(* 3D plot of Cos[x]  Cos[y], shadowed above *)

Needs["Graphics`Graphics3D`"];

ShadowPlot3D[
   Cos[x]  Cos[y], {x, 0, 2 Pi}, {y, 0, 2 Pi}, 
    PlotPoints -> 200, 
    FaceGrids -> {{-1, 0, 0}, {0, 1, 0}, {0, 0, -1}}, 
    SurfaceMesh -> False, 
    ShadowMesh -> False, ShadowPosition -> 1, 
    ColorFunction -> (RGBColor[.9 # , 1 - #, 1 - #] &)
];