How To: Spawn object on raycast collision.

Questions & Answers
1

I have created a plane in my scene that can be used to detect collision. I am trying to create a raycast on mouse click and detect if it's collided with that game object. Then instantiate another game object. I can't seem to figure out how to do this.

// Update is called once per frame
    void Update()
    {
        if(Input.GetButtonDown("Fire1"))
        {
            Ray ray = new Ray(Camera.main.transform.position, Vector3.Normalize(near));
            Vector3 near = Camera.main.ScreenToWorldPoint(new   Vector3(Input.mousePosition.x, Input.mousePosition.y, 0));
            RaycastHit[] raycastHits = Physics.RaycastAll(ray);

            if(raycastHits == GameObject.FindGameObjectWithTag("S_Plane"))
            {

            }

        }

    }
2

Try something like this:

if(Input.GetButtonDown("Fire1"))
{
    Ray ray;
    RaycastHit hit;
    ray = Camera.main.ScreenPointToRay(Input.mousePosition);
    if (Physics.Raycast(ray, out hit, 100.0f))
    {
        if (hit.collider.name=="S_Plane") 
            Instantiate(myPrefab, hit.point, Quaternion.identity);
    }
}

I believe you can also use collider.Raycast in a script on a given object to limit the raycast hit check to that object.

3 
var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
var hit : RaycastHit;
var layerMask = 1 << 8;
var Dummy:GameObject;

if (Input.GetButtonDown ("Fire1")) {
    if (Physics.Raycast (ray, hit, Mathf.Infinity, layerMask)){
        placedObj = Instantiate(Dummy, Vector3(hit.point.x, hit.point.y, hit.point.z) , Quaternion.identity);
        }
    }

Something like this :)