<h2>Let's try to make it work. :D</h2>

<p>1) Place 'Alpha' layer above 'Ambient Occulsion',</p>

<p>2) Change setting in 'TrkMat' of the layer 'Ambient Occulusion' to 'Luma Matte'</p>

<p><em>if Luma Matte is not working, try with 'Alpha Matte' (I'm not sure about your alpha layer :))</em>,
<a href="https://i.sstatic.net/ltpmK.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ltpmK.png" alt="trkmat"></a></p>

<p>3) Precompose 'Alpha' + 'Ambient Occulsion' layers <em>ctrl+shift+c</em>,</p>

<p>4) Set precomposed layer to 'Multiply' Mode.</p>

<p>Done!</p>

CC BY-SA 4.0
2018-06-23T12:36:25.313Z
Absolutely perfect! It was Luma matte that worked, as you suggested... And the solution worked without precompose, and this probably points to something I still do not understand about AE: What additional benefit does precomp offer beyond just stacking things where they are? But THANK YOU !
rcgauer
CC BY-SA 4.0
2018-06-24T15:22:11.313Z
Precomposing is just collapsing layers into one, in this example I recommend precomposing, for cleaner workflow. _becouse propably you are not going to modify alpha channel in AO_ :D
gadas_
CC BY-SA 4.0
2018-06-23T10:21:00.610Z
2018-06-23T10:21:00.610Z
gadas_
<p>I am compositing a modeled sea scene in AE. Here's what I have:</p>

<p><a href="https://i.sstatic.net/4N3xE.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/4N3xE.jpg" alt="enter image description here"></a></p>

<p>Adding in my AO layer gives nice strong shadows as shown:
<a href="https://i.sstatic.net/HZkB3.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/HZkB3.jpg" alt="enter image description here"></a></p>

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

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

<p>As rendered, I have alpha, color pass with alpha, AO and depth (which is driving AE lens blur). I can render anything else needed.
<a href="https://i.sstatic.net/Q9kBj.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Q9kBj.jpg" alt="enter image description here"></a></p>

<after-effects><compositing>
Adding AO render pass in After Effects
rcgauer
# Adding AO render pass in After Effects

(Asked by: username_0 on 2018-06-22)

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

[![enter image description here](https://i.sstatic.net/4N3xE.jpg)](https://i.sstatic.net/4N3xE.jpg)

Adding in my AO layer gives nice strong shadows as shown:
[![enter image description here](https://i.sstatic.net/HZkB3.jpg)](https://i.sstatic.net/HZkB3.jpg)

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.
[![enter image description here](https://i.sstatic.net/Q9kBj.jpg)](https://i.sstatic.net/Q9kBj.jpg)

**Tags:** after-effects, compositing


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## 1 answers

### Answer by username_1 on 2018-06-23. Score: 3 | Accepted answer

## 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 :))*,
[![trkmat](https://i.sstatic.net/ltpmK.png)](https://i.sstatic.net/ltpmK.png)

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

4) Set precomposed layer to 'Multiply' Mode.

Done!

> **Comments:**
> **username_0**: Absolutely perfect! It was Luma matte that worked, as you suggested... And the solution worked without precompose, and this probably points to something I still do not understand about AE: What additional benefit does precomp offer beyond just stacking things where they are? But THANK YOU !  
> **username_1**: Precomposing is just collapsing layers into one, in this example I recommend precomposing, for cleaner workflow. _becouse propably you are not going to modify alpha channel in AO_ :D  

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