Getting world coordinates for UI elements relative to a camera displaying to a render texture

Absolutely, I appreciate the response. The ortho camera view is drawn onto a UI image object. So the grid and brighter circles are 3d objects, and the buttons are drawn on top in the canvas.

So I have 2 ortho cameras, one displaying to the rendertexture, and one for getting coordinates (because apparently outputting to a rendertexture mess those up). The main camera in my scene is perspective but it (shouldn't) have any relevance to what I'm trying to do, since this is entirely for UI.

![alt text][1]

This is the entirety of my code for this thus far.

     public Camera rayCastCam, renderCamera;
     public GameObject inventoryGrid, backgroundPlane, testSphere;
     //Ordered pair of slot buttons and their corresponding world position
     private List<KeyValuePair<InventorySlot, Vector3>> slots = new List<KeyValuePair<InventorySlot, Vector3>>();
 
 
     // Update is called once per frame
     void Update()
     {
         if (Input.GetKeyDown(KeyCode.Alpha1))
         {
             if (slots.Count <= 1)
             {   //get all the world positions
                 GetInventorySlotWOrldPositions();
             }
             foreach (KeyValuePair<InventorySlot, Vector3> slot in slots)
             {   //create placeholder spheres at the world centerpoints gathered in GetInventorySlotWOrldPositions()
                 GameObject item = Instantiate(testSphere, renderCamera.transform);
                 item.transform.position = slot.Value;
             }
         }
     }
 
     //loop through all the buttons and get their world center point
     private void GetInventorySlotWOrldPositions()
     {
         foreach (RectTransform slot in inventoryGrid.GetComponentsInChildren<RectTransform>())
         {
             if (slot.gameObject.GetComponent<InventorySlot>() == null) continue;
 
             //This gets the wrold space at the center of my buttons relative to my ortho camera
             Vector3 point = rayCastCam.ScreenToWorldPoint(slot.position);
             point.z = backgroundPlane.transform.position.z;
 
             //add it to my list of Button/world space pairs
             slots.Add(new KeyValuePair<InventorySlot, Vector3>(slot.gameObject.GetComponent<InventorySlot>(), point));
 
             slot.gameObject.GetComponent<InventorySlot>().SetWorldSpacePosition(point);
         }
     }

I'm happy to provide more details if needed, I'm just not sure what else I can add.

Thanks again. [1]: /storage/temp/165214-annotation-2020-08-10-175826.png