory controller, a peripheral bus, and
a local bus using any of a variety of bus architectures. By way of
example, and not limitation, such architectures include Industry
Standard Architecture (ISA) bus, Micro Channel Architecture (MCA)
bus, Enhanced ISA (EISA) bus, Video Electronics Standards
Association (VESA) local bus, and Peripheral Component Interconnect
(PCI) bus also known as Mezzanine bus.
[0043] Computer 110 typically includes a variety of computer
readable media. Computer readable media can be any available media
that can be accessed by computer 110 and includes both volatile and
nonvolatile media, removable and non-removable media. By way of
example, and not limitation, computer readable media may comprise
computer storage media and communication media. Computer storage
media includes both volatile and nonvolatile, removable and
non-removable media implemented in any method or technology for
storage of information such as computer readable instructions, data
structures, program modules or other data. Computer storage media
includes, but is not limited to, RAM, ROM, EEPROM, flash memory or
other memory technology, CD-ROM, digital versatile disks (DVD) or
other optical disk storage, magnetic cassettes, magnetic tape,
magnetic disk storage or other magnetic storage devices, or any
other medium which can be used to store the desired information and
which can be accessed by computer 110. Communication media
typically embodies computer readable instructions, data structures,
program modules or other data in a modulated data signal such as a
carrier wave or other transport mechanism and includes any
information delivery media. The term "modulated data signal" means
a signal that has one or more of its characteristics set or changed
in such a manner as to encode information in the signal. By way of
example, and not limitation, communication media includes wired
media such as a wired network or direct-wired connection, and
wireless media such as acoustic, RF, infrared and other wireless
media. Combinations of the any of the above should also be included
within the scope of computer readable media.
[0044] The system memory 130 includes computer storage media in the
form of volatile and/or nonvolatile memory such as read only memory
(ROM) 131 and random access memory (RAM) 132. A basic input/output
system 133 (BIOS), containing the basic routines that help to
transfer information between elements within computer 110, such as
during start-up, is typically stored in ROM 131. RAM 132 typically
contains data and/or program modules that are immediately
accessible to and/or presently being operated on by processing unit
120. By way of example, and not limitation, FIG. 1 illustrates
operating system 134, application programs 135, other program
modules 136, and program data 137.
[0045] The computer 110 may also include other
removable/non-removable, volatile/nonvolatile computer storage
media. By way of example only, FIG. 1 illustrates a hard disk drive
141 that reads from or writes to non-removable, nonvolatile
magnetic media, a magnetic disk drive 151 that reads from or writes
to a removable, nonvolatile magnetic disk 152, and an optical disk
drive 155 that reads from or writes to a removable, nonvolatile
optical disk 156 such as a CD ROM or other optical media. Other
removable/non-removable, volatile/nonvolatile computer storage
media that can be used in the exemplary operating environment
include, but are not limited to, magnetic tape cassettes, flash
memory cards, digital versatile disks, digital video tape, solid
state RAM, solid state ROM, and the like. The hard disk drive 141
is typically connected to the system bus 121 through an
non-removable memory interface such as interface 140, and magnetic
disk drive 151 and optical disk drive 155 are typically connected
to the system bus 121 by a removable memory interface, such as
interface 150.
[0046] The drives and their associated computer storage media
discussed above and illustrated in FIG. 1, provide storage of
computer readable instructions, data structures, program modules
and other data for the computer 110. In FIG. 1, for example, hard
disk drive 141 is illustrated as storing operating system 144,
application programs 145, other program modules 146, and program
data 147. Note that these components can either be the same as or
different from operating system 134, application programs 135,
other program modules 136, and program data 137. Operating system
144, application programs 145, other program modules 146, and
program data 147 are given different numbers here to illustrate
that, at a minimum, they are different copies. A user may enter
commands and information into the computer 110 through input
devices such as a keyboard 162 and pointing device 161, commonly
referred to as a mouse, trackball or touch pad. Other input devices
(not shown) may include a microphone, joystick, game pad, satellite
dish, scanner, or the like. These and other input devices are often
connected to the processing unit 120 through a user input interface
160 that is coupled to the system bus 121, but may be connected by
other interface and bus structures, such as a parallel port, game
port or a universal serial bus (USB). A monitor 191 or other type
of display device is also connected to the system bus 121 via an
interface, such as a video interface 190. In addition to the
monitor, computers may also include other peripheral output devices
such as speakers 197 and printer 196, which may be connected
through an output peripheral interface 195. Of particular
significance to the present invention, a camera 163 (such as a
digital/electronic still or video camera, or film/photographic
scanner) capable of capturing a sequence of images 164 can also be
included as an input device to the personal computer 110. Further,
while just one camera is depicted, multiple cameras could be
included as input devices to the personal computer 110. The images
164 from the one or more cameras are input into the computer 110
via an appropriate camera interface 165. This interface 165 is
connected to the system bus 121, thereby allowing the images to be
routed to and stored in the RAM 132, or one of the other data
storage devices associated with the computer 110. However, it is
noted that image data can be input into the computer 110 from any
of the aforementioned computer-readable media as well, without
requiring the use of the camera 163.
[0047] The computer 110 may operate in a networked environment
using logical connections to one or more remote computers, such as
a remote computer 180. The remote computer 180 may be a personal
computer, a server, a router, a network PC, a peer device or other
common network node, and typically includes many or all of the
elements described above relative to the computer 110, although
only a memory storage device 181 has been illustrated in FIG. 1.
The logical connections depicted in FIG. 1 include a local area
network (LAN) 171 and a wide area network (WAN) 173, but may also
include other networks. Such networking environments are
commonplace in offices, enterprise-wide computer networks,
intranets and the Internet.
[0048] When used in a LAN networking environment, the computer 110
is connected to the LAN 171 through a network interface or adapter
170. When used in a WAN networking environment, the computer 110
typically includes a modem 172 or other means for establishing
communications over the WAN 173, such as the Internet. The modem
172, which may be internal or external, may be connected to the
system bus 121 via the user input interface 160, or other
appropriate mechanism. In a networked environment, program modules
depicted relative to the computer 110, or portions thereof, may be
stored in the remote memory storage device. By way of example, and
not limitation, FIG. 1 illustrates remote application programs 185
as residing on memory device 181.
[0049] It will be appreciated that the network connections shown
are exemplary and other means of establishing a communications link
between the computers may be used.
[0050] The exemplary operating environment having now been
discussed, the remaining part of this description section will be
devoted to a description of the program modules embodying the
invention.
2.0 The XWand System
[0051] In a co-pending U.S. patent application entitled "A SYSTEM
AND PROCESS FOR SELECTING OBJECTS IN A UBIQUITOUS COMPUTING
ENVIRONMENT" which was filed on May 31, 2002 and issued Ser. No.
10/160,692, a system and process was introduced that provides a
remote control UI device that is capable of controlling a group of
networked electronic components. More particularly, the UI device,
which will herein be referred to as the XWand, is able to control
the electronic components without having to directly differentiate
among the components or employ a myriad of different control
protocols and transmission schemes. And in order to provide a
natural interaction experience, the present system is operated by
having the user point at the electronic component (or an extension
thereof that he or she wishes to control. In particular, the XWand
provides a remote control UI device that can be simply pointed at
objects in an ubiquitous computing environment that are associated
in some way with controllable, networked electronic components, so
as to select that object for controlling via the network. This can
for example involve pointing the UI device at a wall switch and
pressing a button on the device to turn a light operated by the
switch on or off. The idea is to have a UI device so simple that it
requires no particular instruction or special knowledge on the part
of the user.
