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removing objects (motion tracking) piecewise?

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Peter Wuremoving objects (motion tracking) piecewise?
by on Dec 29, 2011 at 11:22:49 pm

I have a minute long clip with a shoe falling off a dancer on the stage.

I'm able to track the shoe and cover it with a clone of the stage for about 10 seconds when the camera pans around and the shoe is in clear view.

The tracking is applied to a null object. There is a photoshop bitmap used to cover the shoe and is linked to the null object.

Starting from 10 seconds, the camera zooms out and also one end of the shoe gets obscured making it hard to track the scale. Fortunately the camera doesn't change zoom again for quite a while, so I can make a smaller photoshop bitmap to cover this zoomed out shoe.

I have not done this before and have many seemingly trivial questions:

Starting at 10s, I want to use another photoshop object and a new motion tracking. How do I turn off the first photoshop object at 10s, and turn on the second photoshop object at 10s?

Also, some of the frames need to be rotoscoped by hand because when a dancer moves behind the erased shoe, the floor needs to reflect the color of the dance dress. But obviously the photoshop object doesn't do that, so I have to manually paint/clone those frames. Since the top layer is a photoshop layer, do I create a new video layer on top to hold these frame by frame paint?

Most tutorials I found cover one one motion tracking process. If you find one that talks about how to do two motion trackings, one after the other, to remove the same object at different time, please let me know.


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Michael SzalapskiRe: removing objects (motion tracking) piecewise?
by on Dec 30, 2011 at 3:58:18 pm

It sounds like you may have jumped a bit too far ahead of yourself in After Effects. When you have time, it would behoove you to get some proper training starting from the basics [link]

That being said, I'm sure you have a deadline looming, so I shall try to answer your questions as best I can.

[Peter Wu] "I want to use another photoshop object and a new motion tracking. How do I turn off the first photoshop object at 10s, and turn on the second photoshop object at 10s?"
Learn about trimming layers [link]

[Peter Wu] "Since the top layer is a photoshop layer, do I create a new video layer on top to hold these frame by frame paint?"
Yes.

[Peter Wu] "the camera zooms out and also one end of the shoe gets obscured making it hard to track the scale."
You should look into using Mocha for this type of track. In fact, Mocha may be your answer to a lot of this. And it comes free with AE! Unfortunately, it's got a pretty steep learning curve too.

[Peter Wu] "Most tutorials I found cover one one motion tracking process. If you find one that talks about how to do two motion trackings, one after the other, to remove the same object at different time, please let me know."
The reason the tutorials don't go over doing more than one is that you can just do as many as you want in a scene. There's no trick to it. You just trim the layer when you're ready for it to stop and trim the next to when you're ready for it to go.

I'm wondering why you're using Photoshop layers for this. You can do cloning [link] and grabbing of still frames [link] in After Effects too.

Since this will probably help you, here's a whole load of resources for motion tracking and Mocha [link].

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Peter WuRe: removing objects (motion tracking) piecewise?
by on Dec 30, 2011 at 8:37:35 pm

Jumping ahead of myself is right.

I put a sample clip of the video here:






In the first few seconds, the shoe was moving but after that, it is stationery relative to the floor.

The reason I wanted to use a photoshop layer was because I saw that in a tutorial, and I did not realize the clone stamp in AE can change the cloned content with time. After watching more tutorials, and after trying the photoshop layer solution, it is obvious using the clone stamp in AE is the better solution.

The tricky part, I found, is that the floor reflects the bright constume, so any static patch would stand out when it should reflect a costume but doesn't.

so here's my updated plan:

(1) duplicate the video and flip it upside down
(2) blur the video and lower the brightness/contrast to simulate a reflection
(3) track the "horizon" y-axis on the source clip and make the horizon in the reflected clip follow
(4) clone and paint over the shoe using the reflected video
(5) track the shoe so the cloned blob can follow the shoe as the camera pans and zooms

That's the theory. I'm still struggling to execute each step. If it looks like it won't work, or if there's a simpler solution, please let me know.

I've looked at a mocha tutorial but hope I can do without it. Thanks for the links, I will look at them.


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