src/tgp.cpp

   1 /*
   2  * This file is part of OpenTTD.
   3  * 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.
   4  * 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.
   5  * 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/>.
   6  */
   7
   8 /** @file tgp.cpp OTTD Perlin Noise Landscape Generator, aka TerraGenesis Perlin */
   9
  10 #include "stdafx.h"
  11 #include <math.h>
  12 #include "clear_map.h"
  13 #include "void_map.h"
  14 #include "genworld.h"
  15 #include "core/random_func.hpp"
  16 #include "landscape_type.h"
  17
  18 #include "safeguards.h"
  19
  20 /*
  21  *
  22  * Quickie guide to Perlin Noise
  23  * Perlin noise is a predictable pseudo random number sequence. By generating
  24  * it in 2 dimensions, it becomes a useful random map that, for a given seed
  25  * and starting X & Y, is entirely predictable. On the face of it, that may not
  26  * be useful. However, it means that if you want to replay a map in a different
  27  * terrain, or just vary the sea level, you just re-run the generator with the
  28  * same seed. The seed is an int32, and is randomised on each run of New Game.
  29  * The Scenario Generator does not randomise the value, so that you can
  30  * experiment with one terrain until you are happy, or click "Random" for a new
  31  * random seed.
  32  *
  33  * Perlin Noise is a series of "octaves" of random noise added together. By
  34  * reducing the amplitude of the noise with each octave, the first octave of
  35  * noise defines the main terrain sweep, the next the ripples on that, and the
  36  * next the ripples on that. I use 6 octaves, with the amplitude controlled by
  37  * a power ratio, usually known as a persistence or p value. This I vary by the
  38  * smoothness selection, as can be seen in the table below. The closer to 1,
  39  * the more of that octave is added. Each octave is however raised to the power
  40  * of its position in the list, so the last entry in the "smooth" row, 0.35, is
  41  * raised to the power of 6, so can only add 0.001838...  of the amplitude to
  42  * the running total.
  43  *
  44  * In other words; the first p value sets the general shape of the terrain, the
  45  * second sets the major variations to that, ... until finally the smallest
  46  * bumps are added.
  47  *
  48  * Usefully, this routine is totally scalable; so when 32bpp comes along, the
  49  * terrain can be as bumpy as you like! It is also infinitely expandable; a
  50  * single random seed terrain continues in X & Y as far as you care to
  51  * calculate. In theory, we could use just one seed value, but randomly select
  52  * where in the Perlin XY space we use for the terrain. Personally I prefer
  53  * using a simple (0, 0) to (X, Y), with a varying seed.
  54  *
  55  *
  56  * Other things i have had to do: mountainous wasn't mountainous enough, and
  57  * since we only have 0..15 heights available, I add a second generated map
  58  * (with a modified seed), onto the original. This generally raises the
  59  * terrain, which then needs scaling back down. Overall effect is a general
  60  * uplift.
  61  *
  62  * However, the values on the top of mountains are then almost guaranteed to go
  63  * too high, so large flat plateaus appeared at height 15. To counter this, I
  64  * scale all heights above 12 to proportion up to 15. It still makes the
  65  * mountains have flattish tops, rather than craggy peaks, but at least they
  66  * aren't smooth as glass.
  67  *
  68  *
  69  * For a full discussion of Perlin Noise, please visit:
  70  * http://freespace.virgin.net/hugo.elias/models/m_perlin.htm
  71  *
  72  *
  73  * Evolution II
  74  *
  75  * The algorithm as described in the above link suggests to compute each tile height
  76  * as composition of several noise waves. Some of them are computed directly by
  77  * noise(x, y) function, some are calculated using linear approximation. Our
  78  * first implementation of perlin_noise_2D() used 4 noise(x, y) calls plus
  79  * 3 linear interpolations. It was called 6 times for each tile. This was a bit
  80  * CPU expensive.
  81  *
  82  * The following implementation uses optimized algorithm that should produce
  83  * the same quality result with much less computations, but more memory accesses.
  84  * The overall speedup should be 300% to 800% depending on CPU and memory speed.
  85  *
  86  * I will try to explain it on the example below:
  87  *
  88  * Have a map of 4 x 4 tiles, our simplified noise generator produces only two
  89  * values -1 and +1, use 3 octaves with wave length 1, 2 and 4, with amplitudes
  90  * 3, 2, 1. Original algorithm produces:
  91  *
  92  * 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
  93  * 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
  94  * 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
  95  * 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
  96  *
  97  * 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
  98  * 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
  99  * 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
 100  * 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
 101  *
 102  *
 103  * Optimization 1:
 104  *
 105  * 1) we need to allocate a bit more tiles: (size_x + 1) * (size_y + 1) = (5 * 5):
 106  *
 107  * 2) setup corner values using amplitude 3
 108  * {    -3.0        X          X          X          3.0   }
 109  * {     X          X          X          X          X     }
 110  * {     X          X          X          X          X     }
 111  * {     X          X          X          X          X     }
 112  * {     3.0        X          X          X         -3.0   }
 113  *
 114  * 3a) interpolate values in the middle
 115  * {    -3.0        X          0.0        X          3.0   }
 116  * {     X          X          X          X          X     }
 117  * {     0.0        X          0.0        X          0.0   }
 118  * {     X          X          X          X          X     }
 119  * {     3.0        X          0.0        X         -3.0   }
 120  *
 121  * 3b) add patches with amplitude 2 to them
 122  * {    -5.0        X          2.0        X          1.0   }
 123  * {     X          X          X          X          X     }
 124  * {     2.0        X         -2.0        X          2.0   }
 125  * {     X          X          X          X          X     }
 126  * {     1.0        X          2.0        X         -5.0   }
 127  *
 128  * 4a) interpolate values in the middle
 129  * {    -5.0       -1.5        2.0        1.5        1.0   }
 130  * {    -1.5       -0.75       0.0        0.75       1.5   }
 131  * {     2.0        0.0       -2.0        0.0        2.0   }
 132  * {     1.5        0.75       0.0       -0.75      -1.5   }
 133  * {     1.0        1.5        2.0       -1.5       -5.0   }
 134  *
 135  * 4b) add patches with amplitude 1 to them
 136  * {    -6.0       -0.5        1.0        2.5        0.0   }
 137  * {    -0.5       -1.75       1.0       -0.25       2.5   }
 138  * {     1.0        1.0       -3.0        1.0        1.0   }
 139  * {     2.5       -0.25       1.0       -1.75      -0.5   }
 140  * {     0.0        2.5        1.0       -0.5       -6.0   }
 141  *
 142  *
 143  *
 144  * Optimization 2:
 145  *
 146  * As you can see above, each noise function was called just once. Therefore
 147  * we don't need to use noise function that calculates the noise from x, y and
 148  * some prime. The same quality result we can obtain using standard Random()
 149  * function instead.
