On Wednesday, 15 January 2014 at 21:00:57 UTC, Jeroen Bollen
wrote:
How do you correctly create a MersenneTwisterEngine with a
ulong as seed?
If you are trying to create a very large 2D noise generator, this
is how you do it, and you can any degree of smoothness you want:
Create a 2D RNG.
e.g.,
RND2D(x,y) { seed(S + x + N*y); return rand; }
You could use this to generate your whole map very predictably up
to the seed length(at some point it will repeat because of the
finite size of the seed).
If you have any degree of smoothness you do not want to use this
per point unless you do want to have some "noise" which could be
controlled by weighting the RND2D function so intergrid points
are not so random:
RND2D(x,y, xS, yS)
{
s = RND2D(x,y)
sm1m1 = RND2D((int)(x/xS) - 1, (int)(y / yS - 1));
sm1m1 = RND2D((int)(x/xS) - 1, (int)(y / yS + 1));
...
return interpolate(s, x, y, sm1m1, sm1p1, ...);
}
where interpolate returns the modified seed that is partially
based on the seed at the point x,y and partially an interpolation
value between the sub grid points.
Anyways, now that you have your RND2D you don't ever have to
pre-generate your noise. Obviously it is more computationally
expensive though.
I guess this was the function you were looking for before if I
now understand what you are trying to do?
