nerdcruft/libcruft-util
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n/midpoint: add jitter to edge midpoints

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This commit is contained in:
Danny Robson 2015-07-01 00:15:49 +10:00
parent 1cd87f375e
commit ddf9f0a22a
1 changed files with 53 additions and 16 deletions
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69
tools/noise.cpp
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@ -18,6 +18,7 @@
#include "netpbm.hpp"
#include "types.hpp"
#include "cmdopt.hpp"
#include "hash/murmur/murmur2.hpp"
#include "region.hpp"
#include "random.hpp"
@ -163,11 +164,37 @@ diamond (util::image::buffer<float> &img, util::region2u target, float scale, fl
}
void
midpoint (util::image::buffer<float> &img, util::region2u target, float scale, float persistence)
static float
gen (uint64_t seed, util::point2u p)
{
using util::hash::murmur2::mix;
uint64_t v = mix (
seed,
mix (
p.y,
p.x
)
) & 0xffff;
return v / float{0xffff} * 2 - 1;
}
// perturb the centre point by at most scale-units
// average the side points (optionally perturb by sides-units)
//
void
midpoint (util::image::buffer<float> &img, uint64_t seed, util::region2u target, float scale, float persistence, float sides = 0.f)
{
CHECK_EQ (target.e.w % 2, 1);
CHECK_EQ (target.e.h % 2, 1);
CHECK_GE (target.area (), 9);
CHECK_GT (scale, 0);
CHECK_GT (persistence, 0);
CHECK_GE (sides, 0);
auto w = target.w;
auto h = target.h;
@ -175,14 +202,19 @@ midpoint (util::image::buffer<float> &img, util::region2u target, float scale, f
// | |
// 2--3
auto v0 = img[target.p+util::vector2u{0, 0 }];
auto v1 = img[target.p+util::vector2u{w-1,0 }];
auto v2 = img[target.p+util::vector2u{0, h-1}];
auto v3 = img[target.p+util::vector2u{w-1,h-1}];
auto p0 = target.p+util::vector2u{0, 0 };
auto p1 = target.p+util::vector2u{w-1,0 };
auto p2 = target.p+util::vector2u{0, h-1};
auto p3 = target.p+util::vector2u{w-1,h-1};
auto v0 = img[p0];
auto v1 = img[p1];
auto v2 = img[p2];
auto v3 = img[p3];
// do the centre
auto avg = (v0 + v1 + v2 + v3) / 4;
auto val = avg + scale * (util::random<float> () * 2 - 1);
auto val = avg + scale * gen (seed, target.centre ());
auto pos = target.p + target.e / 2;
img[pos] = val;
@ -190,22 +222,27 @@ midpoint (util::image::buffer<float> &img, util::region2u target, float scale, f
// average the sides
auto p01 = target.p + util::vector2u{w/2, 0};
auto p13 = target.p + util::vector2u{w-1, h/2};
auto p32 = target.p + util::vector2u{w/2, h -1};
auto p32 = target.p + util::vector2u{w/2, h-1};
auto p20 = target.p + util::vector2u{0, h/2};
img[p01] = (v0 + v1) / 2;
img[p13] = (v1 + v3) / 2;
img[p32] = (v3 + v2) / 2;
img[p20] = (v2 + v0) / 2;
auto v01 = (v0 + v1) / 2 + sides * scale * gen (seed, p01);
auto v13 = (v1 + v3) / 2 + sides * scale * gen (seed, p13);
auto v32 = (v3 + v2) / 2 + sides * scale * gen (seed, p32);
auto v20 = (v2 + v0) / 2 + sides * scale * gen (seed, p20);
img[p01] = v01;
img[p13] = v13;
img[p32] = v32;
img[p20] = v20;
// recurse
if (target.area () > 9) {
auto e = target.e / 2 + 1;
midpoint (img, {target.p + util::vector2u{ 0, 0 }, e}, scale * persistence, persistence);
midpoint (img, {target.p + util::vector2u{ w/2, 0 }, e}, scale * persistence, persistence);
midpoint (img, {target.p + util::vector2u{ 0, h/2 }, e}, scale * persistence, persistence);
midpoint (img, {target.p + util::vector2u{ w/2, h/2 }, e}, scale * persistence, persistence);
midpoint (img, seed, {target.p + util::vector2u{ 0, 0 }, e}, scale * persistence, persistence, sides);
midpoint (img, seed, {target.p + util::vector2u{ w/2, 0 }, e}, scale * persistence, persistence, sides);
midpoint (img, seed, {target.p + util::vector2u{ 0, h/2 }, e}, scale * persistence, persistence, sides);
midpoint (img, seed, {target.p + util::vector2u{ w/2, h/2 }, e}, scale * persistence, persistence, sides);
}
}