Collider.OnTriggerEnter(Collider)

Parameters

Description

When a GameObject collides with another GameObject, Unity calls OnTriggerEnter.

OnTriggerEnter happens on the FixedUpdate function when two GameObjects collide. The Colliders involved are not always at the point of initial contact.

Note: Both GameObjects must contain a Collider component. One must have Collider.isTrigger enabled, and contain a Rigidbody. If both GameObjects have Collider.isTrigger enabled, no collision happens. The same applies when both GameObjects do not have a Rigidbody component.

To use the following code sample, create a primitive GameObject, and attach a Collider and Rigidbody component to it. Enable Collider.isTrigger and Rigidbody.isKinematic. This GameObject will travel forward, until it collides with another GameObject. When a collision occurs, the direction immediately reverses.

using UnityEngine;

public class Example : MonoBehaviour
{
    private float speed = 2f;

    //Moves this GameObject 2 units a second in the forward direction
    void Update()
    {
        transform.Translate(Vector3.forward * Time.deltaTime * speed);
    }

    //Upon collision with another GameObject, this GameObject will reverse direction
    private void OnTriggerEnter(Collider other)
    {
        speed = speed * -1;
    }
}