1. “We’ve Got Game!” Teaching and Researching Computer Games at WPI Mark Claypool Assistant Professor Computer Science Department Worcester Polytechnic Institute Worcester, MA, USA http://www.cs.wpi.edu/~claypool

2. January 2004 Gamestock, WPI, Worcester, MA, USA2 Outline Interactive Media and Game Development Aspects of Networking Latency and Warcraft III

3. A Proposal for a New Major David Finkel, Computer Science Frederick Bianchi, Humanities and Arts Mark Claypool, Computer Science Michael Gennert, Computer Science Patrick Quinn, Humanities and Arts Interactive Media and Game Development

4. January 2004 Gamestock, WPI, Worcester, MA, USA4 Opportunity Games are growing –In 2000, U.S. economy grew by 7% while computer game industry grew by 15% (International Digital Software Association, 2001) –60% of Americans age 6+ play computer games (International Digital Software Association, 2001) 221+ million computer games sold in 2002 2 games for every household in America Exact labor statistics are difficult to obtain –But indicators are that game companies are hiring –Recent ad by Electronic Arts say “triple digits” Not many 4-year technical degree programs

5. January 2004 Gamestock, WPI, Worcester, MA, USA5 Related Programs Over 60 different academic programs (Game Developer’s Magazine, Game Career Guide 2003) –Many at art schools (no technical component) –Many certificate or 2-year programs CMU offers MA in Entertainment Technology SMU offers 18-month certificate (Guildhall) USC announced minor in game development Few full undergraduate majors at 4-year universities

6. January 2004 Gamestock, WPI, Worcester, MA, USA6 A Proposal for a New Major A Proposal Offered with many existing courses –Some new, core courses Offered with many existing resources –Some new dedicated faculty –Some new gaming labs Benefits of –Attracting new students –Solidifying education of game developers –Future extension to minor and graduate programs

7. January 2004 Gamestock, WPI, Worcester, MA, USA7 The Undergraduate Major Based on: –IGDA Curriculum Framework (Feb 2003) –Examination of other programs –Consultation with GDC, other academics, administration, marketing … Core courses with fundamental ideas for game development Two tracks: –Technical –Artistic Emphasize well-rounded B.S. with game development strength

8. January 2004 Gamestock, WPI, Worcester, MA, USA8 Core Courses Critical Game Studies –Non-technical study of use, history, and industry of games. Develop vocabulary, analyze merits and tools and why some games are successful. Game Development Process –Discuss roles of participants, artistic and technical. Importance of testing and play testing. Students will develop games or parts of games. Social Issues in Game Development –Human need for play, philosophy of games, social interactions in multiplayer games, role of violence and ethical and legal issues for games

9. January 2004 Gamestock, WPI, Worcester, MA, USA9 Technical Track 3 core courses 5 math (Lin Alg, Prob and Stats) 3 science (Physics and Bio) 11 computer science (HCI, Soft Eng, Arch, Networks, Graphics, Animation, AI) 2 advanced technical 3 humanities (Writing, Studio Art) Sufficiency, IQP, MQP

10. January 2004 Gamestock, WPI, Worcester, MA, USA10 Artistic Track 3 core courses 2 science (Physics and Bio) 1 math 3 writing 3 studio art 2 computer art 2 drama or music Sufficiency, IQP, MQP

11. January 2004 Gamestock, WPI, Worcester, MA, USA11 Advanced Courses Two Technical –Programming of games, 2d and 3d game engines, sound and music implementations, networking, latency compensation… Artistic –Visual arts, music, sound and writing for game play, aspects of interactivity…

12. January 2004 Gamestock, WPI, Worcester, MA, USA12 Resources Required Directors for technical an artistic tracks –Could be appointed from WPI faculty Three (new) dedicated faculty –2 in Humanities –1 in Computer Science Game development environment –Software (develop some in-house) –Equipment (general and special purpose) –Space

13. January 2004 Gamestock, WPI, Worcester, MA, USA13 When Might This All Happen? Spring 2004 –Approval by administration and faculty If successful … Summer 2004 –Prepare core courses Academic year 2004-2005 –Core course offerings (experimental) –Marketing –Development of game laboratory Summer 2005 –Advance course preparation Academic year 2005-2006 –All new courses in place –New major in place –New tenure-track faculty hired Academic year 2007+ –Minor, grad program, additional faculty …

14. January 2004 Gamestock, WPI, Worcester, MA, USA14 Outline Interactive Media and Game Development Aspects of Networking –Network Resource Limitations –Compensation Techniques –Security and Cheating Latency and Warcraft III

15. January 2004 Gamestock, WPI, Worcester, MA, USA15 Network Resource Limitations Distributed simulations face three resource limitations –Network bandwidth –Network latency –Host processing power (to handle network) Physical restrictions that the system cannot overcome –Must be considered in the design of the application (More on each, next)

