Question - Check players distance from ai

[jaxParticipant]

Hello, I am currently working on setting up an ai where I need a constraint to check if the player is within a certain range of the ai or not. Would anyone be able to give me an example of code/some information on how I can do this? I originally thought of setting a variable up in memory, and having a script constantly update that variable with the player’s vector 3 position, however I am not sure how to do that either.

[primeKeymaster]

Here’s an example of a custom action that checks to see if an object is within a certain distance range:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using RAIN.Action;
using RAIN.Core;
using RAIN.Representation;
using RAIN.Motion;
[RAINAction("Distance Check")]
public class DistanceCheck : RAINAction
{
    public Expression Target = new Expression();
    public Expression GreaterThan = new Expression();
    public Expression LessThan = new Expression();
    public override ActionResult Execute(AI ai)
    {
        if (Target.IsValid && Target.IsVariable)
        {
            MoveLookTarget tTarget = MoveLookTarget.GetTargetFromVariable(ai.WorkingMemory, Target.VariableName);
            float tDistance = (tTarget.Position - ai.Kinematic.Position).magnitude;
            if (GreaterThan.IsValid && (tDistance <= GreaterThan.Evaluate<float>(ai.DeltaTime, ai.WorkingMemory)))
                return ActionResult.FAILURE;
            if (LessThan.IsValid && (tDistance >= GreaterThan.Evaluate<float>(ai.DeltaTime, ai.WorkingMemory)))
                return ActionResult.FAILURE;
        }
        return ActionResult.SUCCESS;
    }
}

You can use it in the behavior tree and set values for min distance, max distance, and the name of the variable that holds the player position/game object.

[jaxParticipant]

Thanks for that, however I am running into other problems with it. Would there be a way to do that it a custom decision instead? I tried modifying that code to be used in a decision, however it keeps giving me failure. The reason for using a custom decision instead of action, is I want to tell the ai to play a different animation when it it close enough to the player and also run an action to damage the player.

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using RAIN.Action;
using RAIN.Core;
using RAIN.Representation;
using RAIN.Motion;
[RAINDecision]
public class CheckDistance : RAINDecision
{
    public Expression Target = new Expression();
    public Expression GreaterThan = new Expression();
    public Expression LessThan = new Expression();
    public override ActionResult Execute(AI ai)
    {
        if (Target.IsValid && Target.IsVariable)
        {
            MoveLookTarget tTarget = MoveLookTarget.GetTargetFromVariable(ai.WorkingMemory, Target.VariableName);
            float tDistance = (tTarget.Position - ai.Kinematic.Position).magnitude;
            if (GreaterThan.IsValid && (tDistance <= GreaterThan.Evaluate<float>(ai.DeltaTime, ai.WorkingMemory)))
                return ActionResult.FAILURE;
            if (LessThan.IsValid && (tDistance >= GreaterThan.Evaluate<float>(ai.DeltaTime, ai.WorkingMemory)))
                return ActionResult.FAILURE;
        }
        return ActionResult.SUCCESS;
    }
}

[primeKeymaster]

Hmm. Here’s a custom decision that will only run if the target is at a certain distance. If the test passes, it acts like a sequencer:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using RAIN.Action;
using RAIN.Core;
using RAIN.Representation;
using RAIN.Motion;
[RAINDecision("Do When Distance")]
public class DoWhenDistance : RAINDecision
{
    private int _lastRunning = 0;
    public Expression Target = new Expression();
    public Expression GreaterThan = new Expression();
    public Expression LessThan = new Expression();
    public override void Start(RAIN.Core.AI ai)
    {
        base.Start(ai);
        _lastRunning = 0;
    }
    public override ActionResult Execute(RAIN.Core.AI ai)
    {
        ActionResult tResult = ActionResult.SUCCESS;
        if (Target.IsValid && Target.IsVariable)
        {
            MoveLookTarget tTarget = MoveLookTarget.GetTargetFromVariable(ai.WorkingMemory, Target.VariableName);
            float tDistance = (tTarget.Position - ai.Kinematic.Position).magnitude;
            if (GreaterThan.IsValid && (tDistance <= GreaterThan.Evaluate<float>(ai.DeltaTime, ai.WorkingMemory)))
                return ActionResult.FAILURE;
            if (LessThan.IsValid && (tDistance >= GreaterThan.Evaluate<float>(ai.DeltaTime, ai.WorkingMemory)))
                return ActionResult.FAILURE;
        }
        for (; _lastRunning < _children.Count; _lastRunning++)
        {
            tResult = _children[_lastRunning].Run(ai);
            if (tResult != ActionResult.SUCCESS)
                break;
        }
        return tResult;
    }
}

[primeKeymaster]

Keep in mind that you may want to do something totally different and straightforward. You could just decide to evaluate the distance to the target and set it as a variable in AI memory. Then use regular BT structures (like Constraint nodes or Evaluate Expression nodes) to make decisions.

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