• Adobe After Effects Expressions

  Inverting MT Keyframe – HELP PLEASE

  Posted by Alex Kingsmill on March 19, 2009 at 2:37 am

  I need an expression.

  I’ve been scouering the web for the past few hours, and have been trying my best to write my own code, but i’m just still too much of a noob i guess to figure this simple thing.

  I have these motion tracking points. Starting at 0 and moving either up or down into negative and positive numbers. I need to take these numbers, and write an expression that will leave the x and z values alone and invert the y value.

  Now I need to be able to do this either:

  With MT keyframes already in place on the same layer.

  Or through a Null that I pickwhip to somehow.

  If anyone can help me, greatly appreciated, Im really trying to bust my ass on it and learning as much as I can right now. But this thing is really holding me back.

  Filip Vandueren replied 17 years, 4 months ago 2 Members · 1 Reply
• 1 Reply

• 

  Filip Vandueren

  March 19, 2009 at 3:45 am

  I’m a bit confused by you talking about z. Motion tracking is normally 2D, no ?

  Try adding this expression to a motion-track point to invert it’s Y-axis:

  
[value[0], -value[1]];


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