Copyright © 2011, A Dynamic Area of Interest Management and Collaboration Model for P2P MMOGs 張晏誌 行動計算與寬頻網路實驗室 王國禎 教授 1

Copyright © 2011, Introduction 2 The commercial MMOGs use client-server architecture which is expensive to deploy and maintain. For example, “Second Life” has approximately 5000 servers to support the virtual space.

Copyright © 2011, Introduction 3 When a player performs an action or generates an event affecting the virtual space, the game state of all other players influenced by that action or event must be updated. The amount of information required to exchange between players roughly depends on the population of in the interested area.

Copyright © 2011, Introduction 4 There are two extremes to model AOI among the users for distributed simulations. The first one is the static geographical partitioning implemented at the initialization phase of a game or a simulation.

Copyright © 2011, Introduction 5 The second extreme for modeling interest is behavioral. But the ease with which mapping processing resources or servers can be applied in geographic regionalization, little effort has been invested in mapping the behavioral approach

Copyright © 2011, Introduction 6 Even though behavioral modeling is the ultimate goal for managing the interest of the parties, geographic regionalization is not without its merits and can be coupled with behavior-based communications.

Copyright © 2011, AoI Management The interest management for an MMOG can be abstracted using a publish-subscribe model. The space-based area of interest management is typically based on proximity, and can be realized in terms of an aura-nimbus information model. 7

Copyright © 2011, Game Space & AoI 8 Mapping an area of interest into a fixed size zone, i.e. unification of an AOI to a zone, is straightforward. Due to the nature of a game, most of the times an area of interest overlaps multiple zones and breaks the significance of the zone formation. It requires regular inter-zone communication for synchronization.

Copyright © 2011, Game Space & AoI 9 Notation –aoi(pi) is the AoI of player i –G space = ∪ AOI j

Copyright © 2011, Zoneless AoI Management 10 Say, an AOI has k players represented by AOI(i) = {p i 1, p i 2,..., p i k}. We form a convex hull to present such an AOI. A convex hull can be bound with a time complexity of O(nh), where n is the number of points in the set, and h is the number of points in the hull.

Copyright © 2011, Zoneless AoI Management 11 Considering the nature of the game at hand, we do not redefine the convex hull at that instant as we do not know whether the player is returning back soon. Two attributes are incorporated to make the decision while really redefining the convex hull for each candidate. –Time-span –Safty-edge

Copyright © 2011, Zoneless AoI Management 12 Safety-edge Time-span –A temporal reference that used to avoid premature decision.

Copyright © 2011, Inter AoI Communication 13 The simple intersection of two AoIs is good enough to uncover the overlapped members. From the design it is evident that each member of the overlapped AOIs must stay at a safety- edge in each AOIs and being a member of the respective overlays. This ensures each player receives all messages from the all AOIs where it belongs and redeems the necessity of explicit inter-AOI communication.

Copyright © 2011, Simulation and Analysis 14 It seems that the performance improves as the size of AOI increases in terms of the players. So for a moderate sized AOI, i.e. the size of AOI is 30, only 34% players are involved for AOI maintenance.

Copyright © 2011, Reference 15 Dewan Tanvir Ahmed, Shervin Shirmohammadi, “A Dynamic Area of Interest Management and Collaboration Model for P2P MMOGs”, 12th 2008 IEEE/ACM International Symposium on Distributed Simulation and Real-Time Applications