Unity child object sometimes jumps to vector3(0,0,0)

Question

I have a very annoying bug, and I can't get rid of it. The situation is, that I have a parent with the following script attached, and a trigger box2d collider. It has a child, with a rigidbody2d(kinematic, gravity=0, freeze position x, and rotation z), a sprite renderer and a polygon collider (with 4 edges). My problem is, when the scene is loaded, sometimes my child objects (always random how much of them and which ones), jumps to transform.position 0,0,0.

I link the script, that is attached to the parent

using UnityEngine;
using System.Collections;

public class FallingSpikeHazard : MonoBehaviour
{
    public GameObject spike;
    private Rigidbody2D spikeRigidbody;
    [SerializeField]
    private Vector3 startPosition;

    void Awake ()
    {       
        startPosition = spike.transform.localPosition; 
    }

    void Start ()
    {
        spikeRigidbody = spike.GetComponent<Rigidbody2D> ();
        
        Helper.JustReset += ResetMe;
        Invoke ("CheckPosition", Time.deltaTime);
    }

    void CheckPosition ()
    {
        if (spike.transform.localPosition != startPosition) {
            Debug.LogError ("t1" + spike.transform.localPosition);
            spike.transform.localPosition = startPosition;
            Debug.LogError ("t2" + spike.transform.localPosition);
        }
    }

    void OnDestroy ()
    {
        
        Helper.JustReset -= ResetMe;
    }

    void ResetMe ()
    {
        spikeRigidbody.gravityScale = 0;
        spikeRigidbody.isKinematic = true;
        if (startPosition != Vector3.zero) {
            spike.transform.localPosition = startPosition;
        }
    }

    void OnTriggerEnter2D (Collider2D other)
    {
        if (other.gameObject.tag.Equals ("Player")) {
            spikeRigidbody.isKinematic = false;
            spikeRigidbody.gravityScale = 1;
        }
    }
}

Events are not called, in other hand, if I disable the script, it keeps happening. Nothing have reference to these GameObjects. I don't have animations, or animator attached.

What could cause my problem?

Ok guys, there is nothing wrong with the code. The problem is with the RigidBody2d Component. Basically, if you tick the fixed x or y position, it will break your game. Literally. I put a video here to show you what is the actual bug. youtube.com/watch?v=HweD8A-q34Y — BazsBazs
The solution is really simple: if you have to use fixed angles write your own script for it. for the x angle do this: public Rigidbody2d myRigidB; public float fixedX; void FixedUpdate(){ Vector2 myVeloc = myRigidB.velocity; myVeloc = new Vector2(0,myVeloc.y); myRigidB.velocity=myVeloc; transform.position=new vector2(fixedX,transform.position.y); } This script is not tested, but the solution is something like this :) — BazsBazs

user2796283 user2796283 · Accepted Answer · 2015-07-03T00:09:37

You need to have a Rigidbody2D component in the parent GameObject in order for the OnTriggerEnter function to be called.

Unity child object sometimes jumps to vector3(0,0,0)

1 Answers