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Online Virtual Environments: Second Life. Networked Virtual Worlds. Early interest in shared virtual spaces Training Social Scalability Difficult issues Consistency Latency Bandwidth. History. SIMNET.

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Presentation Transcript
networked virtual worlds
Networked Virtual Worlds
  • Early interest in shared virtual spaces
    • Training
    • Social
    • Scalability
  • Difficult issues
    • Consistency
    • Latency
    • Bandwidth
  • 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
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
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 dogfight1
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.
  • 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.
  • 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


  • 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
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 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 park1
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
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

SIMNET First Demo (86)

SIMNET to Army (90)

SIMNET Start (83)

SGI Dogfight (85)

NPS FOG-M (86)

NPS-Stealth (93)


NPS MPS-1 (88)

NPSNET-1 (90)

SGI Flight (84)

NPS VEH (87)

Paradise (93)

BrickNet (91)

Amaze (84)

Doom (93)

DIVE (92)

DIS (93)





A Brief Timeline of Net-VEs
what is second life
What is Second Life?
  • An interactive virtual world
    • “residents” can make or modify virtually anything
    • IP rights form the basis of an economy

From as of Jan. 19th, 2007

what runs sl
What runs SL?
  • From June 6, 2006 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
SL Technology
  • Havok physics engine
  • Dynamic lighting
  • Weather
basic concepts
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