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Stop Motion Tracking Screen Replacement

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Barret BaxterStop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 1:47:41 pm

Hi, so we are being ambitious and attempting our first stop motion. We have a phone that moves around on a table. There is a chroma image with track points on the phone for screen replacement in post. When I bring it into Mocha and After Effects, the track points move out of the search area and looses the track. Has anyone ever tried to track a point in stop motion? Any help would be great; I hope to avoid the frame by frame nightmare.

Thanks,
Barret


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Roei TzorefRe: Stop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 3:08:16 pm

I have tracked stop motion before. there should not be any special problems if the motion is consistent even at low frame rates. can we examine a piece of footage to experiment suggested workflow?

Roei Tzoref
After Effects Artist & Instructor
♫ Ae Blues Tutorials


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Barret BaxterRe: Stop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 3:16:59 pm

Sure, here is a link to our test footage:

https://vimeo.com/185974341
MM

There are some good track points, but AE and Mocha looses them after a frame.

Thoughts?


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Roei TzorefRe: Stop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 5:27:26 pm

it is a private video. if it's under 50mb you can drag and drop here.

Roei Tzoref
After Effects Artist & Instructor
♫ Ae Blues Tutorials


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Barret BaxterRe: Stop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 5:29:17 pm

The pass is MM


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Roei TzorefRe: Stop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 6:41:33 pm
Last Edited By Roei Tzoref on Oct 7, 2016 at 6:44:39 pm

o.k I examined your footage. you have invested so much in the gear, good camera, trackers, couldn't you have shot more frames? :)
if this is a test - the lesson is... shoot more frames! and you don't need the green or the crosses, you have enough information with the phone without anything in there. it will make the compositing look better when you can use screen blend mode and get natural reflection.

there just isn't enough frames to make a consistent movement for the tracker to track. you can track it but it's difficult. you have here 45 frames of movement and a couple of frames still. it's nothing! :) you are better off using the power pin effect manually then struggling with this in mocha. which I have. Mocha lite is not supporting 12fps so you actually have to put your footage in a 15fps comp, send to Mocha, do the tracking, bring it back, place everything in a 12fps comp so it will run at the desired frame rate.

about the track in mocha - don't use perspective, just shear. use angle of 5 degrees to help mocha track the fast rotation movements. this will get you through until frame 66. change to manual track and set the planar surface manually. on frame 67 and change back to large motion set the angle to 10. on frame 71 set it to manual again and move the planar surface to the right place. from here on out I think this is manual labour for you.




Roei Tzoref
After Effects Artist & Instructor
♫ Ae Blues Tutorials


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Barret BaxterRe: Stop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 7:14:44 pm

Thanks for the help, I think Im in manual mode and we plan to limit the amount of camera movement in our final piece. Appreciate the help.

Thanks,
Barret


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Roei TzorefRe: Stop Motion Tracking Screen Replacement
by on Oct 7, 2016 at 7:20:55 pm

Sure. scratch what I said about the green and blue screen. you have rotoscoping there so you will be able to key it out if you use this screen and there isn't much reflection to get anyway.

Roei Tzoref
After Effects Artist & Instructor
♫ Ae Blues Tutorials


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