Question How do you get the screen coordinates of objects on screen

I have this setup, screen size is 800x600, the big square is a plane, the small blue square is a canvas with a RawImage inside it.




What I need is the coordinates of the 2 squares on the screen so I that I can adapt my UI to them.

I can do that easily by taking a screenshot and looking for the coords in an app such as paint.net but of course I need to compute them in Unity.


So for the big rect I get: 67,147 ->327,406
and for the small blue rect I get: 349,249->449,349

But I can't get these coords by using the camera WorldToScreenPoint method. The coordinates that I get don't make any sense.

Code (csharp):

1.  
2. using UnityEngine;
3. using UnityEngine.UI;
4.  
5. public class ScreenCoords : MonoBehaviour
6. {
7.  
8.     [SerializeField] private RawImage rawImage;
9.  
10.  
11.     // Update is called once per frame
12.     void Update()
13.     {
14.         if (Input.GetKeyDown(KeyCode.S))
15.         {
16.             ScreenCapture.CaptureScreenshot(Application.dataPath + "/cameracapture.png");
17.         }
18.         if (Input.GetKeyDown(KeyCode.C))
19.         {
20.             screenCoords("Plane", gameObject.transform);
21.             screenCoords("RawImage", rawImage.transform);
22.         }
23.     }
24.  
25.  
26.     private void screenCoords(string title, Transform transform)
27.     {
28.         Debug.Log($"screen coords for {title}");
29.         Debug.Log($"position->{transform.position}");
30.         Debug.Log($"screen width->{Screen.width} height->{Screen.height}");
31.         var pos = Camera.main.WorldToScreenPoint(transform.position);
32.         Debug.Log($"pos->{pos}");
33.         Debug.Log("=======================================================");
34.     }
35.  
36.  
37. }
38.  
39.  

What am I doing wrong?

 

You'll have to calculate the coordinates for the Canvas element (blue square) different than the object in the world (grey plane).

For the plane, Camera.main.WorldToScreenPoint(worldPosition) should work
You could also use WorldToViewportPoint(Vector3) if you want it in normalized screen sapce

For the Canvas element, your options are a bit trickier and doing some searching for "How to get [normalized] screen position of UI element in unity" might be able to direct you better than I can.

Good luck!

 

Thanks, I think that the transform points to the center of the square with the y coordinate inverted. So, 197,323 becomes 197,277. I still need to figure out how to get the top left and the bottom right corners.

 

The coordinates were wrong, this code seems okish:

Code (csharp):

1.  
2. using UnityEngine;
3. using UnityEngine.UI;
4.  
5. public class ScreenCoords : MonoBehaviour
6. {
7.  
8.     [SerializeField] private RawImage rawImage;
9.  
10.  
11.     // Update is called once per frame
12.     void Update()
13.     {
14.         if (Input.GetKeyDown(KeyCode.S))
15.         {
16.             ScreenCapture.CaptureScreenshot(Application.dataPath + "/cameracapture.png");
17.         }
18.         if (Input.GetKeyDown(KeyCode.C))
19.         {
20.             squareCoords("Plane", gameObject.transform, gameObject.GetComponent<Renderer>());
21.             rawImageCoords("RawImage", rawImage.GetComponent<RectTransform>());
22.         }
23.     }
24.  
25.  
26.     private void squareCoords(string title, Transform transform, Renderer renderer)
27.     {
28.         Debug.Log($"bounds->{renderer.bounds.extents.x}");
29.         Vector3 topLeft = renderer.bounds.center - renderer.bounds.extents;
30.         Vector3 bottomRight = renderer.bounds.center + renderer.bounds.extents;
31.         Debug.Log($"topLeft->{Camera.main.WorldToScreenPoint(topLeft)}");
32.         Debug.Log($"bottomRight->{Camera.main.WorldToScreenPoint(bottomRight)}");
33.         Debug.Log("=======================================================");
34.     }
35.  
36.     private void rawImageCoords(string title, RectTransform rt)
37.     {
38.         Debug.Log($"screen coords for {title}");
39.         Debug.Log($"position->{rt.position}");
40.         Debug.Log($"screen width->{Screen.width} height->{Screen.height}");
41.         var pos = Camera.main.WorldToScreenPoint(rt.position);
42.         Debug.Log($"pos->{pos}");
43.         Debug.Log("=======================================================");
44.         Debug.Log($"transform size->{rt.sizeDelta}");
45.         var p2 = new Vector2(rt.position.x, rt.position.y);
46.         var topLeft =  p2 - rt.sizeDelta / 2 ;
47.         var bottomRight = p2 + rt.sizeDelta / 2;
48.         Debug.Log($"topLeft->{topLeft}");
49.         Debug.Log($"bottomRight->{bottomRight}");
50.     }
51.  
52.  
53. }
54.  
55.  

 

1. var menuCorners = new Vector3[4];
2. menu.GetComponent<RectTransform>().GetWorldCorners(menuCorners);
   
   that might help you get the corners ... you're in territory I am not super familiar with, so unfortunately I can only give little nudges

 

Actually it seems that you have nothing to do at all in case of a canvas image. Of course, my case was super simple with default values.