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 “low-cost” 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”).
A Brief Timeline of Net-VEs
1980 1985 1990 1995
SIM
NE
T S
tart
(83
)
SG
I F
lig
ht
(84)
SG
I D
og
fig
ht
(85)
Am
aze
(84)
SIM
NE
T F
irst
Dem
o (
86)
NP
S F
OG
-M (
86)
NP
S V
EH
(87
)
NP
S M
PS
-1 (
88)
SIM
NE
T t
o A
rmy
(90)
NP
SN
ET
-1 (
90)
Bri
ckN
et (
91)
DIS
(93
)
DIV
E (
92)
NP
S-S
teal
th (
93)
NP
SN
ET
-IV
(93
)D
oo
m (
93)
Par
adis
e (9
3)
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!