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Moving-Obj Path* (Coordinates)
This phase allows you to generate an overall scaling for a moving object that matches its moving camera solve accurately (subject to data availability), without additional information, if the object is stationary or moving in a straight line for a period of time while the camera moves.
Background: when you have a shot with both moving objects and moving cameras, you need to have accurate size control for both the moving object and camera, otherwise you get the "Honey I Shrunk the Kids" effect—it is impossible to tell the difference between a small object moving a little and a big object moving a lot. Getting both scales to match is often difficult. However, if the object stops for a little, or even moves in a straight line, and the camera keeps moving, we can determine the relative scale. It's a good trick!
Using this phase requires that both camera and object be solved. You must select the trackers on the moving object to use. Select trackers that are central to the object, that are as insensitive as possible to any remaining rotation jitter in the object solve. Click the Store Trackers button to solve them in the phase's private tracker selection. By doing this, you also tell SynthEyes what moving object to work on—the parent of the trackers. They must all have the same parent, which must be a moving object.
You must also configure the starting and ending frame numbers, to match the portion of the shot during which the object is stationary or moving at constant velocity.
Finally you should tell SynthEyes whether the object is stationary or at constant velocity—by that we mean moving at a constant speed in a straight line.
When the phase runs, it will determine the optimum object scaling to match the world scaling, then use it to adjust the object to match the world. During the frames you specify, you'll see the object sitting stationary at some location, with a small amount of jitter; or for constant- velocity solves, moving in a straight line. Very cool! However, the results are only as good as your tracks and the extent to which the object is really doing what you said! If a constant velocity object isn't really at constant velocity, that will translate directly to an error in the scale.
Fine Print: You should set up your shot so that its rough initial scaling is within a factor of ten of the correct scaling. The phase considers only solutions that are at most 10x larger or 1/10th smaller than the current size, to avoid spurious crazy solutions.
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