Qualitative Spatial Analysis Part 2

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Qualitative Spatial AnalysisPart 2

• Chris Mansley

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FPS to RTS

• FPS environments are becoming more dynamic and
  simple path-finding is not enough to define
  movement
• Another place that can benefit from this type of
  higher level movement are strategy games

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Terrain Analysis

• Strategy games often have large open spaces and
  valuable resources often with narrow passages
  between them
• It is often helpful to consider these as free
  spaces and connecting corridors

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Terrain Analysis cont.

• Corridors can be considered one-dimensional
  entities that connect two free spaces
• The strategic value of the connection is strictly
  based on the way they connect free space

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Master of Orion

• Turn Based Strategy Game
• Basic build empires game (in space)
• Colonization of different planets in different
  star systems

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AI Goals

• To provide a measure of the strategic value of
  the star system
• Overall, the AI can then choose the best strategy
• Encourage border disputes

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MOO3
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MOO3
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Terrain Analysis

• Inside vs. Outside borders
• If all paths leading way from the system lead
  through one of our planets, its considered inside
• Threatened
• If not within borders or a path exists to another
  civilization without passing through one of our
  systems

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Example
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Selecting New Colonies

• Using the spatial data, star systems are selected
• Uses a series of modifiers to select the correct
  system to try and occupy
• If priorities are the same, square them and
  randomly select the best

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Decision

• Start with 1.0
• If we own planet at star system
• If enemy also has a planet there, multiply 1.5
• Else, we own the system, multiply 0.8
• If system is inside our borders, multiply 0.9
• If outside and has enemy colony, multiply by 0.3
• Etc

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Outcome

• By tweaking the modifiers, the AI gave a sense of
  strategy and borders
• Before using this type, AI would mingle with
  everyone, frustrating the player
• Use the analysis system, to select other factors
  like best target or defenses

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Conclusion

• Reasoning about the game world by NPCs needs to
  be more than simple pathfinding
• Trying to formalize such qualitative concepts
  such as good strategies, best non-direct
  movement, or dynamic environment use, results in
  better game play for everyone

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References

• AI Game Programming Wisdom 2
• Forbus, K., How Qualitative Spatial Reasoning
  Can Improve Strategy Game AIs, IEEE Intelligent
  Systems, July/August 2002
• Master of Orion 3, Quicksilver Software, Inc 2003