• Adobe After Effects Expressions

  Controlling an offset position with an angle slider.

  Posted by Christopher Rutherford on May 24, 2016 at 8:45 pm

  Hey smart people,

  I’m wondering if there’s an elegant way to controlling a layers position using angles & magnitudes as opposed to cartesian coordinates.

  And if not, is there a breakdown somewhere of how turn angle inputs into x/y outputs. From my floundering research thus far noticed there’s a lot of radian conversions & if/then statements for the 4 quadrants but I haven’t been able to parse it beyond that.

  For reference, Dan Ebberts code here almost does what I’m trying to figure out, but I can’t quite deconstruct it in order to control the distance of the offset.

  Thanks,

  EDIT: After a bit more searching I came across GrayMachine’s polar coordinate code. It took a bit of tinkering but I got it to work for myself. However, set the resting position of the layer (that is, the position when the Distance1 slider was 0) at 971,971. Subtracted 11 from 2 lines of code & that managed to work, but I don’t really know /why/.

  d = thisComp.layer(“Master”).effect(“Distance1”)(“Slider”)
  a = thisComp.layer(“Master”).effect(“Angle Control”)(“Angle”)

  angle = a;
  length = d;
  aRad =degreesToRadians( angle – 90);
  x=d*Math.cos(aRad)-11;
  y=d*Math.sin(aRad)-11;
  add(position, [x, y]);

  Christopher Rutherford replied 10 years, 3 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  May 24, 2016 at 9:19 pm

  It should be as straightforward as this:

  a = effect(“Angle Control”)(“Angle”);
  d = effect(“Slider Control”)(“Slider”);
  r = degreesToRadians(a-90);
  x = d*Math.cos(r);
  y = d*Math.sin(r);
  value + [x,y]

  which I think is the same as Harry’s solution. I’m not sure why you’d need any adjustments unless you’ve got parenting w/ rotation or non-uniform scaling involved.

  Dan
• 

  Christopher Rutherford

  May 24, 2016 at 9:31 pm

  Yeah I’d only found it it after posting my question. I still don’t quite understand why an input of 0 gives me an offset position of +11, but I haven’t yet worked out that math.

  But thanks for your time.

Reply to this Discussion! Login or Sign Up