Shadow pass is black

Hi, I’m in cycles and try to the shadow pass from a layer and of course it won’t work: whatever I try the shadow pass is black. Help?

Blend: Shadow pass.blend (5.23 MB)

Use a lamp instead of an emission plane, I don’t believe the shadow pass contains shadows from emitting objects or environment lighting

But… I want to use a HDRI to lit my scene to perfectly fit it in a video… is there anything I can do but wait 'till shadow pass from enviromental lighting become supperted?

but wait 'till shadow pass from enviromental lighting become supperted?

It’s been on the To Do list for a very long time and no indication that it will be implemented in the near future, so if you wait you’ll most likely be wasting your time.
Fake it with some additional lamps in the scene

If the shadow you’re trying to “catch” is being cast onto a single surface (like the floor), you could move all your objects that you want to render on layer one, and the floor on layer two. Your floor will either need a white material, or you can give the shadow pass layer a white material for everything. Set up two render passes, and hide either the floor or the renderable objects for each pass, then composite them back together with your footage. You’ll have to make some tweaks, but overall you can use the image as a shadow pass, more or less:

Sample blend attached, cuz it’s kind of tricky if you’ve never done it before. Lots of trickery possible with Render Layers.
fakeShadowCatcher_EnvLighting.blend (706 KB)

Thanks! Why didn’t I think of rendering a grayscale version o the floor?
Simple and brilliant, just like we all want it :D!