how to check mouse is not over any object in unity

Question

Im working on a way to check mouse is not over any object on scene to put my object in there. i know i can use OnMouseOver function but i have to add it on all objects script. Is there any other way to check my mouse position is not on any object collider? Its a 2d project. thank you for helping

Answer 1

An easy way to handle input over a range of gameobject, is to raycast and handle the input yourself.

Consider doing something like this in the Update loop.

void Update()
{
    if (Input.GetMouseButtonDown(0))
    {
        Vector2 pos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        RaycastHit2D[] hits = Physics2D.RaycastAll(pos, new Vector2(0, 0), 0.01f);

        for (int i = 0; i < hits.Length; i++)
        {
            if (hits[i].collider.tag == "Button")
            {
                 Button button = hits[i].collider.GetComponent<Button>();
                 button.Submit();
            }
        }
    }
}

Answer 2

You can use 2D RayCast to get the desired effect. In the following example I only have it checking when the user clicks, but I'm sure you can work it out from there.

The trick to checking a single point in 2D is to not give the raycast direction as shown below with vector2.zero

using UnityEngine;
using System.Collections;

public class RayCastPoint : MonoBehaviour 
{
    public Camera MainCamera;

    // Use this for initialization
    void Start () 
    {
        if(MainCamera == null)
            Debug.LogError("No MainCamera");
    }

    // Update is called once per frame
    void FixedUpdate () 
    {
        if(Input.GetMouseButtonDown(0))
        {
            var mouseSelection = CheckForObjectUnderMouse();
            if(mouseSelection == null)
            {
                Debug.Log("nothing selected by mouse");
            }
            else
            {
                Debug.Log(mouseSelection.gameObject);
            }
        }
    }

    private GameObject CheckForObjectUnderMouse()
    {
        Vector2 touchPostion = MainCamera.ScreenToWorldPoint(Input.mousePosition);

        RaycastHit2D hit2D = Physics2D.Raycast(touchPostion, Vector2.zero);

        return hit2D.collider != null ? hit2D.collider.gameObject : null;
    }

}