Files @ r8806:1fc0d9e1c2bf
Branch filter:

Location: cpp/openttd-patchpack/source/src/tunnelbridge_cmd.cpp

smatz
(svn r12547) -Feature: invisibility options to make objects invisible instead of transparent
   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
/* $Id$ */

/** @file tunnelbridge_cmd.cpp
 * This file deals with tunnels and bridges (non-gui stuff)
 * @todo seperate this file into two
 */

#include "stdafx.h"
#include "openttd.h"
#include "bridge_map.h"
#include "rail_map.h"
#include "road_map.h"
#include "tile_cmd.h"
#include "landscape.h"
#include "tunnel_map.h"
#include "unmovable_map.h"
#include "viewport_func.h"
#include "command_func.h"
#include "town.h"
#include "variables.h"
#include "bridge.h"
#include "train.h"
#include "water_map.h"
#include "yapf/yapf.h"
#include "newgrf_sound.h"
#include "autoslope.h"
#include "transparency.h"
#include "tunnelbridge_map.h"
#include "strings_func.h"
#include "date_func.h"
#include "functions.h"
#include "vehicle_func.h"
#include "sound_func.h"
#include "signal_func.h"
#include "tunnelbridge.h"
#include "player_base.h"
#include "engine_func.h"

#include "table/sprites.h"
#include "table/strings.h"
#include "table/bridge_land.h"

BridgeSpec _bridge[MAX_BRIDGES];

/** Reset the data been eventually changed by the grf loaded. */
void ResetBridges()
{
	/* First, free sprite table data */
	for (BridgeType i = 0; i < MAX_BRIDGES; i++) {
		if (_bridge[i].sprite_table != NULL) {
			for (uint j = 0; j < 7; j++) free(_bridge[i].sprite_table[j]);
			free(_bridge[i].sprite_table);
		}
	}

	/* Then, wipe out current bidges */
	memset(&_bridge, 0, sizeof(_bridge));
	/* And finally, reinstall default data */
	memcpy(&_bridge, &_orig_bridge, sizeof(_orig_bridge));
}

/** calculate the price factor for building a long bridge.
 * basically the cost delta is 1,1, 1, 2,2, 3,3,3, 4,4,4,4, 5,5,5,5,5, 6,6,6,6,6,6,  7,7,7,7,7,7,7,  8,8,8,8,8,8,8,8,
 */
int CalcBridgeLenCostFactor(int x)
{
	int n;
	int r;

	if (x < 2) return x;
	x -= 2;
	for (n = 0, r = 2;; n++) {
		if (x <= n) return r + x * n;
		r += n * n;
		x -= n;
	}
}

Foundation GetBridgeFoundation(Slope tileh, Axis axis)
{
	if ((tileh == SLOPE_FLAT) ||
	    (((tileh == SLOPE_NE) || (tileh == SLOPE_SW)) && (axis == AXIS_X)) ||
	    (((tileh == SLOPE_NW) || (tileh == SLOPE_SE)) && (axis == AXIS_Y))) return FOUNDATION_NONE;

	return (HasSlopeHighestCorner(tileh) ? InclinedFoundation(axis) : FlatteningFoundation(tileh));
}

/**
 * Determines if the track on a bridge ramp is flat or goes up/down.
 *
 * @param tileh Slope of the tile under the bridge head
 * @param axis Orientation of bridge
 * @return true iff the track is flat.
 */
bool HasBridgeFlatRamp(Slope tileh, Axis axis)
{
	ApplyFoundationToSlope(GetBridgeFoundation(tileh, axis), &tileh);
	/* If the foundation slope is flat the bridge has a non-flat ramp and vice versa. */
	return (tileh != SLOPE_FLAT);
}

static inline const PalSpriteID *GetBridgeSpriteTable(int index, byte table)
{
	const BridgeSpec *bridge = GetBridgeSpec(index);
	assert(table < 7);
	if (bridge->sprite_table == NULL || bridge->sprite_table[table] == NULL) {
		return _bridge_sprite_table[index][table];
	} else {
		return bridge->sprite_table[table];
	}
}


/**
 * Determines the foundation for the north bridge head, and tests if the resulting slope is valid.
 *
 * @param axis Axis of the bridge
 * @param tileh Slope of the tile under the north bridge head; returns slope on top of foundation
 * @param z TileZ corresponding to tileh, gets modified as well
 * @return Error or cost for bridge foundation
 */
static CommandCost CheckBridgeSlopeNorth(Axis axis, Slope *tileh, uint *z)
{
	Foundation f = GetBridgeFoundation(*tileh, axis);
	*z += ApplyFoundationToSlope(f, tileh);

	Slope valid_inclined = (axis == AXIS_X ? SLOPE_NE : SLOPE_NW);
	if ((*tileh != SLOPE_FLAT) && (*tileh != valid_inclined)) return CMD_ERROR;

	if (f == FOUNDATION_NONE) return CommandCost();

	return CommandCost(EXPENSES_CONSTRUCTION, _price.terraform);
}

/**
 * Determines the foundation for the south bridge head, and tests if the resulting slope is valid.
 *
 * @param axis Axis of the bridge
 * @param tileh Slope of the tile under the south bridge head; returns slope on top of foundation
 * @param z TileZ corresponding to tileh, gets modified as well
 * @return Error or cost for bridge foundation
 */
static CommandCost CheckBridgeSlopeSouth(Axis axis, Slope *tileh, uint *z)
{
	Foundation f = GetBridgeFoundation(*tileh, axis);
	*z += ApplyFoundationToSlope(f, tileh);

	Slope valid_inclined = (axis == AXIS_X ? SLOPE_SW : SLOPE_SE);
	if ((*tileh != SLOPE_FLAT) && (*tileh != valid_inclined)) return CMD_ERROR;

	if (f == FOUNDATION_NONE) return CommandCost();

	return CommandCost(EXPENSES_CONSTRUCTION, _price.terraform);
}

bool CheckBridge_Stuff(BridgeType bridge_type, uint bridge_len)
{
	const BridgeSpec *b = GetBridgeSpec(bridge_type);
	uint max; // max possible length of a bridge (with patch 100)

	if (bridge_type >= MAX_BRIDGES) return false;
	if (b->avail_year > _cur_year) return false;

	max = b->max_length;
	if (max >= 16 && _patches.longbridges) max = 100;

	return b->min_length <= bridge_len && bridge_len <= max;
}

/** Build a Bridge
 * @param end_tile end tile
 * @param flags type of operation
 * @param p1 packed start tile coords (~ dx)
 * @param p2 various bitstuffed elements
 * - p2 = (bit 0- 7) - bridge type (hi bh)
 * - p2 = (bit 8-..) - rail type or road types.
 * - p2 = (bit 15  ) - set means road bridge.
 */
CommandCost CmdBuildBridge(TileIndex end_tile, uint32 flags, uint32 p1, uint32 p2)
{
	BridgeType bridge_type;
	RailType railtype = INVALID_RAILTYPE;
	RoadTypes roadtypes = ROADTYPES_NONE;
	uint x;
	uint y;
	uint sx;
	uint sy;
	TileIndex tile_start;
	TileIndex tile_end;
	Slope tileh_start;
	Slope tileh_end;
	uint z_start;
	uint z_end;
	TileIndex tile;
	TileIndexDiff delta;
	uint bridge_len;
	Axis direction;
	CommandCost cost(EXPENSES_CONSTRUCTION);
	CommandCost ret;
	bool replace_bridge = false;
	BridgeType replaced_bridge_type;
	TransportType transport_type;

	/* unpack parameters */
	bridge_type = GB(p2, 0, 8);

	if (p1 >= MapSize()) return CMD_ERROR;

	transport_type = (TransportType)GB(p2, 15, 2);

	/* type of bridge */
	switch (transport_type) {
		case TRANSPORT_ROAD:
			roadtypes = (RoadTypes)GB(p2, 8, 3);
			if (!AreValidRoadTypes(roadtypes) || !HasRoadTypesAvail(_current_player, roadtypes)) return CMD_ERROR;
			break;

		case TRANSPORT_RAIL:
			railtype = (RailType)GB(p2, 8, 8);
			if (!ValParamRailtype(railtype)) return CMD_ERROR;
			break;

		default:
			/* For now, only TRANSPORT_RAIL and TRANSPORT_ROAD are allowed.
			 * But let not this stops us for preparing the future */
			return CMD_ERROR;
	}

	x = TileX(end_tile);
	y = TileY(end_tile);
	sx = TileX(p1);
	sy = TileY(p1);

	/* check if valid, and make sure that (x,y) are smaller than (sx,sy) */
	if (x == sx) {
		if (y == sy) return_cmd_error(STR_5008_CANNOT_START_AND_END_ON);
		direction = AXIS_Y;
		if (y > sy) Swap(y, sy);
	} else if (y == sy) {
		direction = AXIS_X;
		if (x > sx) Swap(x, sx);
	} else {
		return_cmd_error(STR_500A_START_AND_END_MUST_BE_IN);
	}

	/* set and test bridge length, availability */
	bridge_len = sx + sy - x - y - 1;
	if (!CheckBridge_Stuff(bridge_type, bridge_len)) return_cmd_error(STR_5015_CAN_T_BUILD_BRIDGE_HERE);

	/* retrieve landscape height and ensure it's on land */
	tile_start = TileXY(x, y);
	tile_end = TileXY(sx, sy);
	if (IsWaterTile(tile_start) || IsWaterTile(tile_end)) {
		return_cmd_error(STR_02A0_ENDS_OF_BRIDGE_MUST_BOTH);
	}

	tileh_start = GetTileSlope(tile_start, &z_start);
	tileh_end = GetTileSlope(tile_end, &z_end);

	CommandCost terraform_cost_north = CheckBridgeSlopeNorth(direction, &tileh_start, &z_start);
	CommandCost terraform_cost_south = CheckBridgeSlopeSouth(direction, &tileh_end,   &z_end);

	if (z_start != z_end) return_cmd_error(STR_BRIDGEHEADS_NOT_SAME_HEIGHT);

	if (IsBridgeTile(tile_start) && IsBridgeTile(tile_end) &&
			GetOtherBridgeEnd(tile_start) == tile_end &&
			GetTunnelBridgeTransportType(tile_start) == transport_type) {
		/* Replace a current bridge. */

		/* If this is a railway bridge, make sure the railtypes match. */
		if (transport_type == TRANSPORT_RAIL && GetRailType(tile_start) != railtype) {
			return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
		}

		/* Do not replace town bridges with lower speed bridges. */
		if (!(flags & DC_QUERY_COST) && IsTileOwner(tile_start, OWNER_TOWN) &&
				GetBridgeSpec(bridge_type)->speed < GetBridgeSpec(GetBridgeType(tile_start))->speed) {
			Town *t = ClosestTownFromTile(tile_start, UINT_MAX);

			if (t == NULL) {
				return CMD_ERROR;
			} else {
				SetDParam(0, t->index);
				return_cmd_error(STR_2009_LOCAL_AUTHORITY_REFUSES);
			}
		}

		/* Do not replace the bridge with the same bridge type. */
		if (!(flags & DC_QUERY_COST) && bridge_type == GetBridgeType(tile_start)) {
			return_cmd_error(STR_1007_ALREADY_BUILT);
		}

		/* Do not allow replacing another player's bridges. */
		if (!IsTileOwner(tile_start, _current_player) && !IsTileOwner(tile_start, OWNER_TOWN)) {
			return_cmd_error(STR_1024_AREA_IS_OWNED_BY_ANOTHER);
		}

		cost.AddCost((bridge_len + 1) * _price.clear_bridge); // The cost of clearing the current bridge.
		replace_bridge = true;
		replaced_bridge_type = GetBridgeType(tile_start);

		/* Do not remove road types when upgrading a bridge */
		roadtypes |= GetRoadTypes(tile_start);
	} else {
		/* Build a new bridge. */

		bool allow_on_slopes = (!_is_old_ai_player && _patches.build_on_slopes);

		/* Try and clear the start landscape */
		ret = DoCommand(tile_start, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
		if (CmdFailed(ret)) return ret;
		cost = ret;

		if (CmdFailed(terraform_cost_north) || (terraform_cost_north.GetCost() != 0 && !allow_on_slopes))
			return_cmd_error(STR_1000_LAND_SLOPED_IN_WRONG_DIRECTION);
		cost.AddCost(terraform_cost_north);

		/* Try and clear the end landscape */
		ret = DoCommand(tile_end, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
		if (CmdFailed(ret)) return ret;
		cost.AddCost(ret);

		/* false - end tile slope check */
		if (CmdFailed(terraform_cost_south) || (terraform_cost_south.GetCost() != 0 && !allow_on_slopes))
			return_cmd_error(STR_1000_LAND_SLOPED_IN_WRONG_DIRECTION);
		cost.AddCost(terraform_cost_south);
	}

	if (!replace_bridge) {
		TileIndex Heads[] = {tile_start, tile_end};
		int i;

		for (i = 0; i < 2; i++) {
			if (MayHaveBridgeAbove(Heads[i])) {
				if (IsBridgeAbove(Heads[i])) {
					TileIndex north_head = GetNorthernBridgeEnd(Heads[i]);

					if (direction == GetBridgeAxis(Heads[i])) return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);

					if (z_start + TILE_HEIGHT == GetBridgeHeight(north_head)) {
						return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
					}
				}
			}
		}
	}

	/* do the drill? */
	if (flags & DC_EXEC) {
		DiagDirection dir = AxisToDiagDir(direction);
		Owner owner = (replace_bridge && IsTileOwner(tile_start, OWNER_TOWN)) ? OWNER_TOWN : _current_player;

		switch (transport_type) {
			case TRANSPORT_RAIL:
				MakeRailBridgeRamp(tile_start, owner, bridge_type, dir,                 railtype);
				MakeRailBridgeRamp(tile_end,   owner, bridge_type, ReverseDiagDir(dir), railtype);
				break;

			case TRANSPORT_ROAD:
				MakeRoadBridgeRamp(tile_start, owner, bridge_type, dir,                 roadtypes);
				MakeRoadBridgeRamp(tile_end,   owner, bridge_type, ReverseDiagDir(dir), roadtypes);
				break;

			default:
				NOT_REACHED();
				break;
		}
		MarkTileDirtyByTile(tile_start);
		MarkTileDirtyByTile(tile_end);
	}

	delta = (direction == AXIS_X ? TileDiffXY(1, 0) : TileDiffXY(0, 1));
	for (tile = tile_start + delta; tile != tile_end; tile += delta) {
		if (GetTileMaxZ(tile) > z_start) return_cmd_error(STR_BRIDGE_TOO_LOW_FOR_TERRAIN);

		if (MayHaveBridgeAbove(tile) && IsBridgeAbove(tile) && !replace_bridge) {
			/* Disallow crossing bridges for the time being */
			return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
		}

		switch (GetTileType(tile)) {
			case MP_WATER:
				if (!EnsureNoVehicleOnGround(tile)) return_cmd_error(STR_980E_SHIP_IN_THE_WAY);
				if (!IsWater(tile) && !IsCoast(tile)) goto not_valid_below;
				break;

			case MP_RAILWAY:
				if (!IsPlainRailTile(tile)) goto not_valid_below;
				break;

			case MP_ROAD:
				if (IsRoadDepot(tile)) goto not_valid_below;
				break;

			case MP_TUNNELBRIDGE:
				if (IsTunnel(tile)) break;
				if (replace_bridge) break;
				if (direction == DiagDirToAxis(GetTunnelBridgeDirection(tile))) goto not_valid_below;
				if (z_start < GetBridgeHeight(tile)) goto not_valid_below;
				break;

			case MP_UNMOVABLE:
				if (!IsOwnedLand(tile)) goto not_valid_below;
				break;

			case MP_CLEAR:
				break;

			default:
not_valid_below:;
				/* try and clear the middle landscape */
				ret = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
				if (CmdFailed(ret)) return ret;
				cost.AddCost(ret);
				break;
		}

		if (flags & DC_EXEC) {
			SetBridgeMiddle(tile, direction);
			MarkTileDirtyByTile(tile);
		}
	}

	if (flags & DC_EXEC && transport_type == TRANSPORT_RAIL) {
		Track track = AxisToTrack(direction);
		AddSideToSignalBuffer(tile_start, INVALID_DIAGDIR, _current_player);
		YapfNotifyTrackLayoutChange(tile_start, track);
	}

	/* for human player that builds the bridge he gets a selection to choose from bridges (DC_QUERY_COST)
	 * It's unnecessary to execute this command every time for every bridge. So it is done only
	 * and cost is computed in "bridge_gui.c". For AI, Towns this has to be of course calculated
	 */
	if (!(flags & DC_QUERY_COST) || (IsValidPlayer(_current_player) && GetPlayer(_current_player)->is_ai)) {
		bridge_len += 2; // begin and end tiles/ramps

		if (IsValidPlayer(_current_player) && !_is_old_ai_player)
			bridge_len = CalcBridgeLenCostFactor(bridge_len);

		cost.AddCost((int64)bridge_len * _price.build_bridge * GetBridgeSpec(bridge_type)->price >> 8);
	}

	return cost;
}


/** Build Tunnel.
 * @param start_tile start tile of tunnel
 * @param flags type of operation
 * @param p1 railtype or roadtypes. bit 9 set means road tunnel
 * @param p2 unused
 */
CommandCost CmdBuildTunnel(TileIndex start_tile, uint32 flags, uint32 p1, uint32 p2)
{
	TileIndexDiff delta;
	TileIndex end_tile;
	DiagDirection direction;
	Slope start_tileh;
	Slope end_tileh;
	TransportType transport_type = (TransportType)GB(p1, 9, 1);
	uint start_z;
	uint end_z;
	CommandCost cost(EXPENSES_CONSTRUCTION);
	CommandCost ret;

	_build_tunnel_endtile = 0;
	if (transport_type == TRANSPORT_RAIL) {
		if (!ValParamRailtype((RailType)p1)) return CMD_ERROR;
	} else {
		const RoadTypes rts = (RoadTypes)GB(p1, 0, 3);
		if (!AreValidRoadTypes(rts) || !HasRoadTypesAvail(_current_player, rts)) return CMD_ERROR;
	}

	start_tileh = GetTileSlope(start_tile, &start_z);
	direction = GetInclinedSlopeDirection(start_tileh);
	if (direction == INVALID_DIAGDIR) return_cmd_error(STR_500B_SITE_UNSUITABLE_FOR_TUNNEL);

	if (IsWaterTile(start_tile)) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);

	ret = DoCommand(start_tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
	if (CmdFailed(ret)) return ret;

	/* XXX - do NOT change 'ret' in the loop, as it is used as the price
	 * for the clearing of the entrance of the tunnel. Assigning it to
	 * cost before the loop will yield different costs depending on start-
	 * position, because of increased-cost-by-length: 'cost += cost >> 3' */

	delta = TileOffsByDiagDir(direction);
	DiagDirection tunnel_in_way_dir;
	if (OtherAxis(DiagDirToAxis(direction)) == AXIS_X) {
		tunnel_in_way_dir = (TileX(start_tile) < (MapMaxX() / 2)) ? DIAGDIR_SW : DIAGDIR_NE;
	} else {
		tunnel_in_way_dir = (TileY(start_tile) < (MapMaxX() / 2)) ? DIAGDIR_SE : DIAGDIR_NW;
	}

	end_tile = start_tile;

	/** Tile shift coeficient. Will decrease for very long tunnels to avoid exponential growth of price*/
	int tiles_coef = 3;
	/** Number of tiles from start of tunnel */
	int tiles = 0;
	/** Number of tiles at which the cost increase coefficient per tile is halved */
	int tiles_bump = 25;

	for (;;) {
		end_tile += delta;
		end_tileh = GetTileSlope(end_tile, &end_z);

		if (start_z == end_z) break;

		if (!_cheats.crossing_tunnels.value && IsTunnelInWayDir(end_tile, start_z, tunnel_in_way_dir)) {
			return_cmd_error(STR_5003_ANOTHER_TUNNEL_IN_THE_WAY);
		}

		tiles++;
		if (tiles == tiles_bump) {
			tiles_coef++;
			tiles_bump *= 2;
		}

		cost.AddCost(_price.build_tunnel);
		cost.AddCost(cost.GetCost() >> tiles_coef); // add a multiplier for longer tunnels
	}

	/* Add the cost of the entrance */
	cost.AddCost(_price.build_tunnel);
	cost.AddCost(ret);

	/* if the command fails from here on we want the end tile to be highlighted */
	_build_tunnel_endtile = end_tile;

	if (IsWaterTile(end_tile)) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);

	/* slope of end tile must be complementary to the slope of the start tile */
	if (end_tileh != ComplementSlope(start_tileh)) {
		/* Check if there is a structure on the terraformed tile. Do not add the cost, that will be done by the terraforming */
		ret = DoCommand(end_tile, 0, 0, DC_AUTO, CMD_LANDSCAPE_CLEAR);
		if (CmdFailed(ret)) return_cmd_error(STR_5005_UNABLE_TO_EXCAVATE_LAND);

		ret = DoCommand(end_tile, end_tileh & start_tileh, 0, flags, CMD_TERRAFORM_LAND);
		if (CmdFailed(ret)) return_cmd_error(STR_5005_UNABLE_TO_EXCAVATE_LAND);
	} else {
		ret = DoCommand(end_tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
		if (CmdFailed(ret)) return ret;
	}
	cost.AddCost(_price.build_tunnel);
	cost.AddCost(ret);

	if (flags & DC_EXEC) {
		if (transport_type == TRANSPORT_RAIL) {
			MakeRailTunnel(start_tile, _current_player, direction,                 (RailType)GB(p1, 0, 4));
			MakeRailTunnel(end_tile,   _current_player, ReverseDiagDir(direction), (RailType)GB(p1, 0, 4));
			AddSideToSignalBuffer(start_tile, INVALID_DIAGDIR, _current_player);
			YapfNotifyTrackLayoutChange(start_tile, AxisToTrack(DiagDirToAxis(direction)));
		} else {
			MakeRoadTunnel(start_tile, _current_player, direction,                 (RoadTypes)GB(p1, 0, 3));
			MakeRoadTunnel(end_tile,   _current_player, ReverseDiagDir(direction), (RoadTypes)GB(p1, 0, 3));
		}
	}

	return cost;
}


static inline bool CheckAllowRemoveTunnelBridge(TileIndex tile)
{
	/* Floods can remove anything as well as the scenario editor */
	if (_current_player == OWNER_WATER || _game_mode == GM_EDITOR) return true;
	/* Obviously if the bridge/tunnel belongs to us, or no-one, we can remove it */
	if (CheckTileOwnership(tile) || IsTileOwner(tile, OWNER_NONE)) return true;
	/* Otherwise we can only remove town-owned stuff with extra patch-settings, or cheat */
	if (IsTileOwner(tile, OWNER_TOWN) && (_patches.extra_dynamite || _cheats.magic_bulldozer.value)) return true;
	return false;
}

static CommandCost DoClearTunnel(TileIndex tile, uint32 flags)
{
	Town *t = NULL;
	TileIndex endtile;

	if (!CheckAllowRemoveTunnelBridge(tile)) return CMD_ERROR;

	endtile = GetOtherTunnelEnd(tile);

	if (GetVehicleTunnelBridge(tile, endtile) != NULL) return CMD_ERROR;

	_build_tunnel_endtile = endtile;

	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		t = ClosestTownFromTile(tile, (uint)-1); // town penalty rating

		/* Check if you are allowed to remove the tunnel owned by a town
		 * Removal depends on difficulty settings */
		if (!CheckforTownRating(flags, t, TUNNELBRIDGE_REMOVE)) {
			SetDParam(0, t->index);
			return_cmd_error(STR_2009_LOCAL_AUTHORITY_REFUSES);
		}
	}

	/* checks if the owner is town then decrease town rating by RATING_TUNNEL_BRIDGE_DOWN_STEP until
	 * you have a "Poor" (0) town rating */
	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM);
	}

	if (flags & DC_EXEC) {
		if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) {
			/* We first need to request values before calling DoClearSquare */
			DiagDirection dir = GetTunnelBridgeDirection(tile);
			Owner owner = GetTileOwner(tile);

			DoClearSquare(tile);
			DoClearSquare(endtile);

			/* cannot use INVALID_DIAGDIR for signal update because the tunnel doesn't exist anymore */
			AddSideToSignalBuffer(tile,    ReverseDiagDir(dir), owner);
			AddSideToSignalBuffer(endtile, dir,                 owner);

			Track track = AxisToTrack(DiagDirToAxis(dir));
			YapfNotifyTrackLayoutChange(tile,    track);
			YapfNotifyTrackLayoutChange(endtile, track);
		} else {
			DoClearSquare(tile);
			DoClearSquare(endtile);
		}
	}
	return CommandCost(EXPENSES_CONSTRUCTION, _price.clear_tunnel * (GetTunnelBridgeLength(tile, endtile) + 2));
}


static CommandCost DoClearBridge(TileIndex tile, uint32 flags)
{
	DiagDirection direction;
	TileIndexDiff delta;
	TileIndex endtile;
	Town *t = NULL;

	if (!CheckAllowRemoveTunnelBridge(tile)) return CMD_ERROR;

	endtile = GetOtherBridgeEnd(tile);

	if (GetVehicleTunnelBridge(tile, endtile) != NULL) return CMD_ERROR;

	direction = GetTunnelBridgeDirection(tile);
	delta = TileOffsByDiagDir(direction);

	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		t = ClosestTownFromTile(tile, (uint)-1); // town penalty rating

		/* Check if you are allowed to remove the bridge owned by a town
		 * Removal depends on difficulty settings */
		if (!CheckforTownRating(flags, t, TUNNELBRIDGE_REMOVE)) {
			SetDParam(0, t->index);
			return_cmd_error(STR_2009_LOCAL_AUTHORITY_REFUSES);
		}
	}

	/* checks if the owner is town then decrease town rating by RATING_TUNNEL_BRIDGE_DOWN_STEP until
	 * you have a "Poor" (0) town rating */
	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM);
	}

	if (flags & DC_EXEC) {
		/* read this value before actual removal of bridge */
		bool rail = GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL;
		Owner owner = GetTileOwner(tile);
		uint height = GetBridgeHeight(tile);

		DoClearSquare(tile);
		DoClearSquare(endtile);
		for (TileIndex c = tile + delta; c != endtile; c += delta) {
			/* do not let trees appear from 'nowhere' after removing bridge */
			if (IsNormalRoadTile(c) && GetRoadside(c) == ROADSIDE_TREES) {
				uint minz = GetTileMaxZ(c) + 3 * TILE_HEIGHT;
				if (height < minz) SetRoadside(c, ROADSIDE_PAVED);
			}
			ClearBridgeMiddle(c);
			MarkTileDirtyByTile(c);
		}

		if (rail) {
			/* cannot use INVALID_DIAGDIR for signal update because the bridge doesn't exist anymore */
			AddSideToSignalBuffer(tile,    ReverseDiagDir(direction), owner);
			AddSideToSignalBuffer(endtile, direction,                 owner);

			Track track = AxisToTrack(DiagDirToAxis(direction));
			YapfNotifyTrackLayoutChange(tile,    track);
			YapfNotifyTrackLayoutChange(endtile, track);
		}
	}

	return CommandCost(EXPENSES_CONSTRUCTION, (GetTunnelBridgeLength(tile, endtile) + 2) * _price.clear_bridge);
}

static CommandCost ClearTile_TunnelBridge(TileIndex tile, byte flags)
{
	if (IsTunnel(tile)) {
		if (flags & DC_AUTO) return_cmd_error(STR_5006_MUST_DEMOLISH_TUNNEL_FIRST);
		return DoClearTunnel(tile, flags);
	} else { // IsBridge(tile)
		if (flags & DC_AUTO) return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
		return DoClearBridge(tile, flags);
	}

	return CMD_ERROR;
}

/**
 * Draws the pillars under high bridges.
 *
 * @param psid Image and palette of a bridge pillar.
 * @param ti #TileInfo of current bridge-middle-tile.
 * @param axis Orientation of bridge.
 * @param type Bridge type.
 * @param x Sprite X position of front pillar.
 * @param y Sprite Y position of front pillar.
 * @param z_bridge Absolute height of bridge bottom.
 */
static void DrawBridgePillars(const PalSpriteID *psid, const TileInfo* ti, Axis axis, BridgeType type, int x, int y, int z_bridge)
{
	/* Do not draw bridge pillars if they are invisible */
	if (IsInvisibilitySet(TO_BRIDGES)) return;

	SpriteID image = psid->sprite;

	if (image != 0) {
		bool drawfarpillar = !HasBit(GetBridgeSpec(type)->flags, 0);

		/* "side" specifies the side the pillars stand on.
		 * The length of the pillars is then set to the height of the bridge over the corners of this edge.
		 *
		 *                axis==AXIS_X  axis==AXIS_Y
		 *   side==false      SW            NW
		 *   side==true       NE            SE
		 *
		 * I have no clue, why this was done this way.
		 */
		bool side = HasBit(image, 0);

		/* "dir" means the edge the pillars stand on */
		DiagDirection dir = AxisToDiagDir(axis);
		if (side != (axis == AXIS_Y)) dir = ReverseDiagDir(dir);

		/* Determine ground height under pillars */
		int front_height = ti->z;
		int back_height = ti->z;
		GetSlopeZOnEdge(ti->tileh, dir, &front_height, &back_height);

		/* x and y size of bounding-box of pillars */
		int w = (axis == AXIS_X ? 16 : 2);
		int h = (axis == AXIS_X ? 2 : 16);
		/* sprite position of back facing pillar */
		int x_back = x - (axis == AXIS_X ? 0 : 9);
		int y_back = y - (axis == AXIS_X ? 9 : 0);

		for (int cur_z = z_bridge; cur_z >= front_height || cur_z >= back_height; cur_z -= TILE_HEIGHT) {
			/* Draw front facing pillar */
			if (cur_z >= front_height) {
				AddSortableSpriteToDraw(image, psid->pal, x, y, w, h, BB_HEIGHT_UNDER_BRIDGE - 5, cur_z, IsTransparencySet(TO_BRIDGES), 0, 0, -5);
			}

			/* Draw back facing pillar, but not the highest part directly under the bridge-floor */
			if (drawfarpillar && cur_z >= back_height && cur_z < z_bridge - TILE_HEIGHT) {
				AddSortableSpriteToDraw(image, psid->pal, x_back, y_back, w, h, BB_HEIGHT_UNDER_BRIDGE - 5, cur_z, IsTransparencySet(TO_BRIDGES), 0, 0, -5);
			}
		}
	}
}

/**
 * Draws the trambits over an already drawn (lower end) of a bridge.
 * @param x       the x of the bridge
 * @param y       the y of the bridge
 * @param z       the z of the bridge
 * @param offset  number representing whether to level or sloped and the direction
 * @param overlay do we want to still see the road?
 * @param head    are we drawing bridge head?
 */
static void DrawBridgeTramBits(int x, int y, byte z, int offset, bool overlay, bool head)
{
	static const SpriteID tram_offsets[2][6] = { { 107, 108, 109, 110, 111, 112 }, { 4, 5, 15, 16, 17, 18 } };
	static const SpriteID back_offsets[6]    =   {  95,  96,  99, 102, 100, 101 };
	static const SpriteID front_offsets[6]   =   {  97,  98, 103, 106, 104, 105 };

	static const uint size_x[6] = {  1, 16, 16,  1, 16,  1 };
	static const uint size_y[6] = { 16,  1,  1, 16,  1, 16 };
	static const uint front_bb_offset_x[6] = { 15,  0,  0, 15,  0, 15 };
	static const uint front_bb_offset_y[6] = {  0, 15, 15,  0, 15,  0 };

	/* The sprites under the vehicles are drawn as SpriteCombine. StartSpriteCombine() has already been called
	 * The bounding boxes here are the same as for bridge front/roof */
	if (head || !IsInvisibilitySet(TO_BRIDGES)) {
		AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + tram_offsets[overlay][offset], PAL_NONE, x, y, size_x[offset], size_y[offset], 0x28, z, !head && IsTransparencySet(TO_BRIDGES));
	}

	/* Do not draw catenary if it is set invisible */
	if (IsInvisibilitySet(TO_CATENARY)) return;

	AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + back_offsets[offset],  PAL_NONE, x, y, size_x[offset], size_y[offset], 0x28, z, IsTransparencySet(TO_CATENARY));

	/* Start a new SpriteCombine for the front part */
	EndSpriteCombine();
	StartSpriteCombine();

	/* For sloped sprites the bounding box needs to be higher, as the pylons stop on a higher point */
	AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + front_offsets[offset], PAL_NONE, x, y, size_x[offset] + front_bb_offset_x[offset], size_y[offset] + front_bb_offset_y[offset], 0x28, z, IsTransparencySet(TO_CATENARY), front_bb_offset_x[offset], front_bb_offset_y[offset]);
}

/**
 * Draws a tunnel of bridge tile.
 * For tunnels, this is rather simple, as you only needa draw the entrance.
 * Bridges are a bit more complex. base_offset is where the sprite selection comes into play
 * and it works a bit like a bitmask.<p> For bridge heads:
 * @param ti TileInfo of the structure to draw
 * <ul><li>Bit 0: direction</li>
 * <li>Bit 1: northern or southern heads</li>
 * <li>Bit 2: Set if the bridge head is sloped</li>
 * <li>Bit 3 and more: Railtype Specific subset</li>
 * </ul>
 * Please note that in this code, "roads" are treated as railtype 1, whilst the real railtypes are 0, 2 and 3
 */
static void DrawTile_TunnelBridge(TileInfo *ti)
{
	SpriteID image;
	TransportType transport_type = GetTunnelBridgeTransportType(ti->tile);
	DiagDirection tunnelbridge_direction = GetTunnelBridgeDirection(ti->tile);

	if (IsTunnel(ti->tile)) {
		/* Front view of tunnel bounding boxes:
		 *
		 *   122223  <- BB_Z_SEPARATOR
		 *   1    3
		 *   1    3                1,3 = empty helper BB
		 *   1    3                  2 = SpriteCombine of tunnel-roof and catenary (tram & elrail)
		 *
		 */

		static const int _tunnel_BB[4][12] = {
			/*  tunnnel-roof  |  Z-separator  | tram-catenary
			 * w  h  bb_x bb_y| x   y   w   h |bb_x bb_y w h */
			{  1,  0, -15, -14,  0, 15, 16,  1, 0, 1, 16, 15 }, // NE
			{  0,  1, -14, -15, 15,  0,  1, 16, 1, 0, 15, 16 }, // SE
			{  1,  0, -15, -14,  0, 15, 16,  1, 0, 1, 16, 15 }, // SW
			{  0,  1, -14, -15, 15,  0,  1, 16, 1, 0, 15, 16 }, // NW
		};
		const int *BB_data = _tunnel_BB[tunnelbridge_direction];

		bool catenary = false;

		if (transport_type == TRANSPORT_RAIL) {
			image = GetRailTypeInfo(GetRailType(ti->tile))->base_sprites.tunnel;
		} else {
			image = SPR_TUNNEL_ENTRY_REAR_ROAD;
		}

		if (HasTunnelBridgeSnowOrDesert(ti->tile)) image += 32;

		image += tunnelbridge_direction * 2;
		DrawGroundSprite(image, PAL_NONE);
		if (transport_type == TRANSPORT_ROAD) {
			RoadTypes rts = GetRoadTypes(ti->tile);

			if (HasBit(rts, ROADTYPE_TRAM)) {
				static const SpriteID tunnel_sprites[2][4] = { { 28, 78, 79, 27 }, {  5, 76, 77,  4 } };

				DrawGroundSprite(SPR_TRAMWAY_BASE + tunnel_sprites[rts - ROADTYPES_TRAM][tunnelbridge_direction], PAL_NONE);

				/* Do not draw wires if they are invisible */
				if (!IsInvisibilitySet(TO_CATENARY)) {
					catenary = true;
					StartSpriteCombine();
					AddSortableSpriteToDraw(SPR_TRAMWAY_TUNNEL_WIRES + tunnelbridge_direction, PAL_NONE, ti->x, ti->y, BB_data[10], BB_data[11], TILE_HEIGHT, ti->z, IsTransparencySet(TO_CATENARY), BB_data[8], BB_data[9], BB_Z_SEPARATOR);
				}
			}
		} else if (!IsInvisibilitySet(TO_CATENARY) && HasCatenary(GetRailType(ti->tile))) {
			DrawCatenary(ti);

			catenary = true;
			StartSpriteCombine();
			DrawCatenaryOnTunnel(ti);
		}

		AddSortableSpriteToDraw(image + 1, PAL_NONE, ti->x + TILE_SIZE - 1, ti->y + TILE_SIZE - 1, BB_data[0], BB_data[1], TILE_HEIGHT, ti->z, false, BB_data[2], BB_data[3], BB_Z_SEPARATOR);

		if (catenary) EndSpriteCombine();

		/* Add helper BB for sprite sorting, that separate the tunnel from things beside of it */
		AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, ti->x             , ti->y             , BB_data[6], BB_data[7], TILE_HEIGHT, ti->z);
		AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, ti->x + BB_data[4], ti->y + BB_data[5], BB_data[6], BB_data[7], TILE_HEIGHT, ti->z);

		DrawBridgeMiddle(ti);
	} else { // IsBridge(ti->tile)
		const PalSpriteID *psid;
		int base_offset;
		bool ice = HasTunnelBridgeSnowOrDesert(ti->tile);

		if (transport_type == TRANSPORT_RAIL) {
			base_offset = GetRailTypeInfo(GetRailType(ti->tile))->bridge_offset;
			assert(base_offset != 8); // This one is used for roads
		} else {
			base_offset = 8;
		}

		/* as the lower 3 bits are used for other stuff, make sure they are clear */
		assert( (base_offset & 0x07) == 0x00);

		DrawFoundation(ti, GetBridgeFoundation(ti->tileh, DiagDirToAxis(tunnelbridge_direction)));

		/* HACK Wizardry to convert the bridge ramp direction into a sprite offset */
		base_offset += (6 - tunnelbridge_direction) % 4;

		if (ti->tileh == SLOPE_FLAT) base_offset += 4; // sloped bridge head

		/* Table number 6 always refers to the bridge heads for any bridge type */
		psid = &GetBridgeSpriteTable(GetBridgeType(ti->tile), 6)[base_offset];

		if (!ice) {
			DrawClearLandTile(ti, 3);
		} else {
			DrawGroundSprite(SPR_FLAT_SNOWY_TILE + _tileh_to_sprite[ti->tileh], PAL_NONE);
		}

		/* draw ramp */

		/* Draw Trambits as SpriteCombine */
		if (transport_type == TRANSPORT_ROAD) StartSpriteCombine();

		/* HACK set the height of the BB of a sloped ramp to 1 so a vehicle on
		 * it doesn't disappear behind it
		 */
		/* Bridge heads are drawn solid no matter how invisibility/transparency is set */
		AddSortableSpriteToDraw(psid->sprite, psid->pal, ti->x, ti->y, 16, 16, ti->tileh == SLOPE_FLAT ? 0 : 8, ti->z);

		if (transport_type == TRANSPORT_ROAD) {
			RoadTypes rts = GetRoadTypes(ti->tile);

			if (HasBit(rts, ROADTYPE_TRAM)) {
				uint offset = tunnelbridge_direction;
				uint z = ti->z;
				if (ti->tileh != SLOPE_FLAT) {
					offset = (offset + 1) & 1;
					z += TILE_HEIGHT;
				} else {
					offset += 2;
				}
				/* DrawBridgeTramBits() calls EndSpriteCombine() and StartSpriteCombine() */
				DrawBridgeTramBits(ti->x, ti->y, z, offset, HasBit(rts, ROADTYPE_ROAD), true);
			}
			EndSpriteCombine();
		} else if (HasCatenary(GetRailType(ti->tile))) {
			DrawCatenary(ti);
		}

		DrawBridgeMiddle(ti);
	}
}


/** Compute bridge piece. Computes the bridge piece to display depending on the position inside the bridge.
 * bridges pieces sequence (middle parts)
 * bridge len 1: 0
 * bridge len 2: 0 1
 * bridge len 3: 0 4 1
 * bridge len 4: 0 2 3 1
 * bridge len 5: 0 2 5 3 1
 * bridge len 6: 0 2 3 2 3 1
 * bridge len 7: 0 2 3 4 2 3 1
 * #0 - always as first, #1 - always as last (if len>1)
 * #2,#3 are to pair in order
 * for odd bridges: #5 is going in the bridge middle if on even position, #4 on odd (counting from 0)
 * @param north Northernmost tile of bridge
 * @param south Southernmost tile of bridge
 * @return Index of bridge piece
 */
static uint CalcBridgePiece(uint north, uint south)
{
	if (north == 1) {
		return 0;
	} else if (south == 1) {
		return 1;
	} else if (north < south) {
		return north & 1 ? 3 : 2;
	} else if (north > south) {
		return south & 1 ? 2 : 3;
	} else {
		return north & 1 ? 5 : 4;
	}
}


void DrawBridgeMiddle(const TileInfo* ti)
{
	/* Sectional view of bridge bounding boxes:
	 *
	 *  1           2                                1,2 = SpriteCombine of Bridge front/(back&floor) and TramCatenary
	 *  1           2                                  3 = empty helper BB
	 *  1     7     2                                4,5 = pillars under higher bridges
	 *  1 6 88888 6 2                                  6 = elrail-pylons
	 *  1 6 88888 6 2                                  7 = elrail-wire
	 *  1 6 88888 6 2  <- TILE_HEIGHT                  8 = rail-vehicle on bridge
	 *  3333333333333  <- BB_Z_SEPARATOR
	 *                 <- unused
	 *    4       5    <- BB_HEIGHT_UNDER_BRIDGE
	 *    4       5
	 *    4       5
	 *
	 */

	/* Z position of the bridge sprites relative to bridge height (downwards) */
	static const int BRIDGE_Z_START = 3;

	const PalSpriteID* psid;
	uint base_offset;
	TileIndex rampnorth;
	TileIndex rampsouth;
	TransportType transport_type;
	Axis axis;
	uint piece;
	BridgeType type;
	int x;
	int y;
	uint z;

	if (!IsBridgeAbove(ti->tile)) return;

	rampnorth = GetNorthernBridgeEnd(ti->tile);
	rampsouth = GetSouthernBridgeEnd(ti->tile);
	transport_type = GetTunnelBridgeTransportType(rampsouth);

	axis = GetBridgeAxis(ti->tile);
	piece = CalcBridgePiece(
		GetTunnelBridgeLength(ti->tile, rampnorth) + 1,
		GetTunnelBridgeLength(ti->tile, rampsouth) + 1
	);
	type = GetBridgeType(rampsouth);

	if (transport_type == TRANSPORT_RAIL) {
		base_offset = GetRailTypeInfo(GetRailType(rampsouth))->bridge_offset;
	} else {
		base_offset = 8;
	}

	psid = base_offset + GetBridgeSpriteTable(type, piece);
	if (axis != AXIS_X) psid += 4;

	x = ti->x;
	y = ti->y;
	uint bridge_z = GetBridgeHeight(rampsouth);
	z = bridge_z - BRIDGE_Z_START;

	/* Add a bounding box, that separates the bridge from things below it. */
	AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, x, y, 16, 16, 1, bridge_z - TILE_HEIGHT + BB_Z_SEPARATOR);

	/* Draw Trambits as SpriteCombine */
	if (transport_type == TRANSPORT_ROAD) StartSpriteCombine();

	/* Draw floor and far part of bridge*/
	if (!IsInvisibilitySet(TO_BRIDGES)) {
		if (axis == AXIS_X) {
			AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 16, 1, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 0, BRIDGE_Z_START);
		} else {
			AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 1, 16, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 0, BRIDGE_Z_START);
		}
	}

	psid++;

	if (transport_type == TRANSPORT_ROAD) {
		RoadTypes rts = GetRoadTypes(rampsouth);

		if (HasBit(rts, ROADTYPE_TRAM)) {
			/* DrawBridgeTramBits() calls EndSpriteCombine() and StartSpriteCombine() */
			DrawBridgeTramBits(x, y, bridge_z, axis ^ 1, HasBit(rts, ROADTYPE_ROAD), false);
		} else {
			EndSpriteCombine();
			StartSpriteCombine();
		}
	} else if (HasCatenary(GetRailType(rampsouth))) {
		DrawCatenary(ti);
	}

	/* draw roof, the component of the bridge which is logically between the vehicle and the camera */
	if (!IsInvisibilitySet(TO_BRIDGES)) {
		if (axis == AXIS_X) {
			y += 12;
			if (psid->sprite & SPRITE_MASK) AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 16, 4, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 3, BRIDGE_Z_START);
		} else {
			x += 12;
			if (psid->sprite & SPRITE_MASK) AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 4, 16, 0x28, z, IsTransparencySet(TO_BRIDGES), 3, 0, BRIDGE_Z_START);
		}
	}

	/* Draw TramFront as SpriteCombine */
	if (transport_type == TRANSPORT_ROAD) EndSpriteCombine();

	/* Do not draw anything more if bridges are invisible */
	if (IsInvisibilitySet(TO_BRIDGES)) return;

	psid++;
	if (ti->z + 5 == z) {
		/* draw poles below for small bridges */
		if (psid->sprite != 0) {
			SpriteID image = psid->sprite;
			SpriteID pal   = psid->pal;
			if (IsTransparencySet(TO_BRIDGES)) {
				SetBit(image, PALETTE_MODIFIER_TRANSPARENT);
				pal = PALETTE_TO_TRANSPARENT;
			}

			DrawGroundSpriteAt(image, pal, x, y, z);
		}
	} else if (_patches.bridge_pillars) {
		/* draw pillars below for high bridges */
		DrawBridgePillars(psid, ti, axis, type, x, y, z);
	}
}


static uint GetSlopeZ_TunnelBridge(TileIndex tile, uint x, uint y)
{
	uint z;
	Slope tileh = GetTileSlope(tile, &z);

	x &= 0xF;
	y &= 0xF;

	if (IsTunnel(tile)) {
		uint pos = (DiagDirToAxis(GetTunnelBridgeDirection(tile)) == AXIS_X ? y : x);

		/* In the tunnel entrance? */
		if (5 <= pos && pos <= 10) return z;
	} else { // IsBridge(tile)
		DiagDirection dir = GetTunnelBridgeDirection(tile);
		uint pos = (DiagDirToAxis(dir) == AXIS_X ? y : x);

		z += ApplyFoundationToSlope(GetBridgeFoundation(tileh, DiagDirToAxis(dir)), &tileh);

		/* On the bridge ramp? */
		if (5 <= pos && pos <= 10) {
			uint delta;

			if (tileh != SLOPE_FLAT) return z + TILE_HEIGHT;

			switch (dir) {
				default: NOT_REACHED();
				case DIAGDIR_NE: delta = (TILE_SIZE - 1 - x) / 2; break;
				case DIAGDIR_SE: delta = y / 2; break;
				case DIAGDIR_SW: delta = x / 2; break;
				case DIAGDIR_NW: delta = (TILE_SIZE - 1 - y) / 2; break;
			}
			return z + 1 + delta;
		}
	}

	return z + GetPartialZ(x, y, tileh);
}

static Foundation GetFoundation_TunnelBridge(TileIndex tile, Slope tileh)
{
	return IsTunnel(tile) ? FOUNDATION_NONE : GetBridgeFoundation(tileh, DiagDirToAxis(GetTunnelBridgeDirection(tile)));
}


static void GetAcceptedCargo_TunnelBridge(TileIndex tile, AcceptedCargo ac)
{
	/* not used */
}

static void GetTileDesc_TunnelBridge(TileIndex tile, TileDesc *td)
{
	if (IsTunnel(tile)) {
		td->str = (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) ?
			STR_5017_RAILROAD_TUNNEL : STR_5018_ROAD_TUNNEL;
	} else { //so it must be a bridge
		td->str = GetBridgeSpec(GetBridgeType(tile))->transport_name[GetTunnelBridgeTransportType(tile)];
	}
	td->owner = GetTileOwner(tile);
}


static void AnimateTile_TunnelBridge(TileIndex tile)
{
	/* not used */
}

static void TileLoop_TunnelBridge(TileIndex tile)
{
	bool snow_or_desert = HasTunnelBridgeSnowOrDesert(tile);
	switch (_opt.landscape) {
		case LT_ARCTIC:
			if (snow_or_desert != (GetTileZ(tile) > GetSnowLine())) {
				SetTunnelBridgeSnowOrDesert(tile, !snow_or_desert);
				MarkTileDirtyByTile(tile);
			}
			break;

		case LT_TROPIC:
			if (GetTropicZone(tile) == TROPICZONE_DESERT && !snow_or_desert) {
				SetTunnelBridgeSnowOrDesert(tile, true);
				MarkTileDirtyByTile(tile);
			}
			break;

		default:
			break;
	}
}

static void ClickTile_TunnelBridge(TileIndex tile)
{
	/* not used */
}


static TrackStatus GetTileTrackStatus_TunnelBridge(TileIndex tile, TransportType mode, uint sub_mode, DiagDirection side)
{
	TransportType transport_type = GetTunnelBridgeTransportType(tile);
	if (transport_type != mode || (transport_type == TRANSPORT_ROAD && (GetRoadTypes(tile) & sub_mode) == 0)) return 0;

	DiagDirection dir = GetTunnelBridgeDirection(tile);
	if (side != INVALID_DIAGDIR && side != ReverseDiagDir(dir)) return 0;
	return CombineTrackStatus(TrackBitsToTrackdirBits(AxisToTrackBits(DiagDirToAxis(dir))), TRACKDIR_BIT_NONE);
}

static void ChangeTileOwner_TunnelBridge(TileIndex tile, PlayerID old_player, PlayerID new_player)
{
	if (!IsTileOwner(tile, old_player)) return;

	if (new_player != PLAYER_SPECTATOR) {
		SetTileOwner(tile, new_player);
	} else {
		if (CmdFailed(DoCommand(tile, 0, 0, DC_EXEC | DC_BANKRUPT, CMD_LANDSCAPE_CLEAR))) {
			/* When clearing the bridge/tunnel failed there are still vehicles on/in
			 * the bridge/tunnel. As all *our* vehicles are already removed, they
			 * must be of another owner. Therefor this must be a road bridge/tunnel.
			 * In that case we can safely reassign the ownership to OWNER_NONE. */
			assert(GetTunnelBridgeTransportType(tile) == TRANSPORT_ROAD);
			SetTileOwner(tile, OWNER_NONE);
		}
	}
}


static const byte _tunnel_fractcoord_1[4]    = {0x8E, 0x18, 0x81, 0xE8};
static const byte _tunnel_fractcoord_2[4]    = {0x81, 0x98, 0x87, 0x38};
static const byte _tunnel_fractcoord_3[4]    = {0x82, 0x88, 0x86, 0x48};
static const byte _exit_tunnel_track[4]      = {1, 2, 1, 2};

/** Get the trackdir of the exit of a tunnel */
static const Trackdir _road_exit_tunnel_state[DIAGDIR_END] = {
	TRACKDIR_X_SW, TRACKDIR_Y_NW, TRACKDIR_X_NE, TRACKDIR_Y_SE
};
static const byte _road_exit_tunnel_frame[4] = {2, 7, 9, 4};

static const byte _tunnel_fractcoord_4[4]    = {0x52, 0x85, 0x98, 0x29};
static const byte _tunnel_fractcoord_5[4]    = {0x92, 0x89, 0x58, 0x25};
static const byte _tunnel_fractcoord_6[4]    = {0x92, 0x89, 0x56, 0x45};
static const byte _tunnel_fractcoord_7[4]    = {0x52, 0x85, 0x96, 0x49};

static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex tile, int x, int y)
{
	int z = GetSlopeZ(x, y) - v->z_pos;

	if (abs(z) > 2) return VETSB_CANNOT_ENTER;
	const DiagDirection dir = GetTunnelBridgeDirection(tile);

	if (IsTunnel(tile)) {
		byte fc;
		DiagDirection vdir;

		if (v->type == VEH_TRAIN) {
			fc = (x & 0xF) + (y << 4);

			vdir = DirToDiagDir(v->direction);

			if (v->u.rail.track != TRACK_BIT_WORMHOLE && dir == vdir) {
				if (IsFrontEngine(v) && fc == _tunnel_fractcoord_1[dir]) {
					if (!PlayVehicleSound(v, VSE_TUNNEL) && RailVehInfo(v->engine_type)->engclass == 0) {
						SndPlayVehicleFx(SND_05_TRAIN_THROUGH_TUNNEL, v);
					}
					return VETSB_CONTINUE;
				}
				if (fc == _tunnel_fractcoord_2[dir]) {
					v->tile = tile;
					v->u.rail.track = TRACK_BIT_WORMHOLE;
					v->vehstatus |= VS_HIDDEN;
					return VETSB_ENTERED_WORMHOLE;
				}
			}

			if (dir == ReverseDiagDir(vdir) && fc == _tunnel_fractcoord_3[dir] && z == 0) {
				/* We're at the tunnel exit ?? */
				v->tile = tile;
				v->u.rail.track = (TrackBits)_exit_tunnel_track[dir];
				assert(v->u.rail.track);
				v->vehstatus &= ~VS_HIDDEN;
				return VETSB_ENTERED_WORMHOLE;
			}
		} else if (v->type == VEH_ROAD) {
			fc = (x & 0xF) + (y << 4);
			vdir = DirToDiagDir(v->direction);

			/* Enter tunnel? */
			if (v->u.road.state != RVSB_WORMHOLE && dir == vdir) {
				if (fc == _tunnel_fractcoord_4[dir] ||
						fc == _tunnel_fractcoord_5[dir]) {
					v->tile = tile;
					v->u.road.state = RVSB_WORMHOLE;
					v->vehstatus |= VS_HIDDEN;
					return VETSB_ENTERED_WORMHOLE;
				} else {
					return VETSB_CONTINUE;
				}
			}

			if (dir == ReverseDiagDir(vdir) && (
						/* We're at the tunnel exit ?? */
						fc == _tunnel_fractcoord_6[dir] ||
						fc == _tunnel_fractcoord_7[dir]
					) &&
					z == 0) {
				v->tile = tile;
				v->u.road.state = _road_exit_tunnel_state[dir];
				v->u.road.frame = _road_exit_tunnel_frame[dir];
				v->vehstatus &= ~VS_HIDDEN;
				return VETSB_ENTERED_WORMHOLE;
			}
		}
	} else { // IsBridge(tile)

		if (v->IsPrimaryVehicle()) {
			/* modify speed of vehicle */
			uint16 spd = GetBridgeSpec(GetBridgeType(tile))->speed;

			if (v->type == VEH_ROAD) spd *= 2;
			if (v->cur_speed > spd) v->cur_speed = spd;
		}

		if (DirToDiagDir(v->direction) == dir) {
			switch (dir) {
				default: NOT_REACHED();
				case DIAGDIR_NE: if ((x & 0xF) != 0)             return VETSB_CONTINUE; break;
				case DIAGDIR_SE: if ((y & 0xF) != TILE_SIZE - 1) return VETSB_CONTINUE; break;
				case DIAGDIR_SW: if ((x & 0xF) != TILE_SIZE - 1) return VETSB_CONTINUE; break;
				case DIAGDIR_NW: if ((y & 0xF) != 0)             return VETSB_CONTINUE; break;
			}
			if (v->type == VEH_TRAIN) {
				v->u.rail.track = TRACK_BIT_WORMHOLE;
				ClrBit(v->u.rail.flags, VRF_GOINGUP);
				ClrBit(v->u.rail.flags, VRF_GOINGDOWN);
			} else {
				v->u.road.state = RVSB_WORMHOLE;
			}
			return VETSB_ENTERED_WORMHOLE;
		} else if (DirToDiagDir(v->direction) == ReverseDiagDir(dir)) {
			v->tile = tile;
			if (v->type == VEH_TRAIN) {
				if (v->u.rail.track == TRACK_BIT_WORMHOLE) {
					v->u.rail.track = (DiagDirToAxis(dir) == AXIS_X ? TRACK_BIT_X : TRACK_BIT_Y);
					return VETSB_ENTERED_WORMHOLE;
				}
			} else {
				if (v->u.road.state == RVSB_WORMHOLE) {
					v->u.road.state = _road_exit_tunnel_state[dir];
					v->u.road.frame = 0;
					return VETSB_ENTERED_WORMHOLE;
				}
			}
			return VETSB_CONTINUE;
		}
	}
	return VETSB_CONTINUE;
}

static CommandCost TerraformTile_TunnelBridge(TileIndex tile, uint32 flags, uint z_new, Slope tileh_new)
{
	if (_patches.build_on_slopes && AutoslopeEnabled() && IsBridge(tile)) {
		DiagDirection direction = GetTunnelBridgeDirection(tile);
		Axis axis = DiagDirToAxis(direction);
		CommandCost res;
		uint z_old;
		Slope tileh_old = GetTileSlope(tile, &z_old);

		/* Check if new slope is valid for bridges in general (so we can savely call GetBridgeFoundation()) */
		if ((direction == DIAGDIR_NW) || (direction == DIAGDIR_NE)) {
			CheckBridgeSlopeSouth(axis, &tileh_old, &z_old);
			res = CheckBridgeSlopeSouth(axis, &tileh_new, &z_new);
		} else {
			CheckBridgeSlopeNorth(axis, &tileh_old, &z_old);
			res = CheckBridgeSlopeNorth(axis, &tileh_new, &z_new);
		}

		/* Surface slope is valid and remains unchanged? */
		if (!CmdFailed(res) && (z_old == z_new) && (tileh_old == tileh_new)) return CommandCost(EXPENSES_CONSTRUCTION, _price.terraform);
	}

	return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
}

extern const TileTypeProcs _tile_type_tunnelbridge_procs = {
	DrawTile_TunnelBridge,           /* draw_tile_proc */
	GetSlopeZ_TunnelBridge,          /* get_slope_z_proc */
	ClearTile_TunnelBridge,          /* clear_tile_proc */
	GetAcceptedCargo_TunnelBridge,   /* get_accepted_cargo_proc */
	GetTileDesc_TunnelBridge,        /* get_tile_desc_proc */
	GetTileTrackStatus_TunnelBridge, /* get_tile_track_status_proc */
	ClickTile_TunnelBridge,          /* click_tile_proc */
	AnimateTile_TunnelBridge,        /* animate_tile_proc */
	TileLoop_TunnelBridge,           /* tile_loop_clear */
	ChangeTileOwner_TunnelBridge,    /* change_tile_owner_clear */
	NULL,                            /* get_produced_cargo_proc */
	VehicleEnter_TunnelBridge,       /* vehicle_enter_tile_proc */
	GetFoundation_TunnelBridge,      /* get_foundation_proc */
	TerraformTile_TunnelBridge,      /* terraform_tile_proc */
};