[0052] The XWand system includes the aforementioned remote control
UI device in the form of a wireless RF pointer, which includes a
radio frequency (RF) transceiver and various orientation sensors.
The outputs of the sensors are periodically packaged as orientation
messages and transmitted using the RF transceiver to a base
station, which also has a RF transceiver to receive the orientation
messages transmitted by the pointer. There is also a pair of
digital video cameras each of which is located so as to capture
images of the environment in which the pointer is operating from
different viewpoints. A computer, such as a PC, is connected to the
base station and the video cameras. Orientation messages received
by the base station from the pointer are forwarded to the computer,
as are images captured by the video cameras. The computer is
employed to compute the orientation and location of the pointer
using the orientation messages and captured images. The orientation
and location of the pointer is in turn used to determine if the
pointer is being pointed at an object in the environment that is
controllable by the computer via a network connection. If it is,
the object is selected.
[0053] The pointer specifically includes a case having a shape with
a defined pointing end, a microcontroller, the aforementioned RF
transceiver and orientation sensors which are connected to the
microcontroller, and a power supply (e.g., batteries) for powering
these electronic components. In the tested versions of the pointer,
the orientation sensors included at least, an accelerometer that
provides separate x-axis and y-axis orientation signals, and a
magnetometer that provides separate x-axis, y-axis and z-axis
orientation signals. These electronics were housed in a case that
resembled a wand--hence the XWand name.
[0054] The pointer's microcontroller packages and transmits
orientation messages at a prescribed rate. While the
microcontroller could be programmed to accomplish this task by
itself, a command-response protocol was employed in tested versions
of the system. This entailed the computer periodically instructing
the pointer's microcontroller to package and transmit an
orientation message by causing the base station to transmit a
request for the message to the pointer at the prescribed rate. This
prescribed rate could for example be approximately 50 times per
second as it was in tested versions of the system.
[0055] As indicated previously, the orientation messages generated
by the pointer include the outputs of the sensors. To this end, the
pointer's microcontroller periodically reads and stores the outputs
of the orientation sensors. Whenever a request for an orientation
message is received (or it is time to generate such a message if
the pointer is programmed to do so without a request), the
microcontroller includes the last-read outputs from the
accelerometer and magnetometer in the orientation message.
[0056] The pointer also includes other electronic components such
as a user activated switch or button, and a series of light
emitting diodes (LEDs). The user-activated switch, which is also
connected to the microcontroller, is employed for the purpose of
instructing the computer to implement a particular function. To
this end, the state of the switch in regard to whether it is
activated or deactivated at the time an orientation message is
packaged is included in that message for transmission to the
computer. The series of LEDs includes a pair of
differently-colored, visible spectrum LEDs, which are connected to
the microcontroller, and which are visible from the outside of the
pointer's case when lit. These LEDs are used to provide status or
feedback information to the user, and are controlled via
instructions transmitted to the pointer by the computer.
[0057] The foregoing system is used to select an object by having
the user simply point to the object with the pointer. This entails
the computer first inputting the orientation messages transmitted
by the pointer. For each message received, the computer derives the
orientation of the pointer in relation to a predefined coordinate
system of the environment in which the pointer is operating using
the orientation sensor readings contained in the message. In
addition, the video output from the video cameras is used to
ascertain the location of the pointer at a time substantially
contemporaneous with the generation of the orientation message and
in terms of the predefined coordinate system. Once the orientation
and location of the pointer are computed, they are used to
determine whether the pointer is being pointed at an object in the
environment that is controllable by the computer. If so, then that
object is selected for future control actions.
[0058] The computer derives the orientation of the pointer from the
orientation sensor readings contained in the orientation message as
follows. First, the accelerometer and magnetometer output values
contained in the orientation message are normalized. Angles
defining the pitch of the pointer about the x-axis and the roll of
the device about the y-axis are computed from the normalized
outputs of the accelerometer. The normalized magnetometer output
values are then refined using these pitch and roll angles. Next,
previously established correction factors for each axis of the
magnetometer, which relate the magnetometer outputs to the
predefined coordinate system of the environment, are applied to the
associated refined and normalized outputs of the magnetometer. The
yaw angle of the pointer about the z axis is computed using the
refined magnetometer output values. The computed pitch, roll and
yaw angles are then tentatively designated as defining the
orientation of the pointer at the time the orientation message was
generated. It is next determined whether the pointer was in a
right-side up or up-side down position at the time the orientation
message was generated. If the pointer was in the right-side up
position, the previously computed pitch, roll and yaw angles are
designated as the defining the finalized orientation of the
pointer. However, if it is determined that the pointer was in the
up-side down position at the time the orientation message was
generated, the tentatively designated roll angle is corrected
accordingly, and then the pitch, yaw and modified roll angle are
designated as defining the finalized orientation of the pointer. In
the foregoing description, it is assumed that the accelerometer and
magnetometer of the pointer are oriented such that their respective
first axis corresponds to the x-axis which is directed laterally to
a pointing axis of the pointer and their respective second axis
corresponds to the y-axis which is directed along the pointing axis
of the pointer, and the third axis of the magnetometer correspond
to the z-axis which is directed vertically upward when the pointer
is positioned right-side up with the x and y axes lying in a
horizontal plane.
[0059] The computer derives the location of the pointer from the
video output of the video cameras as follows. There is an infrared
(IR) LED connected to the microcontroller that is able to emit IR
light outside the pointer's case when lit. The microcontroller
causes the IR LEDs to flash. In addition, the aforementioned pair
of digital video cameras each have an IR pass filter that results
in the video image frames capturing only IR light emitted or
reflected in the environment toward the camera, including the
flashing from the pointer's IR LED which appears as a bright spot
in the video image frames. The microcontroller causes the IR LED to
flash at a prescribed rate that is approximately one-half the frame
rate of the video cameras. This results in only one of each pair of
image frames produced by a camera having the IR LED flashes
depicted in it. This allows each pair of frames produced by a
camera to be subtracted to produce a difference image, which
depicts for the most part only the IR emissions and reflections
directed toward the camera which appear in one or the other of the
pair of frames but not both (such as the flash from the IR LED of
the pointing device). In this way, the background IR in the
environment is attenuated and the IR flash becomes the predominant
feature in the difference image. The image coordinates of the pixel
in the difference image that exhibits the highest intensity is then
identified using a standard peak detection procedure. A
conventional stereo image technique is then employed to compute the
3D coordinates of the flash for each set of approximately
contemporaneous pairs of image frames generated by the pair of
cameras using the image coordinates of the flash from the
associated difference images and predetermined intrinsic and
extrinsic camera parameters. These coordinates represent the
location of the pointer (as represented by the location of the IR
LED) at the time the video image frames used to compute them were
generated by the cameras.
[0060] The orientation and location of the pointing device at any
given time is used to determine whether the pointing device is
being pointed at an object in the environment that is controllable
by the computer. In order to do so the computer must know what
objects are controllable and where they exist in the environment.
