src/tgp.cpp

   1 /* $Id: tgp.cpp 26056 2013-11-22 21:50:43Z rubidium $ */
   2
   3 /*
   4  * This file is part of OpenTTD.
   5  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
   6  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   7  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
   8  */
   9
  10 /** @file tgp.cpp OTTD Perlin Noise Landscape Generator, aka TerraGenesis Perlin */
  11
  12 #include "stdafx.h"
  13 #include <math.h>
  14 #include "clear_map.h"
  15 #include "void_map.h"
  16 #include "genworld.h"
  17 #include "core/random_func.hpp"
  18 #include "landscape_type.h"
  19
  20 #include "safeguards.h"
  21
  22 /*
  23  *
  24  * Quickie guide to Perlin Noise
  25  * Perlin noise is a predictable pseudo random number sequence. By generating
  26  * it in 2 dimensions, it becomes a useful random map that, for a given seed
  27  * and starting X & Y, is entirely predictable. On the face of it, that may not
  28  * be useful. However, it means that if you want to replay a map in a different
  29  * terrain, or just vary the sea level, you just re-run the generator with the
  30  * same seed. The seed is an int32, and is randomised on each run of New Game.
  31  * The Scenario Generator does not randomise the value, so that you can
  32  * experiment with one terrain until you are happy, or click "Random" for a new
  33  * random seed.
  34  *
  35  * Perlin Noise is a series of "octaves" of random noise added together. By
  36  * reducing the amplitude of the noise with each octave, the first octave of
  37  * noise defines the main terrain sweep, the next the ripples on that, and the
  38  * next the ripples on that. I use 6 octaves, with the amplitude controlled by
  39  * a power ratio, usually known as a persistence or p value. This I vary by the
  40  * smoothness selection, as can be seen in the table below. The closer to 1,
  41  * the more of that octave is added. Each octave is however raised to the power
  42  * of its position in the list, so the last entry in the "smooth" row, 0.35, is
  43  * raised to the power of 6, so can only add 0.001838...  of the amplitude to
  44  * the running total.
  45  *
  46  * In other words; the first p value sets the general shape of the terrain, the
  47  * second sets the major variations to that, ... until finally the smallest
  48  * bumps are added.
  49  *
  50  * Usefully, this routine is totally scaleable; so when 32bpp comes along, the
  51  * terrain can be as bumpy as you like! It is also infinitely expandable; a
  52  * single random seed terrain continues in X & Y as far as you care to
  53  * calculate. In theory, we could use just one seed value, but randomly select
  54  * where in the Perlin XY space we use for the terrain. Personally I prefer
  55  * using a simple (0, 0) to (X, Y), with a varying seed.
  56  *
  57  *
  58  * Other things i have had to do: mountainous wasn't mountainous enough, and
  59  * since we only have 0..15 heights available, I add a second generated map
  60  * (with a modified seed), onto the original. This generally raises the
  61  * terrain, which then needs scaling back down. Overall effect is a general
  62  * uplift.
  63  *
  64  * However, the values on the top of mountains are then almost guaranteed to go
  65  * too high, so large flat plateaus appeared at height 15. To counter this, I
  66  * scale all heights above 12 to proportion up to 15. It still makes the
  67  * mountains have flattish tops, rather than craggy peaks, but at least they
  68  * aren't smooth as glass.
  69  *
  70  *
  71  * For a full discussion of Perlin Noise, please visit:
  72  * http://freespace.virgin.net/hugo.elias/models/m_perlin.htm
  73  *
  74  *
  75  * Evolution II
  76  *
  77  * The algorithm as described in the above link suggests to compute each tile height
  78  * as composition of several noise waves. Some of them are computed directly by
  79  * noise(x, y) function, some are calculated using linear approximation. Our
  80  * first implementation of perlin_noise_2D() used 4 noise(x, y) calls plus
  81  * 3 linear interpolations. It was called 6 times for each tile. This was a bit
  82  * CPU expensive.
  83  *
  84  * The following implementation uses optimized algorithm that should produce
  85  * the same quality result with much less computations, but more memory accesses.
  86  * The overall speedup should be 300% to 800% depending on CPU and memory speed.
  87  *
  88  * I will try to explain it on the example below:
  89  *
  90  * Have a map of 4 x 4 tiles, our simplified noise generator produces only two
  91  * values -1 and +1, use 3 octaves with wave length 1, 2 and 4, with amplitudes
  92  * 3, 2, 1. Original algorithm produces:
  93  *
  94  * h00 = lerp(lerp(-3, 3, 0/4), lerp(3, -3, 0/4), 0/4) + lerp(lerp(-2,  2, 0/2), lerp( 2, -2, 0/2), 0/2) + -1 = lerp(-3.0,  3.0, 0/4) + lerp(-2,  2, 0/2) + -1 = -3.0  + -2 + -1 = -6.0
  95  * h01 = lerp(lerp(-3, 3, 1/4), lerp(3, -3, 1/4), 0/4) + lerp(lerp(-2,  2, 1/2), lerp( 2, -2, 1/2), 0/2) +  1 = lerp(-1.5,  1.5, 0/4) + lerp( 0,  0, 0/2) +  1 = -1.5  +  0 +  1 = -0.5
  96  * h02 = lerp(lerp(-3, 3, 2/4), lerp(3, -3, 2/4), 0/4) + lerp(lerp( 2, -2, 0/2), lerp(-2,  2, 0/2), 0/2) + -1 = lerp(   0,    0, 0/4) + lerp( 2, -2, 0/2) + -1 =    0  +  2 + -1 =  1.0
  97  * h03 = lerp(lerp(-3, 3, 3/4), lerp(3, -3, 3/4), 0/4) + lerp(lerp( 2, -2, 1/2), lerp(-2,  2, 1/2), 0/2) +  1 = lerp( 1.5, -1.5, 0/4) + lerp( 0,  0, 0/2) +  1 =  1.5  +  0 +  1 =  2.5
  98  *