 150  *
 151  */
 152
 153 /** Fixed point type for heights */
 154 typedef int16 height_t;
 155 static const int height_decimal_bits = 4;
 156
 157 /** Fixed point array for amplitudes (and percent values) */
 158 typedef int amplitude_t;
 159 static const int amplitude_decimal_bits = 10;
 160
 161 /** Height map - allocated array of heights (MapSizeX() + 1) x (MapSizeY() + 1) */
 162 struct HeightMap
 163 {
 164         std::vector<height_t> h; //< array of heights
 165         /* Even though the sizes are always positive, there are many cases where
 166          * X and Y need to be signed integers due to subtractions. */
 167         int      dim_x;      //< height map size_x MapSizeX() + 1
 168         int      size_x;     //< MapSizeX()
 169         int      size_y;     //< MapSizeY()
 170
 171         /**
 172          * Height map accessor
 173          * @param x X position
 174          * @param y Y position
 175          * @return height as fixed point number
 176          */
 177         inline height_t &height(uint x, uint y)
 178         {
 179                 return h[x + y * dim_x];
 180         }
 181 };
 182
 183 /** Global height map instance */
 184 static HeightMap _height_map = { {}, 0, 0, 0 };
 185
 186 /** Conversion: int to height_t */
 187 #define I2H(i) ((i) << height_decimal_bits)
 188 /** Conversion: height_t to int */
 189 #define H2I(i) ((i) >> height_decimal_bits)
 190
 191 /** Conversion: int to amplitude_t */
 192 #define I2A(i) ((i) << amplitude_decimal_bits)
 193 /** Conversion: amplitude_t to int */
 194 #define A2I(i) ((i) >> amplitude_decimal_bits)
 195
 196 /** Conversion: amplitude_t to height_t */
 197 #define A2H(a) ((a) >> (amplitude_decimal_bits - height_decimal_bits))
 198
 199 /** Maximum number of TGP noise frequencies. */
 200 static const int MAX_TGP_FREQUENCIES = 10;
 201
 202 /** Desired water percentage (100% == 1024) - indexed by _settings_game.difficulty.quantity_sea_lakes */
 203 static const amplitude_t _water_percent[4] = {70, 170, 270, 420};
 204
 205 /**
 206  * Gets the maximum allowed height while generating a map based on
 207  * mapsize, terraintype, and the maximum height level.
 208  * @return The maximum height for the map generation.
 209  * @note Values should never be lower than 3 since the minimum snowline height is 2.
 210  */
 211 static height_t TGPGetMaxHeight()
 212 {
 213         if (_settings_game.difficulty.terrain_type == CUSTOM_TERRAIN_TYPE_NUMBER_DIFFICULTY) {
 214                 /* TGP never reaches this height; this means that if a user inputs "2",
 215                  * it would create a flat map without the "+ 1". But that would
 216                  * overflow on "255". So we reduce it by 1 to get back in range. */
 217                 return I2H(_settings_game.game_creation.custom_terrain_type + 1) - 1;
 218         }
 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 map_size_bucket = std::min(MapLogX(), MapLogY()) - MIN_MAP_SIZE_BITS;
 240         int max_height_from_table = max_height[_settings_game.difficulty.terrain_type][map_size_bucket];
 241
 242         /* If there is a manual map height limit, clamp to it. */
 243         if (_settings_game.construction.map_height_limit != 0) {
 244                 max_height_from_table = std::min<uint>(max_height_from_table, _settings_game.construction.map_height_limit);
 245         }
 246
 247         return I2H(max_height_from_table);
 248 }
 249
 250 /**
 251  * Get an overestimation of the highest peak TGP wants to generate.
 252  */
 253 uint GetEstimationTGPMapHeight()
 254 {
 255         return H2I(TGPGetMaxHeight());
 256 }
 257
 258 /**
 259  * Get the amplitude associated with the currently selected
 260  * smoothness and maximum height level.
 261  * @param frequency The frequency to get the amplitudes for
 262  * @return The amplitudes to apply to the map.
