invisible objects with shadow

[PhilippeV8]

I was wondering if this could be done ... add an object and give it an invisible material so it's not on the render.  However, it does receive shadow, but doesn't cast shadow itself.
This way we can make the shadow apear to fall on objects or walls that are in the (flat) background ..

[guest84672]

I don't think so. But maybe Jeff M. will know.