  99  * h10 = lerp(lerp(-3, 3, 0/4), lerp(3, -3, 0/4), 1/4) + lerp(lerp(-2,  2, 0/2), lerp( 2, -2, 0/2), 1/2) +  1 = lerp(-3.0,  3.0, 1/4) + lerp(-2,  2, 1/2) +  1 = -1.5  +  0 +  1 = -0.5
 100  * h11 = lerp(lerp(-3, 3, 1/4), lerp(3, -3, 1/4), 1/4) + lerp(lerp(-2,  2, 1/2), lerp( 2, -2, 1/2), 1/2) + -1 = lerp(-1.5,  1.5, 1/4) + lerp( 0,  0, 1/2) + -1 = -0.75 +  0 + -1 = -1.75
 101  * h12 = lerp(lerp(-3, 3, 2/4), lerp(3, -3, 2/4), 1/4) + lerp(lerp( 2, -2, 0/2), lerp(-2,  2, 0/2), 1/2) +  1 = lerp(   0,    0, 1/4) + lerp( 2, -2, 1/2) +  1 =    0  +  0 +  1 =  1.0
 102  * h13 = lerp(lerp(-3, 3, 3/4), lerp(3, -3, 3/4), 1/4) + lerp(lerp( 2, -2, 1/2), lerp(-2,  2, 1/2), 1/2) + -1 = lerp( 1.5, -1.5, 1/4) + lerp( 0,  0, 1/2) + -1 =  0.75 +  0 + -1 = -0.25
 103  *
 104  *
 105  * Optimization 1:
 106  *
 107  * 1) we need to allocate a bit more tiles: (size_x + 1) * (size_y + 1) = (5 * 5):
 108  *
 109  * 2) setup corner values using amplitude 3
 110  * {    -3.0        X          X          X          3.0   }
 111  * {     X          X          X          X          X     }
 112  * {     X          X          X          X          X     }
 113  * {     X          X          X          X          X     }
 114  * {     3.0        X          X          X         -3.0   }
 115  *
 116  * 3a) interpolate values in the middle
 117  * {    -3.0        X          0.0        X          3.0   }
 118  * {     X          X          X          X          X     }
 119  * {     0.0        X          0.0        X          0.0   }
 120  * {     X          X          X          X          X     }
 121  * {     3.0        X          0.0        X         -3.0   }
 122  *
 123  * 3b) add patches with amplitude 2 to them
 124  * {    -5.0        X          2.0        X          1.0   }
 125  * {     X          X          X          X          X     }
 126  * {     2.0        X         -2.0        X          2.0   }
 127  * {     X          X          X          X          X     }
 128  * {     1.0        X          2.0        X         -5.0   }
 129  *
 130  * 4a) interpolate values in the middle
 131  * {    -5.0       -1.5        2.0        1.5        1.0   }
 132  * {    -1.5       -0.75       0.0        0.75       1.5   }
 133  * {     2.0        0.0       -2.0        0.0        2.0   }
 134  * {     1.5        0.75       0.0       -0.75      -1.5   }
 135  * {     1.0        1.5        2.0       -1.5       -5.0   }
 136  *
 137  * 4b) add patches with amplitude 1 to them
 138  * {    -6.0       -0.5        1.0        2.5        0.0   }
 139  * {    -0.5       -1.75       1.0       -0.25       2.5   }
 140  * {     1.0        1.0       -3.0        1.0        1.0   }
 141  * {     2.5       -0.25       1.0       -1.75      -0.5   }
 142  * {     0.0        2.5        1.0       -0.5       -6.0   }
 143  *
 144  *
 145  *
 146  * Optimization 2:
 147  *
 148  * As you can see above, each noise function was called just once. Therefore
 149  * we don't need to use noise function that calculates the noise from x, y and
 150  * some prime. The same quality result we can obtain using standard Random()
 151  * function instead.
 152  *
 153  */
 154
 155 /** Fixed point type for heights */
 156 typedef int16 height_t;
 157 static const int height_decimal_bits = 4;
 158
 159 /** Fixed point array for amplitudes (and percent values) */
 160 typedef int amplitude_t;
 161 static const int amplitude_decimal_bits = 10;
 162
 163 /** Height map - allocated array of heights (MapSizeX() + 1) x (MapSizeY() + 1) */
 164 struct HeightMap
 165 {
 166         height_t *h;         //< array of heights
 167         /* Even though the sizes are always positive, there are many cases where
 168          * X and Y need to be signed integers due to subtractions. */
 169         int      dim_x;      //< height map size_x MapSizeX() + 1
 170         int      total_size; //< height map total size
 171         int      size_x;     //< MapSizeX()
 172         int      size_y;     //< MapSizeY()
 173
 174         /**
 175          * Height map accessor
 176          * @param x X position
 177          * @param y Y position
 178          * @return height as fixed point number
 179          */
 180         inline height_t &height(uint x, uint y)
 181         {
 182                 return h[x + y * dim_x];
 183         }
 184 };
 185
 186 /** Global height map instance */
 187 static HeightMap _height_map = {NULL, 0, 0, 0, 0};
 188
 189 /** Conversion: int to height_t */
 190 #define I2H(i) ((i) << height_decimal_bits)
 191 /** Conversion: height_t to int */
 192 #define H2I(i) ((i) >> height_decimal_bits)
 193
 194 /** Conversion: int to amplitude_t */
 195 #define I2A(i) ((i) << amplitude_decimal_bits)
 196 /** Conversion: amplitude_t to int */
 197 #define A2I(i) ((i) >> amplitude_decimal_bits)
 198
 199 /** Conversion: amplitude_t to height_t */
 200 #define A2H(a) ((a) >> (amplitude_decimal_bits - height_decimal_bits))
 201
 202
 203 /** Walk through all items of _height_map.h */
 204 #define FOR_ALL_TILES_IN_HEIGHT(h) for (h = _height_map.h; h < &_height_map.h[_height_map.total_size]; h++)
 205
 206 /** Maximum number of TGP noise frequencies. */
 207 static const int MAX_TGP_FREQUENCIES = 10;
 208
 209 /** Desired water percentage (100% == 1024) - indexed by _settings_game.difficulty.quantity_sea_lakes */
 210 static const amplitude_t _water_percent[4] = {70, 170, 270, 420};
 211
 212 /**
 213  * Gets the maximum allowed height while generating a map based on
 214  * mapsize, terraintype, and the maximum height level.
 215  * @return The maximum height for the map generation.
 216  * @note Values should never be lower than 3 since the minimum snowline height is 2.
