I love LuxRender!!!! This image cannot be done in Poser, a shadow alone without an object casting it. Shadows have life now and this opens incredible possibilities for scenes.

How was done.
Beside the room that has two walls and a floor there are two planar figures standing on the floor where begins the shadow. The material of the figure was set to "glass" with transmisivity set to 1 and index of refraction also set to 1.

#***** Material 'oni'
MakeNamedMaterial "oni"
   "string type" ["glass"]
   "color Kr" [0 0 0]
   "color Kt" [1 1 1]
   "float index" [1]

Well, this result is nothing "physically correct", a glass with the same index of refraction than air (1.0) is 100% transparent and so it is invisible and can't cast any shadow at all!!!

From old school books,

reflected/incident     = (n1 - n2)/(n1 + n2) = 0
transmitted/incident = 2n1/(n1 + n2)        = 1             In this case n1 = n2 = 1

Any way, the result is very useful and I love it.
     

Stupidity also evolves!