http://wiki.povray.org/content/Reference:User_Defined_Macros#The_macro_Dir
ective#Optional_Parameters
The example for the optional option for macros has a bit too many ";" 't
won't run like that.
cleaned up:
#macro Foo(P1, optional P2)
#ifndef(local.P2) #local P2 = 0; #end // provide default for P2
...
#end
#declare X=1;
#declare Y=2;
Foo(X,Y)
#undef Y
Foo(X,Y)
Foo(X,)
ingo
