AVATARS ON THE NET

Mitra

Chief Network Technology Officer

ParaGraph International

http://www.paragraph.com

http://www.mitra.biz

Avatars on the Net

• The Challenge
• History
• Human Problems
• Technical Problems
• Solutions
• The Future

THE CHALLENGE

• Merging Graphics with Online Services
• Working with what consumers have now

Merging Graphics with Online Services

• Online Services Brings
  • Community
  • Interactivity
  • Dynamics
• Graphics Brings
  • 3D
  • Visually appealing

Working with what consumers have now

• Pentium 90, 16Mb, SVGA
• 14,400 Baud Internet connection
• CD-ROM

HISTORY

• 1D (Text)
• 2D (Images)
• 2.5D
• 3D

1D - Text

• AOL
• IRC
• MUDs

2D - Images

• Habitat and Worlds Away
• Palace

2.5D - Restricted 3D

• Worlds Chat

3D - Full 3D

• Black Sun
• AlphaWorld
• Online
• ParaGraph
• Military Systems

HUMAN PROBLEMS

• Suspend Disbelief
• High Expectations
• Rapid Response
• Rich Worlds
• Interactivity
• Flexibility Vs. Control
• Representing Yourself Online

Suspend Disbelief

• I'm in the Clouds by the Castle

High Expectations

• Movies
• Games

Rapid Response

• Humans react quickly

Rich Worlds

• Textures
• Objects
• Depth
• Lighting

Flexibility vs. Production

• Who builds the world
• Who changes the world

Representing yourself online

• Wide range of Avatars
• Different Avatars

TECHNICAL PROBLEMS

• Rendering
• Client bandwidth
• Server bandwidth
• Server power
• Security v. Flexibility

MORE TECHNICAL PROBLEMS

• Rapidly changing content
• Network quality
• '000s of Avatars
• Composability

Rendering

• Cannot render infinite polygons
• Rendering time vs. Quality
• Sprites vs. Polygons

Client Bandwidth

• Per Avatar per update: Id, Position, Orientation, Velocity
  • = (2 + 3 + 4 + 3) * 4 = 42 bytes
• Network Overhead ~ 30 bytes per packet for a total of 72 bytes
• Sent 5 times a second = 360 bytes per avatar per second
• 1000 avatars in the world = 360K bytes (3.6 MBaud) per second PER CLIENT

Server Bandwidth

• Assume clients using half of 14,400 baud modem = 7Kbaud
• 1000 clients, using 7Kbaud = 7Mbaud = 6 * T1

Server Power

• 1,000 users x 5 updates per second
• sorting ~ n^2

Security v. Flexibility

• Can a downloaded Applet edit your world?

Rapidly Changing Content

• Eats Bandwidth
• Loads servers

Network Quality

• 200 ms - 2 second latency
• 10% packet loss

'000s of Avatars

• Entering new rooms
• Download
• Memory and Disk

Composability

• Portable objects
• Debugging

SOLUTIONS

• Clever Protocols
• Sprites and Polygons
• Crowd Control
• Local Behaviors
• Modular Behaviors
• Distributed Servers
• CD-ROM *and* Net
• Mr Potato Head

Clever Protocols

• 400 bytes per second
• UDP

DIS

• Not designed for people who pay for bandwidth
• Huge packets
• Military orientation
• Multicast

Multicast

• Not widely deployed yet
• Bandwidth ~ n
• Designed for static groups, not rapidly changing
• Designed for large groups, not small

Sprites and Polygons

• Optimize quality for rendering speed

Crowd Control

• Only show neighbors

Local Behaviors

• Reduce network bandwidth
• Reduce latency
• D/D96
• VRML2.0

Modular Behaviors

• D/D96
• Flexible Event Structure
• Modularity
• VRML2.0

Distributed Servers

• Share the load
• Allow scaling to '000s of users

CD-ROM *and* Net

• Downloaded textures
• Some downloaded Geometry
• Changeable portions over the network

Mr Potato Head ®

• Kit of parts
• Repeated textures

FUTURE

• Near
• Further

Near

• '000's of simultaneous users
• Shared State
• Voice
• VRML 2.0
• CD-ROM's

VRML 2.0

• Cleans up VRML 1.0
• Adds Features
• Adds Behavior to VRML 1.0

Cleans up VRML 1.0

• Removes state from scene graph
• Changes geometry

Adds

• Sound
• Elevation Grids
• General Cylinders
• Sensors
• Interpolators

Behaviors

• Adds Behavior to VRML 1.0
• Supports behaviors in multiple languages

Further

• Replaces 2D on the Web
• Immersive
• ???

AVATARS ON THE NET

Mitra

Chief Network Technology Officer

ParaGraph International

http://www.paragraph.com

http://www.mitra.biz