See my response in this thread, this has become easier with Vuforia 1.5:

http://ar.qualcomm.at/node/2002017

- Kim

rennekon wrote:

From my experimentation with Unity, I've found if you don't make an object the child of the ImageTarget, then when you lose tracking the object will continue to be rendered on the device in it's most recent position.

--Kenner

Yes, this works. But I've found that you need to move the device really quickly away from the tracker, otherwise you will lose a portion of the AR content (since it attempts to reposition itself based on the tracker location on each update).

So if you have the AR content showing the way you'd like to keep it when you lose tracking, you must move the device quickly.

Any thoughts on how to get around this?

From my experimentation with Unity, I've found if you don't make an object the child of the ImageTarget, then when you lose tracking the object will continue to be rendered on the device in it's most recent position.

--Kenner

Unfortunately no. The best you could do is stop the camera updates and use the last known pose data to continue placing content, but the camera image would no longer be drawn in the background. If you wanted to play around with this all the code is in TrackerScript.cs, in the LateUpdate method.

In a future update we should be adding a call to native to get the camera image as a bitmap. Then you could draw this image into the background yourself while the camera is paused.

- Kim