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marc.decoster
Known Participant
January 23, 2022
Question

Tracking a traveling out of a device screen

  • January 23, 2022
  • 2 replies
  • 299 views

Hello guys. 

I'll be working on vfx for a commercial next week, using After Effects and Mocha.

The storyboard is quite classical: a picture is fitting the frame, there is traveling out, we discover that that picture is played in a IPad, we continue to travel out, we discover that someone is holding the IPad, the camera pans, we loose the IPad and we end on a wide shot of the room where the character is watching his movie.

I'll use an app like Tracking Marker or Chromascreen to play a "dark" green key with tracking point on the display.

My concern here is: do you think that the DOP should begin the shot INSIDE the device (meaning loosing the borders of the IPad) or should he begin wide enough to keep the entire device visible (in that case, because it is 4K, I'll zoom a bit in post)

I know that the beginning of the traveling is always a bit shaggy or, best case scenario, similar to an "ease out" interpolation. And I know I'll have to "smooth" it to fit it to the zoom out of the movie played inside the device.

So I wondered if a technique is better than an other.

 

Thank you very much for your advices 

 

Marc De Coster

 

 

This topic has been closed for replies.

2 replies

R
Community Expert
Rick GerardCommunity Expert
Community Expert
January 23, 2022

The last thing I. would do would be to add a green screen to the iPad. Design the shot so there is little or no need to create a complex matte because your actor's hand is moving all around the screen. You need detail you can track. A grid pattern or a checkerboard would work just fine. If you need a few frames of roto just do it in Mocha instead of trying to poke a hole in the screen of the iPad. Something like this would work just fine. Just don't make the screen so bright that the colors are projected on the other elements in the screen. 

Any textured surface that Mocha can easily track will do. When the shot gets wide enough you can just expand the track to include the entire iPad. Surfaces with just a few geometric markers on a featureless background do not supply enough detail for Mocha to get a good track. Mocha is looking for patterns in the details, not a couple of small markers.

 

Shoot some test footage. Just shoot it with your Phone, bring the shot into AE and run some test tracks using Mocha. You'll figure out what is needed very quickly.

 

 

    M
    marc.decosterAuthor
    Known Participant
    January 24, 2022

    Thank you for your answer. All of this seems quite logical 🙂 I have several adds to deal with though, and the characters won't do the same actions in each one. In one of them he keeps his hand in front of the screen all the time. For this one, I'll have to deal with the green key, it would be a lot of rotoscope. I guess I'll adapt the technique to every situation, and prepare several background.

     

    Thanx a lot for your advice

     

    Marc

     

    Mylenium
    Mylenium
    Legend
    January 23, 2022

    Depends on how many markers those apps produce, but generally they are too few and a custom image works better. Masking is easier than trying to fix a jittery track. The zoom and pan would depend on how much other usable stuff is there. It may help to place a few extra markers (tape or dots) in places where they can easily be removed, including perhaps on the pad's frame. That's not so much about getting more automated tracking, but rather reference for massaging your keyframes later on. Spatial awareness issues combined with lens distortions can be pretty nasty. Cropping a larger shot would of course be preferable, though depending on teh actual situation it may not necessarily save much time and effort.

     

    Mylenium

      M
      marc.decosterAuthor
      Known Participant
      January 24, 2022

      Thank you. With your answer and Rick's one, I'm confident, it will be OK 🙂

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