This requires a model of the environment. In the XWand system, the
location and extent of objects within the environment that are
controllable by the computer are modeled using 3D Gaussian blobs
defined by a location of the mean of the blob in terms of its
environmental coordinates and a covariance. Two different methods
have been developed to model objects in the environment.
[0061] The first involves the user inputting information
identifying the object that is to be modeled. The user then
activates the switch on the pointing device and traces the outline
of the object. Meanwhile, the computer is running a target training
procedure that causes requests for orientation messages to be sent
to the pointing device a prescribed request rate. The orientation
messages are input as they are received, and for each orientation
message, it is determined whether the switch state indicator
included in the orientation message indicates that the switch is
activated. Whenever it is initially determined that the switch is
not activated, the switch state determination action is repeated
for each subsequent orientation message received until an
orientation message is received which indicates that the switch is
activated. At that point, each time it is determined that the
switch is activated, the location of the pointing device is
ascertained as described previously using the digital video input
from the pair of video cameras. When the user is done tracing the
outline of the object being modeled, he or she deactivates the
switch. The target training process sees this as the switch has
been deactivated after having been activated in the immediately
preceding orientation message. Whenever such a condition occurs,
the tracing procedure is deemed to be complete and a 3D Gaussian
blob representing the object is established using the previously
ascertained pointing device locations stored during the tracing
procedure.
[0062] The second method of modeling objects once again begins by
the user inputting information identifying the object that is to be
modeled. However, in this case the user repeatedly points the
pointer at the object and momentarily activates the switch on the
device, each time pointing the device from a different location
within the environment. Meanwhile, the computer is running a target
training procedure that causes requests for orientation messages to
be sent to the pointing device at a prescribed request rate. Each
orientation message received from the pointing device is input
until the user indicates the target training inputs are complete.
For each orientation message input, it is determined whether the
switch state indicator contained therein indicates that the switch
is activated. Whenever it is determined that the switch is
activated, the orientation of the pointing device is computed as
described previously using orientation sensor readings also
included in the orientation message. In addition, the location of
the pointing device is ascertained using the inputted digital video
from the pair of video cameras. The computed orientation and
location values are stored. Once the user indicates the target
training inputs are complete, the location of the mean of a 3D
Gaussian blob that will be used to represent the object being
modeled is computed from the pointing device's stored orientation
and location values. The covariance of the Gaussian blob is then
obtained in one of various ways. For example, it can be a
prescribed covariance, a user input covariance, or the covariance
can be computed by adding a minimum covariance to the spread of the
intersection points of rays defined by the pointing device's stored
orientation and location values.
[0063] With a Gaussian blob model of the environment in place, the
orientation and location of the pointing device can be is used to
determine whether the pointing device is being pointed at an object
in the environment that is controllable by the computer. In one
version of this procedure, for each Gaussian blob in the model, the
blob is projected onto a plane which is normal to either a line
extending from the location of the pointing device to the mean of
the blob or a ray originating at the location of the pointing
device and extending in a direction defined by the orientation of
the device. The value of the resulting projected Gaussian blob at a
point where the ray intersects the plane is computed. This value
represents the probability that the pointing device is pointing at
the object associated with the blob under consideration. Next, the
probability representing the largest value computed for the
Gaussian blobs, if any, is identified. At this point, the object
associated with the Gaussian blob from which the largest
probability value was derived could be designated as being the
object that the pointing device is pointing at. However, an
alternate thresholding procedure could be employed instead. In this
alternate version, it is first determined whether the probability
value identified as the largest exceeds a prescribed minimum
probability threshold. Only if the threshold is exceeded is the
object associated with the projected Gaussian blob from which the
largest probability value was derived designated as being the
object that the pointer is pointing at. The minimum probability
threshold is chosen to ensure the user is actually pointing at the
object and not just near the object without an intent to select
it.
[0064] In an alternate procedure for determining whether the
pointing device is being pointed at an object in the environment
that is controllable by the computer, for each Gaussian blob, it is
determined whether a ray originating at the location of the
pointing device and extending in a direction defined by the
orientation of the device intersects the blob. Next, for each
Gaussian blob intersected by the ray, it is determined what the
value of the Gaussian blob is at a point along the ray nearest the
location of the mean of the blob. This value represents the
probability that the pointing device is pointing at the object
associated with the Gaussian blob. The rest of the procedure is
similar to the first method in that the object associated with the
Gaussian blob from which the largest probability value was derived
could be designated as being the object that the pointing device is
pointing at. Or alternately, it is first determined whether the
probability value identified as the largest exceeds the prescribed
minimum probability threshold. If the threshold is exceeded, only
then is the object associated with the projected Gaussian blob from
which the largest probability value was derived designated as being
the object that the pointing device is pointing at.
[0065] Users of the XWand are often impressed with the immediate
and natural feel of absolute pointing. However, the pure
geometry-based approach which enables absolute pointing also has a
number of important drawbacks. First, two or more cameras must be
permanently mounted in the room. Besides the difficulty of
installation, such cameras inevitably draw objections related to
privacy. In addition, the cameras must be carefully calibrated to
the room geometry upon installation, and recalibrated if they are
moved. Further, at least two cameras must have clear sight-lines to
the wand at all times. Finally, the three dimensional position of
each active device in the room must be known, and small errors in
the orientation and position information translate to inaccuracy in
pointing, possibly disrupting the interaction.
[0066] Given these objections, alternatives to absolute pointing
would be advantageous with the goal of eliminating the three
dimensional positioning system. One general approach is to place
tags in the environment, but they have drawbacks as well. By design
tags require installation on every active device. Active tags such
as IR beacons, for example, require their own power, while passive
tags such as RF ID tags tend to have limited range, and tags based
on visual features rely on rather sophisticated onboard
processing.
3.0 WorldCursor System
[0067] The foregoing XWand system issues are resolved by the
present system, which will be referred to herein as the WorldCursor
system. The WorldCursor system uses the XWand device (or similar
pointing device) but does not rely on a geometric model of pointing
that requires the three dimensional position of the XWand, nor on
tags placed in the environment, nor on any external sensing in
general. Instead, a laser beam projected in the space gives the
user feedback as to where the system believes the user is pointing,
much in the same way that the cursor icon in "windows, icons, menus
and pointing" (WIMP) interfaces provides feedback to indicate where
the user is pointing with the mouse. In fact, the WorldCursor is
analogous to the mouse and cursor used in traditional GUIs in that
the user may select and interact with a physical device by
positioning the cursor on the device and clicking.
[0068] In the foregoing context, the XWand is employed as a
physical pointing mechanism, and it is coupled with the WorldCursor
which projects a cursor on the physical environment. The
WorldCursor improves upon the XWand by removing the need for
external positioning technology such as video cameras or any other
external position sensing technology, and by enabling the user to
point with a high degree of precision.
[0069] Referring to FIG. 2, the WorldCursor system includes a small
tele-operated motion platform 200 upon which is mounted a laser
pointer. This device is controlled via a wired connection 202 to a
host computer 204, which is also connected to the XWand RF base
station 206. The WorldCursor platform 200 can be programmed to
follow the motion of the XWand 208, such that when the user points
the XWand to the left, for example, the WorldCursor moves a
corresponding amount to the left in real time. The user attends to
the projected laser spot (the cursor) in the environment. By moving
the XWand the user is then able to place the cursor on any object
in the room, as they would place the cursor on an onscreen object
with the mouse. Because only the orientation information from the
XWand is used, and not the XWand's 3-D position, the original XWand
system's requirement of the external computer vision system is
eliminated.
