• Adobe After Effects Expressions

  position of a parented layer

  Posted by Luke Halls on April 27, 2008 at 9:54 pm

  Hi,

  I’m sure i am missing something really simple but…

  Is there a way of working out the position of an offset parented layer including rotation applied to the parent layer?

  thanks

  Luke

  Luke Halls replied 18 years ago 3 Members · 4 Replies
• 4 Replies

• 

  Darby Edelen

  April 27, 2008 at 11:22 pm

  [Luke Halls] “Is there a way of working out the position of an offset parented layer including rotation applied to the parent layer? “

  If I understand what you’re asking, you’ll need to use layer space transformations. Once you make a layer the child of a parent layer, the child’s layer transformations are in the parent’s layer space instead of world space… So what you need to do is transform the child’s transform values from the parent’s layer space to the world space:

  
v = transform.position; //'v' is the value we're transforming

  if(hasParent){ //If this layer has a parent...
l = parent; //The parent layer of this layer
l.toWorld(v); //Return the value 'v' in the layer space of layer 'l' transformed into world space
}
else v; //Otherwise return 'v'


  The above code is specific to the position property. Other properties will require slightly different approaches.

  Darby Edelen
  Lead Designer
  Left Coast Digital
  Santa Cruz, CA
• 

  Dan Ebberts

  April 28, 2008 at 3:46 pm

  World position of child layer:

  L = thisComp.layer(“child”);
  L.toWorld(L.anchorPoint)

  World rotation of child layer:

  L = thisComp.layer(“child”);
  v = L.toWorldVec([1,0,0]);
  radiansToDegrees(Math.atan2(v[1],v[0]))

  Dan
• 

  Dan Ebberts

  April 28, 2008 at 4:04 pm

  Oh yeah, I forgot scale:

  L = thisComp.layer(“child”);
  sx = L.scale[0]/100;
  sy = L.scale[1]/100;

  while (true){
  if( ! L.hasParent) break;
  L = L.parent;
  sx *= L.scale[0]/100;
  sy *= L.scale[1]/100;
  }
  [sx,sy] * 100;

  Dan
• 

  Luke Halls

  April 28, 2008 at 9:51 pm

  Perfect, worked a treat.

  thanks!

  Luke

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