 263  */
 264 static amplitude_t GetAmplitude(int frequency)
 265 {
 266         /* Base noise amplitudes (multiplied by 1024) and indexed by "smoothness setting" and log2(frequency). */
 267         static const amplitude_t amplitudes[][7] = {
 268                 /* lowest frequency ...... highest (every corner) */
 269                 {16000,  5600,  1968,   688,   240,    16,    16}, ///< Very smooth
 270                 {24000, 12800,  6400,  2700,  1024,   128,    16}, ///< Smooth
 271                 {32000, 19200, 12800,  8000,  3200,   256,    64}, ///< Rough
 272                 {48000, 24000, 19200, 16000,  8000,   512,   320}, ///< Very rough
 273         };
 274         /*
 275          * Extrapolation factors for ranges before the table.
 276          * The extrapolation is needed to account for the higher map heights. They need larger
 277          * areas with a particular gradient so that we are able to create maps without too
 278          * many steep slopes up to the wanted height level. It's definitely not perfect since
 279          * it will bring larger rectangles with similar slopes which makes the rectangular
 280          * behaviour of TGP more noticeable. However, these height differentiations cannot
 281          * happen over much smaller areas; we basically double the "range" to give a similar
 282          * slope for every doubling of map height.
 283          */
 284         static const double extrapolation_factors[] = { 3.3, 2.8, 2.3, 1.8 };
 285
 286         int smoothness = _settings_game.game_creation.tgen_smoothness;
 287
 288         /* Get the table index, and return that value if possible. */
 289         int index = frequency - MAX_TGP_FREQUENCIES + lengthof(amplitudes[smoothness]);
 290         amplitude_t amplitude = amplitudes[smoothness][std::max(0, index)];
 291         if (index >= 0) return amplitude;
 292
 293         /* We need to extrapolate the amplitude. */
 294         double extrapolation_factor = extrapolation_factors[smoothness];
 295         int height_range = I2H(16);
 296         do {
 297                 amplitude = (amplitude_t)(extrapolation_factor * (double)amplitude);
 298                 height_range <<= 1;
 299                 index++;
 300         } while (index < 0);
 301
 302         return Clamp((TGPGetMaxHeight() - height_range) / height_range, 0, 1) * amplitude;
 303 }
 304
 305 /**
 306  * Check if a X/Y set are within the map.
 307  * @param x coordinate x
 308  * @param y coordinate y
 309  * @return true if within the map
 310  */
 311 static inline bool IsValidXY(int x, int y)
 312 {
 313         return x >= 0 && x < _height_map.size_x && y >= 0 && y < _height_map.size_y;
 314 }
 315
 316
 317 /**
 318  * Allocate array of (MapSizeX()+1)*(MapSizeY()+1) heights and init the _height_map structure members
 319  * @return true on success
 320  */
 321 static inline bool AllocHeightMap()
 322 {
 323         assert(_height_map.h.empty());
 324
 325         _height_map.size_x = MapSizeX();
 326         _height_map.size_y = MapSizeY();
 327
 328         /* Allocate memory block for height map row pointers */
 329         size_t total_size = (_height_map.size_x + 1) * (_height_map.size_y + 1);
 330         _height_map.dim_x = _height_map.size_x + 1;
 331         _height_map.h.resize(total_size);
 332
 333         return true;
 334 }
 335
 336 /** Free height map */
 337 static inline void FreeHeightMap()
 338 {
 339         _height_map.h.clear();
 340 }
 341
 342 /**
 343  * Generates new random height in given amplitude (generated numbers will range from - amplitude to + amplitude)
 344  * @param rMax Limit of result
 345  * @return generated height
 346  */
 347 static inline height_t RandomHeight(amplitude_t rMax)
 348 {
 349         /* Spread height into range -rMax..+rMax */
 350         return A2H(RandomRange(2 * rMax + 1) - rMax);
 351 }
 352
 353 /**
 354  * Base Perlin noise generator - fills height map with raw Perlin noise.
 355  *
 356  * This runs several iterations with increasing precision; the last iteration looks at areas
 357  * of 1 by 1 tiles, the second to last at 2 by 2 tiles and the initial 2**MAX_TGP_FREQUENCIES
 358  * by 2**MAX_TGP_FREQUENCIES tiles.
 359  */
 360 static void HeightMapGenerate()
 361 {
 362         /* Trying to apply noise to uninitialized height map */
 363         assert(!_height_map.h.empty());
 364
 365         int start = std::max(MAX_TGP_FREQUENCIES - (int)std::min(MapLogX(), MapLogY()), 0);
 366         bool first = true;
 367
 368         for (int frequency = start; frequency < MAX_TGP_FREQUENCIES; frequency++) {
 369                 const amplitude_t amplitude = GetAmplitude(frequency);
 370
 371                 /* Ignore zero amplitudes; it means our map isn't height enough for this
 372                  * amplitude, so ignore it and continue with the next set of amplitude. */
 373                 if (amplitude == 0) continue;
 374
 375                 const int step = 1 << (MAX_TGP_FREQUENCIES - frequency - 1);
 376
 377                 if (first) {
 378                         /* This is first round, we need to establish base heights with step = size_min */
 379                         for (int y = 0; y <= _height_map.size_y; y += step) {
 380                                 for (int x = 0; x <= _height_map.size_x; x += step) {
 381                                         height_t height = (amplitude > 0) ? RandomHeight(amplitude) : 0;
 382                                         _height_map.height(x, y) = height;
 383                                 }
 384                         }
 385                         first = false;
 386                         continue;
 387                 }
 388
 389                 /* It is regular iteration round.
