Keeping the object/3D Model on the screen even when the target is lost (UNITY + Vuforia)

Question

I want to Keep the object/3D Model on the center of mobile screen even when the target is lost (on tracking lost()) and when target found last tracked image model should disappear. I'm using unity.

I tried to follow cloudreco sample but not able to that properly.

for centering of screen i'm using :

GameObject lost = GameObject.Find ("IT"+mTrackableBehaviour.TrackableName);

lost.transform.position=Camera.main.ScreenToWorldPoint(new Vector3(Screen.width/2, Screen.height/2, Camera.main.nearClipPlane) );

I have around 10 image targets with max simultaneous images tracking set to 1.
looking for solution.
Thanks !

EDIT :

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using System.Collections.Generic;
namespace Vuforia
{
    /// <summary>
    /// A custom handler that implements the ITrackableEventHandler interface.
    /// </summary>
    public class dtehedit : MonoBehaviour,
    ITrackableEventHandler
    {

        #region PRIVATE_MEMBER_VARIABLES

        private TrackableBehaviour mTrackableBehaviour;
        private bool firsttime=false;
        //private bool secondtime=false;
        GameObject lost, lostclone;
        #endregion // PRIVATE_MEMBER_VARIABLES



        #region UNTIY_MONOBEHAVIOUR_METHODS

        void Start()
        {
            Debug.Log ("start method before registring");
            mTrackableBehaviour = GetComponent<TrackableBehaviour>();
            if (mTrackableBehaviour)
            {
                mTrackableBehaviour.RegisterTrackableEventHandler(this);
            }
            Debug.Log ("start method after registring");
        }

        #endregion // UNTIY_MONOBEHAVIOUR_METHODS



        #region PUBLIC_METHODS

        /// <summary>
        /// Implementation of the ITrackableEventHandler function called when the
        /// tracking state changes.
        /// </summary>
        public void OnTrackableStateChanged(
            TrackableBehaviour.Status previousStatus,
            TrackableBehaviour.Status newStatus)
        {
            if (newStatus == TrackableBehaviour.Status.DETECTED ||
                newStatus == TrackableBehaviour.Status.TRACKED ||
                newStatus == TrackableBehaviour.Status.EXTENDED_TRACKED)
            {
                OnTrackingFound();
            }
            else
            {
                OnTrackingLost();
            }
        }

        #endregion // PUBLIC_METHODS



        #region PRIVATE_METHODS


        private void OnTrackingFound()
        {
            firsttime = true;
            if (lostclone != null) {
                Debug.Log ("LOST CLONE otf ::" + lostclone.name);
                DestroyObject (lostclone); // (1) if new object is scanned gameobject lostclone is not destroyed
            }

            Renderer[] rendererComponents = GetComponentsInChildren<Renderer>(true);
            Collider[] colliderComponents = GetComponentsInChildren<Collider>(true);

            // Enable rendering:
            foreach (Renderer component in rendererComponents)
            {
                component.enabled = true;
            }

            // Enable colliders:
            foreach (Collider component in colliderComponents)
            {
                component.enabled = true;
            }

            Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " found");
        }


        private void OnTrackingLost()
        {
//          Debug.Log (firsttime);
//          if (!firsttime) {
//              Renderer[] rendererComponents = GetComponentsInChildren<Renderer> (true);
//              Collider[] colliderComponents = GetComponentsInChildren<Collider> (true);
//
//              // Disable rendering:
//              foreach (Renderer component in rendererComponents) {
//                  component.enabled = false;
//              }
//
//              // Disable colliders:
//              foreach (Collider component in colliderComponents) {
//                  component.enabled = false;
//              }
//
//          } else {
//              string itname = mTrackableBehaviour.TrackableName;
//              Debug.Log ("lost trackable name " + itname);
//              GameObject lost = GameObject.Find ("IT" + itname);
// (2) WOrking but dont know how to reposition gameobject after next tracker is found 
//              lost.transform.GetChild(0).transform.position=Camera.main.ScreenToWorldPoint(new Vector3(Screen.width/2, Screen.height/2, Camera.main.nearClipPlane+20) ); 
// (3) workinh but dont know how to reset camera position when next tracker is found
////                Camera.main.transform.position = lost.transform.GetChild(0).transform.position + lost.transform.GetChild(0).transform.forward * 25;
////                Camera.main.transform.LookAt (lost.transform.GetChild(0).transform);
//          }


                            Renderer[] rendererComponents = GetComponentsInChildren<Renderer> (true);
                            Collider[] colliderComponents = GetComponentsInChildren<Collider> (true);

                            // Disable rendering:
                            foreach (Renderer component in rendererComponents) {
                                component.enabled = false;
                            }

                            // Disable colliders:
                            foreach (Collider component in colliderComponents) {
                                component.enabled = false;
                            }
            if (firsttime) {
                string itname = mTrackableBehaviour.TrackableName;
                Debug.Log ("lost trackable name " + itname);
                lost = GameObject.Find ("IT" + itname).transform.GetChild (0).gameObject;
                lostclone = Instantiate (lost) as GameObject; //decoupling
                Debug.Log ("LOST CLONE ::"+lostclone.name);
            }
            Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " lost");
        }

        #endregion // PRIVATE_METHODS
    }
}

for the above code, I tried three methods/approaches to have my 3D Model on screen after tracking lost but none seems to work perfectly or as desired

I have decoupled/cloned my 3d object by instantiate method but when I found tracker again last one is not destroyed (1) and how to make it to come in front of camera

I move my 3dobject to camera on trackinglost but when Again trackingfound how to take my 3dmodel again to original position (2)

I move my camera to my 3dobject after trackinglost but when again trackingfound how to take camera to original position(3)
please have a look at code and please help me .. dont know what i'm missing ...?

