Squad Tactic Formations

Squad Tactics
Presentation By: Danny Powell, Andrew Pro, and Kofi White
Squad Tactics in Real Life
 Swat Teams
 Wolf Packs
 Velociraptors (Jurassic Park)
 Hyenas
 Fighter Squadrons
What is a squad?
 Small team with a goal
 Kill foes, Move there, Defend here, patrol, etc
 Tries to accomplish its goals through coordinated
Even under adversity
 Squad structure can vary
 Casualties, regroupings
 Interference from other friendlies
 Squads sometimes have a leader
 The leader can be prominent, or act like any other
squad member
Team AI
 A conceptual action used by a unit to implement a
specific mission and achieve a specific objective or to
advance toward a specific goal
 Implemented as one or more specific tasks.
Team AI
 The use of teammates has become increasingly
 It’s rather important to make the teammates
convincing though
Team AI: Bad
 Don’t want teammates who will get in your way
 Or run off to the far corners of the map
 Or give away your location
 Or outright sabotage your team…
 http://www.youtube.com/watch?v=LkCNJRfSZBU
Team AI: Good
 Provide back up
 Without stealing the show!
 Follow instructions
 Anticipate beneficial actions
Squad Organization
Player can be squad leader or squad member depending on the game
Example: Early levels of CoD: player is just a member of the squad
Mass Effect: player is the leader of the squad
Decentralized AI
 Interactions between squad members
 Simple extension of individual AI
 Easily combined with level-specific scripting
 However, weak at maneuvers that require autonomy
or tight coordination
 From decentralized interactions, squad maneuvers
Decentralized AI
 Simply and extension of individual AI
 Robustly handles many situations
 Utilizes the variety of capabilities within the team
 Easily combined with scripted squad member
Decentralized Communication
 AI members publish the following info to nearby
squad members
 Their Intentions
(“I’m moving to position <xyz>,” “I’m firing from <xyz>in
direction <p, y> at <xyz>,” “reloading”)
 Their Observations
 (“enemy seen at <xyz>,” “grenade tossed toward <xyz>”)
Solo AI vs. Squad member AI
Solo AI vs. Squad member AI
 Not much of a difference
 So where do we find the squad behavior, let alone
squad tactics?
 http://www.youtube.com/watch?v=_tGOKngtkt4&f
 Birds
Emergent behavior
 The squad behavior comes from the interactions of
the squad members, rather than in their individual
 Functionality originating from the interactions of
elements, rather than from their individual actions.
The emergent high order organized behavior is
generated from lower-level, simpler behavior
 http://www.youtube.com/watch?v=rqzlSj_VngY&fe
Emergent Fire & Maneuver Behavior
 Solo AI: Either fires at a threat, or moves to a better
 Squad member AI:
announces intentions and decisions
Determines actions based on state and intentions and
observations of nearby squad members
Move up if too many teammates are engaging
Ignores already-engaged enemies
 The fire & maneuver tactic emerges from these
Tactical Enhancements
 Stay close to cover
 Don’t block teammates’ lines of fire
 Knowledge of weapon capabilities
 Maintain team cohesion
 Stay spread out
 Keep enemy in sight
Tactical Enhancements
 This can be accomplished by…
 Extend the squad member’s mental picture
 Improve communication between squad members
 Include tactical information about allies
 Adding a “next position” algorithm to tactically improve
 Create squad member subclasses to define specific behavior
Leader, rifleman, machine gunner, sniper, etc.
The Squad Member’s Mental Picture
 Represents what the member “knows”
 For each Squad member
 Position
 Destination/path
 Line of Fire
 For each Opponent
 Known position, state, estimated current position
 Other squad members engaging
 Line of fire
 Other hazards and threats
Personalizing Squad Member Behavior
 Different squad members have different preferences,
and abilities
Riflemen—move quick and often, close in on enemy
Machine gunners—slow, support fire from a static position
Sniper—stay back and engage enemy from a distance
 State also affects position preference
 Favor cover when wounded or reloading
 When team out-mans the enemy, aggressive tactics
are favored
Cons of Emergent Tactics
 Difficult to form long term strategy
 Team members sometimes do unexpected things
 i.e. move around randomly for no reason
 Trouble reaching a decision and executing it
i.e. ambushes
 No autonomy—nobody actually thinks for the squad
 Cannot execute some more sophisticated maneuvers
 Its up to the level designers to design the more
complex behaviors
 Emergent Squad Behavior
Planned Maneuvers
 Asses situation for squad as a whole unit and pick a
course of action
 Possibly reduce demand of CPU by doing
computations only once for squad strategy rather
than doing it individually
 Commands assign goals for squad members… new
commands may interfere with current goals or tasks
of individual soldiers. What can we do?
