Omnibot

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AI Bot for First Person Shooters
João Carlos Gonçalves jcgonc_at_student.dei.uc.pt
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OMNI-BOT - Resume

• Bots
• Resume Omni-Bot
• Game functioning,
• Framework
• Agent structure,
• Goals
• Society and interaction
• between agents,
• Waypoints and traversal,
• Manual routing,
• Scripting,
• Problems and scripting,
• Conclusion

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Whats a bot?

• Everyone who has played a computer game has
  encountered a bot.
• Computer controlled game player.
• Computational equivalent of a robot
• Bot ? Agent

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Why bots?

• Fill a game with more players.
• Help humans to train.
• Execute tasks boring for us.
• Etc.

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OMNI-BOT

• Framework implementing bots in FPS
• Games supported
• Wolfenstein Enemy Territory, Doom 3, Quake 4,
  Fortress Forever, Return To Castle Wolfenstein,
  Team Fortress 2
• BDI agents, internally state machines.
  Oriented towards completing goals while sensing
  their environment.
• Not ALL games fully working (currently).
• Best implementation on W.E.T.

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Enemy Territory- Resume -

• Comprised of various environments (maps) usually
  set in WW2, with different goals (frequently
  contradictory) for the factions.
• Two factions Allies and Axis, equal in
  characteristics, spawning in pre-determinated
  locations.
• Five classes Soldier, Medic, Engineer, Field
  Ops, Covert Ops, each one with its advantages
  and disadvantages.

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Wolfenstein Enemy Territory- Goals -

• Goals like stealing vehicles, escorting or not
  allowing them to move, destroying or constructing
  entities, healing and reviving teammates, etc.
• Completing goals may create contradictory goals
  on the opposing faction.
• Game development may also create or delete
  goals, possibly specific for some faction.
• Show Demo.

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Wolfenstein Enemy Territory

• Limbo, with maps goals for allied faction

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Wolfenstein ET MODs

• SDK for changing game logic available
• Various game modifications (mods) with different
  game plays
• ETPub
• NoQuarter
• ShrubMod
• ETPro
• Jaymod
• True Combat Elite
• PowerBall
• etc.
• Installed on the games directory

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OMNI-BOT

• Independent Library installed on ETs folder
  (usually omni-bot)
• omnibot_et.dll has the implementation
• qagame_mp_x86.dll server side engine (game
  logic)
• cgame_mp_x86.dll ui_mp_x86.dll client
  side engine and graphics (client side logic and
  corresponding graphics)
• Omnibot_et.dll linked by the running mod (must
  support omnis interface)
• mod initializes omnibot and bots are connected
  to the engine as clients (like players)
• supported mods ETPub, Jaymod, NoQuarter

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OMNI-BOT - agent structure

• List of goals, with execution states, positions,
  priorities and availability
• Sensory memory, with list of attractive
  entities, like enemies or aimable things.
• Available weapons, with their preference and
  firing parameters.
• Motor Control, executing the path following
  algorithm as well as the aiming mechanism.

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OMNI-BOT - agent structure

• Simplified version of a BDI agent
• Beliefs Stored on sensory memory
• Desires List of goals
• Intentions desire selected for execution,
  being performed
• Basically a state machine (deterministic finite
  automaton, DFA)

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OMNI-BOT - State Tree

• Show bigger state tree

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OMNI-BOT Agents behaviour
if(incapacitated) do for(medicteam.medics)
evaluation avaliate(medic.proximity)
evaluation avaliate(timer.spawn) decideResp
awn(evaluation) selectEquipment()
while(incapacitated) else updateSensoryMemor
y(world.getNeighborhood()) // additional
behaviour scripts executeScripts() selectEquipm
ent() goal getHighestPriorityAvailableGoal()
// goal may include alternative route path
computePath(goal) // wait for world
events while(not(world.changed)) waypoint
nearestWaypoint(path) motorControl.setDestinati
on(waypoint) if(near(waypoint)) do
execute(goal) while(not(executed(goal)
))

• Simplified algorithm for bots' behaviour.
  Actually implemented in parallel threads, like
  path following, enemy aiming and firing, sensory
  information, etc. (external scripts)

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OMNI-BOT Agents behaviour

• Executed on each server frame (usually 20 per
  second, server side cvar sv_fps)
• Threads and execution details on Debugs
  window, section profiler

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OMNI-BOT - Goals

• Retrieved from the maps script and bsps
  entities
• Following example destroy Side Door, for axis

