invisible surface that will still patch radiosity light?

Hey all, I’m trying match a coffee cup to a photo of a table. To make the cup realistic I want to use and radiosity and a brown plane under it to simulate the table-reflections but I only want to see its reflections and not the object itself. How is this achieved?

Thanks

You use ‘offline’ radiosity

Blender can compute radiosity at render time (new technique) or compute vertexcolors once, and use them in subsequent renders. If you use this second technique you can delete/move away the plane and then do the final rendering

Stefano