 217  */
 218 static height_t TGPGetMaxHeight()
 219 {
 220         /**
 221          * Desired maximum height - indexed by:
 222          *  - _settings_game.difficulty.terrain_type
 223          *  - min(MapLogX(), MapLogY()) - MIN_MAP_SIZE_BITS
 224          *
 225          * It is indexed by map size as well as terrain type since the map size limits the height of
 226          * a usable mountain. For example, on a 64x64 map a 24 high single peak mountain (as if you
 227          * raised land 24 times in the center of the map) will leave only a ring of about 10 tiles
 228          * around the mountain to build on. On a 4096x4096 map, it won't cover any major part of the map.
 229          */
 230         static const int max_height[5][MAX_MAP_SIZE_BITS - MIN_MAP_SIZE_BITS + 1] = {
 231                 /* 64  128  256  512 1024 2048 4096 */
 232                 {   3,   3,   3,   3,   4,   5,   7 }, ///< Very flat
 233                 {   5,   7,   8,   9,  14,  19,  31 }, ///< Flat
 234                 {   8,   9,  10,  15,  23,  37,  61 }, ///< Hilly
 235                 {  10,  11,  17,  19,  49,  63,  73 }, ///< Mountainous
 236                 {  12,  19,  25,  31,  67,  75,  87 }, ///< Alpinist
 237         };
 238
 239         int max_height_from_table = max_height[_settings_game.difficulty.terrain_type][min(MapLogX(), MapLogY()) - MIN_MAP_SIZE_BITS];
 240         return I2H(min(max_height_from_table, _settings_game.construction.max_heightlevel));
 241 }
 242
 243 /**
 244  * Get the amplitude associated with the currently selected
 245  * smoothness and maximum height level.
 246  * @param frequency The frequency to get the amplitudes for
 247  * @return The amplitudes to apply to the map.
 248  */
 249 static amplitude_t GetAmplitude(int frequency)
 250 {
 251         /* Base noise amplitudes (multiplied by 1024) and indexed by "smoothness setting" and log2(frequency). */
 252         static const amplitude_t amplitudes[][7] = {
 253                 /* lowest frequency ...... highest (every corner) */
 254                 {16000,  5600,  1968,   688,   240,    16,    16}, ///< Very smooth
 255                 {24000, 12800,  6400,  2700,  1024,   128,    16}, ///< Smooth
 256                 {32000, 19200, 12800,  8000,  3200,   256,    64}, ///< Rough
 257                 {48000, 24000, 19200, 16000,  8000,   512,   320}, ///< Very rough
 258         };
 259         /*
 260          * Extrapolation factors for ranges before the table.
 261          * The extrapolation is needed to account for the higher map heights. They need larger
 262          * areas with a particular gradient so that we are able to create maps without too
 263          * many steep slopes up to the wanted height level. It's definitely not perfect since
 264          * it will bring larger rectangles with similar slopes which makes the rectangular
 265          * behaviour of TGP more noticable. However, these height differentiations cannot
 266          * happen over much smaller areas; we basically double the "range" to give a similar
 267          * slope for every doubling of map height.
 268          */
 269         static const double extrapolation_factors[] = { 3.3, 2.8, 2.3, 1.8 };
 270
 271         int smoothness = _settings_game.game_creation.tgen_smoothness;
 272
 273         /* Get the table index, and return that value if possible. */
 274         int index = frequency - MAX_TGP_FREQUENCIES + lengthof(amplitudes[smoothness]);
 275         amplitude_t amplitude = amplitudes[smoothness][max(0, index)];
 276         if (index >= 0) return amplitude;
 277
 278         /* We need to extrapolate the amplitude. */
 279         double extrapolation_factor = extrapolation_factors[smoothness];
 280         int height_range = I2H(16);
 281         do {
 282                 amplitude = (amplitude_t)(extrapolation_factor * (double)amplitude);
 283                 height_range <<= 1;
 284                 index++;
 285         } while (index < 0);
 286
 287         return Clamp((TGPGetMaxHeight() - height_range) / height_range, 0, 1) * amplitude;
 288 }
 289
 290 /**
 291  * Check if a X/Y set are within the map.
 292  * @param x coordinate x
 293  * @param y coordinate y
 294  * @return true if within the map
 295  */
 296 static inline bool IsValidXY(int x, int y)
 297 {
 298         return x >= 0 && x < _height_map.size_x && y >= 0 && y < _height_map.size_y;
 299 }
 300
 301
 302 /**
 303  * Allocate array of (MapSizeX()+1)*(MapSizeY()+1) heights and init the _height_map structure members
 304  * @return true on success
 305  */
 306 static inline bool AllocHeightMap()
 307 {
 308         height_t *h;
 309
 310         _height_map.size_x = MapSizeX();
 311         _height_map.size_y = MapSizeY();
 312
 313         /* Allocate memory block for height map row pointers */
 314         _height_map.total_size = (_height_map.size_x + 1) * (_height_map.size_y + 1);
 315         _height_map.dim_x = _height_map.size_x + 1;
 316         _height_map.h = CallocT<height_t>(_height_map.total_size);
 317
 318         /* Iterate through height map and initialise values. */
 319         FOR_ALL_TILES_IN_HEIGHT(h) *h = 0;
 320
 321         return true;
 322 }
 323
 324 /** Free height map */
 325 static inline void FreeHeightMap()
 326 {
 327         free(_height_map.h);
 328         _height_map.h = NULL;
 329 }
 330
 331 /**
 332  * Generates new random height in given amplitude (generated numbers will range from - amplitude to + amplitude)
 333  * @param rMax Limit of result
 334  * @return generated height
 335  */
 336 static inline height_t RandomHeight(amplitude_t rMax)
 337 {
 338         /* Spread height into range -rMax..+rMax */
 339         return A2H(RandomRange(2 * rMax + 1) - rMax);
 340 }
 341
 342 /**
 343  * Base Perlin noise generator - fills height map with raw Perlin noise.
 344  *
 345  * This runs several iterations with increasing precision; the last iteration looks at areas
 346  * of 1 by 1 tiles, the second to last at 2 by 2 tiles and the initial 2**MAX_TGP_FREQUENCIES
 347  * by 2**MAX_TGP_FREQUENCIES tiles.
