Render Passes and After Effects

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  01 January 2007
Render Passes and After Effects


Quick question here...

Can anyone tell me how I would go about combining rendered passes in Adobe After Effects? Do I use blending modes? Keying?

I'm really new to the idea of rendering in passes, so any help would be great!


  01 January 2007
Hi Brian,

It really depends on what you need to do with the passes. The idea behind passes is that you slpit your rendering into 2D layers (each being an image sequence).

These layers work the same way as flat layers in photoshop. Layers to which you can apply all sorts of effects to with different blending modes depending on the need.

Don't forget that XSI has its own built in FX tree... simillar to combustion's tree style set up and US Animation's Camera module... There you can apply the effects you'd like to then render them out into a single image sequence...

>>> Or you may import the passes straight into AFX and work on them in anyway you want.

Usually I composite first in the FX, and do other things in AFX depending on the need. I also mix them somtimes getting an effect from one app and putting it in the other.

I hope that didn't confuse you, make sure you clearly define what you need to do first, then with practice mixiing them up and rendering in passes will work wonders for you!

Good luck!
Some live, some die
In the name of the Samurai
  01 January 2007
Usually you will combine using blending modes. You don't need any keying if you plan ahead how you will combine the passes together with alpha channels and matte passes. I believe keying is useful only when you need to use live footage.


  01 January 2007
Thanks guys! That helps a lot.

Ok, one more question if you don't mind. For rendering a scene with Ambient Occlusion (to get soft shadows and nice indirect lighting), would I do a Diffuse Pass and an Ambient Occlusion pass and then combine those two in AE?

The reason I ask is that I've been trying it this way, but the Diffuse Pass still has harsh, direct lighting on it. What I need is to be able to render a pass WITHOUT any lighting/shadows and then get all of the lighting/shadow elements from the Ambient Occlusion pass.

.....I Think?

Sorry, I'm still really new to this and have NO idea what I'm doing.

  01 January 2007
An AO pass usually is used with an ambient pass as a fill light.

I have been using this way (AFX layer order):

- AO pass (multiply mode) - to add shadow and self occlusion (adjust levels and opacity here)
- Ambient pass (screen mode) - to add some fill lighting to key light pass (use opacity to control how much fill light is needed)
- Key light pass or beauty pass (normal mode) - direct illumination

It reads as:

AO * Ambient + Beauty = final image


  01 January 2007
Nice! That is EXACTLY what I've been needing to know. That clears up so much confusion!

Thanks a lot!

  01 January 2007
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