[0070] Interacting with active devices in the intelligent
environment proceeds much as in the original XWand system. For
example, to turn a household lamp on or off, instead of pointing
directly at the lamp, the user moves the laser spot onto the lamp
and clicks the XWand button. The system determines that the cursor
is on the lamp by comparing the current cursor position with the
recorded cursor position associated with the lamp, collected
beforehand.
3.1 The WorldCursor Device
[0071] In general, the WorldCursor device simply needs to take yaw
and pitch commands in some form and in response move the laser spot
to any desired place (within line of sight of the laser) in the
space in which it is operating. Any device having this capability
will suffice for use in the overall WorldCursor system. In tested
embodiments of the WorldCursor system the aforementioned device
took the form of a motion platform that is mounted on the ceiling,
typically near the center of the room. A prototype of this device
is shown in FIG. 3. It consisted of two high speed miniature
servos, such as the type used on radio-controlled model airplanes.
Specifically, in tested embodiments of the WorldCursor, Expert
Electronic's SL451 High Speed Mini Servos (Model EXRSL451) were
used. One of the servos was mounted for yaw and a second for pitch
control. In one embodiment of the device, both servos were
controlled by a PIC microcontroller, which takes yaw and pitch
commands from the host computer via a RS-232 connection and
converted them to standard servo motor commands. In an alternate
embodiment, an API on the aforementioned host computer takes yaw
and pitch values from the XWand, and converts then to standard
servo motor commands. These commands are then sent to the servos.
It is noted that this latter scenario has the advantage of sending
motor commands that are typically in integer form, rather than
floating point data such as would be the case with pitch and yaw
values.
[0072] Mounted on the servo assembly is a red laser similar to
those used in conventional laser pointers. By controlling the
servos, the platform is able to steer the laser spot to most points
in the room below the ceiling, provided there exists a sight line
to that point. In tested versions of the present system and
process, effective resolution in steering the laser using the
aforementioned servos is about 0.25 degrees or about one half inch
at a distance of 9 feet. The servos were each capable of moving
over nearly a 170 degree range at a speed of 333 degrees per
second. Generally, this configuration resulted in the motion of the
laser being smooth and responsive. However, in the case when the
laser must move from pointing to a location in front of the
platform to a location behind the platform, the pitch motor must
move to the back and the yaw motor must reflect about the vertical
plane separating the front and rear hemispheres. Because the servos
employed in the tested embodiments had a 170 degree range
limitation, there was a discontinuity in this movement of the laser
spot from front to back (i.e., a 20 degree gap at the sides). While
the aforementioned pointing inaccuracy and discontinuity were not
found to be a problem in the tested embodiments, ideally, servos
with a full 180 degree range and higher accuracy could be employed
to resolve these minor deficiencies.
[0073] It is noted that the connection between the WorldCursor base
unit and the host computer could also be of a wireless type.
However, if this is the case care must be taken to ensure there is
no interference with the XWand system.
3.2 World Model for the WorldCursor System
[0074] The WorldCursor points at a given object in the room by
changing the pitch and yaw of the laser with its motors. It is
therefore possible to uniquely associate a given object in the room
with the yaw and pitch value used to point the WorldCursor at the
object. The yaw and pitch values of each object of interest in the
space are the basis for a convenient world model for the
WorldCursor system based on spherical coordinates.
[0075] The spherical coordinate world model is easier to construct
than the full three dimensional model of the original XWand system
as described previously. For example, whereas in the three
dimensional model the user had to either hold the XWand over the
object, or provide several pointing examples used to triangulate
the position of the object, the WorldCursor system need only record
the current yaw and pitch values of the device once the user has
put the cursor on the object. One limitation of this approach is
that the spherical coordinate world model must be re-learned if the
WorldCursor device is moved to a new location.
[0076] Given this, a model of the space that the WorldCursor system
is to operate in can be established as follows. Referring to FIGS.
4A and B, the user initiates a training mode that is part of a
WorldCursor control process running on the host computer (process
action 400). The training mode has the same purpose as a similar
process used in the XWand system--namely to learn where objects of
interest are in the space. More particularly, the user directs the
laser at an object of interest by pointing the XWand so that the
laser spot appears on the approximate center of the object being
modeled and presses the button on the XWand (process action 402).
The control process causes periodic requests to be sent to the
XWand directing it to provide an orientation message in the manner
described previously (process action 404). Any incoming orientation
message transmitted by the pointer is input (process action 406),
and it is determined whether the button state indicator included in
the message indicates that the pointer's button is activated
(process action 408). If not, process actions 406 and 408 are
repeated. When it is discovered that the button state indicator
indicates the button is activated, then in process action 412, the
control process accepts input from the user who enters information
into the host computer that identifies the object being modeled,
including its approximate size (process action 410). Since it was
the control process running on the host computer that received the
pitch and yaw data from the XWand and moved the laser of the
WorldCursor to the target location as described previously, the
pitch and yaw associated with the target spot are known. The
process associates the spherical coordinates of the target location
to the information entered by the user about the corresponding
object (process action 414). In addition, the user-provided size
data is used to establish a circle in spherical coordinates about
the direction the laser is pointed that models the extent of the
object (process action 416). Any incoming orientation message
transmitted by the pointer continues to be input (process action
418) and a determination is made as to whether the button state
indicator included in the messages first indicates that the
pointer's button becomes deactivated and then activated again,
thereby indicating that the user has pushed the XWand button again
(process action 420). If it is, process actions 418 and 420 are
repeated. If it is not, in process action 424, it is determined if
the user has deactivated the training mode (process action 422),
thus indicating all the objects it is desired to model in the space
have been modeled. If the user has not deactivated the training
mode, then process actions 402 through 424 are repeated to "learn"
the next object the user chooses to identify to the system.
Otherwise the process ends.
[0077] Once the objects in the space have been modeled as described
above, user can direct the laser of the WorldCursor to the modeled
objects and act upon them as was done in the XWand system. More
particularly, the user shines the WorldCursor's laser beam on the
object he or she wants to select. It is then determined whether the
laser beam is on an object in the space that is known. Whenever the
laser beam is on a known object, that object is selected for future
control actions.
[0078] To determine if the laser beam is on an object, the user is
required to activate the XWand switch when the laser beam is
shining on the object he or she wants to select. The distance is
computed in spherical coordinates between the current WorldCursor
position and a position stored for each of the modeled objects. For
coordinates (.theta..sub.c, .phi..sub.c,) of the WorldCursor and
coordinates (.theta..sub.i, .phi..sub.i) of the center of a given
object, the user is deemed to be pointing at a modeled object if:
{square root over
((.theta..sub.i-.theta..sub.c).sup.2+(.phi..sub.i-.phi..sub.c).sup.2)}<-
;r.sub.i (1) where radius r.sub.i indicates the size of the object
modeled as a circle in spherical coordinates. It is noted that this
method of determining if the user is pointing at a modeled object
in the environment is clearly much easier than the
previously-described Gaussian blob technique used in connection
with the standalone XWand system.
