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BACKGROUND OF THE INVENTION
This invention relates to methods and systems for presenting virtual
reality experiences to a user. More particularly, this invention relates
to such systems where the user is guided through the experience because
the outcome of the virtual reality experience is constrained.
In theory, a user presented with a virtual reality experience should be
able to enter a virtual world or space and roam through that world or
space at will, interacting as he or she desires with anything that may be
found there, and spending as much time as desired without reaching any
particular destination or objective. However, in certain practical virtual
reality presentations, the experience may be constrained. For example, in
an amusement-type virtual reality attraction, each user, or "guest," can
only be given a limited time in the virtual world, so that other guests
can have an opportunity to share the virtual experience.
In addition, the amount of computing power necessary to present a true,
unconstrained virtual reality experience is very large, and very
expensive. The cost of that amount of computing power would likely be
prohibitive in the context of an amusement ride. Thus, it is necessary to
limit the options given a guest in such an experience, while at the same
time giving the guest the impression that he or she can move anywhere and
do anything in the virtual space.
One way to give a guest such an impression is to present the guest with a
fast-moving experience in which he or she is caught up and swept along.
Such an experience would psychologically lead the guest in certain
directions, minimizing the tendency of the guest to explore portions of
the virtual space that have not been fully programmed. However, such a
technique cannot be guaranteed to prevent the guest from going where he or
she should not go. Moreover, it could not be assured that the guest would
reach a desired objective within the time allotted.
It would be desirable to be able to provide a virtual reality system in
which a user could be guided within a virtual space to a specific
destination within a specific time while providing the impression that the
user is free to roam the virtual space at will.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a virtual reality system in
which a user could be guided within a virtual space to a specific
destination within a specific time while providing the impression that the
user is free to roam the virtual space at will.
In accordance with this invention, there is provided a method of guiding a
user through a virtual reality experience in a virtual world having at
least one virtual space. The method includes projecting the virtual space
in the field of view of the user, and defining at least one nominal path
through the virtual space. An object is projected in the virtual space in
the field of view of the user. The object is moved along the at least one
nominal path, and is prevented from moving other than along the at least
one nominal path. The user is allowed to move within the virtual space,
but is restrained from exceeding a defined distance from the object.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and advantages of the invention will be
apparent upon consideration of the following detailed description, taken
in conjunction with the accompanying drawings, in which like reference
characters refer to like parts throughout, and in which:
FIG. 1 is a perspective view of a user equipped to experience a virtual
reality experience according to the present invention;
FIG. 2 is a schematic plan view of a virtual world which can be presented
by the present invention;
FIG. 3 is a schematic representation of a user virtually tethered to a
leading object in accordance with the present invention;
FIGS. 4A and 4B are schematic representations of how the leading object
guides the user;
FIG. 5 is a flow diagram of a preferred embodiment of a computer program
routine for implementing the leading object according to the invention;
and
FIG. 6 is a schematic diagram useful in understanding the operation of the
computer program routine of FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
The present invention guides a user through a virtual reality experience
toward a desired objective within an allotted time period by providing to
the user a virtual guide to urge him or her through the virtual space.
Thus, as suggested above, the guide might be a virtual character who runs
or flies ahead of the user on a predetermined but invisible path or track
and exhorts the user to follow. For example, the character may shout such
phrases as "Hurry, we'll be late!" or "Come on, it's this way!"
Alternatively, the guide may be an interesting non-living object capable
of movement that entices the user. Either way however, as discussed above,
such psychological tools may not be sufficient to keep the user on track
and on schedule.
Therefore, in accordance with the present invention, the virtual guide is
equipped with a "virtual tether" that is virtually connected between the
guide and the user. Thus, as the guide moves along the path, the user is
forced to come along. The length of the tether is also adjustable, so that
the user can be given more or less leeway depending on the circumstances.
When it is necessary, the tether can be shortened so that the user must be
very close to the guide. On the other hand, at times it may be acceptable
for the user to remain relatively far from the guide.
The virtual tether is implemented in the preferred embodiment of the
invention by providing the ability to the virtual reality simulation
program to control the speed at which it advances, in addition to
providing such control to the user. When the user needs to be urged in a
certain direction, or to change speed, the program control becomes more
dominant.