 390                  * Interpolate height values at odd x, even y tiles */
 391                 for (int y = 0; y <= _height_map.size_y; y += 2 * step) {
 392                         for (int x = 0; x <= _height_map.size_x - 2 * step; x += 2 * step) {
 393                                 height_t h00 = _height_map.height(x + 0 * step, y);
 394                                 height_t h02 = _height_map.height(x + 2 * step, y);
 395                                 height_t h01 = (h00 + h02) / 2;
 396                                 _height_map.height(x + 1 * step, y) = h01;
 397                         }
 398                 }
 399
 400                 /* Interpolate height values at odd y tiles */
 401                 for (int y = 0; y <= _height_map.size_y - 2 * step; y += 2 * step) {
 402                         for (int x = 0; x <= _height_map.size_x; x += step) {
 403                                 height_t h00 = _height_map.height(x, y + 0 * step);
 404                                 height_t h20 = _height_map.height(x, y + 2 * step);
 405                                 height_t h10 = (h00 + h20) / 2;
 406                                 _height_map.height(x, y + 1 * step) = h10;
 407                         }
 408                 }
 409
 410                 /* Add noise for next higher frequency (smaller steps) */
 411                 for (int y = 0; y <= _height_map.size_y; y += step) {
 412                         for (int x = 0; x <= _height_map.size_x; x += step) {
 413                                 _height_map.height(x, y) += RandomHeight(amplitude);
 414                         }
 415                 }
 416         }
 417 }
 418
 419 /** Returns min, max and average height from height map */
 420 static void HeightMapGetMinMaxAvg(height_t *min_ptr, height_t *max_ptr, height_t *avg_ptr)
 421 {
 422         height_t h_min, h_max, h_avg;
 423         int64 h_accu = 0;
 424         h_min = h_max = _height_map.height(0, 0);
 425
 426         /* Get h_min, h_max and accumulate heights into h_accu */
 427         for (const height_t &h : _height_map.h) {
 428                 if (h < h_min) h_min = h;
 429                 if (h > h_max) h_max = h;
 430                 h_accu += h;
 431         }
 432
 433         /* Get average height */
 434         h_avg = (height_t)(h_accu / (_height_map.size_x * _height_map.size_y));
 435
 436         /* Return required results */
 437         if (min_ptr != nullptr) *min_ptr = h_min;
 438         if (max_ptr != nullptr) *max_ptr = h_max;
 439         if (avg_ptr != nullptr) *avg_ptr = h_avg;
 440 }
 441
 442 /** Dill histogram and return pointer to its base point - to the count of zero heights */
 443 static int *HeightMapMakeHistogram(height_t h_min, height_t h_max, int *hist_buf)
 444 {
 445         int *hist = hist_buf - h_min;
 446
 447         /* Count the heights and fill the histogram */
 448         for (const height_t &h : _height_map.h){
 449                 assert(h >= h_min);
 450                 assert(h <= h_max);
 451                 hist[h]++;
 452         }
 453         return hist;
 454 }
 455
 456 /** Applies sine wave redistribution onto height map */
 457 static void HeightMapSineTransform(height_t h_min, height_t h_max)
 458 {
 459         for (height_t &h : _height_map.h) {
 460                 double fheight;
 461
 462                 if (h < h_min) continue;
 463
 464                 /* Transform height into 0..1 space */
 465                 fheight = (double)(h - h_min) / (double)(h_max - h_min);
 466                 /* Apply sine transform depending on landscape type */
 467                 switch (_settings_game.game_creation.landscape) {
 468                         case LT_TOYLAND:
 469                         case LT_TEMPERATE:
 470                                 /* Move and scale 0..1 into -1..+1 */
 471                                 fheight = 2 * fheight - 1;
 472                                 /* Sine transform */
 473                                 fheight = sin(fheight * M_PI_2);
 474                                 /* Transform it back from -1..1 into 0..1 space */
 475                                 fheight = 0.5 * (fheight + 1);
 476                                 break;
 477
 478                         case LT_ARCTIC:
 479                                 {
 480                                         /* Arctic terrain needs special height distribution.
 481                                          * Redistribute heights to have more tiles at highest (75%..100%) range */
 482                                         double sine_upper_limit = 0.75;
 483                                         double linear_compression = 2;
 484                                         if (fheight >= sine_upper_limit) {
 485                                                 /* Over the limit we do linear compression up */
 486                                                 fheight = 1.0 - (1.0 - fheight) / linear_compression;
 487                                         } else {
 488                                                 double m = 1.0 - (1.0 - sine_upper_limit) / linear_compression;
 489                                                 /* Get 0..sine_upper_limit into -1..1 */
 490                                                 fheight = 2.0 * fheight / sine_upper_limit - 1.0;
 491                                                 /* Sine wave transform */
 492                                                 fheight = sin(fheight * M_PI_2);
 493                                                 /* Get -1..1 back to 0..(1 - (1 - sine_upper_limit) / linear_compression) == 0.0..m */
 494                                                 fheight = 0.5 * (fheight + 1.0) * m;
 495                                         }
 496                                 }
 497                                 break;
 498
 499                         case LT_TROPIC:
 500                                 {
 501                                         /* Desert terrain needs special height distribution.
