I understand what you’re trying to do now. I think you realize that in the future, you really need to use a tripod with the camera locked down for this kind of effect because you have added the additional complexity of tracking the camera movement while rotoscoping. Anything you paint on the video now has to also move with the camera as you’re painting it! You would probably need something like After Effects and Motion Track the camera movement, then stabilize the video long enough to do the rotoscoping, then finally apply the motion tracking keyframes to the rotoscoping spline so that it moves with the camera. You also have to mask the moving T-Ball stand which should be in front of the rotoscoping at all times. This is not beginner stuff.
I would get your tripod out, dress your son up in his uniform and take him back out to the field, and shoot it again as a static locked down shot with no camera movement. Don’t use the T-Ball stand. Then all you have to do is follow the head of the bat in the dirt.
~jr
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