Centralized Command Style
 Authoritarian
 Leader knows best
 Soldiers always adopt new plan set by leader
 Coaching
 Soldiers execute tasks at their own discretion
 Soldier has to make own decisions if there is a conflict with the
leader’s commands
The best style would be a mix of the two by
implementing an intelligent message passing system
Command Hierarchy and Message Passing
Tactical Team AI Using a Command Hierarchy
 A move toward real-time decision making instead of
more scripted sequences
 Information passed up the hierarchy, from lower
level soldiers gathering information
 Decisions made and passed back down from highest
Command Hierarchy
Figure 5.5.1
Lower levels carry out orders and higher
levels organize the team and make
Robocode Example
TeamScout message passing
Decision Support
 Individual AI need to know certain things about
environment to carry out orders
 Soldier example from book:
Can reach location x from location z without passing
through y?... Exits for a certain room
 Fill arrays to save specific information about the
environment to make decisions based on that
 Higher levels need to know what each soldier is
doing, and what the priority of their action is
Squad Implementation
 Processor friendly message passing allows for high
level decisions to be made immediately when new
information is present… no polling
 Global data can be kept so information can be
available to all levels at all times, but messages still
passed when info is updated
 Squad should try to carry out complex maneuvers
and perform them logically but not predictably so a
player is not critical of the AI
Choosing A Strategy
Figure 5.5.2
Outflanking Example
Pseudo-code example to check if maneuver is possible
and appropriate before performing
Outflanking Pseudo-code
RoomSeen = Room where opponent has been seen
ReachableDoors = 0
if(NumDoors(RoomSeen)<2) Abort . Not enough doors.
NumBots = FindAvailableBots(AvailBotList,PriorityThreshold)
if(NumBots<2) Abort. Not enough bots.
for each RoomDoor in room RoomSeen
for each bot in AvailBotList
ReachableDoors += 1. Don’t try other bots. Try next Door.
if(ReachableDoors<2) Abort. Can’t reach enough doors.
for each bot in AvailBotList
Create team to preform maneuver, with first bot acting as Captain.
Captain: outflank RoomSeen
Outflanking Example cont’d
 Some details not taken into account, bots may be
available to reach a door in RoomSeen, but may
not be anywhere close
 Consider while actually performing maneuver:
Have bots move to closest door, but also try to have bots
spread evenly between doors
Send message ‘in position’ so Captain can time the attack
What does soldier do after executing command?
Squad Tactics - Formations
What is a Formation
 Squad Formation - a grouping of individuals and
units strategically positioned in order to efficiently
and effectively carry out a premeditated strategy
Formation Utility
 Important for formation to actually contribute to
the actual game play as opposed to being just visual
appeasements for the player.
Formation Dimensions
 Formations can be designed to fit both a 2d and a 3d
2d Formations
 Line
• Column
2d Formations
 Left Flank
• Right Flank
2d Formations
 Wedge
• Vee
Squad Visibility
 Units have limited angle of perception
 Formations often designed to permit maximum
squad visibility
Increased Visibility Formations
 Staggered Line
• Outward Facing
Formation Strategies
 Fixed Formation
 Units are ultimately stationary
 Good for defensive strategies
 Mobile Formation
 Units are moving in formation
 Typically used for offensive strategies (attacking or rallying).
Fixed Formation Considerations
 Organizing Mixed Units
 Reshuffling Formations
 Unit Mobility
 Spacing between Units
 Handling Unit Overflow (More units than allotted
spaces for formation).
 Formation unit requirements
Organizing Mixed Units
 Smart to invoke a strategy which incorporates
units with varying talents
 Implement formation in which units have
complementary skills
Reshuffling Formations
 Sometimes units need to quickly change from one
formation to another.
 More efficient to have units path to the nearest slot
as opposed to pathing to its assigned spot.
Unit Mobility
 When designing your formation it is important to
take into consideration the expected movement of
each unit.
 Info on expected unit movement should be used to
reduce unit collision
Spacing Between Units
 Depending on your strategy it is sometimes better to
have tightly spaced units or loosely spaced units.
Unit Overflow
 When there are more units that need to fall into
formation than there are slots available, a new rank
should be invoked to accommodate the extra units.
Formation Unit Requirements
 Some formations may call for specific unit types in
specific formation positions, similar to a football
offensive line.
Mobile Formation Considerations
 Group Pathing and Movement
 Reacting to Obstacles and Combat
Group Pathing and Movement
 When invoking squad movement there are several
strategies which can be applied to maintain
formation integrity
Leader offset movement
All units move as fast as slowest unit, in order to maintain
formation integrity
Flying V!!!
Reacting to Obstacles and Combat
 Two options
 Go into waiting mode
Maintains integrity of team formation
Seek alternative Path
Will vary the group formation, and may alter the end formation.
 Best to choose the option which best fits your squad
Squad Tactics -Team Members
Primary focuses for Team Members
 Correct Positioning
 Correct Movement
 Correct Behavior
 Supporting the Player
Correct Positioning
 Avoid colliding with player.
 Avoid moving into players field of view
Correct Movement
 NPC team member should never take lead unless
instructed to do so.
i.e. NPC team member should not be the first around
corners unless instructed by player.
If so the NPC team member should do everything to not
jeopardize the players status and should employ tactical
 NPC team member should respect the current
context of the situation
If player wants team to be in stealth mode, the NPC team
member should honor the players request.
 NPC team member should move approximately the
same speed as player.
Correct Behavior
 In the context of a team Shooter
 Use of Cover
 Selective firing
 Reloading
 NPC should behave in such a way that it has its own
self preservation in mind along with the self
preservation of the player
Supporting the Player
 Depending on strategy of the game NPC team
member may act more autonomously or more
 NPC team member should relay information to
player in order to give player a chance to react
i.e., If a threat is detected

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