How to freeze rotation, but stay relative to an object

Questions & Answers
1

I have object1(marble) and object2(player)
this script is on the player object

void Update () 
	{
		player.transform.position = new Vector3(marble.transform.position.x, marble.transform.position.y + 0.45f, marble.transform.position.z);

		transform.LookAt(transform.position + marble.rigidbody.velocity);
	}

All works fine, except all I need is that the player object to not rotate along its x and z axis.
How can I stop the player object to stay relative to the marble object, but to lock its x and z axis?
Freezing the x and z rotation on the player Rigidbody has no affect.
Can someone help?

2

The typical way to solve this kind of problem is to bring the LookAt() point down to the level of the game object:

void Update () {
       player.transform.position = new Vector3(marble.transform.position.x, marble.transform.position.y + 0.45f, marble.transform.position.z);

        Vector3 v3LookPos = transform.position + marble.rigidbody.velocity;
        v3LookPos.y = transform.position.y;
 
       transform.LookAt(v3LookPos);
}