To help understand the answer, here's a quick rundown on how Vuforia handles marker detection. If you take a look at the DefaultTrackableEventHandler script that's attached to the ImageTarget prefab, you'll see that there are events that fire when the when the tracking system finds or loses an Image.
These are OnTrackingFound (line 67) & OnTrackingLost (line 88) in DefaultTrackableEventHandler.cs
If you want to show a Sprite when tracking, all you need to do is put the Image Target prefab (or any other) and make the Sprite a child of the prefab. The enabling and disabling should happen automatically.
However, in case you want to do something more, here's some edited code.
DefaultTrackableEventHandler.cs
//Assign this in the inspector. This is the GameObject that
//has a SpriteRenderer and Collider2D component attached to it
public GameObject spriteGameObject ;
Add the below lines to OnTrackingFound
//Enable both the Sprite Renderer, and the Collider for the sprite
//upon Tracking Found. Note that you can change the type of
//collider to be more specific (such as BoxCollider2D)
spriteGameObject.GetComponent<SpriteRenderer>().enabled = true;
spriteGameObject.GetComponent<Collider2D>().enabled = true;
//EDIT 1
//Have the sprite inherit the position and rotation of the Image
spriteGameObject.transform.position = transform.position;
spriteGameObject.transform.rotation = transform.rotation;
And the below to OnTrackingLost
//Disable both the Sprite Renderer, and the Collider for the sprite
//upon Tracking Lost.
spriteGameObject.GetComponent<SpriteRenderer>().enabled = false;
spriteGameObject.GetComponent<Collider2D>().enabled = false;
Next, your question about detecting clicks on this Sprite. Unity's Monobehaviour fires events for a lot of mouse events, such as OnMouseUp, OnMouseDown etc.
Link to Monobehaviour on Unity's API docs
What you will need is an event called OnMouseUpAsButton
Create a new script called HandleClicks.cs and add the below code to it. Attach this script as a component to the spriteGameObject that you assigned for the above.
public class HandleClicks : MonoBehaviour {
//Event fired when a collider receives a mouse down
//and mouse up event, like the interaction with a button
void OnMouseUpAsButton () {
//Do whatever you want to
Application.LoadLevel("myOtherLevel");
}
}
