How do I get the alpha of a shadow? (C3/Mac)

#1

Hello! I’m a bit of a Combustion newbie so please excuse if this is silly. I have an animated text in a 3D composition. It has a shadow. I want to render the animation without background so I can freely position it in Final Cut Pro. Problem: The shadow alpha doesn’t show up. Using my Shake knowledge I tried to assign the shadow layer to a Set Matte node but nesting constantly breaks my composition. Combustion confuses me. Is there any way to get the shadow alpha?
Thanks!
jwm

#2

I think I know your problem. So far I know it is not possible to render out the raytraced shadow of a 3d composition seperated, but here is a workaround:

  • create a white solid layer as background
  • turn on “invis. to camera” on the text layer (all layers casting shadows)
    Composite Settings:
  • turn off shading and reflections
  • turn on shadows

You will get a black/white image which you can render out or commit to disk.
Use it with the “set matte” operator with input set to “luminance”

#3

Cool, vielen Dank! I’ll try that.

#4

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