Thanks Kim, works like a charm! :)

What worked for me was duplicating the original TrackableEventHandler script that is attached with the ImageMarker prefab and pasted just these lines from Kim`s code:

if (mModel != null)
{
    mModel.transform.position = tb.transform.position;
    mModel.transform.rotation = tb.transform.rotation;
}

Then I switched the original TrackableEventHandler to my custom one, it has the same base functionalities and also sets my model position to the current trackable one.

One option would be to disable the trackables that you aren't interested in:

trackable.enabled = false;

Another option is to have the model present in your scene but not bound to any trackables. You can handle the trackable events by hand yourself, something like this:

using UnityEngine;

// A custom handler that implements the ITrackerEventHandler interface.
public class MatchTrackablePose : MonoBehaviour,
                                  ITrackerEventHandler
{

    public GameObject mModel = null;

    private TrackableBehaviour[] mTrackableBehaviours;

    void Start()
    {
        TrackerBehaviour trackerBehaviour = GetComponent<TrackerBehaviour>();
        if (trackerBehaviour)
        {
            trackerBehaviour.RegisterTrackerEventHandler(this);
        }

        mTrackableBehaviours = (TrackableBehaviour[]) FindObjectsOfType(typeof(TrackableBehaviour));
    }


    // Implementation of the ITrackerEventHandler function called after all
    // trackables have changed.
    public void OnTrackablesUpdated()
    {
        foreach (TrackableBehaviour tb in mTrackableBehaviours)
        {
            if (tb.CurrentStatus == TrackableBehaviour.Status.DETECTED ||
                tb.CurrentStatus == TrackableBehaviour.Status.TRACKED)
            {
                Debug.Log("found trackable " + tb.TrackableName);

                if (mModel != null)
                {
                    mModel.transform.position = tb.transform.position;
                    mModel.transform.rotation = tb.transform.rotation;
                }
            }
        }
    }
}

Note you'll have to add logic to hide the model when the trackable is lost.

- Kim

I think this might be my issue as well. I'm trying to use a complex model with 3 different markers, and i am just brute force copying the model 3 times attached to each marker... But, this might be causing my Unity app to just take too long to load for iOS to just auto-crash it (but it runs when connected by USB)