Command Hierarchy Architecture

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Command Hierarchy Architecture

• Rigel Freeman
• Matt Whitlock
• Errol Campbell
• Jeff Jarrard

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What is an AI Command Hierarchy?

• Organizes and Abstracts decision making
• Modeled after real world military hierarchy
• Information is given to next highest tier
• Direction is given to the next lowest tier

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Why do we care?

• Humans can quickly analyze all known data
• Impractical for AI on even the best systems
• Increases speed and adaptability of search
• Allows competent play without cheating

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How is it implemented?

• Top tier sets overall objective and strategy
• Middle tiers set specific objectives and tactics
• Bottom tier makes individual unit decisions
• Upper tiers increase scope, decrease detail

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Generic Command Hierarchy
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Detail Unit (Soldier) AI

• Purely reactive
• No forward planning
• Defend self if attacked
• Basic low-level decisions

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Detail Squad AI

• Translate squad commands into individual unit
  commands
• Analyze/summarize information from units and pass
  to higher levels

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Detail Platoon AI

• Employ small-scale strategies for obtaining
  simple objectives
• Dispense commands to squads in platoon
• Report significant events to higher levels

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Detail Company AI

• Employ medium-scale strategies for obtaining
  long-term objectives
• Report progress toward obtaining these objectives

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Detail Computer Player AI

• Plan overarching strategy
• Responsible for creation of companies and
  assigning high-level objectives

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Applications

• Strategy RTS, turn-based, war-games
• FPS Single and multi-player
• Team Sports Football, soccer, hockey
• Strategy RPG Real-time, turn-based

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Strategy

• Top tier
• Determine strategy to defeat opponents
• Middle tiers
• Resource mgt., Technology, Army
  production/command
• Company/Platoon/Squad objectives and tactics
• Bottom tier
• Individual unit targets and decisions

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Example Civilization

• Overall goal Conquer opponents
• Must govern city, religious, and tech. growth
• Must build/command army, form alliances
• The multiple aspects lead to many tiers

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Civilization Game in Progress
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FPS

• Top tier
• Determine strategy to defeat opponents
• Middle tiers
• Organize offense and defense
• Size and distribution may vary widely depending
  on game
• Bottom tier
• Individual unit targets and decisions

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Example Battlefield 2

• Commander gives orders to Squad Leaders
• Squad Leaders give orders to individual units
• Individual units follow Squad Leaders orders
• Communication only goes up/down one tier

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Battlefield 2 Commander View
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Team Sports

• Top tier
• Sets lineup and directs play
• Middle tiers
• Organize offense and defense
• Bottom tier
• Individual unit targets and decisions
• Specialized roles that bypass Middle tiers (QB,
  Goalie, etc.)

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Example Madden

• Coach determines lineup and play
• Quarterback acts as Offensive leader
• Offense objective is to gain yardage
• Defense objective is to stop opponents gain

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Madden 06 Offensive Line
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Strategy RPG

• Top tier
• Determines character advancement and strategy
• Middle tiers
• Control questing, skill training, equipment, etc.
• Organize squads for combat
• Bottom tier
• Individual unit targets and decisions

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Example Warcraft III

• Overall Objective Kill Opponents
• Select what Hero characters to train
• Gain XP for Heroes and train skills
• Explore and gather items to equip Heroes

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Warcraft III Heroes
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Problems and Complications

• Rigid resource allocation
• AI cannot interpret all data simultaneously
• Different tiers have different data
• Identical units may interpret data differently

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Variation Project AI

• Creates temporary goals/projects on the fly
• Units assigned to projects based on abilities
• Units can change projects if needed
• Dissolves project once completed