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Enabling PlayerCreated Online Worlds with Grid Computing and Streaming

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Massively Multiplayer Online Games (MMOG) ... Persistent-world online games. Players pay a monthly subscription fee to play the game ... – PowerPoint PPT presentation

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Title: Enabling PlayerCreated Online Worlds with Grid Computing and Streaming


1
Enabling Player-Created Online Worlds with Grid
Computing and Streaming
  • Gamasutra, September 18, 2003

Presented by Daniel Ferstay
2
Overview
  • Massively Multiplayer Online Games (MMOG)
  • And the people who play them
  • Content Distribution problem for MMOG
  • Second Life
  • The Grid
  • Streaming
  • Conclusions and Discussion

3
Massively Multiplayer Online Games (MMOG)
  • The hours and intensity with which players
    engage in games makes for very fast consumption
    of content

4
How many hours and with how much intensity?
  • Google search for everquest addiction gives
    interesting results
  • EverQuest the Latest Addiction, Wired.com,
    July 29, 1999
  • 150000 players total
  • 34000 players online for 3-4 hours each during
    peak night hours
  • EverQuest Widows
  • Yahoo! group that offers a space for people to
    vent and support each other through relationship
    crises.
  • Missed anniversaries, threatened divorce,
    breakups, etc.

5
Good News, Bad News
  • Game players who enjoy the content of a game play
    it a lot.
  • The more players play, the more content they
    consume

6
Question
  • How can game designers provide enough content to
    keep players engaged?
  • Previous approaches
  • Provide large amounts of content in game (Final
    Fantasy)
  • Make content reusable replay value (GranTurismo)
  • Make experience dependent on interaction with
    other human players (Quake)

7
Problem
  • Persistent-world online games
  • Players pay a monthly subscription fee to play
    the game
  • Designers keep players engaged by frequently
    updating interactive content
  • Exploration of 100 hours of content can take only
    a few weeks of game play.
  • This approach is costly
  • Balancing act between time/cost to develop
    content, time to play content and monthly
    subscription fee.

8
Solution
  • Allow players to modify and customize game
    content and features
  • Works well for single player games and FPS where
    customization amounts to modifying local
    configuration files
  • This approach raises technical problems for MMOG

9
Second Life
  • Persistent-World MMOG
  • Online society shaped entirely by its residents
  • Players create/modify their avatars to look and
    sound like anything
  • World landscape is provided but players create
    the objects which populate the world
  • Houses, boats, furniture, art, etc.
  • See The Metaverse in Neal Stephensons Snow
    Crash

10
Second Life
11
Content Distribution Problem
  • How do we distribute player-customized content
    (graphics, sound, geometry, animation, behaviour)
    to other players in real-time?
  • The online world is one big contiguous space
    populated by players who can
  • Create, edit, and move objects
  • The world contains hundreds of thousands of
    objects that have unique
  • Textures, physical properties, shapes,
    permissions, etc.

12
Content Distribution Problem cont.
  • Shipping the games current contents to users in a
    box requires gt 100 CDs
  • Patching users with new in-world content when
    they logged in would require downloads of 10s of
    megabytes per day
  • Storing and manipulating all of the game content
    on a centralized database would yield a
    transaction rate of gt 10000 read/writes per
    second during peak hours
  • These numbers grow linearly with the number of
    players

13
Content Distribution Solution The Grid
  • Distribute the objects across a tiled grid.
  • Each tile in the grid represents one machine
    running a sim
  • Simulates physics, manages objects/behaviours/terr
    ain for a fixed square region of space (16
    acres)

14
The Grid cont.
  • Simulator machines talk to their four nearest
    neighbours in the grid
  • Solves scaling problem as world becomes large
  • As objects move around the world, their
    representations are transferred from simulator to
    simulator
  • Using higher order prediction, players and
    objects transition across simulation borders
    seamlessly.

15
The Grid cont.
  • As players move around the grid, they maintain
    streaming connections only to the simulator
    machines they are near.
  • Simulators compute the information and objects
    that can be seen
  • Transmits only information that is new to the
    player (or has changed)
  • Players need only a thin client (a world viewer)
    to play the game
  • To grow the world, add simulator machines to the
    grid.

16
Streaming
  • Game requires a broadband connection.
  • Average bandwidth to a client 100Kbps
  • Compression is needed
  • Each sim supports 10000 objects players can see
    a large percentage of these.
  • Graphical representations of objects are built
    out of simple geometric shapes.
  • Generalized meshes are too complex and dont
    compress as efficiently

17
Streaming cont.
  • Texture and audio data are compressed
  • Allows players to put thousands of large textures
    and a large number of audio sources into a scene.

18
Streaming is expensive
  • Clients receive information related to
  • Frustum culling, change detection, motion
    interpolation/extrapolation, compression, and
    packet construction and management.
  • Multiple servers stream data to different ports
    on the client machine via UDP
  • UDP allows for a more responsive/controllable
    stream then TCP.
  • Avoids TCPs slow start congestion controls.
  • Reliability built around loss detection and data
    correction
  • Not retransmission

19
Conclusions
  • A Grid of simulators solves the problem of scale
    when users are allowed to create and modify
    objects in a large online world
  • Streaming data to players in real time allows
    users to modify the online world in a
    collaborative and interactive manner.

20
Thank You
  • Any Questions?

21
Discussion
  • In what ways could this game be improved?
  • Graphics are simple, low polygon count
  • Multiple UDP streams get blocked by Firewalls
  • Adaptive congestion control vs. 100Kbps magic
    number for client bandwidth
  • Is it reasonable to expect players to create all
    of the content in the game?
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