Online Virtual Environments:
Second Life
Networked Virtual Worlds
• Early interest in shared virtual spaces
– Training
– Social
– Scalability
• Difficult issues
– Consistency
– Latency
– Bandwidth
History
SIMNET
•The goal of the
SIMNET project (1990)
was to develop a “lowcost” networked virtual
environment for
training small units to
fight as a team.
•Kept bandwidth low
by extrapolating
vehicle position rather
than constant
broadcast
A DIS Networked VE - CCTT
– DIS is the
successor to
SIMNET
– The US
Army's Close
Combat
Tactical
Trainer
(CCTT) is
one of the
larger scale
networked
virtual
environments
.
SGI Flight & Dogfight
– Flight was distributed in networked form on all
SGI workstations sometime after SIGGRAPH
1984 and could be seen in practically every
SGI-outfitted lab at that time, either during the
day on breaks or after hours.
SGI Flight & Dogfight
– Sometime after the release of the networked
version of Flight, in early 1985 it is believed,
SGI engineers modified the code of Flight to
produce the demonstration program Dogfight.
– This modification dramatically upgraded the
visibility of net-VEs as players could now
interact by shooting at each other.
Doom
– On 10 December 1993, id Software released
its shareware game Doom.
– The posting of Doom caught most network
administrators’ eyes when their LANs started
bogging down. Doom did no dead reckoning
and flooded LANs with packets at frame rate.
– This networked ability to blast people in a
believable 3D environment created enormous
demand for further 3D networked games.
NPSNET
– The NPSNET Research Group is the longest
continuing academic research effort in networked
virtual environments. The focus of the group is on
the complete breadth of human-computer
interaction and software technology for
implementing large-scale virtual environments
(LSVEs).
– There have been several generations of software
formally named NPSNET and several precursor
systems.
NPSNET-IV
•NPSNET-IV
Capabilities
– Building walkthroughs.
– Articulated humans mounting/dismounting
capability.
– Networking - play
across the multicast
backbone of Internet.
– Terrain database
integration, terrain paging
(70km x 70km).
– Any vehicle capability - air,
ground, articulated human.
– Testbed for VE NSA issues.
– Interoperability SIMNET/DIS
– Constructive model
integration - Janus World
Modeler
– ModSAF
NPSNET-IV
NPSNET-IV
NPSNET-IV
DIVE
• The Swedish Institute of Computer
Science Distributed Interactive Virtual
Environment (DIVE) is another early and
ongoing academic virtual environment.
Swedish Institute of Computer
Science - DIVE
•However, unlike
SIMNET the entire
database is dynamic
and uses reliable
multicast protocols to
actively replicate new
objects.
The MERL Implementation - Diamond
Park
•The MERL Diamond
Park VE is built using
SPLINE (Scalable
PLatform for INteractive
Environments) which
provides the
implementation of
locales & beacons.
The MERL Implementation - Diamond
Park
•Diamond Park has
multiple users that
interact in the park by
riding around on
bicycles and talking to
each other (Social VR).
MERL Efforts in Large -Scale
Multi-User VEs
• Locales are an efficient method for managing the flow of
data between large numbers of users in a LSVE.
• The concept of locales is based on the idea that while a
VE may be very large, most of what can be observed by
a single user at a given moment is local in nature.
• Each locale has its own multicast address & coordinate
system.
• Beacons - are a special class of objects that can be
located without knowing what locale they are in (to solve
the “how do I join the VE problem”).
1980
1985
NPSNET-1 (90)
SIMNET to Army (90)
BrickNet (91)
DIVE (92)
NPS-Stealth (93)
DIS (93)
NPSNET-IV (93)
Doom (93)
Paradise (93)
NPS MPS-1 (88)
NPS VEH (87)
NPS FOG-M (86)
SIMNET First Demo (86)
SIMNET Start (83)
Amaze (84)
SGI Flight (84)
SGI Dogfight (85)
A Brief Timeline of Net-VEs
1990
1995
What is Second Life?
• An interactive
virtual world
– “residents” can
make or modify
virtually anything
– IP rights form the
basis of an
economy
From secondlife.com as of Jan. 19th, 2007
What runs SL?
• From June 6, 2006 cnet.com article
• 2,579 dual-core Opteron servers
– Each server runs a 16 acre “sim”
– About 3 users per server!
– WoW and others run hundreds/server
SL Technology
• Havok physics engine
• Dynamic lighting
• Weather
Basic Concepts
• World divided into regions
– Each with own server
– Communication with people in one region
• Objects can have local behavior
– Trees wave in breeze
– Computed locally
• Objects are paged in as needed
• Intelligent streaming
– Streams occluders before occluded objects
Let’s take a look!