The Technology of the Game -Latency and Online Games

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The Technology of the Game -Latency and Online
Games

• Mark Claypool

Associate Professor Computer Science
Director Interactive Media and Game Development
Worcester Polytechnic Institute
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(No Transcript)
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Software Engineering Human-Computer
Interaction Computer Architecture Databases Graphi
cs and Animation Artificial Intelligence
Computer Networks
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Outline

• Introduction (done)
• What is latency? (next)
• Why does it matter?
• How much does it matter?
• What can be done?

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What is Network Latency?

• Latency - time to get from source to destination
• There and back (round-trip time)

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Why Does Latency Matter?
Affects responsiveness
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Example of Unresponsiveness
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Why Does Latency Matter?

• Affects consistency

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Example of State Inconsistency
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Why Does Latency Matter?
Affects fairness
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How Much Does Latency Matter?
Depends upon precision of task
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How Much Does Latency Matter?
Depends upon deadline of task
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Precision and Deadline
Lower
Casting Area Spell
Running
Exploring
Shooting Grenades
Precision
Shooting Machine Gun
Fighting
Racing
Combat
Moving
Higher
Drinking Health Potion
Shooting Sniper
Building
Deadline
Tighter
Looser
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Player Performance vs. Latency
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Outline

• Introduction (done)
• What is latency? (done)
• Why does it matter? (done)
• How much does it matter? (done)
• What can be done? (next)
• Time Manipulation

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Latency Compensation - Time Delay

• Server delays processing of events
• Wait until all messages from clients arrive
• Server also sends messages to more distant client
  first, delays messages to closer

Server processes both client commands
Client 1 command arrives
Client 2 command arrives
Time
Time Delay
Disadvantage decreases responsiveness to that
of player with highest latency
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Latency Compensation - Time Warp

• Server rolls-back (warps) to when action taken
  place on client

Disadvantage user may notice when fix state
inconsistency
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The Technology of the Game -Latency and Online
Games

• Mark Claypool

Associate Professor Computer Science
Director Interactive Media and Game Development
Worcester Polytechnic Institute
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References

• Valve Developer Community. Source Multiplayer
  Networking, Online at http//developer.valvesoft
  ware.com/wiki/Source_Multiplayer_Networking
• Mark Claypool and Kajal Claypool. Latency and
  Player Actions in Online Games, Communications
  of the ACM, Volume 49, Issue 11, November 2006.
  Online at http//www.cs.wpi.edu/claypool/papers/
  precision-deadline/
• James Nichols and Mark Claypool. The Effects of
  Latency on Online Madden NFL Football, In
  Proceedings of the 14th ACM International
  Workshop on Network and Operating Systems Support
  for Digital Audio and Video (NOSSDAV), Kinsale,
  County Cork, Ireland, June 16-18, 2004. Online
  at http//www.cs.wpi.edu/claypool/papers/madden/
  
• Grenville Armitage, Mark Claypool, and Philip
  Branch. Networking and Online Games
  Understanding and Engineering Multiplayer
  Internet Games, John Wiley and Sons, Ltd., June
  2006. ISBN 0470018577. Online at
  http//www.cs.wpi.edu/claypool/papers/book/