The panoramic viewing technology can be applied to
applications which require the exploration of real or imaginary
scenes. Some example applications include virtual travel, real
estate property inspection, architecture visualizations, virtual
museums, virtual shopping and virtual reality games.
An example of panoramic movie application is the
commercial CD-ROM title: Star Trek/The Next Generation–
Interactive Technical Manual. This title lets the user navigate
in the Starship Enterprise using panoramic movies. Several
thousand still photographs were shot to create more than two
hundred panoramic images, which cover most areas in the
starship. In addition, many object movies were created from the
The object movie can be applied to visualize a scientific or
engineering simulation. Most simulations require lengthy
computations on sophisticated computers. The simulation
results can be computed for all the possible view orientations
and stored as an object movie which can be inspected by
anyone with a personal computer.
Time-varying environment maps may be used to include
motions in a scene. An example of time-varying environment
maps has been generated using time-lapse photography. A
camera was fixed at the same location and took a panoramic
picture every 30 minutes during a whole day. The resulting
movie shows the time passage while the user is freely looking
Another use of the orientation-independent movie is in
interactive TV. A movie can be broadcast in a 360-degree
format, perhaps using multiple channels. Each TV viewer can
freely control the camera angle locally while watching the
movie. A similar idea called “electronic panning camera” has
been demonstrated for video conferencing applications [29].
Although most applications generated with the image-based
approach are likely to be CD-ROM based in the near future
because of CD-ROM's large storage capacity, the variable
resolution files make the approach practical for network
transmission. A low-resolution panoramic movie takes up less
than 100 KB per node and provides 360-degree panning in a
320x240-pixel window with reasonable quality. As network
speeds improve and better compression technologies become
available, on-line navigation of panoramic spaces may become
more common in the near future. One can use the same spatial
navigation metaphor to browse an informational space. The
ability to attach information to some spatial representations
may make it easier to become familiar with an intricate
6. CONCLUSIONS AND FUTURE DIRECTIONS
The image-based method makes use of environment maps,
in particular cylindrical panoramic images, to compose a
scene. The environment maps are orientation-independent
images, which allow the user to look around in arbitrary view
directions through the use of real-time image processing.
Multiple environment maps can be linked together to define a
scene. The user may move in the scene by jumping through the
maps. The method may be extended to include motions with
time-varying environment maps. In addition, the method
makes use of a two-dimensional array of frames to view an
object from different directions.
The image-based method also provides a solution to the
levels of detail problem in most 3D virtual reality display
systems. Ideally, an object should be displayed in less detail
when it is farther away and in more detail when it is close to the
observer. However, automatically changing the level of detail
is very difficult for most polygon based objects. In practice,
the same object is usually modeled at different detail levels and
the appropriate one is chosen for display based on some
viewing criteria and system performance [30], [31]. This
approach is costly as multiple versions of the objects need to
be created and stored. Since one can not predict how an object
will be displayed in advance, it is difficult to store enough
levels to include all possible viewing conditions.
The image-based method automatically provides the
appropriate level of detail. The images are views of a scene
from a range of locations. As the viewpoint moves from one
location to another within the range, the image associated with
the new location is retrieved. In this way, the scene is always
displayed at the appropriate level of detail.
This method is the underlying technology for QuickTime
VR, a system for creating and interacting with virtual
environments. The system meets most of the objectives that we
described in the introduction. The playback environment
supports most computers and does not require special hardware.
It uses images as a common representation and can therefore
accommodate both real and imaginary scenes. The display
speed is independent of scene complexity and rendering quality.
The making of the Star Trek title in a rather short time frame
(less than 2 months for generating all the panoramic movies of
the Enterprise) has demonstrated the system's relative ease in
creating a complex environment.
The method’s chief limitations are the requirements that the
scene be static and the movement be confined to particular
points. The first limitation may be eased somewhat with the use
of time-varying environment maps. The environment maps
may have motions in some local regions, such as opening a
door. The motion may be triggered by an event or continuously
looping. Because the motions are mostly confined to some
local regions, the motion frames can be compressed efficiently
with inter-frame compression.
Another solution to the static environment constraint is the
combination of image warping and 3D rendering. Since most
backgrounds are static, they can be generated efficiently from
environment maps. The objects which are time-varying or
event driven can be rendered on-the-fly using 3D rendering. The
rendered objects are composited onto the map-generated
background in real-time using layering, alpha masking or z
buffering. Usually, the number of interactive objects which
need to be rendered in real-time is small, therefore, even a
software based 3D renderer may be enough for the task.
Being able to move freely in a photographic scene is more
difficult. For computer rendered scenes, the view interpolation
method may be a solution. The method requires depth and
camera information for automatic image registration. This
information is not easily obtainable from photographic
Another constraint with the current panoramic player is its
limitation in looking straight up or down due to the use of
cylindrical panoramic images. This limitation can be removed
if other types of environment maps, such as cubic or spherical
maps, are used. However, capturing a cubic or a spherical map
photographically may be more difficult than a cylindrical one.
The current player does not require any additional input and
output devices other than those commonly available on
personal computers. However, input devices with more than
two degrees of freedom may be useful since the navigation is
more than two-dimensional. Similarly, immersive stereo
displays combined with 3D sounds may enhance the experience
One of the ultimate goals of virtual reality will be achieved
when one can not discern what is real from what is virtual. With
the ability to use photographs of real scenes for virtual
navigation, we may be one step closer
