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noise-tool: add simple hydraulic erosion

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Danny Robson 2015-06-04 20:06:53 +10:00
parent 42a97816be
commit 6926c95d4d
1 changed files with 99 additions and 2 deletions
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101
tools/noise.cpp
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@ -22,6 +22,97 @@ 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>>;
void
hydraulic_erode (util::image::buffer<float> &height, const unsigned ticks)
{
CHECK_GT (ticks, 0);
std::cerr << "hydraulic_erosion\n";
const float RAINFALL = 0.001f; // quantity of water added each tick
const float SOLUBILITY = 0.1001f; // quantity of land picked up by unit rain
const float EVAPORATION = RAINFALL * .85f; // quantity of water evaporated each tick
auto water = height.alloc ();
CHECK (water.is_packed ());
CHECK (height.is_packed ());
std::fill (water.begin (), water.end (), 0);
for (unsigned t = 0; t < ticks; ++t) {
// apply new rain and erosion
for (auto &w: water)
w += RAINFALL;
for (auto &h: height)
h -= RAINFALL * SOLUBILITY;
float total = 0.f;
// move water to lowest neighbour cell
for (size_t y = 1; y < height.h - 1; ++y)
for (size_t x = 1; x < height.w - 1; ++x) {
const size_t indices[9] = {
(y - 1) * height.s + (x - 1),
(y - 1) * height.s + (x + 0),
(y - 1) * height.s + (x + 1),
(y + 0) * height.s + (x - 1),
(y + 0) * height.s + (x + 0),
(y + 0) * height.s + (x + 1),
(y + 1) * height.s + (x - 1),
(y + 1) * height.s + (x + 0),
(y + 1) * height.s + (x + 1),
};
const float level[9] = {
height[indices[0]] + water[indices[0]],
height[indices[1]] + water[indices[1]],
height[indices[2]] + water[indices[2]],
height[indices[3]] + water[indices[3]],
height[indices[4]] + water[indices[4]],
height[indices[5]] + water[indices[5]],
height[indices[6]] + water[indices[6]],
height[indices[7]] + water[indices[7]],
height[indices[8]] + water[indices[8]],
};
size_t dst = std::min_element (std::begin (level), std::end (level)) - level;
if (dst == 4) // if centre, bail
continue;
// transfer as much water as possible to even the heights
float total_diff = level[4] - level[dst];
float transfer;
if (total_diff > water[4])
transfer = water[4];
else
transfer = (water[4] - total_diff) / 2;
water[indices[ 4]] -= transfer;
water[indices[dst]] += transfer;
total += transfer;
}
// evaporate water, deposit sediment
for (size_t i = 0; i < water.area (); ++i) {
water[i] -= EVAPORATION;
height[i] += SOLUBILITY * EVAPORATION;
}
std::cerr << "eroded: " << total << '\n';
}
// forcibly evaporate all remaining water.
CHECK_EQ (water.area (), height.area ());
for (size_t i = 0; i < water.area (); ++i)
height[i] += water[i] * SOLUBILITY;
}
/// talus: maximum desired slope in radians. [0, 90]
/// resistance: proportion of world to keep. [1, 0]
/// scale: horizontal distance scaling factor (relative to vertical)
@ -177,6 +268,7 @@ adjust_ocean (util::image::buffer<float> &height,
static const unsigned THERMAL_ITERATIONS = 10;
static const unsigned HYDRAULIC_ITERATIONS = 100;
int
@ -247,7 +339,12 @@ main (void)
write_map (img, "raw");
auto soft = img.clone ();
std::cerr << "thermal_erosion\n";
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");
thermal_erode (soft, to_radians (30.f), 1.f / size.w, 0.f);
hydraulic_erode (soft, HYDRAULIC_ITERATIONS);
write_map (soft, "soft");
}