Unwanted jittery behavior

Questions & Answers
1

I have the following code in a script for a 2D game in the XY plane

function FixedUpdate () {
    // Make sure we are absolutely always in the 2D plane and with the right rotation.
    transform.position.z = 0;
    transform.eulerAngles= Vector3 (270,0,0);
    }

function LateUpdate () {
        var realWorldPosition: Vector3 = Camera.main.ScreenToWorldPoint (Input.mousePosition);
        var gamePosition: Vector3 = Vector3(realWorldPosition.x, realWorldPosition.y,0);
        transform.position = gamePosition;
    }

function OnCollisionEnter (collision : Collision) {
   var forceDirection:Vector3 = -1*collision.contacts[0].normal;
    collision.rigidbody.AddForce (forceDirection * pushPower, ForceMode.Impulse);
    }

The GameObject this is attached to moves with the mouse and applies a force to any collider it encounters. The thing is, once a collision occurs, the attached gameobject becomes all jittery for a while. It then goes back to normal, but it's annoying.

I've set infinite linear and rotational drags to its rigidbody, but it doesn't work.

I have no idea how to solve this.

2

You are mixing Physics with transforms. You need to attach this object via a spring joint or something to a parent object that is moved via the mouse to avoid wacky behavior. set the parent object to kinematic. That will allow you to have a RidgidBody on an object while controlling it via transforms.

Avoid any transform modifications to a body under physics control.

transform.position.z = 0; transform.eulerAngles= Vector3 (270,0,0);

this is bad and can be accomplished via constraints on the RidgidBody instead.

Does this object HAVE to have a RidgidBody component? Since you are moving it with the mouse it doesn't sound like you need a RidgidBody attached, just a collider to test for collisions, In fact it sounds like you really need the collider to be a trigger instead and use OnTriggerEnter.

3

Apparently, the problem had to do with the calculation of the object's position and the code controlling the camera's position. They were both inside the LateUpdate function, but in different scripts. I moved them both to the same script, calculated the camera's position and THEN the object's, and it seems to work.