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Locks in Object Tracking
You can also use locks on rigid-body moving objects, in addition to cameras. However, there are several restrictions on this, because moving objects are solved relative their hosting camera path, but the locks are world coordinate system values.
If a moving object has path or orientation locks, then the host camera must have been previously solved, pre-loaded, or pre-keyed, and the camera solving mode set to Refine or Disabled. While some object tracking is often done without a camera track, if you want to apply object constraints in world coordinates, you'll need to track, or at least carefully position, the camera in order to establish the world coordinate system for the
object track. You can use a tripod track for the camera, and a regular track for the object.
Normally, when SynthEyes handles shots with a moving camera and moving object, it solves camera and object simultaneously, optimizing them both for the best overall solution. However, when object locks are present, the camera solution must be known, in order to be able to apply the object locks.
Object locks have very hard-to-think-about impacts on the local coordinate system of the trackers within the object. Most object locks will wind up over-constraining the object coordinate system.
We recommend that object locking be used only to work on the object path, not to try to set up the object coordinate system.
Hint : a simple and reliable Overall Distance constraint will usually be very effective in improving object paths when the object is jittering closer and further from the camera due to a lack of perspective.
While an overall distance constraint on a camera controls the distance from the camera to the origin, an overall distance constraint on a moving object constrains the distance from the moving object's local coordinate system origin to the camera. This makes it especially important to set up a well-chosen coordinate system for the moving object: the origin should be near the center of rotation of the object, so that object rotation does not excessively impact the overall distance.
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