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The plane needs to move correctly relative to the camera; that can be achieved either by having the camera moving in 3-D and a stationary planar tracker, or a stationary camera and the planar tracker moving in 3-D. From the standpoint of a camera match, both are equivalent and neither is necessarily the 'right' answer.
For a shot from a helicopter with a planar tracker on the ground, a moving camera configuration makes sense. For a shot from a camera on a tripod tracking a planar tracker on car driving by, where effects are to be added to the car, a moving object configuration makes sense.
Sometimes artists may prefer a moving object approach (stationary camera) just because it is more familiar and similar to a 2-D environment.
When multiple planar trackers are concerned, a moving object approach is indicated, because the camera can't be positioning correctly with respect to two
differently-moving planes at the same time. For example, changing the hood logos of two racecars battling each other down the straight-away, a two moving-object approach makes sense.
Important : when you have multiple 3-D planar trackers in a scene, you need to make sure they have the same field of view! See Adding More 3-D Planar Trackers.
The situation is a bit more complex when particle effects are involved (or other world- or velocity-dependent effects). Consider adding a smoke trail to a moving steam locomotive, as shot from a helicopter (or tripod shot tracking it). The smoke needs to trail behind the locomotive based on its ground-relative velocity, then rise vertically, ie with no ground-relative velocity. You've tracked the locomotive.
With a moving-camera setup, the locomotive isn't moving at all. With a moving- object setup, the locomotive is moving gradually around relative the camera, and the smoke is going all different directions relative the locomotive, perhaps creating some helix above it. Clearly neither approach is correct!
Instead, you need to also track the ground. Animate the camera relative the ground tracker, and in a second pass, the locomotive tracker as a moving-object tracker. This way, the locomotive moves correctly relative to the stationary ground (world coordinate system), and the smoke particle effect can work properly.
For multi-object situations that require accuracy, conventional 3-D or tripod solves for the camera and moving object (train) may be a better approach.
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