 348  */
 349 static void HeightMapGenerate()
 350 {
 351         /* Trying to apply noise to uninitialized height map */
 352         assert(_height_map.h != NULL);
 353
 354         int start = max(MAX_TGP_FREQUENCIES - (int)min(MapLogX(), MapLogY()), 0);
 355         bool first = true;
 356
 357         for (int frequency = start; frequency < MAX_TGP_FREQUENCIES; frequency++) {
 358                 const amplitude_t amplitude = GetAmplitude(frequency);
 359
 360                 /* Ignore zero amplitudes; it means our map isn't height enough for this
 361                  * amplitude, so ignore it and continue with the next set of amplitude. */
 362                 if (amplitude == 0) continue;
 363
 364                 const int step = 1 << (MAX_TGP_FREQUENCIES - frequency - 1);
 365
 366                 if (first) {
 367                         /* This is first round, we need to establish base heights with step = size_min */
 368                         for (int y = 0; y <= _height_map.size_y; y += step) {
 369                                 for (int x = 0; x <= _height_map.size_x; x += step) {
 370                                         height_t height = (amplitude > 0) ? RandomHeight(amplitude) : 0;
 371                                         _height_map.height(x, y) = height;
 372                                 }
 373                         }
 374                         first = false;
 375                         continue;
 376                 }
 377
 378                 /* It is regular iteration round.
 379                  * Interpolate height values at odd x, even y tiles */
 380                 for (int y = 0; y <= _height_map.size_y; y += 2 * step) {
 381                         for (int x = 0; x <= _height_map.size_x - 2 * step; x += 2 * step) {
 382                                 height_t h00 = _height_map.height(x + 0 * step, y);
 383                                 height_t h02 = _height_map.height(x + 2 * step, y);
 384                                 height_t h01 = (h00 + h02) / 2;
 385                                 _height_map.height(x + 1 * step, y) = h01;
 386                         }
 387                 }
 388
 389                 /* Interpolate height values at odd y tiles */
 390                 for (int y = 0; y <= _height_map.size_y - 2 * step; y += 2 * step) {
 391                         for (int x = 0; x <= _height_map.size_x; x += step) {
 392                                 height_t h00 = _height_map.height(x, y + 0 * step);
 393                                 height_t h20 = _height_map.height(x, y + 2 * step);
 394                                 height_t h10 = (h00 + h20) / 2;
 395                                 _height_map.height(x, y + 1 * step) = h10;
 396                         }
 397                 }
 398
 399                 /* Add noise for next higher frequency (smaller steps) */
 400                 for (int y = 0; y <= _height_map.size_y; y += step) {
 401                         for (int x = 0; x <= _height_map.size_x; x += step) {
 402                                 _height_map.height(x, y) += RandomHeight(amplitude);
 403                         }
 404                 }
 405         }
 406 }
 407
 408 /** Returns min, max and average height from height map */
 409 static void HeightMapGetMinMaxAvg(height_t *min_ptr, height_t *max_ptr, height_t *avg_ptr)
 410 {
 411         height_t h_min, h_max, h_avg, *h;
 412         int64 h_accu = 0;
 413         h_min = h_max = _height_map.height(0, 0);
 414
 415         /* Get h_min, h_max and accumulate heights into h_accu */
 416         FOR_ALL_TILES_IN_HEIGHT(h) {
 417                 if (*h < h_min) h_min = *h;
 418                 if (*h > h_max) h_max = *h;
 419                 h_accu += *h;
 420         }
 421
 422         /* Get average height */
 423         h_avg = (height_t)(h_accu / (_height_map.size_x * _height_map.size_y));
 424
 425         /* Return required results */
 426         if (min_ptr != NULL) *min_ptr = h_min;
 427         if (max_ptr != NULL) *max_ptr = h_max;
 428         if (avg_ptr != NULL) *avg_ptr = h_avg;
 429 }
 430
 431 /** Dill histogram and return pointer to its base point - to the count of zero heights */
 432 static int *HeightMapMakeHistogram(height_t h_min, height_t h_max, int *hist_buf)
 433 {
 434         int *hist = hist_buf - h_min;
 435         height_t *h;
 436
 437         /* Count the heights and fill the histogram */
 438         FOR_ALL_TILES_IN_HEIGHT(h) {
 439                 assert(*h >= h_min);
 440                 assert(*h <= h_max);
 441                 hist[*h]++;
 442         }
 443         return hist;
 444 }
 445
 446 /** Applies sine wave redistribution onto height map */
 447 static void HeightMapSineTransform(height_t h_min, height_t h_max)
 448 {
 449         height_t *h;
 450
 451         FOR_ALL_TILES_IN_HEIGHT(h) {
 452                 double fheight;
 453
 454                 if (*h < h_min) continue;
 455
 456                 /* Transform height into 0..1 space */
 457                 fheight = (double)(*h - h_min) / (double)(h_max - h_min);
 458                 /* Apply sine transform depending on landscape type */
 459                 switch (_settings_game.game_creation.landscape) {
 460                         case LT_TOYLAND:
 461                         case LT_TEMPERATE:
 462                                 /* Move and scale 0..1 into -1..+1 */
 463                                 fheight = 2 * fheight - 1;
 464                                 /* Sine transform */
 465                                 fheight = sin(fheight * M_PI_2);
 466                                 /* Transform it back from -1..1 into 0..1 space */
 467                                 fheight = 0.5 * (fheight + 1);
 468                                 break;
 469
 470                         case LT_ARCTIC:
 471                                 {
 472                                         /* Arctic terrain needs special height distribution.
 473                                          * Redistribute heights to have more tiles at highest (75%..100%) range */
 474                                         double sine_upper_limit = 0.75;
 475                                         double linear_compression = 2;
 476                                         if (fheight >= sine_upper_limit) {
 477                                                 /* Over the limit we do linear compression up */
 478                                                 fheight = 1.0 - (1.0 - fheight) / linear_compression;
 479                                         } else {
 480                                                 double m = 1.0 - (1.0 - sine_upper_limit) / linear_compression;
 481                                                 /* Get 0..sine_upper_limit into -1..1 */
 482                                                 fheight = 2.0 * fheight / sine_upper_limit - 1.0;
 483                                                 /* Sine wave transform */
 484                                                 fheight = sin(fheight * M_PI_2);
 485                                                 /* Get -1..1 back to 0..(1 - (1 - sine_upper_limit) / linear_compression) == 0.0..m */
 486                                                 fheight = 0.5 * (fheight + 1.0) * m;
 487                                         }
 488                                 }
 489                                 break;
 490
 491                         case LT_TROPIC:
 492                                 {
 493                                         /* Desert terrain needs special height distribution.
