Raycast from 2D canvas object to world space

Question

After playing around with the code long enough, I answered my own question. I'll post it here for all or any who have the same problem I had:

Using a Main Camera, with a child Canvas, with a child 'Square UI Object'(cursor). How to make Main Camera use a Raycast that aims at the 'cursor'. And find and get the 'Selected' object returned and use for other scripts...

Using C# in Unity 5.6...

 public class MainCameraControl : MonoBehaviour {
 
     public GameObject cursor;
     public float cursorSpeed;
     public GameObject Selected;
 
     float posX;
     float posY;

     void Start() {}
 
     void Update () {
         KeyboardMove ();
 
         if (Input.GetKeyUp (KeyCode.RightShift))  //The "{ }" doesn't need to be called because there's only one solution
             CheckRay ();                          //Since it's update, you don't want the ray called every frame
 
         if (Input.GetKeyUp (KeyCode.RightControl)) {
             if (Selected != null) {
                 //Destroy (Selected);
                 Debug.Log ("Last selected: " + Selected.name);
             }        
         }
 
     }
 
     private void CheckRay() {
         
         posX = cursor.transform.localPosition.x + 375f;   //These offsets may be needed, or changed for different purposes
         posY = cursor.transform.localPosition.y + 150f;   //Check your scene while game is running, and make sure DrawRay is active
 
         Ray ray = Camera.main.ScreenPointToRay(new Vector3(posX, posY, 0));
             //Debug.DrawRay(ray.origin, ray.direction * 10, Color.yellow);      //DrawRay - delete back slashes to activate
         RaycastHit hit;
         if (Physics.Raycast(ray, out hit, 100))
             Debug.Log("You have selected the " + hit.collider.name);
         Selected = hit.collider.gameObject;
     }
 
     private void KeyboardMove(){         //I created these functions down here, to clean the Update space
 
         if (Input.GetKey (KeyCode.UpArrow))
             cursor.transform.Translate(Vector2.up * cursorSpeed * Time.deltaTime);
         if (Input.GetKey (KeyCode.DownArrow))
             cursor.transform.Translate(Vector2.down * cursorSpeed * Time.deltaTime);
         if (Input.GetKey (KeyCode.LeftArrow))
             cursor.transform.Translate(Vector2.left * cursorSpeed * Time.deltaTime);
         if (Input.GetKey (KeyCode.RightArrow))
             cursor.transform.Translate(Vector2.right * cursorSpeed * Time.deltaTime);
     }
 }

Answer 1

I finally figured it out! The cursor position on the canvas is not only different from worldspace, but it is also a different position when you call ScreenPointToRay (which counts pixels out from the bottom left corner of the canvas, being 0,0).

Here is the proper code for Unity 5.6 in C#:

 public GameObject cursor; //drag n drop UI object in inspector
 public Canvas canvas; //drag n drop canvas in inspector
 float pixelX;
 float pixelY;
 float posX;
 float posY;
 
 void Start () 
 {
     pixelX = canvas.worldCamera.pixelWidth;
     pixelY = canvas.worldCamera.pixelHeight;
 }
 
 void Update(){
     
     CheckRay();
 }
 
 void CheckRay(){
     
     posX = cursor.transform.localPosition.x + pixelX / 2f;   
     posY = cursor.transform.localPosition.y + pixelY / 2f;   
     Vector3 cursorPos = new Vector3 (posX, posY, 0);
     //OR- Ray ray = Camera.main.ScreenPointToRay(new Vector3(posX, posY, 0));
     Ray ray = Camera.main.ScreenPointToRay(cursorPos);
         Debug.DrawRay(ray.origin, ray.direction * 10, Color.yellow);
 
 }

Raycast from 2D canvas object to world space

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