In AR tracking, jitter is a rapid, unwanted fluctuation in the estimated position or orientation of content, making an overlay appear to tremble against its physical reference.
When a still artwork seems to shake
Imagine a digital outline placed over a printed portrait. The print stays still, but the outline moves a little from frame to frame. That trembling is a typical way tracking jitter becomes visible. The tracker continually estimates a pose; small changes in that estimate can become noticeable when the artwork demands precise alignment. The comparison illustrates the symptom, with the movement exaggerated so it is easy to see.
Jitter, drift and stutter describe different symptoms
Jitter fluctuates around a position. Drift is a gradual loss of alignment. Stutter is uneven delivery of frames, so motion advances in visible steps. More than one can happen at once. A low frame rate can make an experience unpleasant even when its tracking is accurate; a high frame rate does not guarantee a steady overlay. Neither symptom proves that the animation file itself is faulty.
What can affect stability
The cause depends on the tracking system. Poorly observed features, reflections or changing viewing conditions can make a pose less reliable. In image tracking, check the visibility and visual detail of the target. In world tracking, the system must also maintain its understanding of the surroundings. An anchor helps organise placement, but it is not a promise of perfect stability. Smoothing can reduce visible shaking while adding latency; an overly smoothed object may seem to lag behind a moving phone.
A useful exhibition check
For an artwork prepared in Painta, compare a simple static overlay with the finished animation on the actual print, under the exhibition lighting. Check both a stationary phone and a slow approach. If only a moving element behaves oddly, inspect its animation; if every overlay shifts together, investigate the tracking conditions. Record the device and viewing distance so another person can repeat the check.
Related concepts and further reading
Google ARCore: motion tracking and environmental understanding
Google ARCore: working with anchors
For a gradual loss of alignment rather than rapid shaking, see Tracking Drift. The distinction helps separate tracking symptoms from an authored animation.