unity3d: how to make a SpotLight follow an object?

Question

I am making an object move in it's update() and turn left right up down according to user input. All I want is to make a spotlight follow the object. Object's Rotation: 0,180,0 SpotLight's Rotation: 90,0,0 Since the rotations are different( and they need to be like that), I cannot make the light follow the object. code :

function Update () {

    SetControl(); // Input Stuff... 

    transform.Translate (0, 0, objectSpeed*Time.deltaTime);

    lightView.transform.eulerAngles=this.transform.eulerAngles;
    lightView.transform.Rotate=this.transform.eulerAngles;
    lightView.transform.Translate(snakeSpeed*Time.deltaTime,0, 0);  //THIS IS INCORRECT

}

lightView is simply pointing to the SpotLight.

Answer 1

All I want is to make a spotlight follow the object.

This is a two-step process. First, find the coordinate position (in world coordinates) of your target. Second, apply that position plus an offset to your spotlight. Since your light is rotated 90° along the x-axis, I assume your light is above and looking down.

var offset = new Vector3(0, 5, 0);

function Update()
{
  // Move this object
  transform.Translate (0, 0, objectSpeed*Time.deltaTime);

  // Move the light to transform's position + offset.
  // Note that the light's rotation has already been set and does
  //  not need to be re-set each frame.
  lightView.transform.position = transform.position + offset;
}

If you want a smoother "following" action, do a linear interpolation over time. Replace

lightView.transform.position = transform.position + offset;

with

lightView.transform.position = Vector3.Lerp(lightView.transform.position, transform.position + offset, Time.deltaTime * smoothingFactor);

where smoothingFactor is any float.

As an aside, it is near death to call transform.* in any kind of recurring game loop, because GameObject.transform is actually a get property that does a component search. Most Unity documentation recommends you cache the transform variable first.

Better code:

var myTrans = transform;    // Cache the transform
var lightTrans = lightView.transform;
var offset = new Vector3(0, 5, 0);

function Update()
{
  // Move this object
  myTrans.Translate (0, 0, objectSpeed*Time.deltaTime);

  // Move the light to transform's position + offset.
  // Note that the light's rotation has already been set and does
  //  not need to be re-set each frame.
  lightTrans.position = myTrans.position + offset;
}

Answer 2

What your looking for is the Unity method Transform.lookAt.

Place the following script on the spotlight. This code will make the object it is attached to, look at another object.

// Drag another object onto it to make the camera look at it.
var target : Transform; 

// Rotate the camera every frame so it keeps looking at the target 
function Update() {
    transform.LookAt(target);
}