nerdcruft/libcruft-util
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n/basis: use murmur mixing for random generator

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This commit is contained in:
Danny Robson 2015-05-26 16:26:43 +10:00
parent b67bb283d1
commit 749e279073
1 changed files with 36 additions and 14 deletions
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50
noise/basis.cpp
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@ -21,6 +21,7 @@
#include "../point.hpp" #include "../point.hpp"
#include "../random.hpp" #include "../random.hpp"
#include "../vector.hpp" #include "../vector.hpp"
#include "../hash/murmur/murmur2.hpp"
#include <algorithm> #include <algorithm>
@ -36,8 +37,15 @@ template <typename T>
T T
generate (intmax_t x, intmax_t y, uint64_t seed) generate (intmax_t x, intmax_t y, uint64_t seed)
{ {
size_t idx = util::noise::permute (x, y, seed); using util::hash::murmur2::mix;
return T(util::noise::LUT[idx]);
T v = mix (seed, mix (uint64_t (y), uint64_t (x))) & 0xffff;
v = v / T{0xffff} * 2 - 1;
CHECK_GE (v, T{0});
CHECK_LE (v, T{1});
return v;
} }
@ -46,13 +54,20 @@ template <>
util::vector2d util::vector2d
generate (intmax_t x, intmax_t y, uint64_t seed) generate (intmax_t x, intmax_t y, uint64_t seed)
{ {
auto u = util::noise::permute (x, y, seed); using util::hash::murmur2::mix;
auto v = util::noise::permute (u ^ seed);
return { auto u = mix (seed, mix (uint64_t (x), uint64_t (y)));
util::noise::LUT[u], auto v = mix (u, seed);
util::noise::LUT[v]
}; auto r = util::vector2d {
(u & 0xffff) / double{0xffff},
(v & 0xffff) / double{0xffff}
} * 2.0 - 1.0;
CHECK_GE (r, double{-1});
CHECK_LE (r, double{ 1});
return r;
} }
//----------------------------------------------------------------------------- //-----------------------------------------------------------------------------
@ -60,13 +75,20 @@ template <>
util::vector2f util::vector2f
generate (intmax_t x, intmax_t y, uint64_t seed) generate (intmax_t x, intmax_t y, uint64_t seed)
{ {
auto u = util::noise::permute (x, y, seed); using util::hash::murmur2::mix;
auto v = util::noise::permute (u ^ seed);
return { auto u = mix (seed, mix (uint64_t (x), uint64_t (y)));
float (util::noise::LUT[u]), auto v = mix (u, seed);
float (util::noise::LUT[v])
}; auto r = util::vector2f {
(u & 0xffff) / float{0xffff},
(v & 0xffff) / float{0xffff}
} * 2.f - 1.f;
CHECK_GE (r, float (-1));
CHECK_LE (r, float ( 1));
return r;
} }