• Adobe After Effects Expressions

  Need help modifying this expression

  Posted by Gene Michael patrick on March 27, 2007 at 12:47 am

  Hi all,

  I need to modify the following expression to create a 180 degree rotation on the Y axis. Hopefully it’s not too difficult.

  The expression is: this_comp. layer(this_layer, -1) . opacity. value_at_time ( time – .1)

  Thanks in advance for you help.

  Gene M. Patrick
  DIRECTV

  Filip Vandueren replied 19 years, 1 month ago 2 Members · 1 Reply
• 1 Reply

• 

  Filip Vandueren

  March 27, 2007 at 1:03 am

  opacity ranges from 0 to 100
  you need rotation, from 0-180

  this would be the easiest way:
  
(this_comp. layer(this_layer, -1) . opacity. value_at_time ( time - .1))*1.8

  you could add value, so the current value of the Y-rotation get’s factored in:
  
value+(this_comp. layer(this_layer, -1) . opacity. value_at_time ( time - .1))*1.8


  or perhaps *-1.8 for 0 to -180, but what if you actually need -90 to +90 etc…

  Anyway if the values start getting a bit more complex it ios better to use an interpolation method like ‘linear’:
  
linear(this_comp.layer(this_layer, -1).opacity.value_at_time( time - .1), 0,100, -90,90)


  this means: look at where a certain number (the result of your expression) is situated between 0 and 100,
  and return the corresponding interpolated number between -90 and 90.

  Oh and avoid using spaces inbetween your .dot notation.

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