 494                                          * Half of tiles should be at lowest (0..25%) heights */
 495                                         double sine_lower_limit = 0.5;
 496                                         double linear_compression = 2;
 497                                         if (fheight <= sine_lower_limit) {
 498                                                 /* Under the limit we do linear compression down */
 499                                                 fheight = fheight / linear_compression;
 500                                         } else {
 501                                                 double m = sine_lower_limit / linear_compression;
 502                                                 /* Get sine_lower_limit..1 into -1..1 */
 503                                                 fheight = 2.0 * ((fheight - sine_lower_limit) / (1.0 - sine_lower_limit)) - 1.0;
 504                                                 /* Sine wave transform */
 505                                                 fheight = sin(fheight * M_PI_2);
 506                                                 /* Get -1..1 back to (sine_lower_limit / linear_compression)..1.0 */
 507                                                 fheight = 0.5 * ((1.0 - m) * fheight + (1.0 + m));
 508                                         }
 509                                 }
 510                                 break;
 511
 512                         default:
 513                                 NOT_REACHED();
 514                                 break;
 515                 }
 516                 /* Transform it back into h_min..h_max space */
 517                 *h = (height_t)(fheight * (h_max - h_min) + h_min);
 518                 if (*h < 0) *h = I2H(0);
 519                 if (*h >= h_max) *h = h_max - 1;
 520         }
 521 }
 522
 523 /**
 524  * Additional map variety is provided by applying different curve maps
 525  * to different parts of the map. A randomized low resolution grid contains
 526  * which curve map to use on each part of the make. This filtered non-linearly
 527  * to smooth out transitions between curves, so each tile could have between
 528  * 100% of one map applied or 25% of four maps.
 529  *
 530  * The curve maps define different land styles, i.e. lakes, low-lands, hills
 531  * and mountain ranges, although these are dependent on the landscape style
 532  * chosen as well.
 533  *
 534  * The level parameter dictates the resolution of the grid. A low resolution
 535  * grid will result in larger continuous areas of a land style, a higher
 536  * resolution grid splits the style into smaller areas.
 537  * @param level Rough indication of the size of the grid sections to style. Small level means large grid sections.
 538  */
 539 static void HeightMapCurves(uint level)
 540 {
 541         height_t mh = TGPGetMaxHeight() - I2H(1); // height levels above sea level only
 542
 543         /** Basically scale height X to height Y. Everything in between is interpolated. */
 544         struct control_point_t {
 545                 height_t x; ///< The height to scale from.
 546                 height_t y; ///< The height to scale to.
 547         };
 548         /* Scaled curve maps; value is in height_ts. */
 549 #define F(fraction) ((height_t)(fraction * mh))
 550         const control_point_t curve_map_1[] = { { F(0.0), F(0.0) },                       { F(0.8), F(0.13) },                       { F(1.0), F(0.4)  } };
 551         const control_point_t curve_map_2[] = { { F(0.0), F(0.0) }, { F(0.53), F(0.13) }, { F(0.8), F(0.27) },                       { F(1.0), F(0.6)  } };
 552         const control_point_t curve_map_3[] = { { F(0.0), F(0.0) }, { F(0.53), F(0.27) }, { F(0.8), F(0.57) },                       { F(1.0), F(0.8)  } };
 553         const control_point_t curve_map_4[] = { { F(0.0), F(0.0) }, { F(0.4),  F(0.3)  }, { F(0.7), F(0.8)  }, { F(0.92), F(0.99) }, { F(1.0), F(0.99) } };
 554 #undef F
 555
 556         /** Helper structure to index the different curve maps. */
 557         struct control_point_list_t {
 558                 size_t length;               ///< The length of the curve map.
 559                 const control_point_t *list; ///< The actual curve map.
 560         };
 561         const control_point_list_t curve_maps[] = {
 562                 { lengthof(curve_map_1), curve_map_1 },
 563                 { lengthof(curve_map_2), curve_map_2 },
 564                 { lengthof(curve_map_3), curve_map_3 },
 565                 { lengthof(curve_map_4), curve_map_4 },
 566         };
 567
 568         height_t ht[lengthof(curve_maps)];
 569         MemSetT(ht, 0, lengthof(ht));
 570
 571         /* Set up a grid to choose curve maps based on location; attempt to get a somewhat square grid */
 572         float factor = sqrt((float)_height_map.size_x / (float)_height_map.size_y);
 573         uint sx = Clamp((int)(((1 << level) * factor) + 0.5), 1, 128);
 574         uint sy = Clamp((int)(((1 << level) / factor) + 0.5), 1, 128);
 575         byte *c = AllocaM(byte, sx * sy);
 576
 577         for (uint i = 0; i < sx * sy; i++) {
 578                 c[i] = Random() % lengthof(curve_maps);
 579         }
 580
 581         /* Apply curves */
 582         for (int x = 0; x < _height_map.size_x; x++) {
 583
 584                 /* Get our X grid positions and bi-linear ratio */
 585                 float fx = (float)(sx * x) / _height_map.size_x + 1.0f;
 586                 uint x1 = (uint)fx;
 587                 uint x2 = x1;
 588                 float xr = 2.0f * (fx - x1) - 1.0f;
 589                 xr = sin(xr * M_PI_2);
 590                 xr = sin(xr * M_PI_2);
 591                 xr = 0.5f * (xr + 1.0f);
 592                 float xri = 1.0f - xr;
 593
 594                 if (x1 > 0) {
 595                         x1--;
 596                         if (x2 >= sx) x2--;
 597                 }
 598
 599                 for (int y = 0; y < _height_map.size_y; y++) {
 600
 601                         /* Get our Y grid position and bi-linear ratio */
 602                         float fy = (float)(sy * y) / _height_map.size_y + 1.0f;
 603                         uint y1 = (uint)fy;
 604                         uint y2 = y1;
 605                         float yr = 2.0f * (fy - y1) - 1.0f;
