• Adobe After Effects Expressions

  Use expression to control “Set Channels” Source layer

  Posted by Daniel Hashimoto on April 12, 2017 at 7:01 pm

  Is there a way to use an expression (script/hack/other effect) to control/set the “Source Layer” dropdown in the Set Channels effect?

  For example, I have a source piece of footage in the comp (Layer 1).
  Below that I have several solids using the Set Channels effect, sourcing Layer 1.
  I’d love to have one Null or something with a Layer Control dropdown that then propogates that selection to the Set Channels effects in all my solids – but the problem is “Source Layer” is not key-frame-able to be linked via expression.

  It’s a bizzare setup, I know – but I’m working in a project where I want to avoid pre-comps, and need the project to be simple enough to use before I hand it off to a team who will need a simple workflow.

  There may even be an effect I don’t know about that allows you to copy a layer’s RGBA and you can control the source layer selection with an expression. Any help much appreciated.

  – Hashi

  Daniel Hashimoto replied 9 years, 1 month ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  April 12, 2017 at 7:36 pm

  You couldn’t do it with an expression, but you could do it with a script, like this simplified example:

  var myLayer = app.project.activeItem.layer(“Layer 1”);
  var myEffect = myLayer.property(“Effects”).property(“Set Channels”);
  var myNewSourceLayer = app.project.activeItem.layer(“replacement.mov”);
  myEffect.property(“Source Layer 1”).setValue(myNewSourceLayer.index);
  myEffect.property(“Source Layer 2”).setValue(myNewSourceLayer.index);
  myEffect.property(“Source Layer 3”).setValue(myNewSourceLayer.index);
  myEffect.property(“Source Layer 4”).setValue(myNewSourceLayer.index);

  Dan
• 

  Daniel Hashimoto

  April 12, 2017 at 7:38 pm

  Appreciate that, Dan!

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