16. January 2004 Gamestock, WPI, Worcester, MA, USA16 Capacity Data sent/received per time LAN – 10 Mbps to 10 Gbps –Limited size and scope WANs – tens of kbps from modems, to 1.5 Mbps (T1, broadband), to 55 Mbps (T3) –Potentially enormous, Global in scope Number of users, size and frequency of messages determines capacity As does transmission technique –Multicast, Unicast, Broadcast

17. January 2004 Gamestock, WPI, Worcester, MA, USA17 Latency Delay when message sent until received –Variation (jitter) also matters Cannot be totally eliminated –Speed of light propagation yields 25-30 ms across Atlantic –With routing and queuing, usually 80 ms Application tolerances: –File download – minutes –Web page download – up to 10 seconds –Interactive audio – 100s of ms MCG latencies tolerance depends upon game –First-Person Shooters – 100s of ms –Real-Time Strategy – up to 1 second –Other games

18. January 2004 Gamestock, WPI, Worcester, MA, USA18 Computational Power Processing to send/receive packets Most devices powerful enough for raw sending –Can saturate LAN Rather, application must process state in each packet Especially critical on resource-constrained devices –i.e.- hand-held console, cell phone, PDA,

19. January 2004 Gamestock, WPI, Worcester, MA, USA19 Outline Interactive Media and Game Development Aspects of Networking –Network Resource Limitations –Compensation Techniques –Security and Cheating Latency and Warcraft III

20. January 2004 Gamestock, WPI, Worcester, MA, USA20 Data and Control Architectures Want consistency –Same state on each node –Needs tightly coupled, low latency, small nodes Want responsiveness –More computation locally to reduce network –Loosely coupled In general, cannot do both. Tradeoffs.

21. January 2004 Gamestock, WPI, Worcester, MA, USA21 Networked Multiplayer Game Architectures Centralized –Use only two-way relay (no short-circuit) –One node holds data so view is consistent at all times –Lacks responsiveness Distributed and Replicated –Allow short-circuit relay –Replicated has copies, used when predictable (ie- non-player characters) –Distributed has local node only, used when unpredictable (ie- players) –May be inconsistent

22. January 2004 Gamestock, WPI, Worcester, MA, USA22 Interest Management – Auras Nodes express area of interest to them –Do not get messages for outside areas - Only circle sent even if world is larger. - Can implement with square to make simpler

23. January 2004 Gamestock, WPI, Worcester, MA, USA23 Interest Management- Focus and Nimbus -nimbus must intersect with focus to receive -Example: Hider has smaller nimbus, so Seeker cannot see, while Hider can see Seeker since Seeker’s nimbus intersects Hider’s focus

24. January 2004 Gamestock, WPI, Worcester, MA, USA24 Dead Reckoning When prediction differs, get “warping” or “rubber-banding” effect (predicted position) (actual position) (“warp”) Based on ocean navigation techniques Predict position based on last known position plus direction –Can also only send updates when deviates past a threshold

25. January 2004 Gamestock, WPI, Worcester, MA, USA25 Security and Cheating Unique to games –Other multi-person applications typically don’t have same type of cheating problems Cheaters want: –Vandalism – create havoc (relatively few) –Dominance – gain advantage (more)

26. January 2004 Gamestock, WPI, Worcester, MA, USA26 Packet and Traffic Tampering Reflex augmentation - enhance cheater’s reactions –Example: aiming proxy monitors opponents movement packets, when cheater fires, improve aim Packet interception – prevent some packets from reaching cheater –Example: suppress damage packets, so cheater is invulnerable Packet replay – repeat event over for added advantage –Example: multiple bullets or rockets if otherwise limited

27. January 2004 Gamestock, WPI, Worcester, MA, USA27 Preventing Packet Tampering Cheaters figure out by changing bytes and observing effects –Prevent by MD5 checksums (fast, public) Still cheaters can: –Reverse engineer checksums –Attack with packet replay So: –Encrypt packets –Add sequence numbers (or encoded sequence numbers) to prevent replay

28. January 2004 Gamestock, WPI, Worcester, MA, USA28 Information Exposure Allows cheater to gain access to replicated, hidden game data (i.e. status of other players) –Passive, since does not alter traffic –Example: defeat “fog of war” in RTS, see through walls in FPS Cannot be defeated by network alone Instead: –Sensitive data should be encoded –Kept in hard-to-detect memory location –Centralized server may detect cheating (example: attack enemy could not have seen) Harder in replicated system, but can still share

29. January 2004 Gamestock, WPI, Worcester, MA, USA29 Outline Interactive Media and Game Development Aspects of Networking Latency and Warcraft III

30. The Effects of Latency on User Performance in Warcraft III Nathan Sheldon, Eric Gerard, Seth Borg, Mark Claypool, Emmanuel Agu ACM NetGames Workshop Redwood City, CA, USA May 2003 http://www.cs.wpi.edu/~claypool/papers/war3/

31. January 2004 Gamestock, WPI, Worcester, MA, USA31 Why Study Warcraft III? Top selling computer game genres –Strategy (27.4%) –Children’s (15.9%) –Shooter (11.5%) –Family Entertainment (9.6%) Warcraft III set sales record –Fastest to sell 1 million copies “Warcraft III - Shatters Sales Records Worldwide...”, Blizzard Press Release, October 2002 “Top Ten Industry Facts”, Interactive Digital Software Association, May 2003.