 606                         yr = sin(yr * M_PI_2);
 607                         yr = sin(yr * M_PI_2);
 608                         yr = 0.5f * (yr + 1.0f);
 609                         float yri = 1.0f - yr;
 610
 611                         if (y1 > 0) {
 612                                 y1--;
 613                                 if (y2 >= sy) y2--;
 614                         }
 615
 616                         uint corner_a = c[x1 + sx * y1];
 617                         uint corner_b = c[x1 + sx * y2];
 618                         uint corner_c = c[x2 + sx * y1];
 619                         uint corner_d = c[x2 + sx * y2];
 620
 621                         /* Bitmask of which curve maps are chosen, so that we do not bother
 622                          * calculating a curve which won't be used. */
 623                         uint corner_bits = 0;
 624                         corner_bits |= 1 << corner_a;
 625                         corner_bits |= 1 << corner_b;
 626                         corner_bits |= 1 << corner_c;
 627                         corner_bits |= 1 << corner_d;
 628
 629                         height_t *h = &_height_map.height(x, y);
 630
 631                         /* Do not touch sea level */
 632                         if (*h < I2H(1)) continue;
 633
 634                         /* Only scale above sea level */
 635                         *h -= I2H(1);
 636
 637                         /* Apply all curve maps that are used on this tile. */
 638                         for (uint t = 0; t < lengthof(curve_maps); t++) {
 639                                 if (!HasBit(corner_bits, t)) continue;
 640
 641                                 bool found = false;
 642                                 const control_point_t *cm = curve_maps[t].list;
 643                                 for (uint i = 0; i < curve_maps[t].length - 1; i++) {
 644                                         const control_point_t &p1 = cm[i];
 645                                         const control_point_t &p2 = cm[i + 1];
 646
 647                                         if (*h >= p1.x && *h < p2.x) {
 648                                                 ht[t] = p1.y + (*h - p1.x) * (p2.y - p1.y) / (p2.x - p1.x);
 649                                                 found = true;
 650                                                 break;
 651                                         }
 652                                 }
 653                                 assert(found);
 654                         }
 655
 656                         /* Apply interpolation of curve map results. */
 657                         *h = (height_t)((ht[corner_a] * yri + ht[corner_b] * yr) * xri + (ht[corner_c] * yri + ht[corner_d] * yr) * xr);
 658
 659                         /* Readd sea level */
 660                         *h += I2H(1);
 661                 }
 662         }
 663 }
 664
 665 /** Adjusts heights in height map to contain required amount of water tiles */
 666 static void HeightMapAdjustWaterLevel(amplitude_t water_percent, height_t h_max_new)
 667 {
 668         height_t h_min, h_max, h_avg, h_water_level;
 669         int64 water_tiles, desired_water_tiles;
 670         height_t *h;
 671         int *hist;
 672
 673         HeightMapGetMinMaxAvg(&h_min, &h_max, &h_avg);
 674
 675         /* Allocate histogram buffer and clear its cells */
 676         int *hist_buf = CallocT<int>(h_max - h_min + 1);
 677         /* Fill histogram */
 678         hist = HeightMapMakeHistogram(h_min, h_max, hist_buf);
 679
 680         /* How many water tiles do we want? */
 681         desired_water_tiles = A2I(((int64)water_percent) * (int64)(_height_map.size_x * _height_map.size_y));
 682
 683         /* Raise water_level and accumulate values from histogram until we reach required number of water tiles */
 684         for (h_water_level = h_min, water_tiles = 0; h_water_level < h_max; h_water_level++) {
 685                 water_tiles += hist[h_water_level];
 686                 if (water_tiles >= desired_water_tiles) break;
 687         }
 688
 689         /* We now have the proper water level value.
 690          * Transform the height map into new (normalized) height map:
 691          *   values from range: h_min..h_water_level will become negative so it will be clamped to 0
 692          *   values from range: h_water_level..h_max are transformed into 0..h_max_new
 693          *   where h_max_new is depending on terrain type and map size.
 694          */
 695         FOR_ALL_TILES_IN_HEIGHT(h) {
 696                 /* Transform height from range h_water_level..h_max into 0..h_max_new range */
 697                 *h = (height_t)(((int)h_max_new) * (*h - h_water_level) / (h_max - h_water_level)) + I2H(1);
 698                 /* Make sure all values are in the proper range (0..h_max_new) */
 699                 if (*h < 0) *h = I2H(0);
 700                 if (*h >= h_max_new) *h = h_max_new - 1;
 701         }
 702
 703         free(hist_buf);
 704 }
 705
 706 static double perlin_coast_noise_2D(const double x, const double y, const double p, const int prime);
 707
 708 /**
 709  * This routine sculpts in from the edge a random amount, again a Perlin
 710  * sequence, to avoid the rigid flat-edge slopes that were present before. The
 711  * Perlin noise map doesn't know where we are going to slice across, and so we
 712  * often cut straight through high terrain. The smoothing routine makes it
 713  * legal, gradually increasing up from the edge to the original terrain height.
 714  * By cutting parts of this away, it gives a far more irregular edge to the
 715  * map-edge. Sometimes it works beautifully with the existing sea & lakes, and
 716  * creates a very realistic coastline. Other times the variation is less, and
 717  * the map-edge shows its cliff-like roots.
 718  *
 719  * This routine may be extended to randomly sculpt the height of the terrain
 720  * near the edge. This will have the coast edge at low level (1-3), rising in
 721  * smoothed steps inland to about 15 tiles in. This should make it look as
 722  * though the map has been built for the map size, rather than a slice through
 723  * a larger map.
 724  *
 725  * Please note that all the small numbers; 53, 101, 167, etc. are small primes
 726  * to help give the perlin noise a bit more of a random feel.