[0079] In some cases the object being modeled in the environment
will be better represented as a polygon rather than a circle. In
addition, in some cases the WorldCursor may be needed to indicate
one or more points on an object with a high degree of precision.
Both of these issues are resolved by modeling the object in
question as a polygon. This is accomplished by inputting a set of
vertices that form a polygonal model of an object. To input the
vertices, the user places the laser spot of the WorldCursor on each
vertex of the polygon representing the object, in turn, while the
WorldCursor system is in a training mode. Once the object is
"trained", the system can then determine if the cursor is on the
polygon by using standard point-in-polygon algorithms used in two
dimensional graphics [1].
[0080] More particularly, a model of a polygonal object in the
space that the WorldCursor system is operating in can be
established as follows. Referring to FIGS. 5A and B, the user
initiates the aforementioned training mode that is part of an
control process running on the host computer, except also
indicating a polygonal object is being modeled (process action
500). The user directs the laser by pointing the XWand so that the
laser spot appears one of the vertices of the object being modeled
and presses the button on the XWand (process action 502). The
procedure then proceeds as before with the control process causing
periodic requests to be sent to the XWand directing it to provide
an orientation message in the manner described previously (process
action 504). Any incoming orientation message transmitted by the
pointer is input (process action 506), and it is determined whether
the button state indicator included in the message indicates that
the pointer's button is activated (process action 508). If not,
process actions 506 and 508 are repeated. When it is discovered
that the button state indicator indicates the button is activated,
the process associates the spherical coordinates of the target
location to the object vertex being modeled (process action 510).
Any incoming orientation message transmitted by the pointer
continues to be input (process action 512) and a determination is
made as to whether the button state indicator included in the
messages first indicates that the pointer's button becomes
deactivated and then activated again, thereby indicating that the
user has pushed the XWand button again (process action 514). If it
is, process actions 512 and 514 are repeated. If it is not, in
process action 518, it is determined if the last vertex has been
identified by the user (process action 516). If so the process
ends. If not, process actions 502 through 518 are repeated to
"learn" the next vertex of the polygon. Optionally, either before
or after the user points out all the vertices of the polygon being
established to the model the object of interest, he or she can
enter information into the host computer that identifies the
object. This information would be associated with the object as
well.
[0081] Once an object has been modeled as a polygon, it might also
be desirable to know precisely where the cursor (i.e., laser spot)
is on the object's surface in a local coordinate system, as
mentioned above. For example, this polygon technique can be used to
determine if the WorldCursor spot is on the active surface of a
computer display, and if so where on that surface. In this way the
WorldCursor can act as a display cursor as well.
[0082] For a four vertex polygonal surface such as a computer
display, the desired location would be the cursor's screen
coordinates. A transform from WorldCursor to screen coordinates
allows the display to be seamlessly incorporated into the rest of
the world model, as described later. In this case, a projective
transform [3] can be used to transform WorldCursor coordinates to
screen coordinates (x, y) as follows: [ wx wy w ] = [ p 11 p 12 p
13 p 21 p 22 p 23 p 31 p 32 1 ] .function. [ .theta. c .PHI. c 1 ]
( 2 ) ##EQU1## The parameters p.sub.ij are determined by solving a
linear system of equations given the four corners of the display in
both WorldCursor and screen coordinates. Here the assumption is
made that the WorldCursor coordinate system is linear in the region
of the display, even though modeled in spherical coordinates--a
valid assumption for typical sized displays.
[0083] More particularly, the projective transform of Eq. (2) takes
coordinates (x, y) into coordinates (x', y') by way of a 3.times.3
matrix with 8 free parameters. Points (x.sub.i, y.sub.i) are the
coordinates of the 4 corners of the polygon in WorldCursor device
coordinates, and the points (x.sub.i', y.sub.i') are the
coordinates of the same 4 corners in local coordinates (e.g.,
screen coordinates of a computer display). These values are
collected in an offline training procedure in which the cursor is
placed on each of the 4 corners of the polygon in turn, as
described previously. The matrix may be expressed as x ' = p 11
.times. x + p 12 .times. y + p 13 p 31 .times. x + p 32 .times. y +
1 , y ' = p 21 .times. x + p 22 .times. y + p 23 p 31 .times. x + p
32 .times. y + 1 , ( 3 ) ##EQU2## Rearranging terms gives:
x'=p.sub.11x+p.sub.12y+p.sub.13-p.sub.31xx'-p.sub.32yx'
y'=p.sub.21x+p.sub.22y+p.sub.23-p.sub.31xy'-p.sub.32yy' (4) From
this linear system it is possible to solve for parameters P.sub.ij
given 4 points (x.sub.i, y.sub.i) which map to corresponding points
(x.sub.i', y.sub.i'): [ x 1 ' y 1 ' x 2 ' y 2 ' x 3 ' y 3 ' x 4 ' y
4 ' ] = [ x 1 y 1 1 0 0 0 - x 1 ' .times. x 1 - x 1 ' .times. y 1 0
0 0 x 1 y 1 1 - y 1 ' .times. x 1 - y 1 ' .times. y 1 x 2 y 2 1 0 0
0 - x 2 ' .times. x 2 - x 2 ' .times. y 2 0 0 0 x 2 y 2 1 y 2 '
.times. x 2 - y 2 ' .times. y 2 x 3 y 3 1 0 0 0 - x 3 ' .times. x 3
- x 3 ' .times. y 3 0 0 0 x 3 y 3 1 - y 3 ' .times. x 3 - y 3 '
.times. y 3 x 4 y 4 1 0 0 0 - x 4 ' .times. x 4 - x 4 ' .times. y 4
0 0 0 x 4 y 4 1 - y 4 ' .times. x 4 - y 4 ' .times. y 4 ]
.function. [ p 11 p 12 p 13 p 21 p 22 p 23 p 31 p 32 ] ( 5 )
##EQU3## During runtime, screen coordinates are computed from
WorldCursor device coordinates using equation (2) above. Note that
this computation is only performed after it is determined that the
cursor is contained within the polygon described by the points
(x.sub.i, y.sub.i). Alternatively, one may always perform this
mapping, and then check if the resulting screen coordinate values
are contained within the polygon described by the points (x.sub.i',
y.sub.i') (a trivial calculation). 3.3 Controlling the WorldCursor
System
[0084] In this section, various techniques for controlling the
WorldCursor with the XWand are presented. The general scheme of the
control mapping is that the WorldCursor should mimic the exact
motion of the XWand, much in the same way that the cursor on a WIMP
interface mimics the motion of the mouse. If (.theta..sub.c,
.phi..sub.c) is the yaw and pitch of the WorldCursor and
(.theta..sub.w, .phi..sub.w) is the yaw and pitch of the XWand,
then (.theta..sub.c, .phi..sub.c).apprxeq.(.theta..sub.w,
.phi..sub.w), at least for an absolute pointing mode as will be
described shortly.
3.3.1 Filtering
[0085] Before passing on the output of the XWand to the WorldCursor
controller, the yaw and pitch values from the XWand are first
filtered to reduce the effects of noise in the sensors and to ease
placing the cursor precisely on a small target. Two filters are
used which average the last n samples (i.e., a box filter). The
first is a very slow filter. For example, in tested versions of the
WorldCursor, this slow filter averaged approximately the last 2.5
seconds worth of sensor data. This filter tends to dampen most
XWand motion and allows the user to move the cursor relatively
slowly for precise positioning. The second filter is much faster.
