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typedef struct {
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HMap *hmap;
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HMap *wmap;
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} Water;
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void waterInit(Water *w, HMap *hmap, HMap *wmap) {
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w->hmap = hmap;
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w->wmap = wmap;
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for(int i = 0; i < HMAP_SIZE; ++i)
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for(int j = 0; j < HMAP_SIZE; ++j)
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w->wmap->map[i][j] = w->hmap->map[i][j];
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}
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void waterRain(Water *w, double k) {
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for(int i = 0; i < HMAP_SIZE; ++i)
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for(int j = 0; j < HMAP_SIZE; ++j)
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w->wmap->map[i][j] += k;
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}
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void waterFall(Water *w, double wk, double hk) {
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static const int di[4] = { -1, 1, 0, 0 };
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static const int dj[4] = { 0, 0, -1, 1 };
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hmapCopy(w->hmap);
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hmapCopy(w->wmap);
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for(int i = 0; i < HMAP_SIZE; ++i) {
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for(int j = 0; j < HMAP_SIZE; ++j) {
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double dz = w->wmap->old[i][j] - w->hmap->old[i][j];
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dz *= 0.25;
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if (dz > 0) {
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double sum = 0;
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double v[4] = {};
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for(int k = 0; k < 4; ++k) {
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int ii = ((i+di[k]) + HMAP_SIZE)%HMAP_SIZE;
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int jj = ((j+dj[k]) + HMAP_SIZE)%HMAP_SIZE;
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double vv = w->wmap->old[i][j] - w->wmap->old[ii][jj];
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if (vv < 0) vv = 0;
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//vv = vv*vv*vv;
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v[k] = vv;
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sum += vv;
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}
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double s = wk*sum;
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if (s > dz) s = dz;
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if (sum > 1e-10) {
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for(int k = 0; k < 4; ++k) {
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int ii = ((i+di[k]) + HMAP_SIZE)%HMAP_SIZE;
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int jj = ((j+dj[k]) + HMAP_SIZE)%HMAP_SIZE;
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double vv = v[k]/sum*s;
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w->wmap->map[ii][jj] += v[k]/sum*s;
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w->wmap->map[i][j] -= vv;
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double dh = w->hmap->old[i][j] - w->hmap->map[ii][jj];
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dh *= 0.25;
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if (dh > 0) {
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vv = vv*hk;
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if (vv > dh) vv = dh;
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w->hmap->map[ii][jj] += vv;
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w->hmap->map[i][j] -= vv;
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}
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}
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}
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}
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}
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}
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}
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double waterEvaporation(Water *w, double k) {
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double sum;
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for(int i = 0; i < HMAP_SIZE; ++i) {
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for(int j = 0; j < HMAP_SIZE; ++j) {
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double dz = w->wmap->map[i][j] - w->hmap->map[i][j];
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if (dz < 0) dz = 0;
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if (dz > k) dz = k;
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sum += dz;
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w->wmap->map[i][j] -= dz;
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}
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}
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return sum;
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}
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void waterCycle(Water *w, double fallK, double erosionK, double evaK) {
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double sum = waterEvaporation(w, evaK);
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waterRain(w, sum/(HMAP_SIZE*HMAP_SIZE));
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for(int i = 0; i < 10; ++i) {
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waterFall(w, fallK/10, erosionK/10);
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printf(".");
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fflush(stdout);
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}
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printf("\n");
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}
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