Matte floor with reflection?

[riggles]

The only thing I can think of that even comes close would be to create a floor plane, assign it a reflective material, and then turn off camera visibility on all other geometry. The floor will pick up the reflection of all the invisible objects, though they won't be cut out of the alpha. Unfortunately, the floor will also catch shadows. This can be reduced by setting the floor diffuse to 0 and the index and spec to 1 (straight mirror). Not ideal at all, but it might give you something worth compositing with in a pinch.

[gordonrobb]

I think there was a discussion about render passes, like reflection, shadow etc being output-able separately some time in the 2.xx cycle. Then I guess it will be more possible to get something useful.

[dsyee]

I guess you could try compositing. Make one shadow-only render, then do another one changing the ground to specular, then overlay the second one on the first with reduced opacity.

I'm not very good at this, but here's an example. It looks screwy because I didn't bother trying to align the ground with the image. You'd need to adjust the shape and angle of the ground plane in order for it to look accurate.






Render passes would probably make this easier...