• Adobe After Effects Expressions

  3D rotation with scale+opacity according to Z position

  Posted by Karim Daire on September 15, 2008 at 11:27 am

  Hi,

  I have made a little slideshow in which I animate photos in a circle rotating in 3d space controlled by a Null object.

  I just don’t get the circle to have depth. The photos on the backside of the circle don’t get small enough and are too confusing, so I need to scale them down, add blur and transparency the farer they are in the back on the z-axis.

  Can anyone help me with an expression? I wonder because since the photos are rotated by a Null Object there is no location other than the original one stored in the seperate photo layers until I take off the parenting to the Null… can you still access the rotated position to read the Z-Axis and use it to trigger a expression for the scale+opacity??

  Also I went nuts to arrange the layers in 3D space on a circle. when rotating them around a center I couldn’t make them auto-orient to the camera, so I had to move them by hand to their locations… I guess there must be scripts for the purpose of arranging layers in 3D space. Any hints??

  Thanks in advance,

  Karim

  Dan Ebberts

  

  replied 17 years, 7 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Dan Ebberts

  September 15, 2008 at 4:08 pm

  You can get the world position of a layer like this:

  toWorld(anchorPoint)

  Are you saying that you have the child layer’s “Auto Orient Towards Camera” turned on but it’s not working?

  Dan
• 

  Karim Daire

  September 15, 2008 at 4:55 pm

  Hello Dan,

  thanks for your reply…
  I got auto orient on and its working now but I had to place all layers by hand. When I moved the anchor point and rotated each layer by x degrees the auto orient would not work. Is that right?? Does auto orient only work for layers which are not rotated??

  As for the expression…

  toWorld(anchorPoint)

  Where do I place it and how do i extract the z-position from it to use e.g. for transparency? Sorry, but I only use exressions rarely and always have to start from scratch.

  Karim

  -Karim-
• 

  Dan Ebberts

  September 15, 2008 at 5:12 pm

  If you’re moving the anchor point, that will definitely mess up the auto orient, because it’s the anchor point that gets oriented towards the camera.

  If you need the world z coordinate for your expression, you just do something like this:

  z = toWorld(anchorPoint)[2];

  Of course, again, if you’ve moved the layer’s anchor point, that will mess up the calculation.

  Then you’d have to do something like this:

  z = toWorld([width/2, height/2, 0])[2];

  Dan

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