 502                                          * Half of tiles should be at lowest (0..25%) heights */
 503                                         double sine_lower_limit = 0.5;
 504                                         double linear_compression = 2;
 505                                         if (fheight <= sine_lower_limit) {
 506                                                 /* Under the limit we do linear compression down */
 507                                                 fheight = fheight / linear_compression;
 508                                         } else {
 509                                                 double m = sine_lower_limit / linear_compression;
 510                                                 /* Get sine_lower_limit..1 into -1..1 */
 511                                                 fheight = 2.0 * ((fheight - sine_lower_limit) / (1.0 - sine_lower_limit)) - 1.0;
 512                                                 /* Sine wave transform */
 513                                                 fheight = sin(fheight * M_PI_2);
 514                                                 /* Get -1..1 back to (sine_lower_limit / linear_compression)..1.0 */
 515                                                 fheight = 0.5 * ((1.0 - m) * fheight + (1.0 + m));
 516                                         }
 517                                 }
 518                                 break;
 519
 520                         default:
 521                                 NOT_REACHED();
 522                                 break;
 523                 }
 524                 /* Transform it back into h_min..h_max space */
 525                 h = (height_t)(fheight * (h_max - h_min) + h_min);
 526                 if (h < 0) h = I2H(0);
 527                 if (h >= h_max) h = h_max - 1;
 528         }
 529 }
 530
 531 /**
 532  * Additional map variety is provided by applying different curve maps
 533  * to different parts of the map. A randomized low resolution grid contains
 534  * which curve map to use on each part of the make. This filtered non-linearly
 535  * to smooth out transitions between curves, so each tile could have between
 536  * 100% of one map applied or 25% of four maps.
 537  *
 538  * The curve maps define different land styles, i.e. lakes, low-lands, hills
 539  * and mountain ranges, although these are dependent on the landscape style
 540  * chosen as well.
 541  *
 542  * The level parameter dictates the resolution of the grid. A low resolution
 543  * grid will result in larger continuous areas of a land style, a higher
 544  * resolution grid splits the style into smaller areas.
 545  * @param level Rough indication of the size of the grid sections to style. Small level means large grid sections.
 546  */
 547 static void HeightMapCurves(uint level)
 548 {
 549         height_t mh = TGPGetMaxHeight() - I2H(1); // height levels above sea level only
 550
 551         /** Basically scale height X to height Y. Everything in between is interpolated. */
 552         struct control_point_t {
 553                 height_t x; ///< The height to scale from.
 554                 height_t y; ///< The height to scale to.
 555         };
 556         /* Scaled curve maps; value is in height_ts. */
 557 #define F(fraction) ((height_t)(fraction * mh))
 558         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)  } };
 559         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)  } };
 560         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)  } };
 561         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) } };
 562 #undef F
 563
 564         /** Helper structure to index the different curve maps. */
 565         struct control_point_list_t {
 566                 size_t length;               ///< The length of the curve map.
 567                 const control_point_t *list; ///< The actual curve map.
 568         };
 569         const control_point_list_t curve_maps[] = {
 570                 { lengthof(curve_map_1), curve_map_1 },
 571                 { lengthof(curve_map_2), curve_map_2 },
 572                 { lengthof(curve_map_3), curve_map_3 },
 573                 { lengthof(curve_map_4), curve_map_4 },
 574         };
 575
 576         height_t ht[lengthof(curve_maps)];
 577         MemSetT(ht, 0, lengthof(ht));
 578
 579         /* Set up a grid to choose curve maps based on location; attempt to get a somewhat square grid */
 580         float factor = sqrt((float)_height_map.size_x / (float)_height_map.size_y);
 581         uint sx = Clamp((int)(((1 << level) * factor) + 0.5), 1, 128);
 582         uint sy = Clamp((int)(((1 << level) / factor) + 0.5), 1, 128);
 583         byte *c = AllocaM(byte, sx * sy);
 584
 585         for (uint i = 0; i < sx * sy; i++) {
 586                 c[i] = Random() % lengthof(curve_maps);
 587         }
 588
 589         /* Apply curves */
 590         for (int x = 0; x < _height_map.size_x; x++) {
 591
 592                 /* Get our X grid positions and bi-linear ratio */
 593                 float fx = (float)(sx * x) / _height_map.size_x + 1.0f;
 594                 uint x1 = (uint)fx;
 595                 uint x2 = x1;
 596                 float xr = 2.0f * (fx - x1) - 1.0f;
 597                 xr = sin(xr * M_PI_2);
 598                 xr = sin(xr * M_PI_2);
 599                 xr = 0.5f * (xr + 1.0f);
 600                 float xri = 1.0f - xr;
 601
 602                 if (x1 > 0) {
 603                         x1--;
 604                         if (x2 >= sx) x2--;
 605                 }
 606
 607                 for (int y = 0; y < _height_map.size_y; y++) {
 608
 609                         /* Get our Y grid position and bi-linear ratio */
 610                         float fy = (float)(sy * y) / _height_map.size_y + 1.0f;
 611                         uint y1 = (uint)fy;
 612                         uint y2 = y1;
 613                         float yr = 2.0f * (fy - y1) - 1.0f;
 614                         yr = sin(yr * M_PI_2);
 615                         yr = sin(yr * M_PI_2);
 616                         yr = 0.5f * (yr + 1.0f);
 617                         float yri = 1.0f - yr;
