Adding AO render pass in After Effects

Question

I am compositing a modeled sea scene in AE. Here's what I have:

Adding in my AO layer gives nice strong shadows as shown:

However it also covers my blue sea (primarily an AE 4color background)....

How can I keep the AO benefits to the shadows on my critters, but also keep my background?

As rendered, I have alpha, color pass with alpha, AO and depth (which is driving AE lens blur). I can render anything else needed.

Answer 1

Let's try to make it work. :D

1) Place 'Alpha' layer above 'Ambient Occulsion',

2) Change setting in 'TrkMat' of the layer 'Ambient Occulusion' to 'Luma Matte'

if Luma Matte is not working, try with 'Alpha Matte' (I'm not sure about your alpha layer :)),

3) Precompose 'Alpha' + 'Ambient Occulsion' layers ctrl+shift+c,

4) Set precomposed layer to 'Multiply' Mode.

Done!