how to make object tumble randomly toward the ground?

Unity Engine
1

i have a breakable bridge, when i walk on it i get a trigger, the breakable treads have rigid bodies (no constraints), this is the code

public class BreakableSurface : MonoBehaviour
{
    public float _BreakWeight;

    public void OnTriggerEnter(Collider other)
    {
        Debug.Log("BreakableSurface OnTriggerEnter " + other.name);

        Transform parent = transform.parent;
        Rigidbody[] _RigidbodyList = parent.GetComponentsInChildren<Rigidbody>();
        foreach (Rigidbody rb in _RigidbodyList)
        {
            rb.drag = Random.Range(.5f, 3f);
            rb.AddTorque(Random.Range(100, 300), Random.Range(100, 300), Random.Range(100, 300));
            rb.isKinematic = false;
        }
    }
}

they fall ok at random speeds but the AddTorque line seems to do nothing, they all fall flat, i want them to tumble. i tried several different values.
any ideas? thanks

2

You cannot add forces or torque to a Kinematic Rigidbody. You should turn off Kinematic body type before you try to do so.

1 Like
3

awesome, so all i had to do was put rb.isKinematic = false; before addTorque
this code works great now

foreach (Rigidbody rb in _RigidbodyList)
        {
            rb.drag = Random.Range(.5f, 3f);
            rb.isKinematic = false;
            rb.AddTorque(Random.Range(0, 30), Random.Range(0, 30), Random.Range(0, 30));         
        }
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4

one more question, my wood planks fall through the terrain and they are gone. how would make it so then collide with the terrain and stay put? thanks

5

By ensuring you have colliders on the “wood planks” and that they are set to actually collide with the terrain and its collider(s).

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6

oh right, i forgot, i didn’t bother to put colliders on the individual planks because i have a trigger zone that covers half a dozen planks in the breakable area. guess i need to add.

for performance reasons, i guess its best to enable those colliders only after the trigger? there’s only a handful of them so maybe not worth the trouble. what do you think?

7

It’s not clear what your set-up is and TBH only you, via the profiler, can determine what the performance is like but it makes sense to not have colliders active that don’t need to be. I guess the main reason to not have the colliders active would be that you’d get collisions on them that you wouldn’t want until triggered.

1 Like
8

thanks again, i decided only to add colliders to a few planks so the area where the player falls doesn’t get too cluttered. seems i need to disable the tread colliders when they are on the bridge or they fall down.

so here is the final working code

public class BreakableSurface : MonoBehaviour
{
    public float _BreakWeight = 30;     // break at 30kg, a bit less than player

    public void OnTriggerEnter(Collider other)
    {
        Debug.Log("BreakableSurface OnTriggerEnter " + other.name);

        Rigidbody otherRb = other.transform.GetComponent<Rigidbody>();
        if (!otherRb)
        {
            Debug.LogError("BreakableSurface OnTriggerEnter " + other.name + "has no Rigidbody");
            return;
        }

        if (otherRb.mass < _BreakWeight)
            return;

        Rigidbody[] _RigidbodyList = transform.parent.GetComponentsInChildren<Rigidbody>();
        foreach (Rigidbody rb in _RigidbodyList)
        {
            rb.drag = Random.Range(.5f, 3f);
            rb.isKinematic = false;
            rb.AddTorque(Random.Range(0, 30), Random.Range(0, 30), Random.Range(0, 30));         
        }

        Collider[] _ColliderList = transform.parent.GetComponentsInChildren<Collider>();
        foreach (Collider col in _ColliderList)
            col.enabled = true;
    }
}
1 Like