Looking for the thread that talks about the vray properties to make a vray material work like the matt - shadow material of MAX. I saw it a couple months ago but can no longer find it. I just want the shadows of an object to be visible without seeing the plane that it is on.
Just right click the object. Open the VRay property menu. Then activate “Matte object” and set “Alpha contribution” to “-1”. Don’t forget to check “Shadows” and “Affect Alpha”.
That’s it. 
Ah - remember: the color of the plane is still visible to VRay. So you might get a red color bleeding from the matte plane if it’s color is red for instance. Just apply a white/grey/black material to the plane to avoid this.
Thanks!