How do I make an enemy lead his shots?

Questions & Answers
1

Hi, I am making a fps from the fps tutorial and have come across a problem. My robots fire at you but you can easily doge by just moving slightly to the side or to keep moving. I want them to lead their shots so they will hit you where your going. Can anyone tell me what to change in my script? Thanks.

AI.js

var attackRange = 30.0;
var shootAngle = 4.0;
var dontComeCloserRange = 5.0;
var delayShootTime = 0.35;
var pickNextWaypointDistance = 2.0;
var target : Transform;

private var lastShot = -10.0;

// Make sure there is always a character controller
@script RequireComponent (CharacterController)

function Start () {
	// Auto setup player as target through tags
	if (target == null && GameObject.FindWithTag("Player"))
		target = GameObject.FindWithTag("Player").transform;

	Patrol();
}

function Patrol () {
	var curWayPoint = AutoWayPoint.FindClosest(transform.position);
	while (true) {
		var waypointPosition = curWayPoint.transform.position;
		// Are we close to a waypoint? -> pick the next one!
		if (Vector3.Distance(waypointPosition, transform.position) < pickNextWaypointDistance)
			curWayPoint = PickNextWaypoint (curWayPoint);

		// Attack the player and wait until
		// - player is killed
		// - player is out of sight		
		if (CanSeeTarget ())
			yield StartCoroutine("AttackPlayer");
		
		// Move towards our target
		MoveTowards(waypointPosition);
		
		yield;
	}
}


function CanSeeTarget () : boolean {
	if (Vector3.Distance(transform.position, target.position) > attackRange)
		return false;
		
	var hit : RaycastHit;
	if (Physics.Linecast (transform.position, target.position, hit))
		return hit.transform == target;

	return false;
}

function Shoot () {
	// Start shoot animation
	animation.CrossFade("shoot", 0.3);

	// Wait until half the animation has played
	yield WaitForSeconds(delayShootTime);
	
	// Fire gun
	BroadcastMessage("Fire");
	
	// Wait for the rest of the animation to finish
	yield WaitForSeconds(animation["shoot"].length - delayShootTime);
}

function AttackPlayer () {
	var lastVisiblePlayerPosition = target.position;
	while (true) {
		if (CanSeeTarget ()) {
			// Target is dead - stop hunting
			if (target == null)
				return;

			// Target is too far away - give up	
			var distance = Vector3.Distance(transform.position, target.position);
			if (distance > shootRange * 3)
				return;
			
			lastVisiblePlayerPosition = target.position;
			if (distance > dontComeCloserRange)
				MoveTowards (lastVisiblePlayerPosition);
			else
				RotateTowards(lastVisiblePlayerPosition);

			var forward = transform.TransformDirection(Vector3.forward);
			var targetDirection = lastVisiblePlayerPosition - transform.position;
			targetDirection.y = 0;

			var angle = Vector3.Angle(targetDirection, forward);

			// Start shooting if close and play is in sight
			if (distance < shootRange && angle < shootAngle)
				yield StartCoroutine("Shoot");
		} else {
			yield StartCoroutine("SearchPlayer", lastVisiblePlayerPosition);
			// Player not visible anymore - stop attacking
			if (!CanSeeTarget ())
				return;
		}

		yield;
	}
}

function SearchPlayer (position : Vector3) {
	// Run towards the player but after 3 seconds timeout and go back to Patroling
	var timeout = 3.0;
	while (timeout > 0.0) {
		MoveTowards(position);

		// We found the player
		if (CanSeeTarget ())
			return;

		timeout -= Time.deltaTime;
		yield;
	}
}

function RotateTowards (position : Vector3) {
	SendMessage("SetSpeed", 0.0);
	
	var direction = position - transform.position;
	direction.y = 0;
	if (direction.magnitude < 0.1)
		return;
	
	// Rotate towards the target
	transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
	transform.eulerAngles = Vector3(0, transform.eulerAngles.y, 0);
}

function MoveTowards (position : Vector3) {
	var direction = position - transform.position;
	direction.y = 0;
	if (direction.magnitude < 0.5) {
		SendMessage("SetSpeed", 0.0);
		return;
	}
	
	// Rotate towards the target
	transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation(direction), rotationSpeed * Time.deltaTime);
	transform.eulerAngles = Vector3(0, transform.eulerAngles.y, 0);

	// Modify speed so we slow down when we are not facing the target
	var forward = transform.TransformDirection(Vector3.forward);
	var speedModifier = Vector3.Dot(forward, direction.normalized);
	speedModifier = Mathf.Clamp01(speedModifier);

	// Move the character
	direction = forward * speed * speedModifier;
	GetComponent (CharacterController).SimpleMove(direction);
	
	SendMessage("SetSpeed", speed * speedModifier, SendMessageOptions.DontRequireReceiver);
}

function PickNextWaypoint (currentWaypoint : AutoWayPoint) {
	// We want to find the waypoint where the character has to turn the least

	// The direction in which we are walking
	var forward = transform.TransformDirection(Vector3.forward);

	// The closer two vectors, the larger the dot product will be.
	var best = currentWaypoint;
	var bestDot = -10.0;
	for (var cur : AutoWayPoint in currentWaypoint.connected) {
		var direction = Vector3.Normalize(cur.transform.position - transform.position);
		var dot = Vector3.Dot(direction, forward);
		if (dot > bestDot && cur != currentWaypoint) {
			bestDot = dot;
			best = cur;
		}
	}
	
	return best;
}
2

You can try using transform.LookAt heres an example:

var Player : Transform;

function Update(){
transform.LookAt(Player);
}

Just attach this to your AI and they might never miss again.

3

The basic idea is to get the velocity of the character and calculate the time of flight of the projectile to their current position. Using the flight time, you can make a rough projection about where the character will be by the time the missile arrives. You then aim at the new position. What I’ve done here is a bit simplified and imperfect, but you are not looking for perfect. And it is untested. It assumes the character is named “Player”. Change as needed.

#pragma strict
var projectile : Rigidbody;
var initialSpeed = 20.0;
var reloadTime = 0.5;
var ammoCount = 20;
private var lastShot = -10.0;

private var cc : CharacterController; 
private var player : Transform;

function Start() {
    var go = GameObject.Find("Player");
    player = go.transform;
    cc = go.GetComponent(CharacterController);
 }

 
function Fire () {
    // Did the time exceed the reload time?
    if (Time.time > reloadTime + lastShot && ammoCount > 0) {
       // create a new projectile, use the same position and rotation as the Launcher.
       var instantiatedProjectile : Rigidbody = Instantiate (projectile, transform.position, transform.rotation);
       
       // Time of flight to reach player
       var t = (player.position - transform.position).magnitude / initialSpeed;
       
       // Project future position
       var futurePos = player.position + cc.velocity * t;
       
       // Aim and fire at that future position
 	   var aim = (futurePos - transform.position).normalized;
       instantiatedProjectile.transform.rotation = Quaternion.LookRotation(aim);
       instantiatedProjectile.velocity = aim * initialSpeed;
 
       // Ignore collisions between the missile and the character controller
       Physics.IgnoreCollision(instantiatedProjectile.collider, transform.root.collider);
 
       lastShot = Time.time;
       ammoCount--;
    }
}