Rigidbody.OnCollisionEnter(Collision)

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);
	}
}