dev-notes/.NET/Unity/Collisions.md

Collisions (Physics)

Rigidbody Component

Enables physycs on the game objects.

Rigidbodies collide with other objects instead of going through them.

Avoid obejct rotation on colisions:

1. Assign Rigidbody component to object
2. Enable Freeze Rotaion in Rigidbody > Constraints

using UnityEngine;
using System.Collections;

public class GameObject : MonoBehaviour {

    Rigidbody = rigidbody;  // game object rigidbody reference container

    void Start()
    {
        rigidbody = GetComponenet<Rigidbody>();  // get rigidbody reference
    }

    void Update()
    {
    }

    // FixedUpdate is calles every x seconds (not influenced by FPS instability)
    // used for physics calculations which sould be FPS independant
    void FixedUpdate()
    {
        Time.fixedDeltaTime;  // fixed amount of time
        Time.timeDelta;  // if called inside FIxedUpadate() behaves like fixedDeltaTime
    }

}

Box Collider Component

Enable Is Trigger to register the collision but avoid blocking the movement of the objects. The trigger can generate a event to signal the contact with the object.

One of the collidng GameObjects must have the Rigidbody component and the other Is Trigger enabled. To detect the collison but avoid computing the physycs Is Kinematic must be enabled in the Rigidbody component.

using UnityEngine;
using System.Collections;

public class GameObject : MonoBehaviour {

    Rigidbody = rigidbody;  // game object rigidbody reference container

    void Start()
    {
        rigidbody = GetComponenet<Rigidbody>();  // get rigidbody reference
    }

    // FixedUpdate is calles every x seconds (not influenced by FPS instability)
    // used for physics calculations which sould be FPS independant
    void FixedUpdate()
    {
        Time.fixedDeltaTime;  // fixed amount of time
        Time.timeDelta;  // if called inside FIxedUpadate() behaves like fixedDeltaTime
    }

    // called on box collision.
    void OnTriggerEnter(Collider triggerCollider) {

        // detect a collison with a perticular GameObject(must have a TAG)
        if (triggerCollider.tag = "tag") {
            Destroy(triggerCollider.gameObject);  // destroy tagged item on collision
            //or
            Destroy(gameObject);  // destroy itself
        }
    }