how to make front and back side of figure appearance differently?

hello Guys i am back

 I made  a 3-D figure(which  has x,y,z component, like cube). what I need is that  the front side of the figure appearance should be different from the back side.In other words the distance between the points randomly generated  on the xy plane should different from that of yz plane.

 is there any one can help?Many thanks