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OMNI-BOT - Goals

• Example of map goals

• x goal -gt bitflag serial y priority z
• bitflag specifying allowed team (axis, allies)
• serial internal goal identification
• priority goal priority (relating to others).
• and more properties

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OMNI-BOT - Society

• By default goals are shared by different agents
  (excluding some cases).
• If not, the goal is assigned by the framework to
  some agent (actually, first come, first served).
• An agent may require support from others
  (ammunition and health / revival). In this case,
  it creates a specific goal (like heal me).
• No negotiation of goals between the agents.
• Individual behaviour

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OMNI-BOT - Waypoints

• Goals are reached by following paths
• Paths created using waypoints
• Directed graphs (typically cyclic)
• Diagonal descending edge connection direction

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OMNI-BOT - Waypoints

• Travelling properties (flags)
• Crouch, prone, sprint, walk, jump, route,
  radius, etc.

• radius of waypoint affects path cornering
• waypoint flag affects bots behaviour when its
  approaching the node or when reaches its radius

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OMNI-BOT Path travelling
Uses Dijkstra's algorithm for waypoint
selection Essentially uses the shortest path from
the source (where the agent selected the goal) to
its destination (where goal resides or next
route point if used)
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OMNI-BOT Routing

• Path travelling easily expected
• Boring for humans
• Solution Manual routing
• Basically a human codes different paths for
  different map traversal
• Goal X travel through waypoint 1, then 2 OR 3,
  then 4, etc. until reach destination
• Define waypoint selection probability
• Route is chosen when goal acquired near first
  route waypoint.

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OMNI-BOT Routing
From SPAWN to GOAL
MapRoutes GOAL ROUTE_SPAWN
ROUTE_A Weight 2.0,, ROUTE_B ,
ROUTE_C Weight 0.66 ROUTE_B Weight
0.5 ROUTE_D , ,,,

• If goal got when at spawn waypoint, choose
  next waypoint from A, B or C, with probabilities
  of 2, 1 and 0.66. Calculate shortest path to
  chosen route point and travel the path
• When arrive to A or B, travel shortest path to
  goals waypoint
• If chose waypoint C and reached it, choose B or
  D (with corresponding probabilities) and
  calculate shortest path to goal. Then travel it.

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OMNI-BOT Scripting

• Written in GameMonkey language
• Add functionality to goals, maps, weapons, bots,
  utils, etc.
• Goal scripts Tells or helps the bot how to
  achieve some goal (map or another)
• Map scripts Control the logic of the map, like
  enabling or disabling routes and goals (for
  instance according to the games progress)
• Weapon scripts Configure how to use and handle
  some weapon or item
• Bot scripts Stores a behaviour which can be
  associated to some bots.
• Utils implement some usefull functions for been
  called in other scripts.

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OMNI-BOT Map scripts

• Goal script example goal_askforhealth.gm
• this.GetPriority()
• if my health lt threshold and Im alive (me, the
  bot) then
• increase this goals priority
• get nearest health pack
• if no pack near, and my team has medics, request
  medical support
• this.update()
• if acquired pack, get packs position, aim
  towards it and try to acquire the pack

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OMNI-BOT Goal scripts
Goal script example bunker.gm

• Store the logic of the map (the bots dont know
  the goals dependencies as well as their
  importance)
• If objective taken ? leave the stairs and attack
  the radio
• If objective returned ? leave the radio and
  attack the stairs
• On map start ? start attacking the stairs,
  forget the radio

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OMNI-BOT Problems

• Human waypointing, quite boring. Done manually.
  Detailed waypoints take time as well as routing
  them.
• Proposed navigational mesh, detailed version of
  waypoints, but with the problem of the mesh
  resolution.

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OMNI-BOT Problems

• Cant plan a sequence of intentions
• No objectives negotiation between agents
  (assigned FCFS)
• Objectives are not assigned to the nearest
  agent
• Human coded intentions order and priorities
• Dont learn the best paths (currently and in
  the past)
• Dont predict (and learn) actions taken by
  others (cooperation and synchronization)

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OMNI-BOT Reference
http//www.omni-bot.com/wiki/index.php?titleMain_
Page http//en.wikipedia.org/wiki/Wolfenstein_Ene
my_Territory http//www.omni-bot.de http//www.gam
asutra.com/gdc2005/features/20050311/isla_01.shtml

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OMNI-BOT Questions
Tuesday, 16 December 2008