The presence of the virtual tether may be masked from the user by
presenting "explanations" in the virtual experience for the change in
speed or direction. A simple "explanation" would be to have the guide
speed up, while shouting at the user to hurry, and then using program
control to increase the speed, hoping that the user attributes the
increase to his or her own reaction to the guide. A more subtle
"explanation" might be to have something happen in the virtual space that
appears random but forces the user in the desired direction at the desired
speed. For example, a strong gust of wind could come up and blow the user,
or, if the virtual experience is at sea, a large wave could be substituted
for the wind. Alternatively, a crowd could come along and the user could
get caught up and shoved along.
The invention is illustrated in the FIGURES in the context of a
particularly preferred embodiment of a virtual reality simulation in which
the user believes that he or she is flying a magic carpet through a cave
to reach a treasure. The cave has several chambers through which the user
must fly, connected by narrow passageways or doorways. In accordance with
the invention, the virtual tether is used to lead the user through the
caves. The tether is shortened as the guide moves into and through
doorways and passageways to (1) keep the user from losing sight of the
guide as it moves to a new chamber, and (2) restrict the user's movements
as he or she passes through narrow spaces. The tether can be made longer
in the large chambers, giving the user the opportunity to explore. In
general, the tether can also be made shorter to keep the user from
approaching an area that may not be fully programmed.
There may be more than one permissible path to take through the virtual
reality experience. In the preferred embodiment, there may be more than
one acceptable path through the cave. Thus, the invention includes the
ability to have the guide leave the predetermined nominal path for a
different predetermined nominal path. Preferably, the guide will move to a
new nominal path when the user, on the end of the tether, moves within a
predetermined distance of the new path.
FIG. 1 shows a user 10 equipped to experience a virtual reality simulation
in accordance with the present invention. The user preferably wears a
helmet 11 including a head-mounted display 12 which fills the user's field
of view with the substantially binocular output of processor 13, to which
it is connected by cable 14. Head-mounted display 12 preferably also
includes sensors (not shown) to determine the user's head movements, so
that no matter where user 10 may turn his or her head, display 12 will
project an image that realistically follows the user's head movements.
User 10 is preferably sitting on a motion base 15 which moves to simulate
the motion of, in the preferred embodiment, a magic carpet, in response to
user manipulation of control device 16 which is disguised to feel, in the
preferred embodiment, like the edge of a carpet.
Processor 13 may suitably be an ONYX Reality Engine 2 parallel computer
from Silicon Graphics, Inc., of Mountain View, Calif., having eight
parallel central processing units. A particularly preferred helmet 11 is
described in copending, commonly-assigned U.S. patent application Ser. No.
08/267,183, filed concurrently herewith and hereby incorporated by
reference in its entirety. A particularly preferred head-mounted display
is described in copending, commonly-assigned U.S. patent application Ser.
No. 08/267,187, U.S. Pat. No. 5,488,508, filed concurrently herewith and
hereby incorporated by reference in its entirety. A particularly preferred
motion base 15 is described in copending, commonly-assigned U.S. patent
application Ser. No. 08/267,787, filed concurrently herewith and hereby
incorporated by reference in its entirety. A particularly preferred
control device 16 is described in copending, commonly-assigned U.S. patent
application Ser. No. 08/267,429, now abandoned, filed concurrently
herewith and hereby incorporated by reference in its entirety.
The invention can be explained by reference to virtual world 20, shown
schematically in FIG. 2. Virtual world 20 is a cave having a mouth 21 and
a plurality of chambers 22, 23, 24, 25 and 26 interconnected by
passageways 27, 28, 29, 200 and 201. The user's objective is to
successfully navigate the cave, surviving various perils (not shown) to
reach chamber 26 which contains a treasure indicated by starburst 202.
Virtual world 20 is projected onto display 12 by processor 13, which also
defines nominal path 203, and alternative nominal path 204, both of which
lead to treasure 202, but through different chambers and passageways.
