How do I center a child object of camera on other object's screen position?

Questions & Answers
1

I have a moveable main camera, and then a child object of that camera that I want to move on its xy plane relative to the camera in a way it stays centered (from the camera’s pov) on a moving object in front of it.

So this is the first thing my undercaffeinated brain coughed up :

( this is in Update of the script attached to the tracking object )

myTransform.localPosition = camTransform.InverseTransformPoint(Camera.main.WorldToViewportPoint(Camera.main.ViewportToWorldPoint(headTransform.position)));

And it doesn’t work at all, it just sticks the tracking object to the moving object in world space. Before I drive myself crazy with this, does anyone know the proper way to do it ?

2

I would shoot a ray from the camera to the center of the screen and place the object on the first point of collision.

3

I figured it out. Answering my own question in case anyone else needs to know:

var myTransform : Transform;
var headTransform : Transform;
var camTransform : Transform;
var dist : float = 13;

private var screenPt : Vector3;
private var worldPt : Vector3;

function Update () 
{
screenPt = Camera.main.WorldToScreenPoint(headTransform.position);
worldPt = Camera.main.ScreenToWorldPoint(Vector3(screenPt.x,screenPt.y,dist));
myTransform.localPosition = camTransform.InverseTransformPoint(worldPt);
}