How to detect a potential collision in Unity?

Question

I have a Unity game I am working on as a hobby and have come across an interesting issue with how to best handle collision detection. My problem here is that my game is a 2D turn-based game, whereby a game object can move a fixed distance each time in a non-grid based world space. I have my game objects currently using BoxCollider2D to handle collision detection, but I need to be able to determine if there will be a collision BEFORE actually making a move, which right now causes the game object to overlap another game object and fire the OnCollisionEnter2D event. The eventual idea here is to allow a player to plan out a move and have a "navigation guide" appear next to the object to show move options based on the game object's move capabilities.

Is it possible to take my game object's collider, transform its position to move or rotate it, see if a collision would occur, but NOT actually move the object itself?

Answer 1

You mean like simply using Rigidbody.SweepTest ? ;)

Tests if a rigidbody would collide with anything, if it was moved through the Scene.

From the example

public class ExampleClass : MonoBehaviour 
{
    public float collisionCheckDistance;
    public bool aboutToCollide;
    public float distanceToCollision;
    public Rigidbody rb;

    void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    void Update()
    {
        RaycastHit hit;
        if (rb.SweepTest(transform.forward, out hit, collisionCheckDistance))
        {
            aboutToCollide = true;
            distanceToCollision = hit.distance;
        }
    }
}

---

Oh just noted that actually this is only for 3D Rigidbody.

For 2D this doesn't exist but can be kind of replicated using instead Collider2D.Cast

Casts the Collider shape into the Scene starting at the Collider position ignoring the Collider itself.