A Rolling Ball (or Furry Mouse)

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‌A Rolling Ball (or Furry Mouse)

Here we want to track something moving around at a constant height on a plane, from a single 2D tracker.

 Start with the ground plane set up properly, either from a moving-camera solve or maybe using single-frame alignment.

 Create a GeoH object that can move only in the horizontal plane (ie X and Y or X and Z unlocked).

 Create a single supervised tracker that tracks the ball/mouse, lock it to the origin of the GeoH object. presto you get a 3-D path moving on the floor,

even with a moving-camera shot.

 BONUS POINTS : Suppose it's a mouse, and it runs up a ramp towards the end of the shot. What to do? Add an additional, non-tracked, GeoH object to be the parent of first one above. At the right time, hand-animate this new parent mesh to tilt upwards to match the ramp. The coordinate system of the main tracking GeoH will be tilted, and the right thing happen.

Note that this task can be performed by some scripts as well, ie Animate Tracker by Mesh Projection, and Make Object from Tracker, and that can be used when the furry critter is running around on more complex objects. You can use the Animate

Tracker by Mesh Projection script to produce a mocap tracker, then use that mocap tracker(s) to drive a hybrid 3D GeoH setup to do even more complex things.

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