A small Unity helper class to convert viewport, screen or world positions to canvas space.

CanvasPositioningExtensions.cs

using UnityEngine;

/// <summary>
/// Small helper class to convert viewport, screen or world positions to canvas space.
/// Only works with screen space canvases.
/// </summary>
/// <example>
/// <code>
/// objectOnCanvasRectTransform.anchoredPosition = specificCanvas.WorldToCanvasPoint(worldspaceTransform.position);
/// </code>
/// </example>
public static class CanvasPositioningExtensions
{
    public static Vector3 WorldToCanvasPosition(this Canvas canvas, Vector3 worldPosition, Camera camera = null)
    {
        if (camera == null)
        {
            camera = Camera.main;
        }
        var viewportPosition = camera.WorldToViewportPoint(worldPosition);
        return canvas.ViewportToCanvasPosition(viewportPosition);
    }

    public static Vector3 ScreenToCanvasPosition(this Canvas canvas, Vector3 screenPosition)
    {
        var viewportPosition = new Vector3(screenPosition.x / Screen.width,
                                           screenPosition.y / Screen.height,
                                           0);
        return canvas.ViewportToCanvasPosition(viewportPosition);
    }

    public static Vector3 ViewportToCanvasPosition(this Canvas canvas, Vector3 viewportPosition)
    {
        var centerBasedViewPortPosition = viewportPosition - new Vector3(0.5f, 0.5f, 0);
        var canvasRect = canvas.GetComponent<RectTransform>();
        var scale = canvasRect.sizeDelta;
        return Vector3.Scale(centerBasedViewPortPosition, scale);
    }
}

Hey excellent work! it saved me a lot!

This is great! I have a big need to know what a UI Image on the canvas would be in World Space. Could someone please help me with this? A CanvasToWorldPosition. Thank you. -- Jeff

I needed world coordinates of different UI elements that was on a Canvas set to Screen Space - Camera. That was I could move the game objects to the location in the HUD and make them disappear once they reached the location. My game is 2D and it works exactly as I needed now. I hope this helps.

UICamera is my camera used for the UI (Screen Space - Camera) setting. I don't use Overlay or World canvas.
thisCanvas is the canvas in the scene.

var position = UICamera.WorldToScreenPoint(MyUIObject.transform.position); position.z = (thisCanvas.transform.position - UICamera.transform.position).magnitude; theLocationOfUIObjectInWorldSpace = Camera.main.ScreenToWorldPoint(position);

Hello!

This is a little modification in case that the camera is not drawn in the 100% of the screen, using the viewport rect

    public static Vector3 WorldToCanvasPosition(this Canvas canvas, Vector3 worldPosition, Camera camera = null, bool useNormalizeViewPort = false)
    {
        if (camera == null)
        {
            camera = Camera.main;
        }
        
        var viewportPosition = camera.WorldToViewportPoint(worldPosition);
        
        if (useNormalizeViewPort)
        {
            Rect normalizedViewPort = camera.rect;
            viewportPosition.x = viewportPosition.x * normalizedViewPort.width + normalizedViewPort.x;
            viewportPosition.y = viewportPosition.y * normalizedViewPort.height + normalizedViewPort.y;
        }
        
        return canvas.ViewportToCanvasPosition(viewportPosition);
    }

Thanks!

Awsome it works for me, just be care about your canvas anchor point. (from ViewportToCanvasPosition its currently using 0.5 0.5), but in my case its 0 1).