 727  */
 728 static void HeightMapCoastLines(uint8 water_borders)
 729 {
 730         int smallest_size = min(_settings_game.game_creation.map_x, _settings_game.game_creation.map_y);
 731         const int margin = 4;
 732         int y, x;
 733         double max_x;
 734         double max_y;
 735
 736         /* Lower to sea level */
 737         for (y = 0; y <= _height_map.size_y; y++) {
 738                 if (HasBit(water_borders, BORDER_NE)) {
 739                         /* Top right */
 740                         max_x = abs((perlin_coast_noise_2D(_height_map.size_y - y, y, 0.9, 53) + 0.25) * 5 + (perlin_coast_noise_2D(y, y, 0.35, 179) + 1) * 12);
 741                         max_x = max((smallest_size * smallest_size / 64) + max_x, (smallest_size * smallest_size / 64) + margin - max_x);
 742                         if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
 743                         for (x = 0; x < max_x; x++) {
 744                                 _height_map.height(x, y) = 0;
 745                         }
 746                 }
 747
 748                 if (HasBit(water_borders, BORDER_SW)) {
 749                         /* Bottom left */
 750                         max_x = abs((perlin_coast_noise_2D(_height_map.size_y - y, y, 0.85, 101) + 0.3) * 6 + (perlin_coast_noise_2D(y, y, 0.45,  67) + 0.75) * 8);
 751                         max_x = max((smallest_size * smallest_size / 64) + max_x, (smallest_size * smallest_size / 64) + margin - max_x);
 752                         if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
 753                         for (x = _height_map.size_x; x > (_height_map.size_x - 1 - max_x); x--) {
 754                                 _height_map.height(x, y) = 0;
 755                         }
 756                 }
 757         }
 758
 759         /* Lower to sea level */
 760         for (x = 0; x <= _height_map.size_x; x++) {
 761                 if (HasBit(water_borders, BORDER_NW)) {
 762                         /* Top left */
 763                         max_y = abs((perlin_coast_noise_2D(x, _height_map.size_y / 2, 0.9, 167) + 0.4) * 5 + (perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.4, 211) + 0.7) * 9);
 764                         max_y = max((smallest_size * smallest_size / 64) + max_y, (smallest_size * smallest_size / 64) + margin - max_y);
 765                         if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
 766                         for (y = 0; y < max_y; y++) {
 767                                 _height_map.height(x, y) = 0;
 768                         }
 769                 }
 770
 771                 if (HasBit(water_borders, BORDER_SE)) {
 772                         /* Bottom right */
 773                         max_y = abs((perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.85, 71) + 0.25) * 6 + (perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.35, 193) + 0.75) * 12);
 774                         max_y = max((smallest_size * smallest_size / 64) + max_y, (smallest_size * smallest_size / 64) + margin - max_y);
 775                         if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
 776                         for (y = _height_map.size_y; y > (_height_map.size_y - 1 - max_y); y--) {
 777                                 _height_map.height(x, y) = 0;
 778                         }
 779                 }
 780         }
 781 }
 782
 783 /** Start at given point, move in given direction, find and Smooth coast in that direction */
 784 static void HeightMapSmoothCoastInDirection(int org_x, int org_y, int dir_x, int dir_y)
 785 {
 786         const int max_coast_dist_from_edge = 35;
 787         const int max_coast_Smooth_depth = 35;
 788
 789         int x, y;
 790         int ed; // coast distance from edge
 791         int depth;
 792
 793         height_t h_prev = I2H(1);
 794         height_t h;
 795
 796         assert(IsValidXY(org_x, org_y));
 797
 798         /* Search for the coast (first non-water tile) */
 799         for (x = org_x, y = org_y, ed = 0; IsValidXY(x, y) && ed < max_coast_dist_from_edge; x += dir_x, y += dir_y, ed++) {
 800                 /* Coast found? */
 801                 if (_height_map.height(x, y) >= I2H(1)) break;
 802
 803                 /* Coast found in the neighborhood? */
 804                 if (IsValidXY(x + dir_y, y + dir_x) && _height_map.height(x + dir_y, y + dir_x) > 0) break;
 805
 806                 /* Coast found in the neighborhood on the other side */
 807                 if (IsValidXY(x - dir_y, y - dir_x) && _height_map.height(x - dir_y, y - dir_x) > 0) break;
 808         }
 809
 810         /* Coast found or max_coast_dist_from_edge has been reached.
 811          * Soften the coast slope */
 812         for (depth = 0; IsValidXY(x, y) && depth <= max_coast_Smooth_depth; depth++, x += dir_x, y += dir_y) {
 813                 h = _height_map.height(x, y);
 814                 h = min(h, h_prev + (4 + depth)); // coast softening formula
 815                 _height_map.height(x, y) = h;
 816                 h_prev = h;
 817         }
 818 }
 819
 820 /** Smooth coasts by modulating height of tiles close to map edges with cosine of distance from edge */
 821 static void HeightMapSmoothCoasts(uint8 water_borders)
 822 {
 823         int x, y;
 824         /* First Smooth NW and SE coasts (y close to 0 and y close to size_y) */
 825         for (x = 0; x < _height_map.size_x; x++) {
 826                 if (HasBit(water_borders, BORDER_NW)) HeightMapSmoothCoastInDirection(x, 0, 0, 1);
 827                 if (HasBit(water_borders, BORDER_SE)) HeightMapSmoothCoastInDirection(x, _height_map.size_y - 1, 0, -1);
 828         }
 829         /* First Smooth NE and SW coasts (x close to 0 and x close to size_x) */
 830         for (y = 0; y < _height_map.size_y; y++) {
 831                 if (HasBit(water_borders, BORDER_NE)) HeightMapSmoothCoastInDirection(0, y, 1, 0);
 832                 if (HasBit(water_borders, BORDER_SW)) HeightMapSmoothCoastInDirection(_height_map.size_x - 1, y, -1, 0);
 833         }
 834 }
 835
 836 /**
 837  * This routine provides the essential cleanup necessary before OTTD can
 838  * display the terrain. When generated, the terrain heights can jump more than
 839  * one level between tiles. This routine smooths out those differences so that
 840  * the most it can change is one level. When OTTD can support cliffs, this
 841  * routine may not be necessary.
