The project was divided into 3 phases. Phase 1 was the concept formation
and definition, Phase 2 was a technological assessment. One of the
conclusions reached in Phase 2 was that the cost of doing broadband
network experiments across large distances would be prohibitively
expensive at present. Additional funds and partners would be needed.
Phase 3 started in January 1994. Its purpose was to design, develop and
demonstrate a preliminary testbed using conventional networking
technologies. The initial testbed would be used to explore the
feasibility of the GreenSpace concept, to provide visibility to the
project to aid in raising additional funds and to find additional
partners.
Phase 3 culminated in a public demonstration linking Tokyo and Seattle in
a realtime VR teleconference during November 14-17, 1994. The demo site
in Tokyo was the NICOGRAPH Convention (the Japanese equivalent of
SIGGRAPH), and the Seattle site was the HITLab.
Participants can hear each other, albeit poorly.
The hardware configuration used for the demo is shown below:
Network Description and Bandwidth Requirements
The trans-Pacific network for this demonstration is illustrated in
subsequent diagrams.
Since we had two participants on each side of the Pacific, we needed to
track the motion of each participant's head (for viewing) and hand (for
interacting with the world). This meant we sent information on 8 tracked
objects across the network. The payload for doing this is:
(8 objects) x (6 DOF) x (32-bit floats) x (30Hz) = 46Kbps
Typically, the loss of bandwidth due to IP encapsulation overhead and
packet collision reduces the payload to about 70% of the line bandwidth.
This means that 8 tracked objects required approximately 46Kbps/0.7 =
64Kbps.
Since we also wanted one mono audio channel to be transmitted
bidirectionally over the net, the payload would be and additional 2 x 8KHz
x 8-bit ulaw samples = 128Kbps. This is telephone quality audio. Again,
taking into account IP overhead, the required bandwidth becomes:
128Kbps/.7 = 183Kbps.
Thus, for a simulation with 2 participants + 1 mono audio channel on each
side, our expected bandwidth requirements were approximately:
183Kbps + 64Kbps = 247Kbps
The ISDN BRI (Basic Rate Interface) has 2 B channels for data and 1 D
channel for signalling and control. Each B channel can carry 56Kbps or
64Kbps, depending on the carrier. Assuming we can get 64Kbps per
B-channel, we need 2 BRI lines to support the 247Kbps requirement above.
Using a bandwidth-on-demand ISDN/Ethernet bridge or router (such as the
Ascend Pipeline 400B), B channels can be combined to form one logical
channel with higher bandwidth. According to the rough calculations above,
we required 4 or more B channels for the demo. To be safe, we used 6 B
channels (3 BRI lines) for the IP traffic.
We also used a conventional video teleconference system so that the crowds
can see each other. The teleconference system required one additional BRI
line.
Phase 2
The objective of GreenSpace II is to apply the concept of distributed
VR to a particular application domain. The chosen application is
architectural design. Architectural design requires a great deal of
coordination and communication between different individuals.
Architects need to communicate design ideas between themselves and
between others. They need to communicate to their clients, engineers,
building officials and many other types of individuals. To
communicate architects traditionally use drawings and models, as well
as normal business communication devices such as the fax machine and
the telephone. A common situation, where architects present their
work, is called the design review or design presentation. In academic
settings this occurs when a student presents his design work to group
of critics, and in a professional setting it occurs when an architect
presents his design ideas to a client. The GreenSpace II efforts have
focused on this common situation of a designer presenting his work to
a particular audience for analysis and commentary .
In March of this year the GreenSpace II technical team working with
the CEDeS lab produced a working prototype for distributed design
reviews in virtual space. To demonstrate this system the CEDeS lab
selected a simple architectural problem the design of a hotel
Guestroom. This program was selected because it was small enough so
as not to require too complex a model for each design proposal, but
yet had enough potential to provide dramatic differences in spatial
quality. Three different guest rooms were designed. For each room
different versions were generated to show the room as an empty space,
and as a furnished room.
In addition a number of tools were implemented which would facilitate a
remote discussion of the architectural space. Each participant is
represented as an avatar with a stylized hand/pointer. In each
alternative guest room there was a work table which had a scale model
of each of the design proposals. This allowed the participants to view
each of the three alternatives while there were immersed within one of
the rooms. To support the architectural discussions of the
participants each of these scale models could be "clipped" with a
clipping tool. This provided a way to "clip" the models in order to
see a plan or section of any one of the designs.
On the table were place additional icons which represented different
versions of each of the three guest rooms. In the first demonstration
of the system each of the three rooms had three associated icons. One
of the icons represented that room rendered in a neutral color and flat
shaded. The second icon represented the room rendered with textures.
These textures were generated by the radiosity application
Lightscape,
and represented a specific lighting condition. The third icon
represented the room with a furnished and illuminated condition. The
current system allows for two additional room alternatives which will
be variations in furnishings, color and/or lighting schemes. By
selecting any one of these icons a participant could move through a
jump-portal to that version of a particular room.
The CEDeS lab and the GreenSpace II team will be carrying out a number
of experimental design reviews with invited architects from the Seattle
professional community and the Department of Architecture. Currently
the system is distributed within the HIT Lab itself. It is planned
that future work will include a geographically remote distributed
implementation of the system.
See Also:
Greenspace VRML Archive
The GreenSpace Project started as a brainchild of Dr. Thomas Furness of HITL and Dr. Masahiro Kawahata of the Fujitsu
Research Institute in April 1993, and is jointly funded by the two
institutions. The goals of the project are to to develop and demonstrate
an immersive communications medium where distant participants feel a sense
of presence in a shared virtual environment, a "virtual common".
Ultimately, the project aims to promote collaboration at a distance among
100 or more participants over broadband networks such as SONET/ATM,
immersed in an environment rich in visual, aural and tactile cues.