1. What exactly is happening with the code that you provided? What doesn't work? 2. I believe you don't need ScreenToWorldPoint, you can position your GameObject where the Camera is and just use the tranform.forward vector to move your GameObject where the camera is looking. — Hristo
On tracking found my 3d model is displayed... I want it to retain on screen until new marker is found. Means when marker is removed 3d model do not disappear from screen . Hope u got it — Nitesh
To do this you need to decouple your GameObject from your ImageTarget I presume. Since they have a child - parent relationship, when the image/marker is lost, your GameObject is being deactivated. — Hristo
Could you please tell me how to do this ..? Should I make camera parent and 3d model child of camera ? I'm new In unity ? Please tell me how to do this ... Thanks ! — Nitesh
I explained how it could be done. There must be some research effort on your side, try to implement it and if it doesn't work come back and edit your post with the code you tried. — Hristo

Hristo Hristo · Accepted Answer · 2017-05-24T17:07:23

I have looked trough your code, fixed it a bit and I believe this should solve your problem.

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using System.Collections.Generic;
namespace Vuforia
{
    /// <summary>
    /// A custom handler that implements the ITrackableEventHandler interface.
    /// </summary>
    public class dtehedit : MonoBehaviour,
    ITrackableEventHandler
    {

        #region PRIVATE_MEMBER_VARIABLES

        private TrackableBehaviour mTrackableBehaviour;
        private bool firsttime = false;
        string itname = "";
        //private bool secondtime=false;
        GameObject lost, lostclone;
        #endregion // PRIVATE_MEMBER_VARIABLES



        #region UNTIY_MONOBEHAVIOUR_METHODS

        void Start()
        {
            Debug.Log("start method before registring");
            mTrackableBehaviour = GetComponent<TrackableBehaviour>();
            if (mTrackableBehaviour)
            {
                mTrackableBehaviour.RegisterTrackableEventHandler(this);
            }
            Debug.Log("start method after registring");
        }

        #endregion // UNTIY_MONOBEHAVIOUR_METHODS



        #region PUBLIC_METHODS

        /// <summary>
        /// Implementation of the ITrackableEventHandler function called when the
        /// tracking state changes.
        /// </summary>
        public void OnTrackableStateChanged(
            TrackableBehaviour.Status previousStatus,
            TrackableBehaviour.Status newStatus)
        {
            if (newStatus == TrackableBehaviour.Status.DETECTED ||
                newStatus == TrackableBehaviour.Status.TRACKED ||
                newStatus == TrackableBehaviour.Status.EXTENDED_TRACKED)
            {
                OnTrackingFound();
            }
            else
            {
                OnTrackingLost();
            }
        }

        #endregion // PUBLIC_METHODS



        #region PRIVATE_METHODS


        private void OnTrackingFound()
        {
            // This is wrong because you never set it to false. Every time a tracker(image) is found it will be the first time - wrong.
            //      firsttime = true;      


            if (lostclone != null)
            {
                Debug.Log("LOST CLONE otf ::" + lostclone.name);
                // DestroyObject(lostclone); // (1) if new object is scanned gameobject lostclone is not destroyed
            }

            //Here you can reset the position of the GameObject back to the parent(tracker)'s position. 
            this.transform.GetChild(0).transform.position = new Vector3(0, 0, 0);

            Renderer[] rendererComponents = GetComponentsInChildren<Renderer>(true);
            Collider[] colliderComponents = GetComponentsInChildren<Collider>(true);

            // Enable rendering:
            foreach (Renderer component in rendererComponents)
            {
                component.enabled = true;
            }

            // Enable colliders:
            foreach (Collider component in colliderComponents)
            {
                component.enabled = true;
            }

            Debug.Log("Trackable " + mTrackableBehaviour.TrackableName + " found");
        }


        private void OnTrackingLost()
        {
            Renderer[] rendererComponents = GetComponentsInChildren<Renderer>(true);
            Collider[] colliderComponents = GetComponentsInChildren<Collider>(true);

            // What you can do is not disable this
            //foreach (Renderer component in rendererComponents)
            //{
            //    component.enabled = false;
            //}

            // Disable colliders: Disable this if you need it diabled only
            foreach (Collider component in colliderComponents)
            {
                component.enabled = false;
            }

            string itname = mTrackableBehaviour.TrackableName;
            Debug.Log("lost trackable name " + itname);
            GameObject lost = GameObject.Find("IT" + itname);
            //(2) WOrking but dont know how to reposition gameobject after next tracker is found

            // This is not decoupling but it should work ( you dont need to find the gameobject you can use [this] instead)
            this.transform.GetChild(0).transform.position = Camera.main.ScreenToWorldPoint(new Vector3(Screen.width / 2, Screen.height / 2, Camera.main.nearClipPlane + 20));
            // Disable rendering:

            itname = mTrackableBehaviour.TrackableName;
            Debug.Log("lost trackable name " + itname);
            lost = GameObject.Find("IT" + itname).transform.GetChild(0).gameObject;
            // this is not I ment by decoupling sory, I ment de parenting -> (gameObject.parent = null)
            //lostclone = Instantiate(lost) as GameObject; //decoupling
        }

        #endregion // PRIVATE_METHODS
    }
}

Keeping the object/3D Model on the screen even when the target is lost (UNITY + Vuforia)

1 Answers