How to restrict touch(swipe) input area in Unity(iphone)

Questions & Answers
1

I am fairly new in UNITY and currently i am working on a developing a POOL game with flick input. (u flick the CUE ball with your finger as input ).
I have succeeded in taking swipe input and move the ball with velocity as per the speed of swipe. what i need to do now is limit the swipe area to certain radius distance of the cue ball. currently the input is taken when u swipe anywhere in the screen. I want to restrict this input area to the CUE ball alone.
My code for the swipe input is as below (this is not my script though i have found it in the UNITY forum)

`
using UnityEngine;
using System.Collections;

public class TouchMonitor : MonoBehaviour {

public Rigidbody ball;

private Vector3 touchStart; 
private Vector3 touchEnd;
private GameObject lineRenderer;    

void Update () {
    if (Input.touchCount > 0)
    {
        Touch t = Input.touches[0];
        if (t.phase == TouchPhase.Began)
        {
            touchStart = t.position;
        }

        if (t.phase == TouchPhase.Ended || t.phase == TouchPhase.Canceled)
        {
            touchEnd = t.position;
            DoInput();
        }
    }

    if (Input.GetButtonDown("Fire1"))
    {
        touchStart = Input.mousePosition;
    }

    if (Input.GetButtonUp("Fire1"))
    {
        touchEnd = Input.mousePosition;
		if(ball.IsSleeping())
        DoInput();
    }
	
	
}

Vector3 getCueBallPosition()
{
	Vector3 ballpos=new Vector3();
	ballpos=ball.transform.position;
	return ballpos;
	
}

void DoInput()
{
    Vector3 p1 = new Vector3();
    Vector3 p2 = new Vector3();
	Vector3 cuePos=getCueBallPosition();
	
    touchStart.z = Camera.main.nearClipPlane+.1f; //push it a little passed the clip plane for camera, just to make sure its visible on screen
    touchEnd.z = Camera.main.nearClipPlane+.1f;
    
	p1 = Camera.main.ScreenToWorldPoint(touchStart);
    p2 = Camera.main.ScreenToWorldPoint(touchEnd);

    CreateLine(p1,p2);

    Vector3 v = p2-p1;
	Debug.Log("Ball Speed");
	
	 ball.AddForce(v*5, ForceMode.Impulse);
	
}



//creates an ugly purple line from pos1 to pos2 in worldspace
void CreateLine(Vector3 p1, Vector3 p2)
{
    Destroy(lineRenderer);
    lineRenderer = new GameObject();
    lineRenderer.name = "LineRenderer";
    LineRenderer lr = (LineRenderer)lineRenderer.AddComponent(typeof(LineRenderer));
    lr.SetVertexCount(2);
    lr.SetWidth(0.001f, 0.001f);
    lr.SetPosition(0, p1);
    lr.SetPosition(1, p2);
}

}`

i tried to get current position of cue ball and check if the initial touch (touch start) is within certain area from the centre of cue ball. but i could not get it working.
If anyone can shed some light in this matter i would be very grateful.
thanks in advance.

2

If I get you right, then you may do the following.

Add a private variable to mark a touch as valid (bool balidTouch = false).

Modify the touch detection:

if (t.phase == TouchPhase.Began)
    {
                if( touchValid = Physics.Raycast( Camera.main.ScreenPointToRay( t.position ) ) )
                          touchStart = t.position;
    }

When you check the end point add this variable as an additional condition:
`

if ( (t.phase == TouchPhase.Ended || t.phase == TouchPhase.Canceled) && touchValid )

This way you need the collider on you ball and it may be a good idea to move it to a separate layer. Then raycast will look like this: Physics.Raycast( ray, Mathf.Infinite, 1 << layerIndex )`. If there are other object between the camera and the ball (or behind) then you need to change the collider layer in order to make this code work (or you may check the object in RaycastHit).