Ball Isn't following Trajectory line : Unity3d

[Ekta-Mehta-D]

Hello Everyone,

I am working on projectile motion. Sometimes my ball does not follow the trajectory line.

Code is here :

#pragma strict
#pragma implicit
#pragma downcast 
var turret : Transform; 
var bulletPrefab : Transform;
private var plane : Plane;
private var power : float = 30;
private var gravity: float = 9.8;
public var distance : float = 1.0f;
public var  predictionLine : LineRenderer;
public var enablePrediction : boolean = true;
public var targetPoint : boolean = true;
var velocity : Vector3;


private var horizontalOffset : float = 0.0f;
private var  lob : float = 0.75f;
var bullet : Transform ;
	
function Awake ()
{
	plane = Plane(-Vector3.forward,turret.position);
	predictionLine.SetWidth(1.0f,1.0f);
	bullet = Instantiate(bulletPrefab, turret.position, turret.rotation);
}	
function Update () 
{ 
	var distanceToPlane : float;
	var hit : RaycastHit; 
    var ray = camera.ScreenPointToRay(Input.mousePosition);   
    var hitPoint : Vector3;
	
	if(plane.Raycast(ray,distanceToPlane))
	{
			hitPoint = ray.GetPoint(distanceToPlane);
			velocity = GetTrajectoryVelocity(turret.position, hitPoint, lob, Physics.gravity);	
			turret.up = velocity;
	}
	
//	if(Input.GetMouseButtonDown(0))
//	{
//		if(plane.Raycast(ray,distanceToPlane))
//		{
//			GameObject.Find("SoccerBall(Clone)").transform.position = turret.position;
//			FireProjectile();
//		}
//	} 
	

	horizontalOffset = Mathf.Clamp(horizontalOffset, -45.0f, 35.0f);
		
	lob += Input.GetAxis("Mouse ScrollWheel") * 0.01f;
	//Debug.Log("lob" + lob);
	lob = Mathf.Clamp(lob, 0.25f, 1.2f);
	
	distance = Mathf.Clamp(distance, 0.25f, 1.5f);

	UpdatePredictionLine();  
		
	if (Input.touchCount > 0) {
		var touch = Input.GetTouch(0);
		
		switch (touch.phase) {
		
		case TouchPhase.Began:
			UpdatePredictionLine();  
			break;
		
		case TouchPhase.Moved:
			UpdatePredictionLine();  
			break;
			
		case TouchPhase.Ended:
			GameObject.Find("SoccerBall(Clone)").transform.position = turret.position;
			UpdatePredictionLine();  
			FireProjectile();
			break;
		   }
	    }
    }

	
        function UpdatePredictionLine() 
    	{
    		predictionLine.SetVertexCount(180);
    		var previousPosition : Vector3 = turret.position;
    		for(var i : int = 0; i < 180; i++)
    		{
    			var currentPosition : Vector3 = GetTrajectoryPoint(turret.position, velocity, i, 1, Physics.gravity);
    			var direction : Vector3= currentPosition - previousPosition;
    			direction.Normalize();
    			
    			var distance : float = Vector3.Distance(currentPosition, previousPosition);
    			
    			var hitInfo : RaycastHit ;
    			if(Physics.Raycast(previousPosition, direction,  hitInfo, distance))
    			{
    				predictionLine.SetPosition(i,hitInfo.point);
    				predictionLine.SetVertexCount(i);
    				break;
    			}
    			
    			previousPosition = currentPosition;
    			predictionLine.SetPosition(i,currentPosition);
    		}
    	}
    	
    	function GetTrajectoryPoint( startingPosition : Vector3 ,  initialVelocity : Vector3 ,  timestep : float,  lob : float ,  gravity : Vector3) : Vector3
    	{
        	var physicsTimestep : float = Time.fixedDeltaTime;
        	var stepVelocity : Vector3 = initialVelocity * physicsTimestep;
    		
    		//Gravity is already in meters per second, so we need meters per second per second
    		var stepGravity : Vector3 = gravity * physicsTimestep * physicsTimestep;
    		
    		return startingPosition + (timestep * stepVelocity) + ((( timestep * timestep + timestep) * stepGravity ) / 2.0f);
    	}
    	
    	function GetTrajectoryVelocity( startingPosition : Vector3,  targetPosition : Vector3,  lob : float ,  gravity : Vector3) : Vector3
    	{
    		var physicsTimestep : float = Time.fixedDeltaTime;
    	    var timestepsPerSecond : float = Mathf.Ceil(1f/physicsTimestep);
    		
    		//By default we set n so our projectile will reach our target point in 1 second
    	    var n : float = lob * timestepsPerSecond;
    		
    	    var a : Vector3 = physicsTimestep * physicsTimestep * gravity;
    		var p : Vector3 = targetPosition;
    		var s : Vector3 = startingPosition;
    	    
    		var velocity : Vector3 = (s + (((n * n + n) * a) / 2f) - p) * -1 / n;
    		//This will give us velocity per timestep. The physics engine expects velocity in terms of meters per second
    		velocity /= physicsTimestep;
    		return velocity;
    	}
    	
    	function FireProjectile() {
    		var rb : Rigidbody = GameObject.Find("SoccerBall(Clone)").GetComponent(Rigidbody);
    		rb.useGravity = true;
    		rb.transform.position = turret.position;
    		
    		rb.AddForce(velocity, ForceMode.Impulse);
    	} 

So what can be the reason? While touching it is changing the velocity?? I could not identify the bug.

It is specially happening with large angle.

Thanks in advance for your help and support…

[hirenkacha]

You need to reset the velocity to zero before firing the bullet. For firing the bullet inside your FireProjectile() just add one line like following

function FireProjectile() 
    {
	    var rb : Rigidbody = GameObject.Find("Ball(Clone)").GetComponent(Rigidbody);
	    rb.useGravity = true;
	    rb.velocity=Vector2.zero;  //<=========== ADD THIS
	    rb.transform.position = turret.position;
	    rb.AddForce(velocity, ForceMode.Impulse);
    } 

Also for PC you can use this functions which will work on android / ios too.

                if(Input.GetKeyDown(KeyCode.Mouse0))
        	    {
        	    	 UpdatePredictionLine();
        	    }
        	    if(Input.GetKey(KeyCode.Mouse0))
        	    {
        	    	 UpdatePredictionLine();
        	    }
        	    if(Input.GetKeyUp(KeyCode.Mouse0))
        	    {
        	    	GameObject.Find("Ball(Clone)").transform.position = turret.position;
        			UpdatePredictionLine();
        			FireProjectile();
        	    }