It depends on what you're doing... I found a hack way of doing it, but I'm sure there is a way to get the actual raytrace data.
Hack way:
Link lights;
Spotlight 1 hits cylinder and plane
Splotlight 2 hits box and plane
Shadows from spotlights deal '-2' Value (H 0.00 S 0.00 V -2.00)
Plane has Lambert or Phong with white color (255 255 255) and 3.000 diffuse
Box and Cylinder visibility = 0 (depends on what you want to do really, you could assign them the lambert/phong also)
Then, on camera, use a lens -> mib_lens_clamp -> Floor 0.000 Ceiling 0.100, Luminance checked, Floor color 255 255 255 (White) Ceil color 0 0 0 (Black)
