Research:NPC AI Behaviour
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General behaviour
Decision scan
Actions affected | AI decision check, every 5.0 seconds |
Description | The main point for actor behaviour selection |
Implementation status | |
Analysis status | Early, incomplete research |
Weight functions
actionGreetWeighting :: (npc, actor) -> weight
if npc is creature: return 0
if actor is not player: return 0
if player is incapacitated: return 0
if player is invisible or player.chameleon >= 75: return 0
if npc.hello == 0: return 0
if npc.currentAIPackage not in { AIWander, AITravel, AIPursue }: return 0
x = iGreetDistanceMultiplier * npc.hello
dist = distance(npc, actor)
if npc has already greeted and dist > 2 * x:
npc resets greeting flag
npc.target = none
elif npc has not greeted and dist < x:
npc.target = actor
return 100
else:
return 0
actionCrimeWeighting :: (npc, actor) -> weight
if npc is creature: return 0
if npc is incapacitated: return 0
if npc.alarm == 0: return 0
if not npc.isGuard: return 0
if actor is not player: return 0
if player is incapacitated: return 0
if player is invisible or player.chameleon >= 75: return 0
if player is resisting arrest: return 0
if bounty < iCrimeThreshold: return 0
weight = npc.alarm + 0.1 * bounty
if weight < 100: return 0
return weight
actionFightWeighting :: (npc, actor) -> weight
if actor is in combat with an npc escort: return 100
if actor is in combat with an actor escorted by npc: return 100
fightTerm = npc.fight
if actor.isWerewolf or (actor is player and player.isKnownWerewolf): fightTerm += iWerewolfFightMod
dist = distanceAttack(npc, actor) # dist function that ignores vertical distance if actor is flying or swimming
weight = iFightDistanceBase - fFightDistanceMultiplier * distance + fFightDispMult * (50 - disp)
if weight < 100: return 0
return weight
actionLookAtWeighting :: (npc, actor) -> weight
if actor is incapacitated: return 0
if actor is invisible or player.chameleon >= 75: return 0
if npc current AI package prevents proximity check: return 0 # unclear conditions
if distance(npc, actor) >= 640: return 0
if actor is an npc escort: return 0
if actor is being escorted by npc: return 0
return 100
Actor scan
For a single actor, labelled npc
actionWeight = 0
selectedAction = none
for each actor in environment: # player is examined first
if actor is dead: continue
if distance(npc, actor) > 7168: continue
# 5-10 more conditions
greetWeight = 0
crimeWeight = 0
if actor is player:
if npc meets condition x: # under research
greetWeight = actionGreetWeighting(npc, actor)
if npc meets condition y: # under research
crimeWeight = actionCrimeWeighting(npc, actor)
fightWeight = actionFightWeighting(npc, actor)
lookAtWeight = actionLookAtWeighting(npc, actor)
action = none
if lookAtWeight > actionWeight:
npc.target = actor
actionWeight = int(lookAtWeight)
action = lookAt
if greetWeight > actionWeight:
npc.target = actor
actionWeight = int(greetWeight)
action = greet
if fightWeight > actionWeight:
npc.target = actor
actionWeight = int(fightWeight)
action = fight
if crimeWeight > actionWeight:
npc.target = actor
actionWeight = int(crimeWeight)
action = uphold the law
if actionWeight != 0 and action != none and npc.target != none:
if some 20 page function: # includes expensive functions like line of sight and sneak
npc.target = 0
actionWeight = 0
action = none
if action != none: selectedAction = action
if action != none: npc switches to selectedAction
Comments
With the lookAt action, the NPC looks at its target's head. The anim controller blends the head pose over time.
Combat behaviour
NPC awareness check
Actions affected | AI decision check, every 5.0 seconds |
Description | Part of the NPC perception state. |
Implementation status | implemented |
Analysis status | Verified |
This check runs every 5 seconds for each NPC. It occurs whether you are sneaking or not, but isn't the same as the combat distance check.
Player side
if sneaking:
sneakTerm = fSneakSkillMult * sneak + 0.2 * agility + 0.1 * luck + bootWeight * fSneakBootMult
else:
sneakTerm = 0
fatigueTerm = fFatigueBase - fFatigueMult*(1 - normalisedFatigue)
where normalisedFatigue is a function of fatigue. empty fatigue bar -> 0.0, full fatigue bar -> 1.0
distTerm = fSneakDistanceBase + fSneakDistanceMultiplier*dist
x = sneakTerm * distTerm * fatigueTerm + chameleon (+ 100 if invisible)
NPC side
npcTerm = npcSneak + 0.2 * npcAgility + 0.1 * npcLuck - npcBlind
npcFatigueTerm = fFatigueBase - fFatigueMult * (1 - normalisedFatigue)
using NPC normalisedFatigue
if PC is behind NPC (180 degrees):
y = npcTerm * npcFatigueTerm * fSneakNoViewMult
else:
y = npcTerm * npcFatigueTerm * fSneakViewMult
Final check
target = x - y
roll 100, win if roll < target
Comments
Appears straightforward and bug-free. NPCs can take up to five seconds to notice you even if you are not sneaking. This function precedes the combat distance check. I have not identified if there is a line of sight check occuring before or after.
According to this formula, NPCs can still detect you when invisible? That seems wrong. Scrawl (talk) 00:25, 7 January 2014 (CET)
Attack frequency
Actions affected | Upon initiating combat, and after each swing/missile |
Description | The semi-random delay inserted between physical attacks. |
Implementation status | Implemented |
Analysis status | Function contains other side effects |
if actor is an npc:
baseDelay = fCombatDelayNPC
else:
baseDelay = fCombatDelayCreature
delay = min(baseDelay + 0.01 * rand 100, baseDelay + 0.9)
if actor is in range to attack with current weapon:
actor will initiate a swing/fire a missile if time since end of last attack >= delay
AI Tendencies
Fight
Affected by calm and frenzy spells.
Flee
Affected by rally and demoralize spells.