Latency Can Kill Precision and Deadline in Online

Latency Can Kill: Precision and Deadline in Online Games Mark Claypool Kajal Claypool Professor of CS Director of IMGD Worcester Polytechnic Institute Staff Scientist MIT Lincoln Labs ACM MMSys Scottsdale, AZ, USA February 2010

Is It Latency or Do You Just Suck? http: //www. youtube. com/watch? v=r 6 Pw. Hkh. EAk. U http: //www. youtube. com/watch? v=Bn 1 n. BR 5 j. Ox 8

Is It Latency or Do You Just Suck? Delayed response “Magic” bullets http: //www. youtube. com/watch? v=r 6 Pw. Hkh. EAk. U Server matters http: //www. youtube. com/watch? v=Bn 1 n. BR 5 j. Ox 8

Outline • Introduction • What is latency for games? • Why does it matter? • How much does it matter? • Do you have evidence? ACM MMSys 4 (done) (next) February 23, 2010

What is Network Latency? Game client • Internet Latency - time to get from source to destination – There and back (round-trip time) ACM MMSys 5 February 23, 2010 Game server

Why Does Latency Matter? User Input Message: User Input Response time Message: Ok User Input Render Input Time Affects responsiveness ACM MMSys 6 February 23, 2010 Process and Validate Input

Example of Unresponsiveness Player is pressing left Player is pressing up Running back goes out of bounds! Player curses

Why Does Latency Matter? Response time User Input Process and Validate Input Message: User Input Render Input Message: Ok with Update Fix Up Time Affects consistency ACM MMSys 8 February 23, 2010

Example of State Inconsistency ACM MMSys 9 February 23, 2010

Why Does Latency Matter? Message: Treasure! User Input Message: Treasure! Message: Get treasure Message: Ok Message: Tough luck! Time Affects fairness ACM MMSys 10 February 23, 2010 User Input

Outline • Introduction • What is latency? • Why does it matter? • How much does it matter? • Do you have evidence? ACM MMSys 11 (done) (next) February 23, 2010

How Much Does Latency Matter? Depends upon precision of action ACM MMSys 12 February 23, 2010

How Much Does Latency Matter? latency now latency later (tight deadline) now (loose deadline) Depends upon deadline of action ACM MMSys later 13 February 23, 2010

Precision and Deadline Higher Precision Lower Third-Person Avatar Running Omnipresent Casting Area Spell Exploring Shooting Grenades Shooting Machine Gun Fighting First-Person Avatar Combat Racing Drinking Health Potion Shooting Sniper Tighter ACM MMSys Moving Deadline 14 February 23, 2010 Building Looser

Player Performance vs. Latency ACM MMSys 15 February 23, 2010

Outline • Introduction • What is latency? • Why does it matter? • How much does it matter? • Do you have evidence? (done) (next) – Methodology – Results ACM MMSys 16 February 23, 2010

Methodology (1 of 3) • Goal: – Vary: precision & deadline of actions – Control : latency – Measure: performance • Modify open source game – BZ Flag http: //www. youtube. com/watch? v=x. MYkw 56 t 1 Gg ACM MMSys 17 February 23, 2010

Methodology (2 of 3) • Varying precision – • Steps: tank size – Larger tanks equal lower precision • Varying deadline – bullet speed – Slower bullets equal looser deadline ACM MMSys 18 1. Made changes 2. Verify and validate 3. Determined game length, number of iterations 4. Ran experiments 5. Analysis February 23, 2010

Methodology (3 of 3) • 8 computer-controlled tanks (bots) • 2 hour runs ACM MMSys 19 February 23, 2010

Results for Precision (Tank Size) ACM MMSys 20 February 23, 2010

Results for Deadline (Bullet Speed) ACM MMSys 21 February 23, 2010

Summary • Latency can kill (your fun!) – Responsiveness, Consistency, Fairness • Amount depends upon player action – Precision – accuracy required to complete action successfully – Deadline – time required to achieve the final outcome of action • Effects grouped based on perspective – First-person avatar – Third-person avatar – Omnipresent ACM MMSys 22 February 23, 2010

What to Do About It? • Network improvements – Shift latency “left” – But mobile, wireless emerging! • Server selection – Shift latency “left” – But limited selection and/or want to play with friends! – And want more players (1000 v 1000)! • Latency compensation techniques - help “deal with it” (so the player doesn’t have to!) – Shift curves “up” – But often tradeoffs (e. g. consistency and responsiveness) ACM MMSys 23 February 23, 2010

Latency Can Kill: Precision and Deadline in Online Games Mark Claypool Kajal Claypool Professor of CS Director of IMGD Worcester Polytechnic Institute Staff Scientist MIT Lincoln Labs ACM MMSys Scottsdale, AZ, USA February 2010

Is It Latency or Do You Just Suck? http: //www. youtube. com/watch? v=r 6 Pw. Hkh. EAk. U http: //www. youtube. com/watch? v=e. Fk. Jkk. Dz. Ua. I http: //www. youtube. com/watch? v=Bn 1 n. BR 5 j. Ox 8

Demonstration of Latency (1) ACM MMSys 26 February 23, 2010

Demonstration of Latency (2) ACM MMSys 27 February 23, 2010

Demonstration of Latency (3) ACM MMSys 28 February 23, 2010

Game Perspectives First Person Linear Third Person Linear Omnipresent Third Person Isometric ACM MMSys 29 February 23, 2010