opf_ship.cpp

00001 /* $Id$ */
00002 
00003 /*
00004  * This file is part of OpenTTD.
00005  * 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.
00006  * 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.
00007  * 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/>.
00008  */
00009 
00012 #include "../../stdafx.h"
00013 #include "../../debug.h"
00014 #include "../../tunnelbridge_map.h"
00015 #include "../../tunnelbridge.h"
00016 #include "../../ship.h"
00017 #include "../../core/random_func.hpp"
00018 #include "opf_ship.h"
00019 
00020 struct RememberData {
00021   uint16 cur_length;
00022   byte depth;
00023   Track last_choosen_track;
00024 };
00025 
00026 struct TrackPathFinder {
00027   TileIndex skiptile;
00028   TileIndex dest_coords;
00029   uint best_bird_dist;
00030   uint best_length;
00031   RememberData rd;
00032   TrackdirByte the_dir;
00033 };
00034 
00035 static bool ShipTrackFollower(TileIndex tile, TrackPathFinder *pfs, uint length)
00036 {
00037   /* Found dest? */
00038   if (tile == pfs->dest_coords) {
00039     pfs->best_bird_dist = 0;
00040 
00041     pfs->best_length = minu(pfs->best_length, length);
00042     return true;
00043   }
00044 
00045   /* Skip this tile in the calculation */
00046   if (tile != pfs->skiptile) {
00047     pfs->best_bird_dist = minu(pfs->best_bird_dist, DistanceMaxPlusManhattan(pfs->dest_coords, tile));
00048   }
00049 
00050   return false;
00051 }
00052 
00053 static void TPFModeShip(TrackPathFinder *tpf, TileIndex tile, DiagDirection direction)
00054 {
00055   if (IsTileType(tile, MP_TUNNELBRIDGE)) {
00056     /* wrong track type */
00057     if (GetTunnelBridgeTransportType(tile) != TRANSPORT_WATER) return;
00058 
00059     DiagDirection dir = GetTunnelBridgeDirection(tile);
00060     /* entering tunnel / bridge? */
00061     if (dir == direction) {
00062       TileIndex endtile = GetOtherTunnelBridgeEnd(tile);
00063 
00064       tpf->rd.cur_length += GetTunnelBridgeLength(tile, endtile) + 1;
00065 
00066       tile = endtile;
00067     } else {
00068       /* leaving tunnel / bridge? */
00069       if (ReverseDiagDir(dir) != direction) return;
00070     }
00071   }
00072 
00073   /* This addition will sometimes overflow by a single tile.
00074    * The use of TILE_MASK here makes sure that we still point at a valid
00075    * tile, and then this tile will be in the sentinel row/col, so GetTileTrackStatus will fail. */
00076   tile = TILE_MASK(tile + TileOffsByDiagDir(direction));
00077 
00078   if (++tpf->rd.cur_length > 50) return;
00079 
00080   TrackBits bits = TrackStatusToTrackBits(GetTileTrackStatus(tile, TRANSPORT_WATER, 0)) & DiagdirReachesTracks(direction);
00081   if (bits == TRACK_BIT_NONE) return;
00082 
00083   assert(TileX(tile) != MapMaxX() && TileY(tile) != MapMaxY());
00084 
00085   bool only_one_track = true;
00086   do {
00087     Track track = RemoveFirstTrack(&bits);
00088     if (bits != TRACK_BIT_NONE) only_one_track = false;
00089     RememberData rd = tpf->rd;
00090 
00091     /* Change direction 4 times only */
00092     if (!only_one_track && track != tpf->rd.last_choosen_track) {
00093       if (++tpf->rd.depth > 4) {
00094         tpf->rd = rd;
00095         return;
00096       }
00097       tpf->rd.last_choosen_track = track;
00098     }
00099 
00100     tpf->the_dir = TrackEnterdirToTrackdir(track, direction);
00101 
00102     if (!ShipTrackFollower(tile, tpf, tpf->rd.cur_length)) {
00103       TPFModeShip(tpf, tile, TrackdirToExitdir(tpf->the_dir));
00104     }
00105 
00106     tpf->rd = rd;
00107   } while (bits != TRACK_BIT_NONE);
00108 }
00109 
00110 static void OPFShipFollowTrack(TileIndex tile, DiagDirection direction, TrackPathFinder *tpf)
00111 {
00112   assert(IsValidDiagDirection(direction));
00113 
00114   /* initialize path finder variables */
00115   tpf->rd.cur_length = 0;
00116   tpf->rd.depth = 0;
00117   tpf->rd.last_choosen_track = INVALID_TRACK;
00118 
00119   ShipTrackFollower(tile, tpf, 0);
00120   TPFModeShip(tpf, tile, direction);
00121 }
00122 
00123 static const byte _ship_search_directions[6][4] = {
00124   { 0, 9, 2, 9 },
00125   { 9, 1, 9, 3 },
00126   { 9, 0, 3, 9 },
00127   { 1, 9, 9, 2 },
00128   { 3, 2, 9, 9 },
00129   { 9, 9, 1, 0 },
00130 };
00131 
00132 static const byte _pick_shiptrack_table[6] = {1, 3, 2, 2, 0, 0};
00133 
00134 static uint FindShipTrack(const Ship *v, TileIndex tile, DiagDirection dir, TrackBits bits, TileIndex skiptile, Track *track)
00135 {
00136   TrackPathFinder pfs;
00137   uint best_bird_dist = 0;
00138   uint best_length    = 0;
00139   byte ship_dir = v->direction & 3;
00140 
00141   pfs.dest_coords = v->dest_tile;
00142   pfs.skiptile = skiptile;
00143 
00144   Track best_track = INVALID_TRACK;
00145 
00146   do {
00147     Track i = RemoveFirstTrack(&bits);
00148 
00149     pfs.best_bird_dist = UINT_MAX;
00150     pfs.best_length = UINT_MAX;
00151 
00152     OPFShipFollowTrack(tile, (DiagDirection)_ship_search_directions[i][dir], &pfs);
00153 
00154     if (best_track != INVALID_TRACK) {
00155       if (pfs.best_bird_dist != 0) {
00156         /* neither reached the destination, pick the one with the smallest bird dist */
00157         if (pfs.best_bird_dist > best_bird_dist) goto bad;
00158         if (pfs.best_bird_dist < best_bird_dist) goto good;
00159       } else {
00160         if (pfs.best_length > best_length) goto bad;
00161         if (pfs.best_length < best_length) goto good;
00162       }
00163 
00164       /* if we reach this position, there's two paths of equal value so far.
00165        * pick one randomly. */
00166       uint r = GB(Random(), 0, 8);
00167       if (_pick_shiptrack_table[i] == ship_dir) r += 80;
00168       if (_pick_shiptrack_table[best_track] == ship_dir) r -= 80;
00169       if (r <= 127) goto bad;
00170     }
00171 good:;
00172     best_track = i;
00173     best_bird_dist = pfs.best_bird_dist;
00174     best_length = pfs.best_length;
00175 bad:;
00176 
00177   } while (bits != 0);
00178 
00179   *track = best_track;
00180   return best_bird_dist;
00181 }
00182 
00186 Track OPFShipChooseTrack(const Ship *v, TileIndex tile, DiagDirection enterdir, TrackBits tracks)
00187 {
00188   assert(IsValidDiagDirection(enterdir));
00189 
00190   TileIndex tile2 = TILE_ADD(tile, -TileOffsByDiagDir(enterdir));
00191   Track track;
00192 
00193   /* Let's find out how far it would be if we would reverse first */
00194   TrackBits b = TrackStatusToTrackBits(GetTileTrackStatus(tile2, TRANSPORT_WATER, 0)) & DiagdirReachesTracks(ReverseDiagDir(enterdir)) & v->state;
00195 
00196   uint distr = UINT_MAX; // distance if we reversed
00197   if (b != 0) {
00198     distr = FindShipTrack(v, tile2, ReverseDiagDir(enterdir), b, tile, &track);
00199     if (distr != UINT_MAX) distr++; // penalty for reversing
00200   }
00201 
00202   /* And if we would not reverse? */
00203   uint dist = FindShipTrack(v, tile, enterdir, tracks, 0, &track);
00204 
00205   if (dist <= distr) return track;
00206   return INVALID_TRACK; // We could better reverse
00207 }

Generated on Sat Dec 26 20:06:03 2009 for OpenTTD by  doxygen 1.5.6