For example, in tested versions of the WorldCursor, this fast
filter averaged approximately the last 0.3 seconds worth of sensor
data. This fast filter is appropriate for fast XWand movement, when
the sensor noise is not as apparent, and responsiveness is
desired.
[0086] While the user could switch between the filter modes
manually via input to the host computer, the WorldCursor control
process running on that computer preferably switches between the
slow and fast filters automatically. This is accomplished as
follows. Referring to FIG. 6, and presuming that the fast filter is
the initial default selection, it is first determined if the
average speed of the cursor movement has fallen below a prescribed
slow speed threshold .tau..sub.slow (process action 600). If not,
then the speed of the cursor continues to be monitored by
periodically repeating process action 600. It is noted that the
speed of the cursor is determined by taking the estimated position
returned by the fast filter, and computing the difference between
that estimate and the same estimate computed in the previous time
step, to get speed. In addition, the speed can be checked at any
appropriate interval that ensures the cursor behaves in the
aforementioned controlled manner. In tested embodiments of the
control process, the speed was checked every time step (e,g., about
50 Hz). If it is determined in process action 600 that the cursor
speed has fallen below the prescribed slow speed threshold, then in
process action 602 the WorldCursor control process switches to the
aforementioned slow filter. The cursor speed is then monitored
again. More particularly, it is determined if the average speed of
the cursor movement goes above a prescribed fast speed threshold
.tau..sub.fast (process action 604). If not, then the speed of the
cursor continues to be monitored by periodically repeating process
action 604 in the manner employed previously. In general, the fast
speed threshold .tau..sub.fast is much higher than the slow speed
threshold. This prevents frequent shifts and ensures a smooth
transition between filter modes at the appropriate times. While
other values can be employed as desired, in tested embodiments of
the control process .tau..sub.slow was set to 0.05 radians/second
and .tau..sub.fast was set to 0.5 radians/second. If it is
determined in process action 604 that the cursor speed has risen
above the prescribed fast speed threshold, then in process action
606 the WorldCursor control process switches to the aforementioned
fast filter. At this point, the filter selection procedure
continues by repeating actions 600 through 606, for as long as the
WorldCursor system is activated. In this way, a balance of speed,
responsiveness and a fine degree of control are maintained.
3.3.2 Absolute vs. Relative Pointing
[0087] In the absolute pointing mode, the WorldCursor's laser
ideally points at the same place as the XWand. The most basic
control mapping to compute WorldCursor yaw and pitch
(.theta..sub.c, .phi..sub.c) from the XWand yaw and pitch
(.theta..sub.w, .phi..sub.w) to produce this absolute pointing is,
.theta..sub.c=.theta..sub.c0+.theta..sub.w-.theta..sub.w0 (6)
.phi..sub.c=.phi..sub.c0+.phi..sub.w-.phi..sub.w0 (7) where
(.theta..sub.c0, .phi..sub.c0) and (.theta..sub.w0, .phi..sub.w0)
are offset angles for the WorldCursor and XWand, respectively.
These offsets are set to align the origins of the XWand and
WorldCursor in a one time calibration procedure.
[0088] However, unless the WorldCursor platform and the XWand are
very close to one another, it will be impossible to choose offsets
(.theta..sub.c0, .phi..sub.c0) and (.theta..sub.w0, .phi..sub.w0)
such that the XWand points directly at the WorldCursor laser spot
throughout the range of pointing in the room. It will be possible
to achieve approximate correspondence for a limited range of angles
such as one wall of a room, but as soon as the WorldCursor is
brought onto the opposite facing wall, for example, the
correspondence will be far off.
[0089] It is not clear if users require even approximate
correspondence for successful use of the device. Users' experience
with mice suggests that absolute correspondence is not necessary.
Much in the same way that users easily adapt to the relative
movement of mouse and cursor, users of the WorldCursor may be able
to adapt to the lack of absolute pointing, subject to the
limitation that the laser spot is in their field of view. Thus, a
relative pointing mode where the WorldCursor's laser spot moves
with the movement of the XWand, but does not point at the same
place in the environment, may be an acceptable operating condition.
However, a number of procedures can be employed by which the
WorldCursor and XWand can be brought into alignment to at least
partially restore absolute pointing, and obtain other useful
information about the environment as well. These alignment
procedures will now be described in the section below.
3.3.2.1 Clutching
[0090] One procedure that the user can employ to re-establish the
XWand-WorldCursor correspondence involves a "clutching" technique.
This is an operation analogous to picking up a computer mouse,
moving it in air, and putting the mouse down on the desk again,
without the cursor moving. To clutch, the user clicks the XWand
button while the WorldCursor control process is in operational mode
(as opposed to training mode). At that point the laser dot stops
moving with the XWand. The user may then reorient the XWand, lining
it up so that it points directly at the laser spot. When ready to
resume WorldCursor operation, the user clicks the button again and
the laser spot resumes moving. At this moment new offset values
(.theta..sub.c0, .phi..sub.c0) and (.theta..sub.w0, .phi..sub.w0)
are also collected.
[0091] More particularly, referring to FIGS. 7A and B, the user
initiates the operational mode of the WorldCursor control process,
if it is not already active (process action 700). In the
operational mode, the control process normally accepts XWand pitch
and yaw inputs, computes the corresponding pitch and yaw for the
WorldCursor laser, and sends commands to the WorldCursor unit to
move the laser to match the computed pitch and yaw values, all in
the manner described previously. This normal operation continues
until the user presses the XWand button to initiate the clutching
operation (process action 702). Specifically, the control process
causes periodic requests to be sent to the XWand directing it to
provide an orientation message (process action 704), and any
incoming orientation message is input (process action 706). These
orientation messages include the aforementioned XWand pitch and yaw
values that are used to move the laser. They also include the XWand
button state indicator. Thus, when a message is received it
determined whether the button indicator indicates that the
pointer's button is activated (process action 708). If not, normal
operations are continued and process actions 706 and 708 are
repeated. However, if it is discovered that the button state
indicator indicates the button has been activated, then in process
action 710, the control process ceases providing movement commands
to the WorldCursor device and the laser spot remains stationary in
its last position. The user then points the XWand at the location
where the laser spot is shining (process action 714) and releases
the button. Any incoming orientation message transmitted by the
XWand continues to be input (process action 712) and a
determination is made as to whether the button state indicator
included in the messages first indicates that the pointer's button
becomes deactivated and then activated again, thereby indicating
that the user has pushed the XWand button again (process action
716). If it has not, process actions 712 and 716 are repeated.
However, if it has, new offset values for the WorldCursor device
and the XWand are collected (process action 718) and normal
operations are resumed (process action 720).
[0092] Note that the user may use the foregoing clutching technique
not to align the XWand with the WorldCursor, but to establish a
particular desired range of operation for the XWand. For example,
by clutching the user may set offsets so that the XWand may be held
comfortably at the side of the body while the WorldCursor appears
on a surface in front of the user. The procedure is the same except
that the user does not point the XWand at the laser spot, but
instead orients it as desired. This option put the WorldCursor
system into a relative pointing mode as explained above.
