• Adobe After Effects Expressions

  CLAMP or LINEAR to limit scale?

  Posted by David Rodriguez on June 24, 2008 at 10:30 am

  temp = thisComp.layer(“UPDOWN”).transform.position[1];
  [temp, temp]

  I am using the above expression on the scale property of an object to tie it to the vertical movement of another layer. What I need is to limit the horizontal scale of the object between 65% and 100% and the vertical scale of the object between 75% and 100%
  I did some searching around and the best I can figure is that I need to use CLAMP or LINEAR. I do not know which I need and how to insert it into the existing expression. I’m a little lost here.

  Any help is much appreciated.
  David

  Filip Vandueren replied 17 years, 10 months ago 2 Members · 6 Replies
• 6 Replies

• 

  David Rodriguez

  June 24, 2008 at 11:05 am

  I have it working with x,y together.

  temp = thisComp.layer(“BOTTLE 2”).transform.position[1];
  result = linear(temp, 150, 280, 75, 100);

  [result,result]

  I am so bad at this stuff, my apologies for being a dufus but how do I make this work for x and y separately?
• 

  Filip Vandueren

  June 24, 2008 at 11:24 am

  Hi David, position and scale are 2- (or 3-) dimensional properties. They have an x and a y component.
  Motionscript uses an Array syntax or a list to assign those numbers.
  For example: [100,50]
  You can retrieve one component from a property by using it’s index: x=0, y=1 like this:

  x = position[0];
  y = position[1];

  since the linear() method likes to work with numbers, not lists/arrays, we apply the linear to x and y separately, then put the result back in a 2-dimensional array (because scale will give an error if it only gets a number as a result of the expression):

  
x_temp = thisComp.layer("UPDOWN").transform.position[0];
y_temp = thisComp.layer("UPDOWN").transform.position[1];

  x_result = linear(x_temp, 150, 280, 65, 100);
  y_result = linear(y_temp, 150, 280, 75, 100);

  [x_result, y_result] ;

  I hope that makes sense. You’ll have to tweak the numbers in that linear expressions probably.
• 

  David Rodriguez

  June 24, 2008 at 11:36 am

  Thanks!

  So if I wanted both X and Y scale to be affected differently by the vertical motion of another layer I could use

  x = position[1];
  y = position[1];

  x_temp = thisComp.layer(“UPDOWN”).transform.position[1];
  y_temp = thisComp.layer(“UPDOWN”).transform.position[1];

  x_result = linear(x_temp, 150, 280, 65, 100);
  y_result = linear(y_temp, 150, 280, 75, 100);

  [x_result, y_result] ;

  ?
• 

  Filip Vandueren

  June 24, 2008 at 12:22 pm

  yes, though you only need to “sample” the vertical motion once: you can/should use the same variable in two different formulas.
  Also the first two lines have no use here: you’re defining x and y as the componenets of this layer’s position, then you don’t use it in the rest of the expression.
  So your code works, but could be simplified like this:

  
y_temp = thisComp.layer("UPDOWN").transform.position[1];

  x_result = linear(y_temp, 150, 280, 65, 100);
  y_result = linear(y_temp, 150, 280, 75, 100);

  [x_result, y_result] ;


  notice I used y_temp in both formulae.
• 

  David Rodriguez

  June 24, 2008 at 1:29 pm

  I understand. Thank you!
  So I could use the following for an independent X,Y scale expression based on the X position of a layer called “UPDOWN”

  wichita = thisComp.layer(“UPDOWN”).transform.position[0];

  x_boogedy = linear(wichita, 150, 280, 65, 100);
  y_boogedy = linear(wichita, 150, 280, 75, 100);

  [x_boogedy, y_boogedy] ;
• 

  Filip Vandueren

  June 24, 2008 at 6:40 pm

  Correct

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