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

NET

Sta

rt (8

3)

SGI F

light

(84)

SGI D

ogfig

ht (8

5)

Am

aze

(84)

SIM

NET

Firs

t Dem

o (8

6)N

PS F

OG

-M (8

6)

NPS

VEH

(87)

NPS

MPS

-1 (8

8)

SIM

NET

to A

rmy

(90)

NPS

NET

-1 (9

0)

Bric

kNet

(91)

DIS

(93)

DIV

E (9

2)N

PS-S

teal

th (9

3)

NPS

NET

-IV (9

3)D

oom

(93)

Para

dise

(93)

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!