nerdcruft/libcruft-util
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noise-tool: add simple thermal erosion

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This commit is contained in:
Danny Robson 2015-06-04 17:16:46 +10:00
parent 851f7b9351
commit 86d51f182f
1 changed files with 81 additions and 4 deletions
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85
tools/noise.cpp
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@ -22,6 +22,75 @@ template struct util::noise::fractal::rmf<float, util::noise::basis::constant<fl
template struct util::noise::fractal::hetero<float, util::noise::basis::worley<float,2>>;
/// talus: maximum desired slope in radians. [0, 90]
/// resistance: proportion of world to keep. [1, 0]
/// scale: horizontal distance scaling factor (relative to vertical)
void
thermal_erode (util::image::buffer<float> &height,
const float talus,
const float scale,
const float resistance)
{
CHECK_LIMIT (talus, 0, to_radians (90.f));
CHECK_GT (scale, 0);
CHECK_LIMIT (resistance, 0, 1);
// maximum height difference
const auto maxdiff = scale * std::atan (talus);
float total = 0.f;
for (size_t y = 1; y < height.h - 1; ++y)
for (size_t x = 1; x < height.w - 1; ++x) {
float centre = height[y * height.s + x];
float h[9] = {
height[(y - 1) * height.s + (x - 1)],
height[(y - 1) * height.s + (x + 0)],
height[(y - 1) * height.s + (x + 1)],
height[(y + 0) * height.s + (x - 1)],
height[(y + 0) * height.s + (x + 0)],
height[(y + 0) * height.s + (x + 1)],
height[(y + 1) * height.s + (x - 1)],
height[(y + 1) * height.s + (x + 0)],
height[(y + 1) * height.s + (x + 1)],
};
float diff = 0.f;
unsigned dests = 0;
for (size_t i = 0; i < elems (h); ++i) {
if (h[i] < centre - maxdiff) {
dests++;
diff = std::max (diff, centre - h[i]);
}
}
if (diff < maxdiff)
continue;
float size = diff * (1 - resistance) / 2;
float dist = size / dests;
total += size;
height[y * height.s + x] -= size;
if (h[0] < centre) height[(y - 1) * height.s + (x - 1)] += dist;
if (h[1] < centre) height[(y - 1) * height.s + (x + 0)] += dist;
if (h[2] < centre) height[(y - 1) * height.s + (x + 1)] += dist;
if (h[3] < centre) height[(y + 0) * height.s + (x - 1)] += dist;
if (h[5] < centre) height[(y + 0) * height.s + (x + 1)] += dist;
if (h[6] < centre) height[(y + 1) * height.s + (x - 1)] += dist;
if (h[7] < centre) height[(y + 1) * height.s + (x + 0)] += dist;
if (h[8] < centre) height[(y + 1) * height.s + (x + 1)] += dist;
}
std::cerr << "eroded: " << total << '\n';
}
// create a coloured map with this gradient (from libnoise tut3)
static const struct {
float scale;
@ -76,6 +145,7 @@ write_map (const util::image::buffer<float> &map, boost::filesystem::path name)
}
// offset a map so a fixed percentage of tiles are below the water height
void
adjust_ocean (util::image::buffer<float> &height,
const float percentage = .2f)
@ -88,16 +158,16 @@ adjust_ocean (util::image::buffer<float> &height,
std::array<unsigned,256> buckets{ 0 };
for (const auto h: height)
buckets[h * 255]++;
buckets[size_t (h * 255u)]++;
size_t pivot = 0;
for (size_t accum = 0, target = percentage * height.area (); pivot < buckets.size (); ++pivot) {
for (size_t accum = 0, target = size_t (percentage * height.area ()); pivot < buckets.size (); ++pivot) {
accum += buckets[pivot];
if (accum > target)
break;
}
std::cerr << "pivot: " << pivot << '\n';
std::cerr << "ocean pivot: " << pivot << '\n';
float offset = WATER_HEIGHT - pivot / 256.f;
for (auto &h: height)
@ -106,6 +176,9 @@ adjust_ocean (util::image::buffer<float> &height,
static const unsigned THERMAL_ITERATIONS = 10;
int
main (void)
{
@ -171,6 +244,10 @@ main (void)
adjust_ocean (img, 0.2f);
// write the images to disk
write_map (img, "noise");
write_map (img, "raw");
auto soft = img.clone ();
for (size_t i = 0; i < THERMAL_ITERATIONS; ++i)
thermal_erode (soft, to_radians (0.f), 1.f / size.w, 0.f);
write_map (img, "soft");
}