Processor 13 also projects guide 30 (shown schematically in FIGS. 3-4B),
which in the preferred embodiment may take the form of a talking bird, and
virtually connects guide 30 to user 10 (shown schematically in FIGS. 3-4B)
with virtual tether 31. As seen in FIG. 3, tether 31 is relatively long
(although more tether is "reeled up" inside guide 30) and user 10 is
moving in a direction, indicated by arrow A, that differs from the
direction of motion of guide 30 along path 203. In FIGS. 4A and 4B, user
10 is passing through chamber 24. In FIG. 4A, user 10 is in the middle of
chamber 24, and, given a long tether 31, is exploring back wall 40, and
moving in the direction of arrow B. In FIG. 4B, guide 30 has advanced
along path 203 to a point where it and user 10 must exit chamber 24 to
enter passage 29. As can be seen, tether 31 has been shortened to a
minimum length (a large amount of tether 31 can be seen "reeled up" inside
guide 30), and user 10 is constrained to follow directly behind guide 30.
In addition, as discussed above, tether 31 can be shortened, and guide 30
moved faster along path 203, when user 10 takes too long on his or her own
to advance toward treasure 202 based on the time constraints of the
virtual reality experience.
As discussed above, virtual world 20' includes an alternate path 204
leading user 10 through chamber 25 instead of chamber 24. Processor 13 may
be programmed to select path 203 or 204 based on steering inputs by user
10 at or near point 205 (FIG. 2). Thus, if user 10 veers left to explore
back wall 206 of chamber 23, he may end up on path 204. Alternatively, or
additionally, processor 13 may be programmed to change from path 203 to
path 204, or vice-versa, if user 10, tethered to guide 30 on one path or
the other, moves to within a certain distance of the alternate path. Thus,
user 10 might end up on path 203 after passing point 205, but may then
decide to fly around chamber 23. If in doing so he comes close to path
204, processor 13 may move guide 30 onto path 204. The distance within
which user 10 must approach an alternate path before guide 30 is switched
to it may be constant, or may be variable. For example, to switch to path
204 near back wall 206, user 10 may have to actually cross path 204. But
to switch to path 204 near passage 200, the user may not have to get as
close to path 204; this allows processor 13 to switch user 10 to path 204
on sensing that he or she is flying toward passage 200 without waiting for
him or her to actually reach the entrance to passage 200. Of course, user
10, once having switched paths, could switch back depending on the elapsed
time or on the spatial constraints in chamber 23; in a bigger chamber,
there would be fewer constraints.
FIG. 5 shows a flow diagram of a preferred embodiment of a software routine
50 for implementing the present invention. Routine 50 is preferably a
loop, starting at 51 and ending at 52, within the larger virtual reality
simulation program (not shown), which is executed substantially
continually in processor 13 to update the user's speed and position.
At step 53, the leader object is placed on the selected animation path.
Next at step 54, the system checks to see if the user is closer to the
leader object than a preferred leading distance, LEADER.sub.--
OBJECT.sub.-- LEAD.sub.-- DISTANCE. If so, then the user is too close to
the leader object, and the system moves to test 55 to determine if the
reason is that the leader object has reached the end of the path. If not,
then at step 56 the leader object is moved further along the path to
maintain the desired leading distance. Note that LEADER.sub.--
OBJECT.sub.-- LEAD.sub.-- DISTANCE can be dynamically variable, changing
as the user moves through different parts of the virtual space, as
discussed above. Thus, LEADER OBJECT LEAD DISTANCE may represent the
current length of virtual tether 31.
If the user is not closer to the leader object than LEADER.sub.--
OBJECT.sub.-- LEAD.sub.-- DISTANCE (test 54), or is closer but the leader
object has reached the end of the path (test 55), then the system moves to
test 57 to determine whether or not the user is closer to the leader
object than a minimum acceptable leading distance, LEADER.sub.--
MIN.sub.-- DISTANCE. If the user is at least as close to the leader object
as LEADER.sub.-- MIN.sub.-- DISTANCE, then the user has effectively caught
up to the leader object and the program controlled portion of the user's
speed of progress through the virtual space is set to zero at step 58, and
the program proceeds to step 506 (discussed below). Note that if test 57
is reached because of a negative result at test 54, then test 57 cannot
yield a negative result. Thus step 58 will only be reached when test 57 is
reached as a result of a positive result at test 55. In fact, in an
alternative embodiment (not shown), a negative result at test 54 could
lead directly to step 59 (discussed below), with test 57 only being
reached from a positive result at test 55.