 618
 619                         if (y1 > 0) {
 620                                 y1--;
 621                                 if (y2 >= sy) y2--;
 622                         }
 623
 624                         uint corner_a = c[x1 + sx * y1];
 625                         uint corner_b = c[x1 + sx * y2];
 626                         uint corner_c = c[x2 + sx * y1];
 627                         uint corner_d = c[x2 + sx * y2];
 628
 629                         /* Bitmask of which curve maps are chosen, so that we do not bother
 630                          * calculating a curve which won't be used. */
 631                         uint corner_bits = 0;
 632                         corner_bits |= 1 << corner_a;
 633                         corner_bits |= 1 << corner_b;
 634                         corner_bits |= 1 << corner_c;
 635                         corner_bits |= 1 << corner_d;
 636
 637                         height_t *h = &_height_map.height(x, y);
 638
 639                         /* Do not touch sea level */
 640                         if (*h < I2H(1)) continue;
 641
 642                         /* Only scale above sea level */
 643                         *h -= I2H(1);
 644
 645                         /* Apply all curve maps that are used on this tile. */
 646                         for (uint t = 0; t < lengthof(curve_maps); t++) {
 647                                 if (!HasBit(corner_bits, t)) continue;
 648
 649                                 [[maybe_unused]] bool found = false;
 650                                 const control_point_t *cm = curve_maps[t].list;
 651                                 for (uint i = 0; i < curve_maps[t].length - 1; i++) {
 652                                         const control_point_t &p1 = cm[i];
 653                                         const control_point_t &p2 = cm[i + 1];
 654
 655                                         if (*h >= p1.x && *h < p2.x) {
 656                                                 ht[t] = p1.y + (*h - p1.x) * (p2.y - p1.y) / (p2.x - p1.x);
 657 #ifdef WITH_ASSERT
 658                                                 found = true;
 659 #endif
 660                                                 break;
 661                                         }
 662                                 }
 663                                 assert(found);
 664                         }
 665
 666                         /* Apply interpolation of curve map results. */
 667                         *h = (height_t)((ht[corner_a] * yri + ht[corner_b] * yr) * xri + (ht[corner_c] * yri + ht[corner_d] * yr) * xr);
 668
 669                         /* Readd sea level */
 670                         *h += I2H(1);
 671                 }
 672         }
 673 }
 674
 675 /** Adjusts heights in height map to contain required amount of water tiles */
 676 static void HeightMapAdjustWaterLevel(amplitude_t water_percent, height_t h_max_new)
 677 {
 678         height_t h_min, h_max, h_avg, h_water_level;
 679         int64 water_tiles, desired_water_tiles;
 680         int *hist;
 681
 682         HeightMapGetMinMaxAvg(&h_min, &h_max, &h_avg);
 683
 684         /* Allocate histogram buffer and clear its cells */
 685         int *hist_buf = CallocT<int>(h_max - h_min + 1);
 686         /* Fill histogram */
 687         hist = HeightMapMakeHistogram(h_min, h_max, hist_buf);
 688
 689         /* How many water tiles do we want? */
 690         desired_water_tiles = A2I(((int64)water_percent) * (int64)(_height_map.size_x * _height_map.size_y));
 691
 692         /* Raise water_level and accumulate values from histogram until we reach required number of water tiles */
 693         for (h_water_level = h_min, water_tiles = 0; h_water_level < h_max; h_water_level++) {
 694                 water_tiles += hist[h_water_level];
 695                 if (water_tiles >= desired_water_tiles) break;
 696         }
 697
 698         /* We now have the proper water level value.
 699          * Transform the height map into new (normalized) height map:
 700          *   values from range: h_min..h_water_level will become negative so it will be clamped to 0
 701          *   values from range: h_water_level..h_max are transformed into 0..h_max_new
 702          *   where h_max_new is depending on terrain type and map size.
 703          */
 704         for (height_t &h : _height_map.h) {
 705                 /* Transform height from range h_water_level..h_max into 0..h_max_new range */
 706                 h = (height_t)(((int)h_max_new) * (h - h_water_level) / (h_max - h_water_level)) + I2H(1);
 707                 /* Make sure all values are in the proper range (0..h_max_new) */
 708                 if (h < 0) h = I2H(0);
 709                 if (h >= h_max_new) h = h_max_new - 1;
 710         }
 711
 712         free(hist_buf);
 713 }
 714
 715 static double perlin_coast_noise_2D(const double x, const double y, const double p, const int prime);
 716
 717 /**
 718  * This routine sculpts in from the edge a random amount, again a Perlin
 719  * sequence, to avoid the rigid flat-edge slopes that were present before. The
 720  * Perlin noise map doesn't know where we are going to slice across, and so we
 721  * often cut straight through high terrain. The smoothing routine makes it
 722  * legal, gradually increasing up from the edge to the original terrain height.
 723  * By cutting parts of this away, it gives a far more irregular edge to the
 724  * map-edge. Sometimes it works beautifully with the existing sea & lakes, and
 725  * creates a very realistic coastline. Other times the variation is less, and
 726  * the map-edge shows its cliff-like roots.
 727  *
 728  * This routine may be extended to randomly sculpt the height of the terrain
 729  * near the edge. This will have the coast edge at low level (1-3), rising in
 730  * smoothed steps inland to about 15 tiles in. This should make it look as
 731  * though the map has been built for the map size, rather than a slice through
 732  * a larger map.
 733  *
 734  * Please note that all the small numbers; 53, 101, 167, etc. are small primes
 735  * to help give the perlin noise a bit more of a random feel.
