Difference between revisions of "Ai Overview"
Line 38: | Line 38: | ||
AddView("chaseRange",SearchMobileInRange(chaseViewRange,false,false,true)) | AddView("chaseRange",SearchMobileInRange(chaseViewRange,false,false,true)) | ||
</syntaxhighlight> | </syntaxhighlight> | ||
+ | |||
+ | And at the end of the file we find the Event Handler in case some Mobile enters that range and triggered the view: | ||
+ | <syntaxhighlight lang="lua"> | ||
+ | --On the target coming into range | ||
+ | RegisterEventHandler(EventType.EnterView, "chaseRange", | ||
+ | function (objRef) | ||
+ | HandleMobEnterView(objRef,false) | ||
+ | end) | ||
+ | </syntaxhighlight> | ||
+ | |||
+ | So it seems that <code>HandleMobEnterView</code> is our canditate doing the real stuff. Below is a shortened vgersion stripped off from comments and DebugMessages: | ||
+ | <syntaxhighlight lang="lua"> | ||
+ | function HandleMobEnterView(mobileObj,ignoreVision,forceAttack) | ||
+ | if (ignoreVision == nil) then ignoreVision = false end | ||
+ | if not(AI.IsActive()) then return end | ||
+ | if (not AI.IsValidTarget(mobileObj)) then | ||
+ | return | ||
+ | end | ||
+ | local isFriend = IsFriend(mobileObj) | ||
+ | if (forceAttack) then | ||
+ | isFriend = false | ||
+ | end | ||
+ | if (not isFriend) then | ||
+ | AI.AddToAggroList(mobileObj,2) | ||
+ | if (forceAttack) then | ||
+ | this:SendMessage("AttackEnemy",mobileObj,true) | ||
+ | else | ||
+ | AI.StateMachine.ChangeState("Alert") | ||
+ | end | ||
+ | end | ||
+ | end | ||
+ | </syntaxhighlight> | ||
+ | |||
+ | |||
Revision as of 20:31, 1 November 2016
Ai Overview
This article is about helping to understand how the Ai in Shards Online works.
Some Basics:
The Artificial Intelligence for NPCs follows a general Ai Principle which is the cycle of
- Sense
- Think
- Act
The model of implementation is a Finite State Machine(FSM). [Wikipedia Article Finite State Machine]
To understand how an FSM would transition from one state (e.g. "Idle") to another state (e.g. "Combat") in Shards Online (SO) it is important to understand the first step: "Sense".
How does an NPC sense the world?
There are several ways:
- Messages
- Messages using the
Sendmessage
function tell the NPC someone or something sent it a message. To understand Messages the NPC needs to have the appropriate EventHandlers. - Views
- Views are added to objects by using the
AddView
function. A view is basically a search function performed on a configurably regular basis which triggers an event if something matching that search function enters its configured range. Mobiles can carry around views with them. - FindObjects
- The
FindObjects
function can be executed whenever an NPC needs to find something.
Each of these sensing mechanisms can call functions provided by the core Ai which lives in base_ai_state_machine.lua
.
SchedulePulse() AI.StateMachine.Init(initialState) AI.StateMachine.Shutdown() AI.StateMachine.ChangeState(newState) AI.StateMachine.ChangeSubState(newState) AI.StateMachine.EndSubStates(success,reason) HandleAiPulse()
Especially important is function AI.StateMachine.ChangeState(newState) which could be called when something happens our NPC needs to react to, e.g. a wolf entering the perception range of a turkey.
In base_ai_mob.lua
we find the following line of code in the initialization part:
AddView("chaseRange",SearchMobileInRange(chaseViewRange,false,false,true))
And at the end of the file we find the Event Handler in case some Mobile enters that range and triggered the view:
--On the target coming into range
RegisterEventHandler(EventType.EnterView, "chaseRange",
function (objRef)
HandleMobEnterView(objRef,false)
end)
So it seems that HandleMobEnterView
is our canditate doing the real stuff. Below is a shortened vgersion stripped off from comments and DebugMessages:
function HandleMobEnterView(mobileObj,ignoreVision,forceAttack)
if (ignoreVision == nil) then ignoreVision = false end
if not(AI.IsActive()) then return end
if (not AI.IsValidTarget(mobileObj)) then
return
end
local isFriend = IsFriend(mobileObj)
if (forceAttack) then
isFriend = false
end
if (not isFriend) then
AI.AddToAggroList(mobileObj,2)
if (forceAttack) then
this:SendMessage("AttackEnemy",mobileObj,true)
else
AI.StateMachine.ChangeState("Alert")
end
end
end