In either embodiment, if at test 57 the user is farther from the leader
object than LEADER.sub.-- MIN.sub.-- DISTANCE, the system proceeds through
a series of steps designed to make sure that the user follows, and stays
within a predetermined distance from, the leader object. First, the system
recognizes that the user may not even be facing the leader object and at
step 59 the program portion of the orientation control is moved by a
predetermined percentage, THETA.sub.-- PERCENT, toward the leader object
(rather than forcing the user suddenly to face the leader object). Next,
at test 500 the system determines whether or not the user is facing within
a predetermined angular threshold toward the leader object. If not, that
means that the user is moving in a direction completely away from the
leader object, and at step 503 the program speed is decreased to prevent
the user from going too far in the wrong direction before his or her
course can be corrected (thus reeling in the virtual tether), and the
system proceeds to step 506 (discussed below).
If at test 500 the user is facing within the angular threshold toward the
leader object, then the system proceeds to test 501 to determine whether
or not the user is closer to the leader object than LEADER.sub.--
OBJECT.sub.-- LEAD.sub.-- DISTANCE. If not, the user is not too close to
the leader object and the system advances to test 504 to determine if the
program control is already at maximum speed. If not, then at step 505 the
program speed is increased and the system advances to step 506 (discussed
below). If at test 504 the program is already at maximum speed, the system
advances directly to step 506.
If at test 501 the user is closer to the leader object than LEADER.sub.--
OBJECT.sub.-- LEAD.sub.-- DISTANCE, then the user is too close and must be
slowed down, and the system advances to test 502 to see if the program
control is already at zero speed. If program speed is still greater than
zero, then at step 503 program speed is decreased and the system advances
to step 506. If at test 502 program speed is found to be zero already,
then the system advances directly to step 506.
The steps recited up to this point are carried out to keep the user's speed
and distance from the leader object under control to substantially the
maximum extent possible using only program controls. By speeding up and
slowing down the program, the user can be kept further from leader object
30 than a minimum radius r.sub.1 (see FIG. 6) corresponding to
LEADER.sub.-- MIN.sub.-- DISTANCE, but not farther from leader object 30
than a maximum radius r.sub.2 corresponding to LEADER.sub.-- OBJECT.sub.--
LEAD.sub.-- DISTANCE, thereby keeping user 10 within zone 60 relative to
leader object 30. Of course, as discussed above, the variables
representing radii r.sub.1 and r.sub.2 can be dynamically variable,
changing as user 10 moves through the virtual space to take into account
the characteristics (e.g., narrow or wide open) of the current location,
or to take into account elapsed time (e.g., after a certain elapsed time
user 10 may be given less freedom of movement if he or she has proceeded
too slowly, so that the leader object can advance user 10 to the objective
within the allotted time).
Having adjusted the program control as much as possible at 58, 502, 503,
504 or 505, the system at step 506 determines what speed and directional
commands user 10 is inputting at control device 16. At steps 507 and 508,
the user inputs are blended with the program inputs and used to update the
position and orientation of user 10 at step 509 before the loop ends at
52.
The loop 50 preferably is continually repeated to update user position and
orientation. The relative weights given to user inputs and program inputs
in steps 507-509 preferably change dynamically depending on the location
of user 10 in the virtual space, and on elapsed time, or on other factors,
thereby implementing the virtual tether as described above. As shown in
FIG. 5, the update of user position in step 509 is actually described as
an update of the position and orientation of the user's vehicle (e.g.,
magic carpet). This is because user 10 is allowed to turn his or her head
to any orientation; in the preferred embodiment, the program can only
control the vehicle (on the other hand, user and vehicle position, as
opposed to orientation, are virtually identical, at least for purposes of
the preferred embodiment).
Thus it is seen that a virtual reality system is provided in which a user
can be guided within a virtual space to a specific destination within a
specific time while providing the impression that the user is free to roam
the virtual space at will. One skilled in the art will appreciate that the
present invention can be practiced by other than the described
embodiments, which are presented for purposes of illustration and not of
limitation, and the present invention is limited only by the claims that
follow.
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