 736  */
 737 static void HeightMapCoastLines(uint8 water_borders)
 738 {
 739         int smallest_size = std::min(_settings_game.game_creation.map_x, _settings_game.game_creation.map_y);
 740         const int margin = 4;
 741         int y, x;
 742         double max_x;
 743         double max_y;
 744
 745         /* Lower to sea level */
 746         for (y = 0; y <= _height_map.size_y; y++) {
 747                 if (HasBit(water_borders, BORDER_NE)) {
 748                         /* Top right */
 749                         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);
 750                         max_x = std::max((smallest_size * smallest_size / 64) + max_x, (smallest_size * smallest_size / 64) + margin - max_x);
 751                         if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
 752                         for (x = 0; x < max_x; x++) {
 753                                 _height_map.height(x, y) = 0;
 754                         }
 755                 }
 756
 757                 if (HasBit(water_borders, BORDER_SW)) {
 758                         /* Bottom left */
 759                         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);
 760                         max_x = std::max((smallest_size * smallest_size / 64) + max_x, (smallest_size * smallest_size / 64) + margin - max_x);
 761                         if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
 762                         for (x = _height_map.size_x; x > (_height_map.size_x - 1 - max_x); x--) {
 763                                 _height_map.height(x, y) = 0;
 764                         }
 765                 }
 766         }
 767
 768         /* Lower to sea level */
 769         for (x = 0; x <= _height_map.size_x; x++) {
 770                 if (HasBit(water_borders, BORDER_NW)) {
 771                         /* Top left */
 772                         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);
 773                         max_y = std::max((smallest_size * smallest_size / 64) + max_y, (smallest_size * smallest_size / 64) + margin - max_y);
 774                         if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
 775                         for (y = 0; y < max_y; y++) {
 776                                 _height_map.height(x, y) = 0;
 777                         }
 778                 }
 779
 780                 if (HasBit(water_borders, BORDER_SE)) {
 781                         /* Bottom right */
 782                         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);
 783                         max_y = std::max((smallest_size * smallest_size / 64) + max_y, (smallest_size * smallest_size / 64) + margin - max_y);
 784                         if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
 785                         for (y = _height_map.size_y; y > (_height_map.size_y - 1 - max_y); y--) {
 786                                 _height_map.height(x, y) = 0;
 787                         }
 788                 }
 789         }
 790 }
 791
 792 /** Start at given point, move in given direction, find and Smooth coast in that direction */
 793 static void HeightMapSmoothCoastInDirection(int org_x, int org_y, int dir_x, int dir_y)
 794 {
 795         const int max_coast_dist_from_edge = 35;
 796         const int max_coast_Smooth_depth = 35;
 797
 798         int x, y;
 799         int ed; // coast distance from edge
 800         int depth;
 801
 802         height_t h_prev = I2H(1);
 803         height_t h;
 804
 805         assert(IsValidXY(org_x, org_y));
 806
 807         /* Search for the coast (first non-water tile) */
 808         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++) {
 809                 /* Coast found? */
 810                 if (_height_map.height(x, y) >= I2H(1)) break;
 811
 812                 /* Coast found in the neighborhood? */
 813                 if (IsValidXY(x + dir_y, y + dir_x) && _height_map.height(x + dir_y, y + dir_x) > 0) break;
 814
 815                 /* Coast found in the neighborhood on the other side */
 816                 if (IsValidXY(x - dir_y, y - dir_x) && _height_map.height(x - dir_y, y - dir_x) > 0) break;
 817         }
 818
 819         /* Coast found or max_coast_dist_from_edge has been reached.
 820          * Soften the coast slope */
 821         for (depth = 0; IsValidXY(x, y) && depth <= max_coast_Smooth_depth; depth++, x += dir_x, y += dir_y) {
 822                 h = _height_map.height(x, y);
 823                 h = std::min<uint>(h, h_prev + (4 + depth)); // coast softening formula
 824                 _height_map.height(x, y) = h;
 825                 h_prev = h;
 826         }
 827 }
 828
 829 /** Smooth coasts by modulating height of tiles close to map edges with cosine of distance from edge */
 830 static void HeightMapSmoothCoasts(uint8 water_borders)
 831 {
 832         int x, y;
 833         /* First Smooth NW and SE coasts (y close to 0 and y close to size_y) */
 834         for (x = 0; x < _height_map.size_x; x++) {
 835                 if (HasBit(water_borders, BORDER_NW)) HeightMapSmoothCoastInDirection(x, 0, 0, 1);
 836                 if (HasBit(water_borders, BORDER_SE)) HeightMapSmoothCoastInDirection(x, _height_map.size_y - 1, 0, -1);
 837         }
 838         /* First Smooth NE and SW coasts (x close to 0 and x close to size_x) */
 839         for (y = 0; y < _height_map.size_y; y++) {
 840                 if (HasBit(water_borders, BORDER_NE)) HeightMapSmoothCoastInDirection(0, y, 1, 0);
 841                 if (HasBit(water_borders, BORDER_SW)) HeightMapSmoothCoastInDirection(_height_map.size_x - 1, y, -1, 0);
 842         }
 843 }
 844
 845 /**
 846  * This routine provides the essential cleanup necessary before OTTD can
 847  * display the terrain. When generated, the terrain heights can jump more than
 848  * one level between tiles. This routine smooths out those differences so that
 849  * the most it can change is one level. When OTTD can support cliffs, this
 850  * routine may not be necessary.
