• Adobe After Effects

  Rendering 3d Shadows with transparency

  Posted by Ross Gerbasi on May 24, 2007 at 4:06 pm

  Ok, so I have checked around for info on getting a 3D comp to have floor shadows only.

  The solution seems to be making a white solid, matching it up to the floor, and having it accept shadows, then changing the blend mode to Multiply.

  Cool that looks great when I have a background behind the comp. BUT now I wanna take this composition and render it out using millions+ for transparent video in flash. The catch is I need that shadow attached to it. When I turn off my background layer to go transparent with everything I, ofcourse, see the white solid again.

  Is there any way to make a 3d object only receive shadows? So nothing but the shadow will show, that does not involve blending modes. That will support exporting.

  Any help? thanks guys!
  -ross

  Steven Kutny replied 17 years, 8 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Ross Gerbasi

  May 24, 2007 at 10:59 pm

  Dave thanks for posting! 🙂 I know I am new here and some of your posts have saved me a crap load of time. Your totally right, but I was really just looking for a solution to the problem.

  Actually it ended up being quicker to just do it that way, the old copy, color and flip.

  BUT for anyone wondering. I did find a solution.

  Start with
  Some comp with a 3d character or something that you want to cast shadows.
  New White Solid.
  Make it 3d.
  Make a light.
  On your character set the material options to Cast Shadows and not to accept light or shadows.
  Set the white solid to accept shadows, not lights and not cast shadows.
  Position in the scene as a floor and Pre-Comp as Floor.
  Collapse Transforms
  Inside Floor comp set mode to Silhoutte Luma
  Back in the main comp make sure you have some background behind the floor. (Black Solid will do it)

  The Siloutte Luma will cut into the Black Solid giving you transparency with just a shadow. If you need other parts of your scene rendered just go back into the floor clip and create more white solids to take up space.

  Your layers should look like this
  Main Comp
  Light
  Character
  Floor Comp
  Black Solid

  Floor Comp
  White Solid for Floor (silhoutte luma)
  Other Solid for wall
  …

  🙂 Hope this makes sense, and I know its madness… So honestly Black solid and feather mask is a good solution 🙂 Or Copy comp, tweak and blur… But for those as crazy as me… here is a trick.

  thanks
  -ross
• 

  Steven Kutny

  August 29, 2008 at 9:17 pm

  wow, this is huge to me, a great tip! thanks so much for finding a solution and posting back to your original question.

  Thanks,

  Steve

  Steven Kutny
  Digital Artist
  http://www.stevenkutny.com

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