3.3.2.2 Exploiting Room Geometry to Automatically Re-Establish
Correspondence
[0093] Another procedure that the user can employ to establish and
maintain a reasonable correspondence between the XWand and
WorldCursor without clutching involves exploiting the geometry of a
room in which the WorldCursor system is operating. If the geometry
of the room is known in terms of a 3D coordinate system, including
the position of each wall, the WorldCursor device, and the XWand
itself, then the WorldCursor may be controlled such that the XWand
always points directly at the laser spot.
[0094] More particularly, if the 3D coordinates of the vertices of
the walls in the room are known, and the 3D position and
orientation of the XWand are also known, it is possible to compute
the precise point on the wall that the XWand is pointing toward
using standard polygonal analysis techniques. Then, using simple
trigonometry (i.e., right triangle analysis in both the yaw and
pitch planes), this 3-D `wall point` can then be related back to
the known 3D position of the WorldCursor device to compute an
updated value of the yaw and pitch (.theta..sub.c, .phi..sub.c)
that is used to point the laser at the aforementioned point on the
wall.
[0095] By relying on the three dimensional position of the XWand,
it may seem like the very same problem that it is desired to remove
in developing the WorldCursor is being re-introduced--namely the
XWand's reliance on external 3-D positioning technology. In
practice, however, it is sufficient to know the room geometry only
approximately and still achieve a useable alignment that requires
no clutching. For example, it will typically suffice to fix the
assumed XWand position in the middle of a typical office space,
even though this may not coincide with its actual position. Of
course, such an assumption may not provide an accurate alignment of
the XWand and WorldCursor. However, in situations where relative
pointing is acceptable this assumption can be made. Further other
assumed XWand locations could be used instead to make the alignment
more accurate. This is particularly useful when it is believed that
the XWand will be at or near a particular position most of the time
(e.g., the room occupant's desk). Again, this relies on the fact
that users tend to be tolerant to constant offsets in alignment
similar to that found in using relative pointing mechanisms such as
computer mice.
3.3.2.3 Inferring 3D XWand Position to Re-Establish
Correspondence
[0096] A more accurate variation of the foregoing room geometry
exploitation technique that can produce near absolute pointing
results involves combining the geometry exploitation technique with
the clutching procedure to determine the 3D location of the XWand
in the room. If the user is clutching as described previously so
that the XWand points at the laser spot, each clutching operation
provides information that can be related mathematically to the 3D
position of the XWand. After as few as two clutching operations, it
is possible to compute the 3D position of the XWand.
[0097] More particularly, for each clutching operation performed
with the WorldCursor laser spot shining on one of the walls whose
vertices coordinates are known, there is an associated wall point
p.sub.i, as well as a vector w.sub.i that defines a ray pointing
from the XWand to the wall point. These values are collected at the
end of the clutching operation, after the user has realigned the
XWand with the laser spot of the WorldCursor and pressed the XWand
button to resume WorldCursor control. Essentially, the wall point
pi can be computed via standard polygonal analysis techniques since
the 3D coordinates of the vertices of the walls in the room are
known, as are the 3D position of the WorldCursor base and
orientation of its laser (i.e., the direction the laser is pointing
from the base). The vector w.sub.i is defined by the orientation of
the XWand that is determined as described previously. Assuming the
XWand position x is held constant over a number of successive
clutching operations, then x+s.sub.iw.sub.i=p.sub.i (8) where
s.sub.i is a scalar. It is noted that the "wall points" can
actually be any point on any surface in the space that is modeled
as a polygon via the procedure described previously.
[0098] XWand position x can be found by solving the linear system
of equations generated via successive clutching operations using a
standard least squares approach. A minimum of two clutching
operations are required, but for robustness it is be desirable to
collect several, particularly if some of the rays w.sub.i are
similar, in which case the solution will be sensitive to small
errors in w.sub.i.
[0099] Once the estimate of the XWand position has been updated,
the control procedure described in Section 3.3.2.2 is used to
maintain XWand-WorldCursor correspondence. So long as the actual
position of the XWand does not change dramatically, no more
clutching operations will be necessary to maintain the
correspondence. It is noted that this online calibration requires
no more clutching operations than the system which does not exploit
the approximate room geometry, and in the long run requires fewer
clutching operations if the user does not move about the room
often. The user would only be aware of the procedure in that after
a while no more clutching operations would be required to keep the
cursor and the wand in alignment.
[0100] Accordingly, referring to FIG. 8, the XWand-WorldCursor
correspondence can be maintained by first determining if a
clutching procedure been performed (process action 800). If a
clutching operation was not performed, action 800 is periodically
repeated. However, if a clutching operation was performed, the 3D
location of the point on the wall where the WorldCursor laser spot
was shining during the clutching operation is computed (process
action 802). In addition, the vector defining a ray pointing from
the XWand to the same point on the wall is computed (process action
804). It is next determined if a prescribed number of clutching
procedures have been performed (process action 806). If not,
process actions 800 through 806 are repeated. If the prescribed
number is met, then the 3D position of the XWand is computed
(process action 808). Next, the point on the wall that the XWand is
directed toward as it pointed around the space is periodically
computed, as is the yaw and pitch values that will direct the
WorldCursor laser at that point (process action 810). The
WorldCursor laser is directed with these yaw and pitch values
whenever they are computed (process action 812). Finally, the
entire process (i.e., process actions 800 through 812) is repeated
for a long as the WorldCursor is in operation.
[0101] It is noted that the number of clutching operations that
must be performed before the XWand-WorldCursor correspondence is
updated can alternately be determined based on how different each
of the aforementioned rays w.sub.i are to each other, rather than
using an absolute number. For example, in one method, if the latest
ray to be computed does not differ from the previous rays computed
since the last correspondence update by a prescribed threshold
difference, then it is not counted in terms of how many clutching
operations are required. In this way, any errors in the computation
of the rays will not have a significant impact on the overall
correspondence computations.
[0102] It should be noted that some assumptions are made in regard
to the foregoing procedures for establishing and maintaining the
XWand-WorldCursor correspondence. For example, it is assumed that
the user is clutching to re-establish XWand and WorldCursor
correspondence, and not to create a relative pointing relationship
between them. In addition, it is assumed that the user in not
moving about the room, but instead remains in the same location. It
is noted, however, that most users are likely to use the XWand from
one a small set of static locations, much as the TV remote control
is likely to be used from either the couch or the easy chair.
Accordingly, this assumption is quite valid.
3.4 Establishing a 3D Model of the Space Using the WorldCursor
[0103] In the foregoing procedures, it was assumed a polygonal
model of the space was available. However, if this is not the case,
it is possible to construct one given that the positions of the
XWand and WorldCursor devices are known. More particularly, given
the 3D location of XWand and its orientation (i.e., the direction
it is pointing) in combination with the 3D location of the
WorldCursor (which in this coordinate system could be designated as
the origin if desired) and its orientation (which is assumed to be
directed at the same point as the XWand via the aforementioned
clutching operation), then, it is possible to solve for unknown
wall points p.sub.i using simple trigonometry. Specifically, a
triangle is formed by the 3D position of the XWand, the 3D position
of the Worldcursor device, and the unknown wall point p.sub.i.
