How can i get rubber effect using unity 4

As i am new to unity i want to design a game similar to angry birds i need support that how can get elastic effect using unity.
I want the effect as shown in this video “- YouTube” I heard about procedural joints if the above video deals with the same concept can anyone clearly explain how can i work with procedural joints.

You don’t need any sophisticated elastic effect for a game like Angry Birds: simply save the position where you pressed the mouse button, drag the bird while the button is pressed, and accelerate the bird in the direction (start position - end position) when released.

That’s an example:

var bird: GameObject; // drag the bird object here
var force: float = 10.0;
var stretchSound: AudioClip;
var shotSound: AudioClip;

private var startPoint: Vector3;
private var drag = false;

function Update(){
  // get mouse pointer in world space:
  var pos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
  pos.z = 0; // make sure it's at Z = 0 
  if (drag)){ // drag bird while button pressed
    bird.transform.position = pos;
  }
  if (Input.GetMouseButtonDown(0)){ // mouse button pressed:
    drag = true; // start dragging
    startPoint = pos; // save initial position
    bird.rigidbody.isKinematic = true; // deactivate bird physics
    if (stretchSound){ // start stretching sound, if any
      audio.clip = stretchSound;
      audio.Play();
    }
  }
  if (Input.GetMouseButtonUp(0)){ // mouse button released:
    drag = false; // stop dragging
    bird.rigidbody.isKinematic = false; // activate bird physics
    var dir = startPoint - pos; // calculate direction and intensity
    bird.rigidbody.velocity = dir * force; // apply to the rigidbody
    if (shotSound){ // play shot sound, if any
      audio.clip = shotSound;
      audio.Play();
    }
  }
}

This script may be attached to the camera (add an AudioSource to the camera). The camera must be in orthographic mode and with rotation (0,0,0), and the bird must be a rigidbody with Is Kinematic checked and constraints set to freeze Z position and X,Y rotation. The action will happen at Z=0, thus you may place the slingshot a little ahead (Z = -1, for instance) and the scenery behind (Z = 10, for instance). If you don’t have the appropriate sounds, download them from here: stretch sound and shoot sound.