• Adobe After Effects

  Mocha 3, After Effects CC & 3D Motion Tracking of an Object (face) shot static against a green screen

  Posted by John Harron on November 30, 2013 at 1:14 am

  Hello There,

  I’ve been trying to figure this one out for awhile.
  I shot an actor against a green screen and I would like to acquire a 3D track on his head so I can apply 3d elements to his face using Element 3D.

  There is a tutorial on the imagineer website that sort of covers this but the shot is not static. In order a acquire the necessary 3D info the background needs to be tracked… in my case there is really nothing to track.

  Wondering if anyone might have any suggestions on how to do this!

  Many Thanks,
  -John

  Roland R. kahlenberg replied 12 years, 10 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Roland R. kahlenberg

  November 30, 2013 at 3:42 am

  For mocha’s 3D Camera Solve, you will want at least 2 planar surfaces to be successfully tracked. A face can be broken down into different planar surfaces. See if this info helps.

  HTH
  RoRK

  Intensive mocha & AE Training in Singapore and Other Dangerous Locations

  Imagineer Systems (mocha) Certified Instructor
  & Adobe After Effects CS6 ACE/ACI
• 

  John Harron

  November 30, 2013 at 3:53 pm

  Hey There Roland and many thanks for the reply!
  So I went ahead and tracked the mouth, the eye area and the tip of the nose I then went to the solve tab and solved for them – one note… there’s a PTZ option & Parallax but no static camera option.. Not sure if this is effecting the outcome. Anyway I got a 98% solve so I figure we’re in business.

  I copied the solve (3D data) to the clipboard and imported using the importer for AE… I then imported my 3D element layer and pickwhipped the positions (XY & Z) to the center Null… As you can see below the result is off… it seems as if the camera has interpreted some sort of a move shrinking the null/element over time (see below)

  https://dl.dropboxusercontent.com/u/9724232/Comp%206.mp4

  This is a pretty simple track but ultimately I’d like to get this to the point where I can track a character from facing front to profile and utilize element 3D to give the effect dimension…

  Any thoughts?
• 

  Roland R. kahlenberg

  December 1, 2013 at 1:07 am

  [John Harron] “This is a pretty simple track but ultimately I’d like to get this to the point where I can track a character from facing front to profile and utilize element 3D to give the effect dimension…”

  You’re pushing it if you go for a full-on side profile. Some perspective change should be fine – but not too much.

  You should want some camera movement – otherwise it’s not a camera solve. I suggest you re-try the experiment with some camera movement. Allow the camera to capture Parallax as it’s important to the camera solve. Place a tracking thingy on the background so that there are at least two planes for the tracking engine to calculate parallax for the camera solve.

  Google “Grimm mocha” for examples of face tracking.

  In your specific example, you may have tracked the eyes etc but results really depend on your tracking splines – where you’ve placed them. I’m not too keen on the eyes cos it has a lot of movement that is contrary to the head movement.

  Checkout these great tutorials for examples –
  https://provideocoalition.com/pvcexclusive/video/face_replacement_part_1_basic

  https://provideocoalition.com/pvcexclusive/story/face_replacement_part_2_advanced

  HTH
  RoRK

  Intensive mocha & AE Training in Singapore and Other Dangerous Locations

  Imagineer Systems (mocha) Certified Instructor
  & Adobe After Effects CS6 ACE/ACI

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