Wandering,Chase and Idle AI in Unity 3D.

[BANANAMAN]

I want an AI wherein the object with the AI will initially idle when the game starts,Suddenly wander/move around at random and when the player control object reaches a certain range it begins to chase it.

I was thinking of having the AI have 3 states,Wandering,Chase and Idle where Idle is the default AI. From time to time it will mostly wander around the scene (while switching to idle state depending on a random integer) but then when the player controlled object is within a certain distance from it the AI will switch to chase state.

pesudo-code

Case:idle
//do nothing/play idle animation
status = rand()
if (status <= 0.5)
{
state = wander;
}
break;
Case:wander
//wander around/play wander animation
if ((plyrdist <= AIx) || (plyerdist <= AIy) || (plyrdist <= AIz))
{
state = chase;
}
else
{
status = rand()
if (status <= 0.5)
{
state = wander;
}
if ((status >= 0.5)&&(status <= 0.9))
{
state = idle;
}
}
break;

is there another way that's much more efficient to accomplish this?

 

[neo34rd]

I noticed that you have 3 states but only 2 cases. It might be easier to write your switch cases with the help of a FSM chart. I always do that before I start coding to help me see flaws of my AI systems and simple ways to optimize my code. In some cases I combine certain states together even.

Case:wander
//wander around/play wander animation
if ((plyrdist <= AIx) || (plyerdist <= AIy) || (plyrdist <= AIz))
{
state = chase;
}
else
{
status = rand()
if (status <= 0.5)
{
state = wander;
}
if ((status >= 0.5)&&(status <= 0.9))
{
state = idle;
}
}
break;

Btw there is a chance that when you chase you would suddenly switch back to idle suddenly.

 

[BANANAMAN]

Would this be slightly better?

chasethreashold = 3000;

CHARACTER_STATE:
Idle
Chase
Wander

void Start()
{
animation.Play("up_sword");
animation.Blend("idle");
currentState = CHARACTER_STATE.IDLE;
}

void Update()
{
case Idle:
//Do idling stuff
status = rand();
if((status >= 1000)||(status <= 3000));
{
currentState = CHARACTER_STATE.Wander;
}
break;
Case Wander:
//wandering stuff
if ((plyrdist <= AIx) || (plyerdist <= AIy) || (plyrdist <= AIz))
{
state = chase;
}
if(((plyrdistx+chasethreashold)<= AIx) || ((plyrdisty+chasethreashold) <= AIy) || ((plyrdistz+chasethreashold) <= AIz))
{
status = rand()
if (status <= 0.5)
{
state = wander;
}
}

The AI would now continue chasing until a certain distance is achieved between them. Would this prevent it from wandering in the middle of a chase?

 

[neo34rd]

Did you know that you can do this (playerpos.Position - aiPos.Position).magnitude in Unity3D?
Use the prefab function availble in Unity3D to help you along. They all inherit a few useful math functions like above.

For your AI bit I suggest you remove this bit:

if(((plyrdistx+chasethreashold)<= AIx) || ((plyrdisty+chasethreashold) <= AIy) || ((plyrdistz+chasethreashold) <= AIz))
{
status = rand()
if (status <= 0.5)
{
state = wander;
}
}

Into a chase case.
This will prevent confusion for you and it will prevent an AI state lock in the chase state.

Btw I am assuming state == currentState?

Also note that there is only a:

status = rand()
if (status <= 0.5)

Chance when the AI is out of the chasethreashold for it to return to the wander state. Also note that once your AI goes into the wander/chase state it can NEVER return to the idle state because there is no handle for that.

 

[BANANAMAN]

Did you know that you can do this (playerpos.Position - aiPos.Position).magnitude in Unity3D?
Use the prefab function availble in Unity3D to help you along. They all inherit a few useful math functions like above.

Can you explain further or link me to a tutorial?

 

[neo34rd]

Here are a few references for you:

Asset Workflow: http://unity3d.com/support/documentation/Manual/Asset Workflow.html
Prefabs: http://unity3d.com/support/documentation/Manual/Prefabs.

Here is a script reference for Transform: http://unity3d.com/support/documentation/ScriptReference/Transform.html

If your units/ai are game objects they should have the transform component. You can access this component by doing this:

myUnit.Transform.Position

This would return the units Vector3 position in the game world. With that you can do this:

const var alertDist : float = 500;
currentDistance = (myUnit.transform.position - aiUnit.transform.position).magnitude;

if ( currentDistance <= alertDist )
{
currentState = E_AI_STATE.CHASE;
}

You can also do this:

currentDistance = Vector.Distance( myUnit.transform.position, aiUnit.transform.position );