Is It Latency or Do You Just Suck? Deadline in Online Games Mark - PDF document

4/4/2013 Latency Can Kill: Precision and Is It Latency or Do You Just Suck? Deadline in Online Games Mark Claypool Kajal Claypool Professor of CS Staff Scientist Director of IMGD MIT Lincoln Labs Worcester Polytechnic Institute http://www.youtube.com/watch?v=r6PwHkhEAkU ACM MMSys Scottsdale, AZ, USA February 2010 Is It Latency or Do You Just Suck? Is It Latency or Do You Just Suck? Delayed response “Magic” bullets http://www.youtube.com/watch?v=r6PwHkhEAkU Server matters http://www.youtube.com/watch?v=Bn1nBR5jOx8 http://www.youtube.com/watch?v=Bn1nBR5jOx8 What is Network Latency? Outline • Introduction (done) • What is latency for games? (next) Game • Why does it matter? client Internet • How much does it matter? • Do you have evidence? Game • Latency - time to get from source to destination server – There and back ( round-trip time ) 1

4/4/2013 Why Does Latency Matter? Example of Unresponsiveness User Input Process Message: User Input and Player is pressing left Player is pressing up Response Validate time Input Message: Render Ok User Input Input Time Affects responsiveness Running back goes out of bounds! Player curses Example of State Inconsistency Why Does Latency Matter? User Response Input time Process Message: User Input and Render Input Validate Input Message: Fix Ok with Update Up Time Affects consistency Why Does Latency Matter? Outline • Introduction (done) • What is latency? (done) Message: Message: Treasure! Treasure! User • Why does it matter? Input (done) Message: User Get treasure Input Message: • How much does it matter? (next) Message: Get treasure Ok • Do you have evidence? Message: Tough luck! Time Affects fairness 2

4/4/2013 Depends Upon Game Phase How Much Does Latency Matter? (Name that game?) Depends upon precision of action Latency matters most in “Play” phase Play Game Perspectives How Much Does Latency Matter? latency latency First Person Linear Third Person Linear now later now later (tight deadline) (loose deadline) Depends upon deadline of action Omnipresent Third Person Isometric (Name those games? Newer examples?) Precision and Deadline Categorization of Player Actions Third-Person Avatar Omnipresent Lower Casting Running Area Spell Precision Exploring Shooting Grenades Shooting Machine Gun Fighting First-Person Avatar Racing Combat Moving Higher Shooting Drinking Sniper Health Potion Building Tighter Looser Deadline 3

4/4/2013 Player Performance vs. Latency Outline • Introduction (done) • What is latency? (done) • Why does it matter? (done) • How much does it matter? (done) • Do you have evidence? (next) – Methodology – Results Methodology (1 of 3) Methodology (2 of 3) • Goal: • Varying precision – • Steps: – Vary: precision & deadline of actions tank size 1. Made changes – Control : latency – Larger tanks equal 2. Verify and validate – Measure: performance lower precision 3. Determined game • Varying deadline – length, number of • Modify open source game iterations bullet speed – BZ Flag 4. Ran experiments – Slower bullets equal 5. Analysis looser deadline http://www.youtube.com/watch?v=xMYkw56t1Gg Methodology (3 of 3) Results for Precision (Tank Size) • 8 computer-controlled tanks (bots) • 2 hour runs 4

4/4/2013 Results for Precision and Deadline Results for Deadline (Bullet Speed) (Lagged tank – 1000 ms) Actions w/higher precision and tighter deadline (bottom left) have lower score for the lagged player than actions w/lower precision and looser deadline (top right). Summary Future Work? • 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 Future Work • 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) 5