 851  */
 852 static void HeightMapSmoothSlopes(height_t dh_max)
 853 {
 854         for (int y = 0; y <= (int)_height_map.size_y; y++) {
 855                 for (int x = 0; x <= (int)_height_map.size_x; x++) {
 856                         height_t h_max = std::min(_height_map.height(x > 0 ? x - 1 : x, y), _height_map.height(x, y > 0 ? y - 1 : y)) + dh_max;
 857                         if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 858                 }
 859         }
 860         for (int y = _height_map.size_y; y >= 0; y--) {
 861                 for (int x = _height_map.size_x; x >= 0; x--) {
 862                         height_t h_max = std::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;
 863                         if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 864                 }
 865         }
 866 }
 867
 868 /**
 869  * Height map terraform post processing:
 870  *  - water level adjusting
 871  *  - coast Smoothing
 872  *  - slope Smoothing
 873  *  - height histogram redistribution by sine wave transform
 874  */
 875 static void HeightMapNormalize()
 876 {
 877         int sea_level_setting = _settings_game.difficulty.quantity_sea_lakes;
 878         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;
 879         const height_t h_max_new = TGPGetMaxHeight();
 880         const height_t roughness = 7 + 3 * _settings_game.game_creation.tgen_smoothness;
 881
 882         HeightMapAdjustWaterLevel(water_percent, h_max_new);
 883
 884         byte water_borders = _settings_game.construction.freeform_edges ? _settings_game.game_creation.water_borders : 0xF;
 885         if (water_borders == BORDERS_RANDOM) water_borders = GB(Random(), 0, 4);
 886
 887         HeightMapCoastLines(water_borders);
 888         HeightMapSmoothSlopes(roughness);
 889
 890         HeightMapSmoothCoasts(water_borders);
 891         HeightMapSmoothSlopes(roughness);
 892
 893         HeightMapSineTransform(I2H(1), h_max_new);
 894
 895         if (_settings_game.game_creation.variety > 0) {
 896                 HeightMapCurves(_settings_game.game_creation.variety);
 897         }
 898
 899         HeightMapSmoothSlopes(I2H(1));
 900 }
 901
 902 /**
 903  * The Perlin Noise calculation using large primes
 904  * The initial number is adjusted by two values; the generation_seed, and the
 905  * passed parameter; prime.
 906  * prime is used to allow the perlin noise generator to create useful random
 907  * numbers from slightly different series.
 908  */
 909 static double int_noise(const long x, const long y, const int prime)
 910 {
 911         long n = x + y * prime + _settings_game.game_creation.generation_seed;
 912
 913         n = (n << 13) ^ n;
 914
 915         /* Pseudo-random number generator, using several large primes */
 916         return 1.0 - (double)((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0;
 917 }
 918
 919
 920 /**
 921  * This routine determines the interpolated value between a and b
 922  */
 923 static inline double linear_interpolate(const double a, const double b, const double x)
 924 {
 925         return a + x * (b - a);
 926 }
 927
 928
 929 /**
 930  * This routine returns the smoothed interpolated noise for an x and y, using
 931  * the values from the surrounding positions.
 932  */
 933 static double interpolated_noise(const double x, const double y, const int prime)
 934 {
 935         const int integer_X = (int)x;
 936         const int integer_Y = (int)y;
 937
 938         const double fractional_X = x - (double)integer_X;
 939         const double fractional_Y = y - (double)integer_Y;
 940
 941         const double v1 = int_noise(integer_X,     integer_Y,     prime);
 942         const double v2 = int_noise(integer_X + 1, integer_Y,     prime);
 943         const double v3 = int_noise(integer_X,     integer_Y + 1, prime);
 944         const double v4 = int_noise(integer_X + 1, integer_Y + 1, prime);
 945
 946         const double i1 = linear_interpolate(v1, v2, fractional_X);
 947         const double i2 = linear_interpolate(v3, v4, fractional_X);
 948
 949         return linear_interpolate(i1, i2, fractional_Y);
 950 }
 951
 952
 953 /**
 954  * This is a similar function to the main perlin noise calculation, but uses
 955  * the value p passed as a parameter rather than selected from the predefined
 956  * sequences. as you can guess by its title, i use this to create the indented
 957  * coastline, which is just another perlin sequence.
 958  */
 959 static double perlin_coast_noise_2D(const double x, const double y, const double p, const int prime)
 960 {
 961         double total = 0.0;
 962
 963         for (int i = 0; i < 6; i++) {
 964                 const double frequency = (double)(1 << i);
 965                 const double amplitude = pow(p, (double)i);
 966
 967                 total += interpolated_noise((x * frequency) / 64.0, (y * frequency) / 64.0, prime) * amplitude;
 968         }
 969
 970         return total;
 971 }
 972
 973
 974 /** A small helper function to initialize the terrain */
 975 static void TgenSetTileHeight(TileIndex tile, int height)
 976 {
 977         SetTileHeight(tile, height);
 978
 979         /* Only clear the tiles within the map area. */
 980         if (IsInnerTile(tile)) {
 981                 MakeClear(tile, CLEAR_GRASS, 3);
 982         }
 983 }
 984
 985 /**
 986  * The main new land generator using Perlin noise. Desert landscape is handled
 987  * different to all others to give a desert valley between two high mountains.
 988  * Clearly if a low height terrain (flat/very flat) is chosen, then the tropic
 989  * areas won't be high enough, and there will be very little tropic on the map.
 990  * Thus Tropic works best on Hilly or Mountainous.
 991  */
 992 void GenerateTerrainPerlin()
 993 {
 994         if (!AllocHeightMap()) return;
 995         GenerateWorldSetAbortCallback(FreeHeightMap);
 996
 997         HeightMapGenerate();
 998
 999         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
1000
1001         HeightMapNormalize();
1002
1003         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
1004
1005         /* First make sure the tiles at the north border are void tiles if needed. */
1006         if (_settings_game.construction.freeform_edges) {
1007                 for (uint x = 0; x < MapSizeX(); x++) MakeVoid(TileXY(x, 0));
1008                 for (uint y = 0; y < MapSizeY(); y++) MakeVoid(TileXY(0, y));
1009         }
1010
1011         int max_height = H2I(TGPGetMaxHeight());
1012
1013         /* Transfer height map into OTTD map */
1014         for (int y = 0; y < _height_map.size_y; y++) {
1015                 for (int x = 0; x < _height_map.size_x; x++) {
1016                         TgenSetTileHeight(TileXY(x, y), Clamp(H2I(_height_map.height(x, y)), 0, max_height));
1017                 }
1018         }
1019
1020         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
1021
1022         FreeHeightMap();
1023         GenerateWorldSetAbortCallback(nullptr);
1024 }