• Adobe After Effects Expressions

  Converting Track Data to onscreen text readout?

  Posted by Adam Taylor on January 8, 2009 at 10:34 am

  I want to create an effect to simulate some kind of electronic viewfinder.

  It needs to have various windows that display numeric readouts, and i would like to have the numbers be driven by motion taken from the live action element. Ideally, i want three separate numbers…elevation, pan and tilt.

  Obviously I can extract the motion using trackers but thats as far as i can get…i get stuck beyond that point, and i’m sure the answer will involve Expressions!

  How can i take data from a tracker, and apply it to a text element so that the text is in some way controlled by the data?

  thanks
  Adam

  Adam Taylor
  Video Editor/Audio Mixer/ Compositor/Motion GFX/Barista
  Character Options Ltd
  Oldham, UK

  http://www.sculptedbliss.co.uk

  Xavier Khonje replied 17 years, 4 months ago 3 Members · 7 Replies
• 7 Replies

• 

  Adam Taylor

  January 8, 2009 at 12:37 pm

  I have worked out part of the answer and now have the data from a tracker x position appearing onscreen and animating with the track data….

  the only problem is the number being displayed is showing to 12 decimal places which is far too many digits!!.

  How do i tell AE to only display 3 decimal places?

  thanks
  Adam

  Adam Taylor
  Video Editor/Audio Mixer/ Compositor/Motion GFX/Barista
  Character Options Ltd
  Oldham, UK

  http://www.sculptedbliss.co.uk
• 

  Dan Ebberts

  January 8, 2009 at 2:12 pm

  Like this:

  thisComp.layer(“your movie”).motionTracker(“Tracker 1”)(“Track Point 1”).attachPoint[0].toFixed(3)

  Dan
• 

  Adam Taylor

  January 8, 2009 at 2:36 pm

  Many thanks Dan,

  i have tried that several times and keep getting an error message saying “…expression result must be of dimension 2, not 1.”

  Any idea what that means?

  regards
  Adam

  Adam Taylor
  Video Editor/Audio Mixer/ Compositor/Motion GFX/Barista
  Character Options Ltd
  Oldham, UK

  http://www.sculptedbliss.co.uk
• 

  Adam Taylor

  January 8, 2009 at 2:40 pm

  please ignore my stupidity Dan….just realised the expression was not working because i applied it to a different layer!!

  Pass the dunce hat…i’ll be in the corner!

  Adam Taylor
  Video Editor/Audio Mixer/ Compositor/Motion GFX/Barista
  Character Options Ltd
  Oldham, UK

  http://www.sculptedbliss.co.uk
• 

  Xavier Khonje

  January 9, 2009 at 5:19 am

  hey Adam am trying to figure out something like that two
  I hope you don’t mind but can you share what you did,
  thanks in advance

  xavier
• 

  Adam Taylor

  January 9, 2009 at 9:25 am

  certainly xavier…

  First, the track data was copied into a null object.
  i typed some text and placed it onscreen roughly where i needed it, then twirled down the layer properties, opened the Text properties and alt clicked the Source Text stopwatch. Then i dragged the pickwhip to the Null/Motion Trackers/Track Point 1/Attach Point and held it to the x coordinates and released.
  This then puts the current track data into the text file. The code that Dan gave was the finishing touch to truncate the numeric value to show only 3 numbers after the decimal point instead of 12 !!

  Repeat the process but using the y coordinate if you want to have 2 text layers showing the two different axis.
  regards
  Adam

  Adam Taylor
  Video Editor/Audio Mixer/ Compositor/Motion GFX/Barista
  Character Options Ltd
  Oldham, UK

  http://www.sculptedbliss.co.uk
• 

  Xavier Khonje

  January 14, 2009 at 5:16 pm

  thanks a bunch adam
  its like another key to a collection of my own

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