1. Latency and Player Actions in Online Games Mark Claypool & Kajal Claypool Worcester Polytechnic Institute Communications of the ACM, Nov. 2006 Presented by Te-Yuan Huang

2. Outline Goal & Contribution Game Classification Game Phases Action Categorization

3. Goal & Contributions of the Work Clarify the effects of latency on player actions Categorize the actions Benefit Game designers Network designers Game players

4. Game Classification Interaction model how the player interacts with the game world Perspective how the player views the game world

5. Game Classification (Cont.) Interaction model Avatar model First Person Perspective Third Person Perspective Omnipresent model Mostly a bird eyes’ view

6. Game Phases Setup Players select starting parameters Or load previous game info. Interact mostly with local game program Low network traffic Not significantly affected by latency Synchronization Play Transition

7. Game Phases (Cont.) Setup Synchronization Synchronize game state and parameter settings High bit rate No user interactions involved Not affected by latency Play Transition

8. Game Phases (Cont.) Setup Synchronization Play Actually played Moderate bit rate Small packet send frequently Significantly affected by latency Transition

9. Game Phases (Cont.) Setup Synchronization Play Transition Loading game information from local disk Ex: Map Low bit rate No player interactions Unaffected by latency

10. Game Phases (Cont.)

11. Two properties of the actions Precision the degree of accuracy required to complete the action successfully Deadline the time required to complete the action the tighter the deadline is required the greater the impact of latency

12. Why Precision Matters? the higher the precision required the greater the impact of latency on performance.

13. Why Deadline Matters?

14. Two properties of the actions

15. Test environment

16. Avatar, First Person Tournament 2003, a First Person Shooter Game RC Racing, A Racing Game 35% sharp drop Steep Increase

17. Avatar, Third Person Madden NFL, a Sport GameEverquest 2, a Third-Person RPG no steep drop until 500 ms no steep incr. until 800 ms

18. Omnipresent Warcraft III, a real-time strategy game No much differences

19. Summary

20. My Conclusion Rich Information Try to generalize information in some way The effect of latency is still vague Still no way to quantify the effect Details about the experiment are missing Do not know whether the data is also player dependent No thorough comparisons in test part Do not know if the games they choose are representative More aspect can be discussed Not only latency, delay jitter … etc