How can I detect a Gameobject touching another gameObject without using collider2D's?

Question

I have fish gameObjects that have colliders2D so that I can click and move them. I added fish food with Collider2D's but it was hard for me to click on the fish. After I disabled the fish food collider2D it was easier to click on the fish. Is there an alternative when detecting two gameObjeccts without colliders?

Answer 1

Don't use OnMouseDown. Having this in your project forces Unity to cast rays for you in the most generic way, which is often less efficient and less precise than casting them yourself.

Make your own script that can filter to the physics layer you care about.

public class FishClicker : MonoBehaviour {

    public LayerMask whatIsFish;

    public float clickRadius = 0.1f;

    void Update() {

        if (Input.GetMouseButtonDown(0)) {
            var mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
            var hit = Physics2D.OverlapCircle(mousePos, clickRadius, whatIsFish);

            if (hit != null) {
                var fish = hit.GetComponentInParent<Fish>();

                if (fish != null) { fish.DoClickThing(); }
            }
        }
    }
}