You need to create a Track Matte from the 3D layer. Duplicate your 3D layer and place the duplicate above the feathered solid. So your time line will contain, in order:
3D layer (Duplicate)
Feathered shadow solid
Now set the Track Matte of the feathered solid to Alpha Matte. It should automatically turn off visibility of the 3D Duplicate layer, and use the alpha channel of it to restrict the shadow layer.
Thankyou! That was exactly what I was looking for!
I was in the shower today and trying to think of the logic behind it, and I actually thought of doing that. It all makes sense now
Hmm I tried the track matte and it works, but for some reason I'm getting a 1 pixel outline around everything..
I have the black solid feathered, opacity, etc. as the shadow and when Its over it, there is about 1 pixel surrounding the 3d that has none of the shadow, so it gives it an odd bright outline.
I have a picture as an example.
I tried scaling the shadow matte but that only made the outline really dark and not blend nice.
Any suggestions why this is happening? Thanks
Pre-multiplied alpha channels often result in a bit of a fringe during this process. Just apply Effects/Matte/Simple Choker to the matte layer (duplicated 3D layer) with a value of -1 or so.
Just a footnote: this forum often witholds "Attachment" files like you posted, for virus checking. It's still not visible as I type this. If you post images using the image tool (little camera icon) it will be accessible to other forum users immediately.
Okay, thanks for your help.