1
Weve 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
Outline

• Interactive Media and Game Development
• Aspects of Networking
• Latency and Warcraft III

3
A Proposal for a New Major
Interactive Media and Game Development

• David Finkel, Computer Science
• Frederick Bianchi, Humanities and Arts
• Mark Claypool, Computer Science
• Michael Gennert, Computer Science
• Patrick Quinn, Humanities and Arts

4
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
Related Programs

• Over 60 different academic programs
• (Game Developers 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
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
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
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
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
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
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
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
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
Outline

• Interactive Media and Game Development
• Aspects of Networking
• Network Resource Limitations
• Compensation Techniques
• Security and Cheating
• Latency and Warcraft III

15
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
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
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
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
Outline

• Interactive Media and Game Development
• Aspects of Networking
• Network Resource Limitations
• Compensation Techniques
• Security and Cheating
• Latency and Warcraft III

20
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
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
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
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
• Seekers nimbus intersects Hiders focus

24
Dead Reckoning

• Based on ocean navigation techniques
• Predict position based on last known position
  plus direction
• Can also only send updates when deviates past a
  threshold

• When prediction differs, get warping or
  rubber-banding effect

25
Security and Cheating

• Unique to games
• Other multi-person applications typically dont
  have same type of cheating problems
• Cheaters want
• Vandalism create havoc (relatively few)
• Dominance gain advantage (more)

26
Packet and Traffic Tampering

• Reflex augmentation - enhance cheaters 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
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
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
Outline

• Interactive Media and Game Development
• Aspects of Networking
• Latency and Warcraft III

30
The Effects of Latencyon 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
Why Study Warcraft III?

• Top selling computer game genres
• Strategy (27.4)
• Childrens (15.9)
• Shooter (11.5)
• Family Entertainment (9.6)
• Warcraft III set sales record
• Fastest to sell 1 million copies

Top Ten Industry Facts, Interactive Digital
Software Association, May 2003.
Warcraft III - Shatters Sales Records
Worldwide..., Blizzard Press Release, October
2002
32
Network Games and Latency

• Latency degrades performance of interactive
  applications
• Web-browsing seconds
• Internet phone 100s of milliseconds
• First Person Shooters (FPS) 100s 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
Outline

• Introduction ?
• Experiments ?
• Analysis
• Conclusions

34
Warcraft III Overview

• RTS User Interaction
• Components
• Exploration
• Building
• Combat

35
Exploration Map

• Performance?
• Time
• (to reach end)

36
Building Map

• Performance?
• Time
• (to build tech-
• nology tree)

37
Combat Map

• Performance?
• Games Won
• Unit Scores

38
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
Outline

• Introduction ?
• Experiments ?
• Analysis
• Application Level ?
• Network Level
• User Level
• Conclusions

40
Building and Latency
41
Exploration and Latency
42
Combat and Latency (1)
43
Combat and Latency (2)
44
Outline

• Introduction ?
• Experiments ?
• Analysis
• Application Level ?
• Network Level ?
• User Level
• Conclusions

45
Bandwidth
3.8 Kbps
4.0 Kbps
6.8 Kbps
46
Inter-Packet Times
47
Payload Distributions
48
Payload Distributions and Latency
49
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
Outline

• Introduction ?
• Experiments ?
• Analysis
• Application Level ?
• Network Level ?
• User Level ?
• Conclusions

51
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
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
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
Weve 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