Unity - How can I get the target screen coordinates

May 1, 2013 - 8:45am #1

This article explains how to obtain the projected screen coordinates (pixels) of a generic 3D point located on an Image Target plane.

For ease of reference, we refer to the Image Targets Unity sample.

Steps:

  • create a new project in Unity
  • import the image targets sample package and open the image targets scene
  • create a C# script, call it TargetScreenCoords for instance
  • drag the script above onto one of your image target objects in the scene view
  • put the following code into the script:
using UnityEngine;
using System.Collections;

public class TargetScreenCoords : MonoBehaviour {
	
	private ImageTargetBehaviour mImageTargetBehaviour = null;
	
	// Use this for initialization
	void Start () {
		// We retrieve the ImageTargetBehaviour component
		// Note: This only works if this script is attached to an ImageTarget
		mImageTargetBehaviour = GetComponent<ImageTargetBehaviour>();
		
		if (mImageTargetBehaviour == null)
		{
			Debug.Log ("ImageTargetBehaviour not found ");
		}
	}
	
	// Update is called once per frame
	void Update () {
		if (mImageTargetBehaviour == null)
		{
			Debug.Log ("ImageTargetBehaviour not found");
			return;
		}
		
		Vector2 targetSize = mImageTargetBehaviour.GetSize();
		float targetAspect = targetSize.x / targetSize.y;
		
		// We define a point in the target local reference 
		// we take the bottom-left corner of the target, 
		// just as an example
		// Note: the target reference plane in Unity is X-Z, 
		// while Y is the normal direction to the target plane
		Vector3 pointOnTarget = new Vector3(-0.5f, 0, -0.5f/targetAspect); 
		
		// We convert the local point to world coordinates
		Vector3 targetPointInWorldRef = transform.TransformPoint(pointOnTarget);
		
		// We project the world coordinates to screen coords (pixels)
		Vector3 screenPoint = Camera.main.WorldToScreenPoint(targetPointInWorldRef);
		
		Debug.Log ("target point in screen coords: " + screenPoint.x + ", " + screenPoint.y);
		
	}
}

Build and run the app and observe the logs showing the screen coordinates of a target point (as per script code above).

 

Topic locked