MonoBehaviour.OnTriggerEnter(Collider)

Parameters

Description

OnTriggerEnter is called when the GameObject collides with another GameObject.

The given other Collider has details about the trigger event, such as the name of its GameObject. Either of the two GameObjects must have a Rigidbody component. The Rigidbody component has both Rigidbody.useGravity and Rigidbody.isKinematic set to false. These prevents the GameObject from falling under gravity and having kinematic behavior. One Collider has Collider.isTrigger set to true. The GameObject with Collider.isTrigger set to true has OnTriggerEnter called when the other GameObject touches or passes through it. OnTriggerEnter occurs after FixedUpdate ends.

A disabled GameObject receives the OnTriggerEnter message.

using UnityEngine;

// MonoBehaviour.OnTriggerEnter example.
//
// A cube is based in the center of the world. A small white sphere is added
// to the world and it can move anywhere in the Scene. The cube changes
// color each time the sphere enters the cube. As the sphere leaves the cube,
// the cube reverts back to white.

public class Example : MonoBehaviour
{
    private float moveSpeed = 3.0f;
    private GameObject sphere;

    void Awake()
    {
        // Create the ground.
        GameObject ground = GameObject.CreatePrimitive(PrimitiveType.Quad);
        ground.transform.rotation = Quaternion.Euler(90, 0, 0);
        ground.transform.localScale = new Vector3(6, 6, 6);
        ground.transform.position = new Vector3(0, -0.5f, 0);

        // Make sure the BoxCollider is a trigger.
        BoxCollider boxCollider = gameObject.GetComponent<BoxCollider>();
        boxCollider.isTrigger = true;

        // Create a sphere to interact with this cube.
        sphere = GameObject.CreatePrimitive(PrimitiveType.Sphere);
        sphere.gameObject.transform.position = new Vector3(1f, 0, 0);
        sphere.gameObject.transform.localScale = new Vector3(0.5f, 0.5f, 0.5f);

        // Add a Rigidbody to the sphere.
        // The sphere does not touch the ground.
        sphere.gameObject.AddComponent<Rigidbody>();
        sphere.gameObject.GetComponent<Rigidbody>().useGravity = false;
    }

    void Update()
    {
        // Move the sphere based on a/d and s/w.
        Transform sphereTransform = sphere.gameObject.transform;
        sphereTransform.Translate(Vector3.forward * Time.deltaTime * Input.GetAxis("Vertical") * moveSpeed);
        sphereTransform.Translate(Vector3.right * Time.deltaTime * Input.GetAxis("Horizontal") * moveSpeed);

        LimitSphere(sphereTransform);
    }

    private void OnTriggerEnter(Collider other)
    {
        // Change the cube color to green.
        MeshRenderer meshRend = GetComponent<MeshRenderer>();
        meshRend.material.color = Color.green;
        Debug.Log(other.name);
    }

    private void OnTriggerExit(Collider other)
    {
        // Revert the cube color to white.
        MeshRenderer meshRend = GetComponent<MeshRenderer>();
        meshRend.material.color = Color.white;
    }

    // Keep sphere inside a xz square of 2 units.
    private void LimitSphere(Transform sphereTransform)
    {
        if (sphereTransform.position.x < -1.0f)
        {
            sphereTransform.position = new Vector3(-1.0f, 0.0f, sphereTransform.position.z);
        }

        if (sphereTransform.position.x > 1.0f)
        {
            sphereTransform.position = new Vector3(1.0f, 0.0f, sphereTransform.position.z);
        }

        if (sphereTransform.position.z < -1.0f)
        {
            sphereTransform.position = new Vector3(sphereTransform.position.x, 0.0f, -1.0f);
        }

        if (sphereTransform.position.z > 1.0f)
        {
            sphereTransform.position = new Vector3(sphereTransform.position.x, 0.0f, 1.0f);
        }
    }
}