# How to swing an object by linear Interpolation?

i want to swing this game object with one key input.can any one help me out by trying to use linear interpolation.

Hi there,

I’ve played around with this and you can get the desired effect by using the Quaternion.FromToRotation function. This will swing an object towards a set direction and allow for it to swing back just as far. Here’s some code below to get you started:

``````public class CMP_Swing : MonoBehaviour
{
[Tooltip("How fast you want the swing to swing")]
public float SpeedOfSwing = .001f;
[Tooltip("The direction that we want to swing in")]
public Vector3 DirectionOfSwing;

//The original rotation of the object
private Quaternion OriginQuat;
private Quaternion ForwardQuat;
private Quaternion BackQuat;
//We set alpha to .5 so that we're at a rest position when we start the script
private float alpha = .5f;
private float direction = 1;

void Awake()
{
//Get our current rotation in case we want to reset the rotation at any point.
OriginQuat = transform.rotation;

//Get our quarternions based on our current transform. We get the positive and the negative so that we can lerp between them.
ForwardQuat = Quaternion.FromToRotation(transform.forward, DirectionOfSwing);
BackQuat = Quaternion.FromToRotation(transform.forward, -DirectionOfSwing);
}

// Use this for initialization
void Start()
{

}

// Update is called once per frame
void Update()
{
//Get an up/down key
var axis = Input.GetAxis("Vertical");
if (axis != 0) //If we've pressed the up/down key
{
//Set the objects rotation to the lerp of the forward and back quartenions
transform.rotation = Quaternion.Lerp(ForwardQuat, BackQuat, alpha);
//Add to our alpha so we can continue moving and multiply it by direction so that we can determine which direction it rotates
alpha += Time.deltaTime * SpeedOfSwing * direction;
//Clamp the alpha between 0 and 1 to ensure that if we hold a key down when alpha is 1 or 0, alpha will never go beyond those values
alpha = Mathf.Clamp01(alpha);
//Set direction to be the direction we pressed
direction = axis;
}
}
}
``````