"clipka" <nomail@nomail> wrote in message 
news:web.4a141b4b38187d7ef708085d0@news.povray.org...
> "Tim Attwood" <tim### [at] anti-spamcomcastnet> wrote:
>> Seed is probably one of the commands that would belong in
>> the environment section, along with camera, photons, and radiosity.
>> It's part of the starting state of the renderer.
>
> Not if it's used in some huge macro. In that case, it's part of the 
> starting
> state of the macro.

Sure, but a normal macro that isn't redefined multiple times
would belong in the environment section too... any subroutine
that can be compiled once would go there. With some
4.0 macro syntax to make it clear that is what is going on hopefully.

>> RNG_Identifier = random_number_generator {
>>    [type POV36 | mersenne_twister]
>>    seed Float | Float_Identifier
>> };
>>
>> It's a bit more verbose, but it's more amenable to be
>> extended in the future.
>
> I'd actually favor something like:
>
> My_Random_Stream = Pov36_Rng(4711);
> My_Random_Number = My_Random_Stream.getNext();
>
> Other_Random_Stream = Mersenne_Twister_Rng(...);
> Other_Random_Number = Other_Random_Stream.getNext();
>
> i.e. sort of defining the different RNGs as different, independent objects
> (which just "happen" to use the same method identifier to get the next 
> value).
>
> But that's "future music" as we'd say in German.

That would be hard on the parser, every RNG command would be
at the top level, if they're inside a common constructor then at the top
level there's just the check for the constructor.

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