Possibility to generate periodic noise

[realisim]

It would be nice if we could generate periodic (tileable) noise. Of course it does not apply to all noises, but Perlin and Cellular noise are good canditate.

Periodic noise should also work when they are used with the fractal pertubations (FBM or other).

Since not all noise are subject to periodicity, maybe a predicate in the form: bool CanBePeriodic(NoiseType iNoiseType) const;

and to mimic GetNoise function:

FN_DECIMAL GetPeriodicNoise(FN_DECIMAL x, FN_DECIMAL y);
FN_DECIMAL GetPeriodicNoise(FN_DECIMAL x, FN_DECIMAL y, FN_DECIMAL z);