• Adobe After Effects Expressions

  City lights reacting to music

  Posted by Karl Koehler on January 6, 2015 at 3:49 pm

  Greetings to you!

  I posted this problem over in the basics-forum and was told, this might be better off here at expressions.
  So i’ll just copy and paste here, hope you don’t mind:

  this new project of mine gives me a challenge I can’t solve for myself.
  My skill set and understanding of After Effects puts me fairly in the “basic”, or maybe “amateur” section
  and because I’m certain that some scripting is required to get this right, I need help.

  So the basic premise of the project is that I need city lights at night, like streetlamps, to be reacting to musical cues. And since this will be a music video, there’re going to be some.
  The shots are purposely almost always vistas, never say in the middle of a lively street so that the contrast between the light and the dark is definite. Starting with lonely streets with maybe 2-3 lamps and detailed cues, ending in very wide shots of the city.
  Only the opacity (exposure/glow) is affected by the cues, meaning the intensity changes with whatever the instruments, or the vocals are doing.
  Available to me are After Effects and the plugin Soundkeys.
  I also have the separate tracks for each instrument and the vocals.
  So in a scene with 1-30 lights, I’m already able to work up a solution that works and looks adequately nice, using individual mask for streetlamps, windows, etc…
  But since the finale builds up to the whole cityscape at night, I feel that masking every single lamp or window isn’t the right way to go.
  So, is it possible to write an expression that not only , based on the keyframes made by Soundkeys or the Audio to Keyframes option, distributes the cues to already bright spots in the footage without drawing a billion masks, and then even randomising these lights so that not all of them react simultaneously?
  While a solution without masking might be a long shot, I’m actually okay with drawing 300 of them. But I don’t know how to write an expression to distribute the triggers randomly between them individually or in clusters.

  I also thought there may be a solution in duplicating the footage, color keying all the bright lights, inverting the thing, making a solid composite, applying the synchronous exposure and glow to all of them and using an expression to randomly alternate the transparency of the layer?

  I’m not sure if I communicated my problem well, but I hope someone gives me a break.
  Next thing for me, I need to learn is how to script.
  And I thank you for your time in advance!

  Karl Koehler replied 11 years, 8 months ago 1 Member · 0 Replies
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