32. January 2004 Gamestock, WPI, Worcester, MA, USA32 Network Games and Latency Latency degrades performance of interactive applications –Web-browsing – seconds –Internet phone – 100’s of milliseconds –First Person Shooters (FPS) – 100’s of milliseconds Real-Time Strategy (RTS)? Knowing effects of latency useful for –Building better network games –Building better networks to support games (QoS)  Effects of Latency on Warcraft III (RTS)

33. January 2004 Gamestock, WPI, Worcester, MA, USA33 Outline Introduction  Experiments  Analysis Conclusions

34. January 2004 Gamestock, WPI, Worcester, MA, USA34 Warcraft III Overview RTS User Interaction Components: Exploration Building Combat

35. January 2004 Gamestock, WPI, Worcester, MA, USA35 Exploration Map Performance? Time (to reach end)

36. January 2004 Gamestock, WPI, Worcester, MA, USA36 Building Map Performance? Time (to build tech- nology tree)

37. January 2004 Gamestock, WPI, Worcester, MA, USA37 Combat Map Performance? Games Won Unit Scores

38. January 2004 Gamestock, WPI, Worcester, MA, USA38 Controlling Latency Warcraft III uses client-server –Set computer B as server (also a client) –Set computer C or D as client NIST Net on computer A –Induce latency [0 ms to 3500 ms]

39. January 2004 Gamestock, WPI, Worcester, MA, USA39 Outline Introduction  Experiments  Analysis –Application Level  –Network Level –User Level Conclusions

40. January 2004 Gamestock, WPI, Worcester, MA, USA40 Building and Latency

41. January 2004 Gamestock, WPI, Worcester, MA, USA41 Exploration and Latency

42. January 2004 Gamestock, WPI, Worcester, MA, USA42 Combat and Latency (1)

43. January 2004 Gamestock, WPI, Worcester, MA, USA43 Combat and Latency (2)

44. January 2004 Gamestock, WPI, Worcester, MA, USA44 Outline Introduction  Experiments  Analysis –Application Level  –Network Level  –User Level Conclusions

45. January 2004 Gamestock, WPI, Worcester, MA, USA45 Bandwidth 3.8 Kbps 4.0 Kbps 6.8 Kbps

46. January 2004 Gamestock, WPI, Worcester, MA, USA46 Inter-Packet Times

47. January 2004 Gamestock, WPI, Worcester, MA, USA47 Payload Distributions

48. January 2004 Gamestock, WPI, Worcester, MA, USA48 Payload Distributions and Latency

49. January 2004 Gamestock, WPI, Worcester, MA, USA49 Commands and Latency Pilot studies suggest 6 bytes of overhead per command Remove 6 bytes from each packet payload Add up remaining command payloads

50. January 2004 Gamestock, WPI, Worcester, MA, USA50 Outline Introduction  Experiments  Analysis –Application Level  –Network Level  –User Level  Conclusions

51. January 2004 Gamestock, WPI, Worcester, MA, USA51 User-Level Analysis 0-500 ms latency, users could easily adjust 800+ ms, game appeared erratic –Degradation in gaming experience 500-800 ms degradation depended upon –User More skilled were more sensitive –Strategy Micro managers were more sensitive Combat managers were more sensitive

52. January 2004 Gamestock, WPI, Worcester, MA, USA52 Conclusions Typical Internet latencies do not significantly affect user performance in Warcraft III –Some effect on exploration –No statistical effect on building or combat RTS game play emphasizes “strategy” (which takes 10s of seconds or minutes), not “real-time” RTS games less sensitive to latency than are FPS –RTS in QoS class similar to that of Web browsing At the network level: –Small packets with low bandwidth –Command aggregation at higher latencies

53. January 2004 Gamestock, WPI, Worcester, MA, USA53 Ongoing Work Effects of latency on user strategies Other RTS games (done!) –Age of Mythology –Command and Conquer: Generals Effects of latency on other genres –First Person Shooter (UT 2003) –Multiplayer Role Playing Game Effects of loss

54. “We’ve Got Game!” Teaching and Researching Computer Games at WPI Mark Claypool Assistant Professor Computer Science Department Worcester Polytechnic Institute Worcester, MA, USA http://www.cs.wpi.edu/~claypool