Index of /Kuliah2016-2017/KecerdasanBuatanUntukGame

(1)

Artificial Intelligence in Game

Design

(2)

Coordinated Movement

• Steering of individual character based on movement of other characters

– Organized movement

– Cooperating in pursuit of overall goal

• Moving group in formation

– Creating formations

(3)

Fixed Formations

• Line

• Circle

• “V” formation

(4)

Leader‐Based Steering

• “Leader” steers towards goal

• Followers have slots

– Fixed position relative to leader

– Move with leader

– Followers seek _{location of slot}

leader

Fixed distance,

orientation WRT leader

leader

Left flank Right

flank Right

rear

slots

(5)

Leader‐Based Steering

• Problem if leader has to steer around obstacles

• Followers will also steer for no good reason!

• Need greater degree of independence

(6)

Leader Marker Steering

• “Invisible” leader marker leads formation

– All characters have slots relative to leader marker

– Leader marker not affected by obstacles

Fixed distance, orientation WRT leader marker

Leader marker Left

flank Right

rear

slots

(7)

Leader Marker Steering

• Followers steer around obstacles

– Use blending/priorities to determine steering

– May have other goals (seek cover, avoid collisions, etc.)

Leader marker Right

side

Seek

slot

Avoid

obstacle Seek cover

Final steering

Avoid

(8)

Leader Marker Steering

• Problem if many obstacles in squad path

– Leader marker not affected

– Followers are slowed by obstacles – Followers get far behind leader

• Leader marker should move slow if necessary

– Target velocity of leader = Average current velocity of squad

Left flank Right

flank Right

rear

Front

(9)

Leader Marker Steering

• Problem if some units slower than others

– Smaller MaxVel, MaxAccel

– Larger units _ slower to steer past

– Target velocity of leader = Minimum velocity of units in squad

Left flank Right

flank

(10)

Hierarchical Formations

• Large units usually consist of smaller squads also in fixed relative locations

– Have overall leader marker

– Leader markers of individual squads have slots in overall unit

Heavy weapons Infantry Infantry

Flankers Flankers

(11)

Slot Assignment

• Different slots in a formation may require different abilities • Given group of characters, how should those slots be filled?

• Example: Heavy weapon escort group

Hand to Hand Weaponry Hand to Hand

Weaponry

Long Distance Weaponry

Hand to Hand Weaponry

(12)

Slot Assignment

• Different characters have different abilities

– Can represent fit to role numerically

Swords‐ man

Pikeman Axeman Archer Catapult Cannon Grenadier

Hand to

Hand 10 10 10 4 0 0 3

Long

Distance 0 3 0 10 0 0 7

Heavy

(13)

Minimal Cost Slot Assignment

• Goal:

Assign slots to maximize score (or minimize “cost”)

Weaponry

Heavy Weaponry

Total score: 10

Weaponry

Heavy Weaponry

(14)

Minimal Cost Slot Assignment

• Not feasible to check all possible assignments

– n _characters_ O₍n_{!) possible assignments}

• Greedy algorithm

– Start with hardest to assign characters first

– Characters with greatest variance between slot scores

second

third

fourth

last

Weaponry

(15)

Dynamic Slot Assignment

• May need to reassign slots dynamically

– Squad members removed

• May need to factor in cost of empty slot

– Can use to put preferences on filled slots

• Without a heavy weapon, no purpose for squad!

– Can use to put preferences on numbers in slots

• Ok to have one hand to hand slot in front, but not to have

none in front _{Hand to Hand}

Weaponry

Empty = 10 Hand to Hand

Weaponry

Empty = 15

Empty = 15 Hand to Hand Weaponry

Empty = 20

Empty = 5 Heavy Weaponry

(16)

Minimal Cost Slot Assignment

• Example:

Weaponry

Empty Heavy Weaponry

Total score: 54 Hand to Hand

Weaponry

Empty Hand to Hand

Weaponry

Heavy Weaponry

(17)

Minimal Cost Slot Assignment

• If costs too great, may need to change squad type

– Try all squad types of new group size

• Example:

Hand to Hand Weaponry Long Distance

Weaponry

New attack squad Hand to Hand

Weaponry Hand to Hand

Weaponry

Empty Heavy Weaponry

(18)

Squad Cover Movement

• Squad moves one at a time

– Rearmost member moves to next cover position – Rest of squad remains stationary, providing cover

• Squad as a whole must move in desired direction

(19)

Cover Cover

Squad Cover Movement

• Can still use formation slots

• Based on nearest cover instead of fixed formation

Slot B

Slot D Slot C

Slot A

Cover

(20)

Squad Cover Movement

• Choose squad member furthest from goal

• Choosing next cover point

– In direction of squad goal

• Often done by targeting a “squad anchor point” in center of formation

– Not used by another member of squad

– Within cover range of rest of squad

• May not necessarily put in front of rest of squad

• Move squad member slot to that cover point

– Squad member will seek _that slot

(21)

Squad Cover Movement

Cover

Cover Range of

coverage

Cover Cover

(22)

State‐Based Movement

• Character does not begin movement until signaled to do so by another character

• Direction/type of steering depends on location/steering of other characters

State 1A

Steering for this state

Character A State 2A

State 1B

Character B State 2B

Change in character A state

Causes change in character B state

(23)

Play‐Based Steering

• Typical in most team sports games

(24)

Play‐Based Steering

Arrive at pocket

Quarterback

FollowPath route,

Avoid defenders

Receiver

Wander, Avoid

defenders

At route end and open

defenders

Throw:

Pursue(football, receiver)

Pursue

football

(25)

State‐Based Implementation

• Character A _{sets flag in central repository for team in}

state exit

Reciever3

RunRoute state

void Exit() { …

repository.setFlag( this, “open”, true);

…

Who set flag

Flag name, value

Team Repository

Sender Flag Value Reciever3 open true

(26)

State‐Based Implementation

• Character B _{checks for flag as input in checkTransitions}

method to determine whether to change state

Quarterback

WaitForReciever state

int CheckTransitions() { …

if (repository.getFlag( Reciever3, “open”)) { return THROW_STATE;

} …

Team Repository

Sender Flag Value Reciever3 open true

(27)

Handling Failed States

• Example:

– Target receiver never open

– Quarterback must eventually take another action

• Choose another receiver • Scramble

– Need a state timeout to recognize this

(28)

Handling Failed States

Arrive at pocket

Quarterback

FollowPath route,

Avoid defenders

Receiver

defenders

At route end and open

defenders

Throw:

Pursue(football, receiver)

Pursue

football

Football thrown

Seek goal

Avoid defenders 3 seconds