 842  */
 843 static void HeightMapSmoothSlopes(height_t dh_max)
 844 {
 845         for (int y = 0; y <= (int)_height_map.size_y; y++) {
 846                 for (int x = 0; x <= (int)_height_map.size_x; x++) {
 847                         height_t h_max = min(_height_map.height(x > 0 ? x - 1 : x, y), _height_map.height(x, y > 0 ? y - 1 : y)) + dh_max;
 848                         if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 849                 }
 850         }
 851         for (int y = _height_map.size_y; y >= 0; y--) {
 852                 for (int x = _height_map.size_x; x >= 0; x--) {
 853                         height_t h_max = min(_height_map.height(x < _height_map.size_x ? x + 1 : x, y), _height_map.height(x, y < _height_map.size_y ? y + 1 : y)) + dh_max;
 854                         if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 855                 }
 856         }
 857 }
 858
 859 /**
 860  * Height map terraform post processing:
 861  *  - water level adjusting
 862  *  - coast Smoothing
 863  *  - slope Smoothing
 864  *  - height histogram redistribution by sine wave transform
 865  */
 866 static void HeightMapNormalize()
 867 {
 868         int sea_level_setting = _settings_game.difficulty.quantity_sea_lakes;
 869         const amplitude_t water_percent = sea_level_setting != (int)CUSTOM_SEA_LEVEL_NUMBER_DIFFICULTY ? _water_percent[sea_level_setting] : _settings_game.game_creation.custom_sea_level * 1024 / 100;
 870         const height_t h_max_new = TGPGetMaxHeight();
 871         const height_t roughness = 7 + 3 * _settings_game.game_creation.tgen_smoothness;
 872
 873         HeightMapAdjustWaterLevel(water_percent, h_max_new);
 874
 875         byte water_borders = _settings_game.construction.freeform_edges ? _settings_game.game_creation.water_borders : 0xF;
 876         if (water_borders == BORDERS_RANDOM) water_borders = GB(Random(), 0, 4);
 877
 878         HeightMapCoastLines(water_borders);
 879         HeightMapSmoothSlopes(roughness);
 880
 881         HeightMapSmoothCoasts(water_borders);
 882         HeightMapSmoothSlopes(roughness);
 883
 884         HeightMapSineTransform(I2H(1), h_max_new);
 885
 886         if (_settings_game.game_creation.variety > 0) {
 887                 HeightMapCurves(_settings_game.game_creation.variety);
 888         }
 889
 890         HeightMapSmoothSlopes(I2H(1));
 891 }
 892
 893 /**
 894  * The Perlin Noise calculation using large primes
 895  * The initial number is adjusted by two values; the generation_seed, and the
 896  * passed parameter; prime.
 897  * prime is used to allow the perlin noise generator to create useful random
 898  * numbers from slightly different series.
 899  */
 900 static double int_noise(const long x, const long y, const int prime)
 901 {
 902         long n = x + y * prime + _settings_game.game_creation.generation_seed;
 903
 904         n = (n << 13) ^ n;
 905
 906         /* Pseudo-random number generator, using several large primes */
 907         return 1.0 - (double)((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0;
 908 }
 909
 910
 911 /**
 912  * This routine determines the interpolated value between a and b
 913  */
 914 static inline double linear_interpolate(const double a, const double b, const double x)
 915 {
 916         return a + x * (b - a);
 917 }
 918
 919
 920 /**
 921  * This routine returns the smoothed interpolated noise for an x and y, using
 922  * the values from the surrounding positions.
 923  */
 924 static double interpolated_noise(const double x, const double y, const int prime)
 925 {
 926         const int integer_X = (int)x;
 927         const int integer_Y = (int)y;
 928
 929         const double fractional_X = x - (double)integer_X;
 930         const double fractional_Y = y - (double)integer_Y;
 931
 932         const double v1 = int_noise(integer_X,     integer_Y,     prime);
 933         const double v2 = int_noise(integer_X + 1, integer_Y,     prime);
 934         const double v3 = int_noise(integer_X,     integer_Y + 1, prime);
 935         const double v4 = int_noise(integer_X + 1, integer_Y + 1, prime);
 936
 937         const double i1 = linear_interpolate(v1, v2, fractional_X);
 938         const double i2 = linear_interpolate(v3, v4, fractional_X);
 939
 940         return linear_interpolate(i1, i2, fractional_Y);
 941 }
 942
 943
 944 /**
 945  * This is a similar function to the main perlin noise calculation, but uses
 946  * the value p passed as a parameter rather than selected from the predefined
 947  * sequences. as you can guess by its title, i use this to create the indented
 948  * coastline, which is just another perlin sequence.
 949  */
 950 static double perlin_coast_noise_2D(const double x, const double y, const double p, const int prime)
 951 {
 952         double total = 0.0;
 953
 954         for (int i = 0; i < 6; i++) {
 955                 const double frequency = (double)(1 << i);
 956                 const double amplitude = pow(p, (double)i);
 957
 958                 total += interpolated_noise((x * frequency) / 64.0, (y * frequency) / 64.0, prime) * amplitude;
 959         }
 960
 961         return total;
 962 }
 963
 964
 965 /** A small helper function to initialize the terrain */
 966 static void TgenSetTileHeight(TileIndex tile, int height)
 967 {
 968         SetTileHeight(tile, height);
 969
 970         /* Only clear the tiles within the map area. */
 971         if (IsInnerTile(tile)) {
 972                 MakeClear(tile, CLEAR_GRASS, 3);
 973         }
 974 }
 975
 976 /**
 977  * The main new land generator using Perlin noise. Desert landscape is handled
 978  * different to all others to give a desert valley between two high mountains.
 979  * Clearly if a low height terrain (flat/very flat) is chosen, then the tropic
 980  * areas wont be high enough, and there will be very little tropic on the map.
 981  * Thus Tropic works best on Hilly or Mountainous.
 982  */
 983 void GenerateTerrainPerlin()
 984 {
 985         if (!AllocHeightMap()) return;
 986         GenerateWorldSetAbortCallback(FreeHeightMap);
 987
 988         HeightMapGenerate();
 989
 990         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
 991
 992         HeightMapNormalize();
 993
 994         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
 995
 996         /* First make sure the tiles at the north border are void tiles if needed. */
 997         if (_settings_game.construction.freeform_edges) {
 998                 for (int y = 0; y < _height_map.size_y - 1; y++) MakeVoid(_height_map.size_x * y);
 999                 for (int x = 0; x < _height_map.size_x;     x++) MakeVoid(x);
1000         }
1001
1002         int max_height = H2I(TGPGetMaxHeight());
1003
1004         /* Transfer height map into OTTD map */
1005         for (int y = 0; y < _height_map.size_y; y++) {
1006                 for (int x = 0; x < _height_map.size_x; x++) {
1007                         TgenSetTileHeight(TileXY(x, y), Clamp(H2I(_height_map.height(x, y)), 0, max_height));
1008                 }
1009         }
1010
1011         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
1012
1013         FreeHeightMap();
1014         GenerateWorldSetAbortCallback(NULL);
1015 }