//a transition from white to black
//note the interesting texture
//warning, this rendering is very slow... be patient
paper 0

//random and Mod from DBN book
//the randomness helps to make it look more natural
Number Mod X Y
   Value (X-(Y*(X/Y)))
Number Random D
   Set A 5
   Set B 2
   Set C (D*A + 1)
   Set D 
   Value ( *