Squad Tactics

Presentation By: Danny Powell, Andrew Pro, and Kofi White

Squad Tactics in Real Life

Swat TeamsWolf PacksVelociraptors (Jurassic Park)HyenasFighter 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 actions Even under adversity

Squad structure can vary Casualties, regroupings Interference from other friendlies

Leader

Squads sometimes have a leaderThe leader can be prominent, or act like any

other squad member

Team AI

Tactics

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 prevalent

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 mapOr give away your locationOr outright sabotage your team…http://www.youtube.com/watch?v=LkCNJRfS

ZBU

Team AI: Good

Provide back up Without stealing the show!

Follow instructionsAnticipate beneficial actions

Squad Organization

Player can be squad leader or squad member depending on the gameExample: 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 membersSimple extension of individual AIEasily combined with level-specific scriptingHowever, weak at maneuvers that require

autonomy or tight coordinationFrom decentralized interactions, squad

maneuvers emerge…

Decentralized AI

Simply and extension of individual AIRobustly handles many situationsUtilizes the variety of capabilities within the

teamEasily combined with scripted squad member

actions

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 differenceSo where do we find the squad behavior, let

alone squad tactics? http://www.youtube.com/watch?v=_tGOKngtk

t4&feature=player_embeddedBirds

Emergent behavior

The squad behavior comes from the interactions of the squad members, rather than in their individual actions.

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&feature=player_embedded#

Emergent Fire & Maneuver Behavior

Solo AI: Either fires at a threat, or moves to a better position

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 interactions

Tactical Enhancements

Stay close to coverDon’t block teammates’ lines of fireKnowledge of weapon capabilitiesMaintain team cohesionStay spread outKeep 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 movement 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 strategyTeam members sometimes do unexpected

things i.e. move around randomly for no reason

Trouble reaching a decision and executing it unanimously 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

Counter-Strike

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 commandsThe 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 level

Command Hierarchy

Commander

Captain

Sergeant

Soldier

Orders Information

Figure 5.5.1

Lower levels carry out orders and higher levels organize the team and make decisions

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 roomFill arrays to save specific information

about the environment to make decisions based on that information

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

Figure 5.5.3

Pseudo-code example to check if maneuver is possible and appropriate before performing

Outflanking Pseudo-code RoomSeen = Room where opponent has been seenReachableDoors = 0if(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 AvailBotListif(CanReachWithoutRoom(RoomSeen, RoomDoorLeadsTo(RoomDoor),AvailBot.Room))

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 mold

2d Formations

Line • Column

2d Formations

Left Flank • Right Flank

2d Formations

Wedge • Vee

Squad Visibility

Units have limited angle of perceptionFormations 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 UnitsReshuffling FormationsUnit MobilitySpacing between UnitsHandling 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 FormationsSometimes 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 MobilityWhen 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 MovementReacting 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

http://www.youtube.com/watch?v=7qZj-DW3eFU Flocking 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 strategy

Squad Tactics -Team Members

Primary focuses for Team Members

Correct PositioningCorrect MovementCorrect BehaviorSupporting the Player

Correct PositioningAvoid 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 strategies

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 cohesively.

NPC team member should relay information to player in order to give player a chance to react i.e., If a threat is detected

Bottom Line: THE PLAYER IS THE MOST IMPORTANT!