Since the 3D position of the XWand and the 3D position of the
Worldcursor device are known, the distance between them can be
computed. In addition, since the orientation of the XWand and the
laser beam are known, it follows that two of the angles of the
aforementioned triangle are also known. Thus, the wall point
p.sub.i can be uniquely determined using standard trigonometric
methods. In this way the 3D position of objects and devices in the
room may be learned, much as in the original XWand system. For
example, the user while holding the XWand in substantially the same
location within the space would point it at an object (e.g., at its
center) or to the vertices of a polygon representing an object of
interest in the space (including the walls) to establish their 3D
location and then enter information about the object, similar to
the previously described procedure for establishing a model of the
space in terms of spherical coordinates.
[0104] Thus, with a sufficient number of clutching operations to
maintain the XWand-WorldCursor correspondence intact, it would be
possible to learn the entire room geometry, including a polygonal
model of the walls (which could then be used to thereafter run the
foregoing procedures for maintaining the XWand-WorldCursor
correspondence more automatically). However, it should be noted
that even in this scenario, no more clutching operations would be
necessary than in the case of not using a geometric model.
[0105] The foregoing procedure for learning geometry from clutching
operations raises some interesting possibilities for inferring
geometry over the normal use of the device, without relying on a
special training mode or a lengthy upfront training session. This
has interesting implications for ubiquitous computing applications,
many of which rely on geometric models to develop location based
services, and to reason about user co-presence and proximity to
devices. One significant barrier to deploying such systems will be
the construction of the necessary geometric models, especially in
the home. The foregoing feature of the WorldCursor system can
provide a solution for this problem.
4.0 Applications
4.1 Home Automation
[0106] The WorldCursor system is capable of performing all the home
automation-related tasks of the original XWand system, including
turning on and off lights via X10 (i.e., a powerline-based home
automation system), selecting and manipulating the media player
with gestures to control track and volume, and finally selecting
and controlling a cursor on a display.
[0107] The WorldCursor improves on the XWand system by giving the
user much more precision in selecting devices. In the original
XWand system, for example, it would be difficult without audio
feedback to select one of two devices that are located 18 inches
apart from 12 feet away. This is due not only to the limited
precision of the XWand system, but also in users' limited precision
in pointing. This uncertainty can be addressed by placing a laser
pointer (always on) on the XWand itself, but only up to the
precision of the XWand signal processing algorithms.
[0108] The WorldCursor precision can be exploited in one
application where to control the media player, the user puts the
WorldCursor on one of several paper icons (play, pause, next track,
previous track) hung on the wall. The user "presses" the media
player button by pushing the XWand button. Menus and other
traditional GUI metaphors may also be used.
4.2 Display Surfaces
[0109] In the original XWand system, the user may control a cursor
on a console by first pointing the XWand at the console, and
entering a cursor control mode by clicking the XWand button.
Exiting the cursor control mode is accomplished by clicking on a
special button presented in the interface during cursor control
mode.
[0110] With the precision afforded by the WorldCursor, it is
possible to improve upon this interaction by seamlessly integrating
the display surface in the world model, without needing to enter a
special cursor control mode. For example, once the four corners of
the display are specified with the WorldCursor, the calculations
described in Section 3.2 may be used to determine if the cursor is
on the display. If the cursor is on the display, the laser is
turned off, and the prospective projection equations are used to
move the cursor to the exact spot on the display where the laser
would be if it had not been turned off. Once the user moves the
cursor off the display, the cursor is hidden and the laser is
turned back on. Because of the nature of the WorldCursor geometric
model, the registration between the two coordinate systems can be
quite precise.
[0111] Further, with networked WorldCursor client processes it will
be possible to extend this functionality across multiple displays
simultaneously, moving from display to display seamlessly.
[0112] The drawback of the WorldCursor display integration is that
the control of a small display from across the room can be quite
difficult, since the size of the `mousing surface` is related to
the angle subtended by the display. In the XWand system, this
problem is avoided in the special cursor control mode by using a
constant scaled range of angles for control that is independent of
where the user is located in the room. One approach to address this
limitation is to nonlinearly warp the coordinate system in the
neighborhood of the display.
4.3 Learning Geometric Models
[0113] Besides using the WorldCursor to `point out` devices to the
system, it may also be used by the system to `point out` devices to
the user. For example, if the intelligent environment knew where
the user's lost keys were, the WorldCursor system might direct the
user's attention to their location in response to the user's
query.
4.4 Non-Veridical Behavior
[0114] Thus far WorldCursor control and applications which strive
to replicate the exact motions of the user's manipulations of the
XWand have been explored. There may also be interesting
possibilities in considering how this one to one mapping may be
violated.
[0115] For example, in [2] users' ability to finely control a
standard laser pointer in an object selection task is studied. In
part, performing object selection and other GUI related tasks with
a laser pointer is difficult because it is surprisingly difficult
to hold a laser pointer still. In Section 3.3.1, a switching filter
technique was described which can be used to significantly dampen
the motion of the cursor when the user is moving the XWand slowly.
The WorldCursor can thus do for laser pointer-based interaction
what `SteadyCam` has done for home videos, by eliminating the
jitter and noise associated with standard laser pointers. This
damping filter is especially useful in working with display
surfaces, where often GUI elements are small and densely packed.
Thus, the WorldCursor system can act as an improved laser
pointer.
[0116] In an environment where there are many selectable objects,
it may be advantageous to employ a "Snap To" feature for the
WorldCursor. If the user guides the cursor near an active device, a
simple spring model may be used to bring the cursor precisely on
the target. For example, a simple distance threshold can be
employed such that if the laser beam is moved to a location near an
object that is within the threshold distance, it is automatically
redirected to the shine on that object. Not only may this ease
target selection, it also is a convenient way to alert the user to
the fact that the object is active and selectable.
[0117] In the case when the XWand is used with gestures to control
the currently selected device, the WorldCursor can be used to `play
back` the gesture as a way to teach the user the available gestures
for that device.
[0118] As with the mouse, users of the WorldCursor attend the
cursor and almost never look at the XWand itself. In some cases
users have difficulty finding the laser spot, particularly in the
case when the cursor is `parked` at a location in the environment
out of the field of view, as in the beginning of a clutching
operation. One solution to this problem is to bring the cursor to a
`home` position after a period of inactivity, or to animate the
laser spot to draw the user's attention when the XWand is first
picked up.
[0119] While throughout the foregoing description of the
WorldCursor system the XWand was employed as a pointing device,
this need not be the case. Generally, any conventional pointing
device could be used to steer the WorldCursor laser. For example, a
computer mouse, track ball, or gamepad could be adapted to this
purpose. Of course, some of the above-described features of the
XWand-WorldCursor combination would not be possible, such as the
absolute pointing mode and 3D modeling features, because of the
lack of pointer orientation data. However, the conventional
pointing devices can support features such as spherical coordinate
modeling and object selection, the above-described display surface
feature, and general laser pointer-type functions.
5.0. References
[1] Haines, E. (1994) In Graphics Gems IV (Ed, Heckbert, P.)
Academic Press, pp. 24-46.
[2] Myers, B. A., R. Bhatnagar, J. Nichols, C. H. Peck, D. Kong, R.
Miller, and A. C. Long (2002), Interacting At a Distance: Measuring
the Performance of Laser Pointers and Other Devices, in Proceedings
CHI Minneapolis, Minn.
[3] Zisserman, H. R. a. A. (2000) Multiple View Geometry in
Computer Vision, Cambridge University Press.
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