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!