Warp nous illumina en ce 2009-05-19 13:11 -->
>   I have discussed with the team about the idea of adding alternative,
> higher-quality random number generators to POV-Ray 3.7. The current generator
> would be kept for backwards compatibility, but alternatives would be offered.
> 
>   The only thing which is a bit open is the exact syntax for this. So far
> this is the best idea:
> 
>   Enhance seed() so that it will take an optional second parameter, which
> would specify the RNG algorithm used. It would default to the current RNG.
> The rand() function would remain unchanged (internally it smartly selects
> the proper RNG from the type of seed given to it). In other words, you would
> be able to do, for example, like this:
> 
> #declare S1 = seed(1234); // Use the current RNG
> #declare S2 = seed(1234, 1); // Identical to the above.
> #declare S3 = seed(1234, 2); // Use second RNG algorithm.
> 
>   Additional algorithms might be added in the future. As mentioned, rand()
> would be unchanged, so its usage would be the same:
> 
> #declare RandomValue1 = rand(S1);
> #declare RandomValue2 = rand(S3);
> 
>   The current RNG uses a 32-bit seed, so a single parameter to seed() is
> enough to get all possible streams. However, higher-quality random number
> generators usually support much longer seeds, so it would be possible to
> choose among a vastly larger amount of RNG streams. Thus it would be very
> nice if larger seeds could be specified.
> 
>   The problem here is one of syntax. How to do this? Here are the ideas
> so far:
> 
> 1) Simply don't support seeds larger than 32-bit. This would work, but would
>    be a bit of a bummer because the capabilities of higher-quality RNGs
>    wouldn't be fully utilized.
> 
>    Alternatively, since seed() actually takes a (64-bit) float rather than
>    a 32-bit integer, the seed range could be somewhat enlarged by taking
>    the entire float range into account. This would allow using seeds of
>    about 52 bits. (But it's still a long shot from the thousands of bits
>    supported by higher-quality RNGs.)
> 
> 2) Make it possible to give either a regular float (as now), or an array
>    of floats as the first parameter of seed(). This way larger seeds can
>    be specified as an array.
> 
>    While a bit cumbersome, it's not as bad as it may sound at first, because
>    it's possible to do eg. this:
> 
>      #declare S = seed(array[4] { 1, 2, 3, 4 }, 2);
> 
>    It would still be nicer if something less cumbersome could be used,
>    though...
> 
> 3) Use an alternative function for long seeds. For example:
> 
>      #declare S = longseed(2, 1, 2, 3, 4);
> 
>    (where the first parameter specifies the RNG type used.)
> 
>    One small cosmetic problem with this is, however, that it's a bit
>    inconsistent with the seed() function. seed() takes the RNG type as
>    the second parameter, while longseed() would take it as the first
>    parameter. This can be a bit confusing.
> 
> 4) Create an entirely new syntax for specifying a group of values. This,
>    however, would be laborious and should preferably be avoided.
> 
> 
>   Opinions and additional ideas will be appreciated.
> 
An option could be to do something similar to the noise generators. You can 
select witch one to use in the global_settings section, with a default one.

It should be possible to add something like:
random_gemerator 2

The generator 1 would be the number 1, the actualy proposed one number 2, and 
there is room to add some other generators.

I also like the idea of been able to use a float as the seed. Providing a float, 
like 1.0 would automaticaly sellect the new generator.

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