Another compositing challenge to you node gurus :)

This would be such a huge help to me if someone could show me very clearly how I can set the render layers and node setups to this properly.

  1. Currently due to render time issues, I am rendering a backplate seperately. And then doing animations with only forground elements.

  2. I am using a shadowcatcher kind of a set up which has worked well, and then multiplying shadows with background plate (please see current setup) The shadow catcher works nice because it also picks up reflected color as well just the shadow.

  3. then compostitng via alpha over, the 3d elements over that.

The problem …

  1. I want to do the compositing of the shadows and 3d elements in Aftereffects instead of blender.

  2. So basically I need to get the shadow only (using the current catching tecnique) to render seperately
    so that I can lay the resulting shadow layer and multiply it in AE over the background layer.

  3. The reason for all of this is that these animations often take hours and hours to render , so if I make a change or screw up something on my background plate and need to change I have to rerender the whole thing over.

The challenge :slight_smile:

  • please visually (via screengrabs if at all possible) show me how to properly set this up, with render passes or whatever it takes.

(this is the way I am currently doing it)


How the layers need to be setup for the current shadowcatcher thing to work correctly


This is what I would like to be able to do somehow


Wishing you American Blenderheads a Happy Thanksgiving… you qualify for a second helping of Turkey if you can help me out :slight_smile:

Look into the file output node, that node can have multiple outputs from multiple inputs… you can get this saved as separate png / jpg files or one multilayered exr file if that suits your cause.

Usually what i do for these sorts of shots is rendering the 3D scene in a totally separate file to the comp… that way I can tweak the comp to my hearts content and not having to re-render the 3D scene. Multilayer EXR files are your friend!

@doublebishop THANKS SO MUCH! this file output worked great for what I am looking to do…

But I would like to post these 3 images and ask a couple more questions…

This is how I did the set up for the file output node…


This is the result, when bringing the 2 outputed files from blender into After Effects and adding the background plate (in aftereffects)
It provides me so much more flexability in case I need to change the background. On the shadow layer in AE, I simply set this to multiply.


But I am noticing 1 difference… please see below image… this is what came out of blender when I was doing all the compositing inside of blender


This is what I am seeing different…

If you look at just the road, and compare the 2 images, you will notice when using the file output method that the “road” (which is actually the shadow catcher(I made the entire road a shadow catcher for this project), is darker, than the “road” when compositing it all in blender. There are no differences in the background… only where the shadowcatcher was. Now the beauty is that I can manually change this easily in AE.

But my new questions are…

  1. should I be doing any additional file outputs in blender, like AO when outputting the passes in blender? I’m using cycles, I have no ambient occlusion in the world setting when doing any of these tests. But is there actually ambient occulsion occuring naturally that I should also be trying to get using the file output node?

  2. In using this file output node, I noticed an option to use node format… it was checked by default, so I just left it. But if anyone knows, why would you not have that checked?

If anyone is interested, I found a video tutorial on the file output node, that helped me figure out, how to get the different outputs to go into seperate folders , the tutorial was done with BI, but the basics are the same… this can be found here

Thanks again Double Bishop… you qualify for a second helping of turkey :slight_smile: