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 "clear_map.h"
  12 #include "void_map.h"
  13 #include "genworld.h"
  14 #include "core/random_func.hpp"
  15 #include "landscape_type.h"
  16
  17 #include "safeguards.h"
  18
  19 /*
  20  *
  21  * Quickie guide to Perlin Noise
  22  * Perlin noise is a predictable pseudo random number sequence. By generating
  23  * it in 2 dimensions, it becomes a useful random map that, for a given seed
  24  * and starting X & Y, is entirely predictable. On the face of it, that may not
  25  * be useful. However, it means that if you want to replay a map in a different
  26  * terrain, or just vary the sea level, you just re-run the generator with the
  27  * same seed. The seed is an int32_t, and is randomised on each run of New Game.
  28  * The Scenario Generator does not randomise the value, so that you can
  29  * experiment with one terrain until you are happy, or click "Random" for a new
  30  * random seed.
  31  *
  32  * Perlin Noise is a series of "octaves" of random noise added together. By
  33  * reducing the amplitude of the noise with each octave, the first octave of
  34  * noise defines the main terrain sweep, the next the ripples on that, and the
  35  * next the ripples on that. I use 6 octaves, with the amplitude controlled by
  36  * a power ratio, usually known as a persistence or p value. This I vary by the
  37  * smoothness selection, as can be seen in the table below. The closer to 1,
  38  * the more of that octave is added. Each octave is however raised to the power
  39  * of its position in the list, so the last entry in the "smooth" row, 0.35, is
  40  * raised to the power of 6, so can only add 0.001838...  of the amplitude to
  41  * the running total.
  42  *
  43  * In other words; the first p value sets the general shape of the terrain, the
  44  * second sets the major variations to that, ... until finally the smallest
  45  * bumps are added.
  46  *
  47  * Usefully, this routine is totally scalable; so when 32bpp comes along, the
  48  * terrain can be as bumpy as you like! It is also infinitely expandable; a
  49  * single random seed terrain continues in X & Y as far as you care to
  50  * calculate. In theory, we could use just one seed value, but randomly select
  51  * where in the Perlin XY space we use for the terrain. Personally I prefer
  52  * using a simple (0, 0) to (X, Y), with a varying seed.
  53  *
  54  *
  55  * Other things i have had to do: mountainous wasn't mountainous enough, and
  56  * since we only have 0..15 heights available, I add a second generated map
  57  * (with a modified seed), onto the original. This generally raises the
  58  * terrain, which then needs scaling back down. Overall effect is a general
  59  * uplift.
  60  *
  61  * However, the values on the top of mountains are then almost guaranteed to go
  62  * too high, so large flat plateaus appeared at height 15. To counter this, I
  63  * scale all heights above 12 to proportion up to 15. It still makes the
  64  * mountains have flattish tops, rather than craggy peaks, but at least they
  65  * aren't smooth as glass.
  66  *
  67  *
  68  * For a full discussion of Perlin Noise, please visit:
  69  * http://freespace.virgin.net/hugo.elias/models/m_perlin.htm
  70  *
  71  *
  72  * Evolution II
  73  *
  74  * The algorithm as described in the above link suggests to compute each tile height
  75  * as composition of several noise waves. Some of them are computed directly by
  76  * noise(x, y) function, some are calculated using linear approximation. Our
  77  * first implementation of perlin_noise_2D() used 4 noise(x, y) calls plus
  78  * 3 linear interpolations. It was called 6 times for each tile. This was a bit
  79  * CPU expensive.
  80  *
  81  * The following implementation uses optimized algorithm that should produce
  82  * the same quality result with much less computations, but more memory accesses.
  83  * The overall speedup should be 300% to 800% depending on CPU and memory speed.
  84  *
  85  * I will try to explain it on the example below:
  86  *
  87  * Have a map of 4 x 4 tiles, our simplified noise generator produces only two
  88  * values -1 and +1, use 3 octaves with wave length 1, 2 and 4, with amplitudes
  89  * 3, 2, 1. Original algorithm produces:
  90  *
  91  * 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
  92  * 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
  93  * 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
  94  * 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
  95  *
  96  * 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
  97  * 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
  98  * 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
  99  * 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
 100  *
 101  *
 102  * Optimization 1:
 103  *
 104  * 1) we need to allocate a bit more tiles: (size_x + 1) * (size_y + 1) = (5 * 5):
 105  *
 106  * 2) setup corner values using amplitude 3
 107  * {    -3.0        X          X          X          3.0   }
 108  * {     X          X          X          X          X     }
 109  * {     X          X          X          X          X     }
 110  * {     X          X          X          X          X     }
 111  * {     3.0        X          X          X         -3.0   }
 112  *
 113  * 3a) interpolate values in the middle
 114  * {    -3.0        X          0.0        X          3.0   }
 115  * {     X          X          X          X          X     }
 116  * {     0.0        X          0.0        X          0.0   }
 117  * {     X          X          X          X          X     }
 118  * {     3.0        X          0.0        X         -3.0   }
 119  *
 120  * 3b) add patches with amplitude 2 to them
 121  * {    -5.0        X          2.0        X          1.0   }
 122  * {     X          X          X          X          X     }
 123  * {     2.0        X         -2.0        X          2.0   }
 124  * {     X          X          X          X          X     }
 125  * {     1.0        X          2.0        X         -5.0   }
 126  *
 127  * 4a) interpolate values in the middle
 128  * {    -5.0       -1.5        2.0        1.5        1.0   }
 129  * {    -1.5       -0.75       0.0        0.75       1.5   }
 130  * {     2.0        0.0       -2.0        0.0        2.0   }
 131  * {     1.5        0.75       0.0       -0.75      -1.5   }
 132  * {     1.0        1.5        2.0       -1.5       -5.0   }
 133  *
 134  * 4b) add patches with amplitude 1 to them
 135  * {    -6.0       -0.5        1.0        2.5        0.0   }
 136  * {    -0.5       -1.75       1.0       -0.25       2.5   }
 137  * {     1.0        1.0       -3.0        1.0        1.0   }
 138  * {     2.5       -0.25       1.0       -1.75      -0.5   }
 139  * {     0.0        2.5        1.0       -0.5       -6.0   }
 140  *
 141  *
 142  *
 143  * Optimization 2:
 144  *
 145  * As you can see above, each noise function was called just once. Therefore
 146  * we don't need to use noise function that calculates the noise from x, y and
 147  * some prime. The same quality result we can obtain using standard Random()
 148  * function instead.
 149  *
 150  */
 151
 152 /** Fixed point type for heights */
 153 using Height = int16_t;
 154 static const int height_decimal_bits = 4;
 155
 156 /** Fixed point array for amplitudes (and percent values) */
 157 using Amplitude = int;
 158 static const int amplitude_decimal_bits = 10;
 159
 160 /** Height map - allocated array of heights (MapSizeX() + 1) x (MapSizeY() + 1) */
 161 struct HeightMap
 162 {
 163         std::vector<Height> h; //< array of heights
 164         /* Even though the sizes are always positive, there are many cases where
 165          * X and Y need to be signed integers due to subtractions. */
 166         int      dim_x;      //< height map size_x Map::SizeX() + 1
 167         int      size_x;     //< Map::SizeX()
 168         int      size_y;     //< Map::SizeY()
 169
 170         /**
 171          * Height map accessor
 172          * @param x X position
 173          * @param y Y position
 174          * @return height as fixed point number
 175          */
 176         inline Height &height(uint x, uint y)
 177         {
 178                 return h[x + y * dim_x];
 179         }
 180 };
 181
 182 /** Global height map instance */
 183 static HeightMap _height_map = { {}, 0, 0, 0 };
 184
 185 /** Conversion: int to Height */
 186 #define I2H(i) ((i) << height_decimal_bits)
 187 /** Conversion: Height to int */
 188 #define H2I(i) ((i) >> height_decimal_bits)
 189
 190 /** Conversion: int to Amplitude */
 191 #define I2A(i) ((i) << amplitude_decimal_bits)
 192 /** Conversion: Amplitude to int */
 193 #define A2I(i) ((i) >> amplitude_decimal_bits)
 194
 195 /** Conversion: Amplitude to Height */
 196 #define A2H(a) ((a) >> (amplitude_decimal_bits - height_decimal_bits))
 197
 198 /** Maximum number of TGP noise frequencies. */
 199 static const int MAX_TGP_FREQUENCIES = 10;
 200
 201 /** Desired water percentage (100% == 1024) - indexed by _settings_game.difficulty.quantity_sea_lakes */
 202 static const Amplitude _water_percent[4] = {70, 170, 270, 420};
 203
 204 /**
 205  * Gets the maximum allowed height while generating a map based on
 206  * mapsize, terraintype, and the maximum height level.
 207  * @return The maximum height for the map generation.
 208  * @note Values should never be lower than 3 since the minimum snowline height is 2.
 209  */
 210 static Height TGPGetMaxHeight()
 211 {
 212         if (_settings_game.difficulty.terrain_type == CUSTOM_TERRAIN_TYPE_NUMBER_DIFFICULTY) {
 213                 /* TGP never reaches this height; this means that if a user inputs "2",
 214                  * it would create a flat map without the "+ 1". But that would
 215                  * overflow on "255". So we reduce it by 1 to get back in range. */
 216                 return I2H(_settings_game.game_creation.custom_terrain_type + 1) - 1;
 217         }
 218
 219         /**
 220          * Desired maximum height - indexed by:
 221          *  - _settings_game.difficulty.terrain_type
 222          *  - min(Map::LogX(), Map::LogY()) - MIN_MAP_SIZE_BITS
 223          *
 224          * It is indexed by map size as well as terrain type since the map size limits the height of
 225          * a usable mountain. For example, on a 64x64 map a 24 high single peak mountain (as if you
 226          * raised land 24 times in the center of the map) will leave only a ring of about 10 tiles
 227          * around the mountain to build on. On a 4096x4096 map, it won't cover any major part of the map.
 228          */
 229         static const int max_height[5][MAX_MAP_SIZE_BITS - MIN_MAP_SIZE_BITS + 1] = {
 230                 /* 64  128  256  512 1024 2048 4096 */
 231                 {   3,   3,   3,   3,   4,   5,   7 }, ///< Very flat
 232                 {   5,   7,   8,   9,  14,  19,  31 }, ///< Flat
 233                 {   8,   9,  10,  15,  23,  37,  61 }, ///< Hilly
 234                 {  10,  11,  17,  19,  49,  63,  73 }, ///< Mountainous
 235                 {  12,  19,  25,  31,  67,  75,  87 }, ///< Alpinist
 236         };
 237
 238         int map_size_bucket = std::min(Map::LogX(), Map::LogY()) - MIN_MAP_SIZE_BITS;
 239         int max_height_from_table = max_height[_settings_game.difficulty.terrain_type][map_size_bucket];
 240
 241         /* If there is a manual map height limit, clamp to it. */
 242         if (_settings_game.construction.map_height_limit != 0) {
 243                 max_height_from_table = std::min<uint>(max_height_from_table, _settings_game.construction.map_height_limit);
 244         }
 245
 246         return I2H(max_height_from_table);
 247 }
 248
 249 /**
 250  * Get an overestimation of the highest peak TGP wants to generate.
 251  */
 252 uint GetEstimationTGPMapHeight()
 253 {
 254         return H2I(TGPGetMaxHeight());
 255 }
 256
 257 /**
 258  * Get the amplitude associated with the currently selected
 259  * smoothness and maximum height level.
 260  * @param frequency The frequency to get the amplitudes for
 261  * @return The amplitudes to apply to the map.
 262  */
 263 static Amplitude GetAmplitude(int frequency)
 264 {
 265         /* Base noise amplitudes (multiplied by 1024) and indexed by "smoothness setting" and log2(frequency). */
 266         static const Amplitude amplitudes[][7] = {
 267                 /* lowest frequency ...... highest (every corner) */
 268                 {16000,  5600,  1968,   688,   240,    16,    16}, ///< Very smooth
 269                 {24000, 12800,  6400,  2700,  1024,   128,    16}, ///< Smooth
 270                 {32000, 19200, 12800,  8000,  3200,   256,    64}, ///< Rough
 271                 {48000, 24000, 19200, 16000,  8000,   512,   320}, ///< Very rough
 272         };
 273         /*
 274          * Extrapolation factors for ranges before the table.
 275          * The extrapolation is needed to account for the higher map heights. They need larger
 276          * areas with a particular gradient so that we are able to create maps without too
 277          * many steep slopes up to the wanted height level. It's definitely not perfect since
 278          * it will bring larger rectangles with similar slopes which makes the rectangular
 279          * behaviour of TGP more noticeable. However, these height differentiations cannot
 280          * happen over much smaller areas; we basically double the "range" to give a similar
 281          * slope for every doubling of map height.
 282          */
 283         static const double extrapolation_factors[] = { 3.3, 2.8, 2.3, 1.8 };
 284
 285         int smoothness = _settings_game.game_creation.tgen_smoothness;
 286
 287         /* Get the table index, and return that value if possible. */
 288         int index = frequency - MAX_TGP_FREQUENCIES + lengthof(amplitudes[smoothness]);
 289         Amplitude amplitude = amplitudes[smoothness][std::max(0, index)];
 290         if (index >= 0) return amplitude;
 291
 292         /* We need to extrapolate the amplitude. */
 293         double extrapolation_factor = extrapolation_factors[smoothness];
 294         int height_range = I2H(16);
 295         do {
 296                 amplitude = (Amplitude)(extrapolation_factor * (double)amplitude);
 297                 height_range <<= 1;
 298                 index++;
 299         } while (index < 0);
 300
 301         return Clamp((TGPGetMaxHeight() - height_range) / height_range, 0, 1) * amplitude;
 302 }
 303
 304 /**
 305  * Check if a X/Y set are within the map.
 306  * @param x coordinate x
 307  * @param y coordinate y
 308  * @return true if within the map
 309  */
 310 static inline bool IsValidXY(int x, int y)
 311 {
 312         return x >= 0 && x < _height_map.size_x && y >= 0 && y < _height_map.size_y;
 313 }
 314
 315
 316 /**
 317  * Allocate array of (MapSizeX()+1)*(MapSizeY()+1) heights and init the _height_map structure members
 318  * @return true on success
 319  */
 320 static inline bool AllocHeightMap()
 321 {
 322         assert(_height_map.h.empty());
 323
 324         _height_map.size_x = Map::SizeX();
 325         _height_map.size_y = Map::SizeY();
 326
 327         /* Allocate memory block for height map row pointers */
 328         size_t total_size = static_cast<size_t>(_height_map.size_x + 1) * (_height_map.size_y + 1);
 329         _height_map.dim_x = _height_map.size_x + 1;
 330         _height_map.h.resize(total_size);
 331
 332         return true;
 333 }
 334
 335 /** Free height map */
 336 static inline void FreeHeightMap()
 337 {
 338         _height_map.h.clear();
 339 }
 340
 341 /**
 342  * Generates new random height in given amplitude (generated numbers will range from - amplitude to + amplitude)
 343  * @param rMax Limit of result
 344  * @return generated height
 345  */
 346 static inline Height RandomHeight(Amplitude rMax)
 347 {
 348         /* Spread height into range -rMax..+rMax */
 349         return A2H(RandomRange(2 * rMax + 1) - rMax);
 350 }
 351
 352 /**
 353  * Base Perlin noise generator - fills height map with raw Perlin noise.
 354  *
 355  * This runs several iterations with increasing precision; the last iteration looks at areas
 356  * of 1 by 1 tiles, the second to last at 2 by 2 tiles and the initial 2**MAX_TGP_FREQUENCIES
 357  * by 2**MAX_TGP_FREQUENCIES tiles.
 358  */
 359 static void HeightMapGenerate()
 360 {
 361         /* Trying to apply noise to uninitialized height map */
 362         assert(!_height_map.h.empty());
 363
 364         int start = std::max(MAX_TGP_FREQUENCIES - (int)std::min(Map::LogX(), Map::LogY()), 0);
 365         bool first = true;
 366
 367         for (int frequency = start; frequency < MAX_TGP_FREQUENCIES; frequency++) {
 368                 const Amplitude amplitude = GetAmplitude(frequency);
 369
 370                 /* Ignore zero amplitudes; it means our map isn't height enough for this
 371                  * amplitude, so ignore it and continue with the next set of amplitude. */
 372                 if (amplitude == 0) continue;
 373
 374                 const int step = 1 << (MAX_TGP_FREQUENCIES - frequency - 1);
 375
 376                 if (first) {
 377                         /* This is first round, we need to establish base heights with step = size_min */
 378                         for (int y = 0; y <= _height_map.size_y; y += step) {
 379                                 for (int x = 0; x <= _height_map.size_x; x += step) {
 380                                         Height height = (amplitude > 0) ? RandomHeight(amplitude) : 0;
 381                                         _height_map.height(x, y) = height;
 382                                 }
 383                         }
 384                         first = false;
 385                         continue;
 386                 }
 387
 388                 /* It is regular iteration round.
 389                  * Interpolate height values at odd x, even y tiles */
 390                 for (int y = 0; y <= _height_map.size_y; y += 2 * step) {
 391                         for (int x = 0; x <= _height_map.size_x - 2 * step; x += 2 * step) {
 392                                 Height h00 = _height_map.height(x + 0 * step, y);
 393                                 Height h02 = _height_map.height(x + 2 * step, y);
 394                                 Height h01 = (h00 + h02) / 2;
 395                                 _height_map.height(x + 1 * step, y) = h01;
 396                         }
 397                 }
 398
 399                 /* Interpolate height values at odd y tiles */
 400                 for (int y = 0; y <= _height_map.size_y - 2 * step; y += 2 * step) {
 401                         for (int x = 0; x <= _height_map.size_x; x += step) {
 402                                 Height h00 = _height_map.height(x, y + 0 * step);
 403                                 Height h20 = _height_map.height(x, y + 2 * step);
 404                                 Height h10 = (h00 + h20) / 2;
 405                                 _height_map.height(x, y + 1 * step) = h10;
 406                         }
 407                 }
 408
 409                 /* Add noise for next higher frequency (smaller steps) */
 410                 for (int y = 0; y <= _height_map.size_y; y += step) {
 411                         for (int x = 0; x <= _height_map.size_x; x += step) {
 412                                 _height_map.height(x, y) += RandomHeight(amplitude);
 413                         }
 414                 }
 415         }
 416 }
 417
 418 /** Returns min, max and average height from height map */
 419 static void HeightMapGetMinMaxAvg(Height *min_ptr, Height *max_ptr, Height *avg_ptr)
 420 {
 421         Height h_min, h_max, h_avg;
 422         int64_t h_accu = 0;
 423         h_min = h_max = _height_map.height(0, 0);
 424
 425         /* Get h_min, h_max and accumulate heights into h_accu */
 426         for (const Height &h : _height_map.h) {
 427                 if (h < h_min) h_min = h;
 428                 if (h > h_max) h_max = h;
 429                 h_accu += h;
 430         }
 431
 432         /* Get average height */
 433         h_avg = (Height)(h_accu / (_height_map.size_x * _height_map.size_y));
 434
 435         /* Return required results */
 436         if (min_ptr != nullptr) *min_ptr = h_min;
 437         if (max_ptr != nullptr) *max_ptr = h_max;
 438         if (avg_ptr != nullptr) *avg_ptr = h_avg;
 439 }
 440
 441 /** Dill histogram and return pointer to its base point - to the count of zero heights */
 442 static int *HeightMapMakeHistogram(Height h_min, [[maybe_unused]] Height h_max, int *hist_buf)
 443 {
 444         int *hist = hist_buf - h_min;
 445
 446         /* Count the heights and fill the histogram */
 447         for (const Height &h : _height_map.h){
 448                 assert(h >= h_min);
 449                 assert(h <= h_max);
 450                 hist[h]++;
 451         }
 452         return hist;
 453 }
 454
 455 /** Applies sine wave redistribution onto height map */
 456 static void HeightMapSineTransform(Height h_min, Height h_max)
 457 {
 458         for (Height &h : _height_map.h) {
 459                 double fheight;
 460
 461                 if (h < h_min) continue;
 462
 463                 /* Transform height into 0..1 space */
 464                 fheight = (double)(h - h_min) / (double)(h_max - h_min);
 465                 /* Apply sine transform depending on landscape type */
 466                 switch (_settings_game.game_creation.landscape) {
 467                         case LT_TOYLAND:
 468                         case LT_TEMPERATE:
 469                                 /* Move and scale 0..1 into -1..+1 */
 470                                 fheight = 2 * fheight - 1;
 471                                 /* Sine transform */
 472                                 fheight = sin(fheight * M_PI_2);
 473                                 /* Transform it back from -1..1 into 0..1 space */
 474                                 fheight = 0.5 * (fheight + 1);
 475                                 break;
 476
 477                         case LT_ARCTIC:
 478                                 {
 479                                         /* Arctic terrain needs special height distribution.
 480                                          * Redistribute heights to have more tiles at highest (75%..100%) range */
 481                                         double sine_upper_limit = 0.75;
 482                                         double linear_compression = 2;
 483                                         if (fheight >= sine_upper_limit) {
 484                                                 /* Over the limit we do linear compression up */
 485                                                 fheight = 1.0 - (1.0 - fheight) / linear_compression;
 486                                         } else {
 487                                                 double m = 1.0 - (1.0 - sine_upper_limit) / linear_compression;
 488                                                 /* Get 0..sine_upper_limit into -1..1 */
 489                                                 fheight = 2.0 * fheight / sine_upper_limit - 1.0;
 490                                                 /* Sine wave transform */
 491                                                 fheight = sin(fheight * M_PI_2);
 492                                                 /* Get -1..1 back to 0..(1 - (1 - sine_upper_limit) / linear_compression) == 0.0..m */
 493                                                 fheight = 0.5 * (fheight + 1.0) * m;
 494                                         }
 495                                 }
 496                                 break;
 497
 498                         case LT_TROPIC:
 499                                 {
 500                                         /* Desert terrain needs special height distribution.
 501                                          * Half of tiles should be at lowest (0..25%) heights */
 502                                         double sine_lower_limit = 0.5;
 503                                         double linear_compression = 2;
 504                                         if (fheight <= sine_lower_limit) {
 505                                                 /* Under the limit we do linear compression down */
 506                                                 fheight = fheight / linear_compression;
 507                                         } else {
 508                                                 double m = sine_lower_limit / linear_compression;
 509                                                 /* Get sine_lower_limit..1 into -1..1 */
 510                                                 fheight = 2.0 * ((fheight - sine_lower_limit) / (1.0 - sine_lower_limit)) - 1.0;
 511                                                 /* Sine wave transform */
 512                                                 fheight = sin(fheight * M_PI_2);
 513                                                 /* Get -1..1 back to (sine_lower_limit / linear_compression)..1.0 */
 514                                                 fheight = 0.5 * ((1.0 - m) * fheight + (1.0 + m));
 515                                         }
 516                                 }
 517                                 break;
 518
 519                         default:
 520                                 NOT_REACHED();
 521                                 break;
 522                 }
 523                 /* Transform it back into h_min..h_max space */
 524                 h = (Height)(fheight * (h_max - h_min) + h_min);
 525                 if (h < 0) h = I2H(0);
 526                 if (h >= h_max) h = h_max - 1;
 527         }
 528 }
 529
 530 /**
 531  * Additional map variety is provided by applying different curve maps
 532  * to different parts of the map. A randomized low resolution grid contains
 533  * which curve map to use on each part of the make. This filtered non-linearly
 534  * to smooth out transitions between curves, so each tile could have between
 535  * 100% of one map applied or 25% of four maps.
 536  *
 537  * The curve maps define different land styles, i.e. lakes, low-lands, hills
 538  * and mountain ranges, although these are dependent on the landscape style
 539  * chosen as well.
 540  *
 541  * The level parameter dictates the resolution of the grid. A low resolution
 542  * grid will result in larger continuous areas of a land style, a higher
 543  * resolution grid splits the style into smaller areas.
 544  * @param level Rough indication of the size of the grid sections to style. Small level means large grid sections.
 545  */
 546 static void HeightMapCurves(uint level)
 547 {
 548         Height mh = TGPGetMaxHeight() - I2H(1); // height levels above sea level only
 549
 550         /** Basically scale height X to height Y. Everything in between is interpolated. */
 551         struct ControlPoint {
 552                 Height x; ///< The height to scale from.
 553                 Height y; ///< The height to scale to.
 554         };
 555         /* Scaled curve maps; value is in height_ts. */
 556 #define F(fraction) ((Height)(fraction * mh))
 557         const ControlPoint curve_map_1[] = { { F(0.0), F(0.0) },                       { F(0.8), F(0.13) },                       { F(1.0), F(0.4)  } };
 558         const ControlPoint 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)  } };
 559         const ControlPoint 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)  } };
 560         const ControlPoint 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) } };
 561 #undef F
 562
 563         /** Helper structure to index the different curve maps. */
 564         struct ControlPointList {
 565                 size_t length;            ///< The length of the curve map.
 566                 const ControlPoint *list; ///< The actual curve map.
 567         };
 568         static const ControlPointList curve_maps[] = {
 569                 { lengthof(curve_map_1), curve_map_1 },
 570                 { lengthof(curve_map_2), curve_map_2 },
 571                 { lengthof(curve_map_3), curve_map_3 },
 572                 { lengthof(curve_map_4), curve_map_4 },
 573         };
 574
 575         Height ht[lengthof(curve_maps)];
 576         MemSetT(ht, 0, lengthof(ht));
 577
 578         /* Set up a grid to choose curve maps based on location; attempt to get a somewhat square grid */
 579         float factor = sqrt((float)_height_map.size_x / (float)_height_map.size_y);
 580         uint sx = Clamp((int)(((1 << level) * factor) + 0.5), 1, 128);
 581         uint sy = Clamp((int)(((1 << level) / factor) + 0.5), 1, 128);
 582         std::vector<byte> c(static_cast<size_t>(sx) * sy);
 583
 584         for (uint i = 0; i < sx * sy; i++) {
 585                 c[i] = Random() % lengthof(curve_maps);
 586         }
 587
 588         /* Apply curves */
 589         for (int x = 0; x < _height_map.size_x; x++) {
 590
 591                 /* Get our X grid positions and bi-linear ratio */
 592                 float fx = (float)(sx * x) / _height_map.size_x + 1.0f;
 593                 uint x1 = (uint)fx;
 594                 uint x2 = x1;
 595                 float xr = 2.0f * (fx - x1) - 1.0f;
 596                 xr = sin(xr * M_PI_2);
 597                 xr = sin(xr * M_PI_2);
 598                 xr = 0.5f * (xr + 1.0f);
 599                 float xri = 1.0f - xr;
 600
 601                 if (x1 > 0) {
 602                         x1--;
 603                         if (x2 >= sx) x2--;
 604                 }
 605
 606                 for (int y = 0; y < _height_map.size_y; y++) {
 607
 608                         /* Get our Y grid position and bi-linear ratio */
 609                         float fy = (float)(sy * y) / _height_map.size_y + 1.0f;
 610                         uint y1 = (uint)fy;
 611                         uint y2 = y1;
 612                         float yr = 2.0f * (fy - y1) - 1.0f;
 613                         yr = sin(yr * M_PI_2);
 614                         yr = sin(yr * M_PI_2);
 615                         yr = 0.5f * (yr + 1.0f);
 616                         float yri = 1.0f - yr;
 617
 618                         if (y1 > 0) {
 619                                 y1--;
 620                                 if (y2 >= sy) y2--;
 621                         }
 622
 623                         uint corner_a = c[x1 + sx * y1];
 624                         uint corner_b = c[x1 + sx * y2];
 625                         uint corner_c = c[x2 + sx * y1];
 626                         uint corner_d = c[x2 + sx * y2];
 627
 628                         /* Bitmask of which curve maps are chosen, so that we do not bother
 629                          * calculating a curve which won't be used. */
 630                         uint corner_bits = 0;
 631                         corner_bits |= 1 << corner_a;
 632                         corner_bits |= 1 << corner_b;
 633                         corner_bits |= 1 << corner_c;
 634                         corner_bits |= 1 << corner_d;
 635
 636                         Height *h = &_height_map.height(x, y);
 637
 638                         /* Do not touch sea level */
 639                         if (*h < I2H(1)) continue;
 640
 641                         /* Only scale above sea level */
 642                         *h -= I2H(1);
 643
 644                         /* Apply all curve maps that are used on this tile. */
 645                         for (uint t = 0; t < lengthof(curve_maps); t++) {
 646                                 if (!HasBit(corner_bits, t)) continue;
 647
 648                                 [[maybe_unused]] bool found = false;
 649                                 const ControlPoint *cm = curve_maps[t].list;
 650                                 for (uint i = 0; i < curve_maps[t].length - 1; i++) {
 651                                         const ControlPoint &p1 = cm[i];
 652                                         const ControlPoint &p2 = cm[i + 1];
 653
 654                                         if (*h >= p1.x && *h < p2.x) {
 655                                                 ht[t] = p1.y + (*h - p1.x) * (p2.y - p1.y) / (p2.x - p1.x);
 656 #ifdef WITH_ASSERT
 657                                                 found = true;
 658 #endif
 659                                                 break;
 660                                         }
 661                                 }
 662                                 assert(found);
 663                         }
 664
 665                         /* Apply interpolation of curve map results. */
 666                         *h = (Height)((ht[corner_a] * yri + ht[corner_b] * yr) * xri + (ht[corner_c] * yri + ht[corner_d] * yr) * xr);
 667
 668                         /* Readd sea level */
 669                         *h += I2H(1);
 670                 }
 671         }
 672 }
 673
 674 /** Adjusts heights in height map to contain required amount of water tiles */
 675 static void HeightMapAdjustWaterLevel(Amplitude water_percent, Height h_max_new)
 676 {
 677         Height h_min, h_max, h_avg, h_water_level;
 678         int64_t water_tiles, desired_water_tiles;
 679         int *hist;
 680
 681         HeightMapGetMinMaxAvg(&h_min, &h_max, &h_avg);
 682
 683         /* Allocate histogram buffer and clear its cells */
 684         int *hist_buf = CallocT<int>(h_max - h_min + 1);
 685         /* Fill histogram */
 686         hist = HeightMapMakeHistogram(h_min, h_max, hist_buf);
 687
 688         /* How many water tiles do we want? */
 689         desired_water_tiles = A2I(((int64_t)water_percent) * (int64_t)(_height_map.size_x * _height_map.size_y));
 690
 691         /* Raise water_level and accumulate values from histogram until we reach required number of water tiles */
 692         for (h_water_level = h_min, water_tiles = 0; h_water_level < h_max; h_water_level++) {
 693                 water_tiles += hist[h_water_level];
 694                 if (water_tiles >= desired_water_tiles) break;
 695         }
 696
 697         /* We now have the proper water level value.
 698          * Transform the height map into new (normalized) height map:
 699          *   values from range: h_min..h_water_level will become negative so it will be clamped to 0
 700          *   values from range: h_water_level..h_max are transformed into 0..h_max_new
 701          *   where h_max_new is depending on terrain type and map size.
 702          */
 703         for (Height &h : _height_map.h) {
 704                 /* Transform height from range h_water_level..h_max into 0..h_max_new range */
 705                 h = (Height)(((int)h_max_new) * (h - h_water_level) / (h_max - h_water_level)) + I2H(1);
 706                 /* Make sure all values are in the proper range (0..h_max_new) */
 707                 if (h < 0) h = I2H(0);
 708                 if (h >= h_max_new) h = h_max_new - 1;
 709         }
 710
 711         free(hist_buf);
 712 }
 713
 714 static double perlin_coast_noise_2D(const double x, const double y, const double p, const int prime);
 715
 716 /**
 717  * This routine sculpts in from the edge a random amount, again a Perlin
 718  * sequence, to avoid the rigid flat-edge slopes that were present before. The
 719  * Perlin noise map doesn't know where we are going to slice across, and so we
 720  * often cut straight through high terrain. The smoothing routine makes it
 721  * legal, gradually increasing up from the edge to the original terrain height.
 722  * By cutting parts of this away, it gives a far more irregular edge to the
 723  * map-edge. Sometimes it works beautifully with the existing sea & lakes, and
 724  * creates a very realistic coastline. Other times the variation is less, and
 725  * the map-edge shows its cliff-like roots.
 726  *
 727  * This routine may be extended to randomly sculpt the height of the terrain
 728  * near the edge. This will have the coast edge at low level (1-3), rising in
 729  * smoothed steps inland to about 15 tiles in. This should make it look as
 730  * though the map has been built for the map size, rather than a slice through
 731  * a larger map.
 732  *
 733  * Please note that all the small numbers; 53, 101, 167, etc. are small primes
 734  * to help give the perlin noise a bit more of a random feel.
 735  */
 736 static void HeightMapCoastLines(uint8_t water_borders)
 737 {
 738         int smallest_size = std::min(_settings_game.game_creation.map_x, _settings_game.game_creation.map_y);
 739         const int margin = 4;
 740         int y, x;
 741         double max_x;
 742         double max_y;
 743
 744         /* Lower to sea level */
 745         for (y = 0; y <= _height_map.size_y; y++) {
 746                 if (HasBit(water_borders, BORDER_NE)) {
 747                         /* Top right */
 748                         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);
 749                         max_x = std::max((smallest_size * smallest_size / 64) + max_x, (smallest_size * smallest_size / 64) + margin - max_x);
 750                         if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
 751                         for (x = 0; x < max_x; x++) {
 752                                 _height_map.height(x, y) = 0;
 753                         }
 754                 }
 755
 756                 if (HasBit(water_borders, BORDER_SW)) {
 757                         /* Bottom left */
 758                         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);
 759                         max_x = std::max((smallest_size * smallest_size / 64) + max_x, (smallest_size * smallest_size / 64) + margin - max_x);
 760                         if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
 761                         for (x = _height_map.size_x; x > (_height_map.size_x - 1 - max_x); x--) {
 762                                 _height_map.height(x, y) = 0;
 763                         }
 764                 }
 765         }
 766
 767         /* Lower to sea level */
 768         for (x = 0; x <= _height_map.size_x; x++) {
 769                 if (HasBit(water_borders, BORDER_NW)) {
 770                         /* Top left */
 771                         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);
 772                         max_y = std::max((smallest_size * smallest_size / 64) + max_y, (smallest_size * smallest_size / 64) + margin - max_y);
 773                         if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
 774                         for (y = 0; y < max_y; y++) {
 775                                 _height_map.height(x, y) = 0;
 776                         }
 777                 }
 778
 779                 if (HasBit(water_borders, BORDER_SE)) {
 780                         /* Bottom right */
 781                         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);
 782                         max_y = std::max((smallest_size * smallest_size / 64) + max_y, (smallest_size * smallest_size / 64) + margin - max_y);
 783                         if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
 784                         for (y = _height_map.size_y; y > (_height_map.size_y - 1 - max_y); y--) {
 785                                 _height_map.height(x, y) = 0;
 786                         }
 787                 }
 788         }
 789 }
 790
 791 /** Start at given point, move in given direction, find and Smooth coast in that direction */
 792 static void HeightMapSmoothCoastInDirection(int org_x, int org_y, int dir_x, int dir_y)
 793 {
 794         const int max_coast_dist_from_edge = 35;
 795         const int max_coast_Smooth_depth = 35;
 796
 797         int x, y;
 798         int ed; // coast distance from edge
 799         int depth;
 800
 801         Height h_prev = I2H(1);
 802         Height h;
 803
 804         assert(IsValidXY(org_x, org_y));
 805
 806         /* Search for the coast (first non-water tile) */
 807         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++) {
 808                 /* Coast found? */
 809                 if (_height_map.height(x, y) >= I2H(1)) break;
 810
 811                 /* Coast found in the neighborhood? */
 812                 if (IsValidXY(x + dir_y, y + dir_x) && _height_map.height(x + dir_y, y + dir_x) > 0) break;
 813
 814                 /* Coast found in the neighborhood on the other side */
 815                 if (IsValidXY(x - dir_y, y - dir_x) && _height_map.height(x - dir_y, y - dir_x) > 0) break;
 816         }
 817
 818         /* Coast found or max_coast_dist_from_edge has been reached.
 819          * Soften the coast slope */
 820         for (depth = 0; IsValidXY(x, y) && depth <= max_coast_Smooth_depth; depth++, x += dir_x, y += dir_y) {
 821                 h = _height_map.height(x, y);
 822                 h = static_cast<Height>(std::min<uint>(h, h_prev + (4 + depth))); // coast softening formula
 823                 _height_map.height(x, y) = h;
 824                 h_prev = h;
 825         }
 826 }
 827
 828 /** Smooth coasts by modulating height of tiles close to map edges with cosine of distance from edge */
 829 static void HeightMapSmoothCoasts(uint8_t water_borders)
 830 {
 831         int x, y;
 832         /* First Smooth NW and SE coasts (y close to 0 and y close to size_y) */
 833         for (x = 0; x < _height_map.size_x; x++) {
 834                 if (HasBit(water_borders, BORDER_NW)) HeightMapSmoothCoastInDirection(x, 0, 0, 1);
 835                 if (HasBit(water_borders, BORDER_SE)) HeightMapSmoothCoastInDirection(x, _height_map.size_y - 1, 0, -1);
 836         }
 837         /* First Smooth NE and SW coasts (x close to 0 and x close to size_x) */
 838         for (y = 0; y < _height_map.size_y; y++) {
 839                 if (HasBit(water_borders, BORDER_NE)) HeightMapSmoothCoastInDirection(0, y, 1, 0);
 840                 if (HasBit(water_borders, BORDER_SW)) HeightMapSmoothCoastInDirection(_height_map.size_x - 1, y, -1, 0);
 841         }
 842 }
 843
 844 /**
 845  * This routine provides the essential cleanup necessary before OTTD can
 846  * display the terrain. When generated, the terrain heights can jump more than
 847  * one level between tiles. This routine smooths out those differences so that
 848  * the most it can change is one level. When OTTD can support cliffs, this
 849  * routine may not be necessary.
 850  */
 851 static void HeightMapSmoothSlopes(Height dh_max)
 852 {
 853         for (int y = 0; y <= (int)_height_map.size_y; y++) {
 854                 for (int x = 0; x <= (int)_height_map.size_x; x++) {
 855                         Height h_max = std::min(_height_map.height(x > 0 ? x - 1 : x, y), _height_map.height(x, y > 0 ? y - 1 : y)) + dh_max;
 856                         if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 857                 }
 858         }
 859         for (int y = _height_map.size_y; y >= 0; y--) {
 860                 for (int x = _height_map.size_x; x >= 0; x--) {
 861                         Height 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;
 862                         if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 863                 }
 864         }
 865 }
 866
 867 /**
 868  * Height map terraform post processing:
 869  *  - water level adjusting
 870  *  - coast Smoothing
 871  *  - slope Smoothing
 872  *  - height histogram redistribution by sine wave transform
 873  */
 874 static void HeightMapNormalize()
 875 {
 876         int sea_level_setting = _settings_game.difficulty.quantity_sea_lakes;
 877         const Amplitude 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;
 878         const Height h_max_new = TGPGetMaxHeight();
 879         const Height roughness = 7 + 3 * _settings_game.game_creation.tgen_smoothness;
 880
 881         HeightMapAdjustWaterLevel(water_percent, h_max_new);
 882
 883         byte water_borders = _settings_game.construction.freeform_edges ? _settings_game.game_creation.water_borders : 0xF;
 884         if (water_borders == BORDERS_RANDOM) water_borders = GB(Random(), 0, 4);
 885
 886         HeightMapCoastLines(water_borders);
 887         HeightMapSmoothSlopes(roughness);
 888
 889         HeightMapSmoothCoasts(water_borders);
 890         HeightMapSmoothSlopes(roughness);
 891
 892         HeightMapSineTransform(I2H(1), h_max_new);
 893
 894         if (_settings_game.game_creation.variety > 0) {
 895                 HeightMapCurves(_settings_game.game_creation.variety);
 896         }
 897
 898         HeightMapSmoothSlopes(I2H(1));
 899 }
 900
 901 /**
 902  * The Perlin Noise calculation using large primes
 903  * The initial number is adjusted by two values; the generation_seed, and the
 904  * passed parameter; prime.
 905  * prime is used to allow the perlin noise generator to create useful random
 906  * numbers from slightly different series.
 907  */
 908 static double int_noise(const long x, const long y, const int prime)
 909 {
 910         long n = x + y * prime + _settings_game.game_creation.generation_seed;
 911
 912         n = (n << 13) ^ n;
 913
 914         /* Pseudo-random number generator, using several large primes */
 915         return 1.0 - (double)((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0;
 916 }
 917
 918
 919 /**
 920  * This routine determines the interpolated value between a and b
 921  */
 922 static inline double linear_interpolate(const double a, const double b, const double x)
 923 {
 924         return a + x * (b - a);
 925 }
 926
 927
 928 /**
 929  * This routine returns the smoothed interpolated noise for an x and y, using
 930  * the values from the surrounding positions.
 931  */
 932 static double interpolated_noise(const double x, const double y, const int prime)
 933 {
 934         const int integer_X = (int)x;
 935         const int integer_Y = (int)y;
 936
 937         const double fractional_X = x - (double)integer_X;
 938         const double fractional_Y = y - (double)integer_Y;
 939
 940         const double v1 = int_noise(integer_X,     integer_Y,     prime);
 941         const double v2 = int_noise(integer_X + 1, integer_Y,     prime);
 942         const double v3 = int_noise(integer_X,     integer_Y + 1, prime);
 943         const double v4 = int_noise(integer_X + 1, integer_Y + 1, prime);
 944
 945         const double i1 = linear_interpolate(v1, v2, fractional_X);
 946         const double i2 = linear_interpolate(v3, v4, fractional_X);
 947
 948         return linear_interpolate(i1, i2, fractional_Y);
 949 }
 950
 951
 952 /**
 953  * This is a similar function to the main perlin noise calculation, but uses
 954  * the value p passed as a parameter rather than selected from the predefined
 955  * sequences. as you can guess by its title, i use this to create the indented
 956  * coastline, which is just another perlin sequence.
 957  */
 958 static double perlin_coast_noise_2D(const double x, const double y, const double p, const int prime)
 959 {
 960         double total = 0.0;
 961
 962         for (int i = 0; i < 6; i++) {
 963                 const double frequency = (double)(1 << i);
 964                 const double amplitude = pow(p, (double)i);
 965
 966                 total += interpolated_noise((x * frequency) / 64.0, (y * frequency) / 64.0, prime) * amplitude;
 967         }
 968
 969         return total;
 970 }
 971
 972
 973 /** A small helper function to initialize the terrain */
 974 static void TgenSetTileHeight(TileIndex tile, int height)
 975 {
 976         SetTileHeight(tile, height);
 977
 978         /* Only clear the tiles within the map area. */
 979         if (IsInnerTile(tile)) {
 980                 MakeClear(tile, CLEAR_GRASS, 3);
 981         }
 982 }
 983
 984 /**
 985  * The main new land generator using Perlin noise. Desert landscape is handled
 986  * different to all others to give a desert valley between two high mountains.
 987  * Clearly if a low height terrain (flat/very flat) is chosen, then the tropic
 988  * areas won't be high enough, and there will be very little tropic on the map.
 989  * Thus Tropic works best on Hilly or Mountainous.
 990  */
 991 void GenerateTerrainPerlin()
 992 {
 993         if (!AllocHeightMap()) return;
 994         GenerateWorldSetAbortCallback(FreeHeightMap);
 995
 996         HeightMapGenerate();
 997
 998         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
 999
1000         HeightMapNormalize();
1001
1002         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
1003
1004         /* First make sure the tiles at the north border are void tiles if needed. */
1005         if (_settings_game.construction.freeform_edges) {
1006                 for (uint x = 0; x < Map::SizeX(); x++) MakeVoid(TileXY(x, 0));
1007                 for (uint y = 0; y < Map::SizeY(); y++) MakeVoid(TileXY(0, y));
1008         }
1009
1010         int max_height = H2I(TGPGetMaxHeight());
1011
1012         /* Transfer height map into OTTD map */
1013         for (int y = 0; y < _height_map.size_y; y++) {
1014                 for (int x = 0; x < _height_map.size_x; x++) {
1015                         TgenSetTileHeight(TileXY(x, y), Clamp(H2I(_height_map.height(x, y)), 0, max_height));
1016                 }
1017         }
1018
1019         IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
1020
1021         FreeHeightMap();
1022         GenerateWorldSetAbortCallback(nullptr);
1023 }