Legacy Documentation: Version 5.1
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Rigidbody.OnCollisionEnter(Collision)

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Description

OnCollisionEnter is called when this collider/rigidbody has begun touching another rigidbody/collider.

In contrast to OnTriggerEnter, OnCollisionEnter is passed the Collision class and not a Collider. The Collision class contains information about contact points, impact velocity etc. If you don't use collisionInfo in the function, leave out the collisionInfo parameter as this avoids unneccessary calculations. Notes: Collision events are only sent if one of the colliders also has a non-kinematic rigidbody attached. Collision events will be sent to disabled MonoBehaviours, to allow enabling Behaviours in response to collisions.

#pragma strict
var audio: AudioSource;
function Start() {
	audio = GetComponent.<AudioSource>();
}
function OnCollisionEnter(collision: Collision) {
	// Debug-draw all contact points and normals
	for (var contact: ContactPoint in collision.contacts) {
		Debug.DrawRay(contact.point, contact.normal, Color.white);
	}
	// Play a sound if the colliding objects had a big impact.		
	if (collision.relativeVelocity.magnitude > 2)
		audio.Play();
}
using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { AudioSource audio; void Start() { audio = GetComponent<AudioSource>(); } void OnCollisionEnter(Collision collision) { // Debug-draw all contact points and normals foreach (ContactPoint contact in collision.contacts) { Debug.DrawRay(contact.point, contact.normal, Color.white); } // Play a sound if the colliding objects had a big impact. if (collision.relativeVelocity.magnitude > 2) audio.Play(); } }

Another example:

#pragma strict
// A grenade
// instantiates a explosion prefab when hitting a surface
// then destroys itself
public var explosionPrefab: Transform;
function OnCollisionEnter(collision: Collision) {
	var contact: ContactPoint = collision.contacts[0];
	// Rotate the object so that the y-axis faces along the normal of the surface
	var rot: Quaternion = Quaternion.FromToRotation(Vector3.up, contact.normal);
	var pos: Vector3 = contact.point;
	Instantiate(explosionPrefab, pos, rot);
	Destroy(gameObject);
}
// A grenade
	// instantiates a explosion prefab when hitting a surface
	// then destroys itself
using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { public Transform explosionPrefab; void OnCollisionEnter(Collision collision) { ContactPoint contact = collision.contacts[0]; // Rotate the object so that the y-axis faces along the normal of the surface Quaternion rot = Quaternion.FromToRotation(Vector3.up, contact.normal); Vector3 pos = contact.point; Instantiate(explosionPrefab, pos, rot); Destroy(gameObject); } }