Actually, it might make more sense in explaining that macro to insert a value as
in:

#macro testfinish(V) finish {ambient V} #end

That way, you could change the value (V) when calling the macro, like so:

testfinish(.7)

-- Dave

>



"wealthychef" <nomail@nomail> wrote:
> "Tim Attwood" <tim### [at] comcastnet> wrote:
> > > Care to expand on that a little?  Why wouldn't it work?   What is going
> > > on?
> > > Clue, please.  :-)
> >
> > POV finds a finish identifier, not a finish statement,
> > identifiers and statements aren't interchangeable.
> > It expects usage like ...
> >
> > #declare testfinish = finish {ambient 0.7};
> >
> > triangle {
> >     v0, v1, v2
> >     texture {
> >       pigment { Red }
> >       finish { testfinish }
> >     }
> > }
> >
> > Declare statements shouldn't be confused with macros.
> > A macro substitutes the lines directly into the calling
> > code instead of using identifiers. Example...
> >
> > #macro testfinish() finish {ambient 0.7} #end
> >
> > triangle {
> >     v0, v1, v2
> >     texture {
> >       pigment { Red }
> >       testfinish()
> >    }
> > }
> >
> > Here testfinish() is replaced by "finish {ambient 0.7}"
> > which is a finish statement instead of a finish identifier.
>
> thank you.  This point has been confusing me for years about Povray, as I only
> occasionally dabble in it.  So it seems as though in a #declare statement, the
> "finish {ambient 0.7}" piece is somehow compiled (?) into a "finish
> identifier?"   What is the difference between an identifier and a statement?
> Is this true:  "finish" is to "identifier" in Povray as "integer" is to
> "variable" in C?
> Aha! I think I get it:
>
> If I were to say
> #declare testtexture texture { pigment {Red} finish {ambient 0.7} };
>
> I then use it like this:
>
> triangle {
> v0,v1,v2
>  texture {testtexture}
> }
>
> Thank you.  It's interesting and revealing.

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