• Adobe After Effects Expressions

  sampleimage

  Posted by Rob Moffett on May 20, 2009 at 4:50 am

  I was playing with Dan’s sampleimage expressions, and would like to have the alpha value of a specified layer control the rotation of a layer.

  I pasted this expression on the Y-axis of my layer…

  target = thisComp.layer(“background”);
  a=target.sampleImage(transform.position, [width, height]/2, true, time)[3];
  linear(a, 0, 0.36, 0, 180)

  But get this error: sampleimage() must be 2 numbers
  What am I doing wrong? Was I close?

  Rob Moffett replied 16 years, 12 months ago 1 Member · 2 Replies
• 2 Replies

• 

  Rob Moffett

  May 20, 2009 at 5:01 am

  Ok, so I discovered that the error “must be 2 numbers” is because the layer i want to effect is a 3D layer, and is returning 3 numbers (xyz)

  Is there a way around this, or is the sampleimage expression limited to 2D?
• 

  Rob Moffett

  May 20, 2009 at 5:06 am

  Ha, worked it out. Here’s the solution if anyone wants it.

  target = thisComp.layer(“background”);
  a=target.sampleImage([transform.position[0],transform.position[1]], [width, height]/2, true, time)[3];
  value=linear(a, 0, 0.36, 0, 180)

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