Collision Detection

Unity Engine
1

Im new at untty

I have 2 asteroids which when they randomly bump into each other i want them to move apart again yet I cant even get a simple test oncollisionfunction to work

example
(the asteroids have rigidbodies and isKinematic is false.)

function OnCollisionEnter (collision : Collision)
{
print("collided with "+collision.gameObject.tag)
}

is it something to do with the move function of the asteroids, I am currently moving the asteroids using

function Update ()
{
transform.Translate(Vector3.up * speed * Time.deltaTime);
}

but I also have tried:-

function FixedUpdate ()
{
rigidbody.MovePosition(rigidbody.position + speed * Time.deltaTime);
}

Is there something Im missing ?

2

Hello there!

If you want to directly move the positions, use Kinematic bodies. Otherwise move the bodies with forces, rigidbody.AddForce() would be the method to look at in this case.

3

Does using addforce make any difference to the OnCollisionEnter function. I have tried putting addforce into the Fixedupdate function of the asteroid but the asteroid then just keeps gathering more and more speed. I have therefore put it into the Start function but the asteroid doesnt move at all.

I am currently using transform.translate within the update function (as per my earlier post). So as Addforce didnt seem to be doingthe job i went back to this method and I tried switching Kinematic to true, but it doesnt make any difference. The onCollisionEnter function still fails to Fire.

using OntriggerEnter works fine but I really need the information that only OnCollisionEnter can provide.

Update: Using rigidbody.moveposition in the Fixedupdate function has now got things moving but still no collisions are occurring, grrr

4

Can anyone explain to me the difference between rigidbody.moveposition and transform.Translate. If i simply want to move a gameobject I normally use transform.Translate but it seems if I want to check for OnCollisionEnter I must move my gameobject using rigidbody.Moveposition.

I have 2 problems with this, 1. as explained above nothing I do seems to create a Collision 2. When moving a gameobject using Moveposition the object is not in the position I expect it to be, it seems to be lagging behind. What exactly am I moving with Moveposition, is it the gameobject ? or just the Collider ? this is frustrating, been at it all day saturday :frowning:

Im simply trying to get 2 bubbles to notice that they have collided so that i can bounce them away from each other.

Here is the code

var bubbleSpeed : Vector3 ;

function Start()
{
bubbleSpeed= Vector3(0,Random.Range(1.0,10.0),0);
rigidbody.MovePosition(rigidbody.position + bubbleSpeed * Time.deltaTime);
}

function FixedUpdate ()
{

rigidbody.MovePosition(rigidbody.position + bubbleSpeed * Time.deltaTime); //move the bubble up the screen
transform.Translate(bubbleSpeed * Time.deltaTime); // move the bubble up the screen (lol I know im doing this twice but some stupid issue means i have to move the rigidbody and the transform)
transform.Rotate( bubbleSpeed* Time.deltaTime); //slowly rotate the bubble

// check for top of screen
if (transform.position.y > 50)
{
ResetBubble ();
}
}

function ResetBubble()
{
//Reset the position of the bubble back to bottom of screen
var sphereColor : Color;

rigidbody.position.y = 2;
rigidbody.position.x = Random.Range(15.0,33.0);

bubbleSpeed= Vector3(0,Random.Range(1.0,10.0),0);

rigidbody.MovePosition(rigidbody.position + bubbleSpeed * Time.deltaTime);

}

function OnCollisionEnter (collision : Collision)

{ //why isnt this colliding ???
Debug.Log("collided with "+collision.gameObject.tag);

}

5

Your sphere collider have “is trigger” option turned on, so instead of "function OnCollisionEnter " you need to use "function OnTriggerEnter " or just turn off “is trigger”. I guess :slight_smile: