src/ground_vehicle.cpp

   1 /* $Id$ */
   2
   3 /*
   4  * This file is part of OpenTTD.
   5  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
   6  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   7  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
   8  */
   9
  10 /** @file ground_vehicle.cpp Implementation of GroundVehicle. */
  11
  12 #include "stdafx.h"
  13 #include "train.h"
  14 #include "roadveh.h"
  15 #include "depot_func.h"
  16
  17 /**
  18  * Recalculates the cached total power of a vehicle. Should be called when the consist is changed.
  19  */
  20 template <class T, VehicleType Type>
  21 void GroundVehicle<T, Type>::PowerChanged()
  22 {
  23         assert(this->First() == this);
  24         const T *v = T::From(this);
  25
  26         uint32 total_power = 0;
  27         uint32 max_te = 0;
  28         uint32 number_of_parts = 0;
  29         uint16 max_track_speed = v->GetDisplayMaxSpeed();
  30
  31         for (const T *u = v; u != NULL; u = u->Next()) {
  32                 uint32 current_power = u->GetPower() + u->GetPoweredPartPower(u);
  33                 total_power += current_power;
  34
  35                 /* Only powered parts add tractive effort. */
  36                 if (current_power > 0) max_te += u->GetWeight() * u->GetTractiveEffort();
  37                 number_of_parts++;
  38
  39                 /* Get minimum max speed for this track. */
  40                 uint16 track_speed = u->GetMaxTrackSpeed();
  41                 if (track_speed > 0) max_track_speed = min(max_track_speed, track_speed);
  42         }
  43
  44         byte air_drag;
  45         byte air_drag_value = v->GetAirDrag();
  46
  47         /* If air drag is set to zero (default), the resulting air drag coefficient is dependent on max speed. */
  48         if (air_drag_value == 0) {
  49                 uint16 max_speed = v->GetDisplayMaxSpeed();
  50                 /* Simplification of the method used in TTDPatch. It uses <= 10 to change more steadily from 128 to 196. */
  51                 air_drag = (max_speed <= 10) ? 192 : max(2048 / max_speed, 1);
  52         } else {
  53                 /* According to the specs, a value of 0x01 in the air drag property means "no air drag". */
  54                 air_drag = (air_drag_value == 1) ? 0 : air_drag_value;
  55         }
  56
  57         this->gcache.cached_air_drag = air_drag + 3 * air_drag * number_of_parts / 20;
  58
  59         max_te *= 10000; // Tractive effort in (tonnes * 1000 * 10 =) N.
  60         max_te /= 256;   // Tractive effort is a [0-255] coefficient.
  61         if (this->gcache.cached_power != total_power || this->gcache.cached_max_te != max_te) {
  62                 /* Stop the vehicle if it has no power. */
  63                 if (total_power == 0) this->vehstatus |= VS_STOPPED;
  64
  65                 this->gcache.cached_power = total_power;
  66                 this->gcache.cached_max_te = max_te;
  67                 SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
  68                 SetWindowWidgetDirty(WC_VEHICLE_VIEW, this->index, WID_VV_START_STOP);
  69         }
  70
  71         this->gcache.cached_max_track_speed = max_track_speed;
  72 }
  73
  74 /**
  75  * Recalculates the cached weight of a vehicle and its parts. Should be called each time the cargo on
  76  * the consist changes.
  77  */
  78 template <class T, VehicleType Type>
  79 void GroundVehicle<T, Type>::CargoChanged()
  80 {
  81         assert(this->First() == this);
  82         uint32 weight = 0;
  83
  84         for (T *u = T::From(this); u != NULL; u = u->Next()) {
  85                 uint32 current_weight = u->GetWeight();
  86                 weight += current_weight;
  87                 /* Slope steepness is in percent, result in N. */
  88                 u->gcache.cached_slope_resistance = current_weight * u->GetSlopeSteepness() * 100;
  89         }
  90
  91         /* Store consist weight in cache. */
  92         this->gcache.cached_weight = max<uint32>(1, weight);
  93         /* Friction in bearings and other mechanical parts is 0.1% of the weight (result in N). */
  94         this->gcache.cached_axle_resistance = 10 * weight;
  95
  96         /* Now update vehicle power (tractive effort is dependent on weight). */
  97         this->PowerChanged();
  98 }
  99
 100 /**
 101  * Calculates the acceleration of the vehicle under its current conditions.
 102  * @return Current acceleration of the vehicle.
 103  */
 104 template <class T, VehicleType Type>
 105 int GroundVehicle<T, Type>::GetAcceleration() const
 106 {
 107         /* Templated class used for function calls for performance reasons. */
 108         const T *v = T::From(this);
 109         int32 speed = v->GetCurrentSpeed(); // [km/h-ish]
 110
 111         /* Weight is stored in tonnes. */
 112         int32 mass = this->gcache.cached_weight;
 113
 114         /* Power is stored in HP, we need it in watts. */
 115         int32 power = this->gcache.cached_power * 746;
 116
 117         int32 resistance = 0;
 118
 119         bool maglev = v->GetAccelerationType() == 2;
 120
 121         const int area = v->GetAirDragArea();
 122         if (!maglev) {
 123                 /* Static resistance plus rolling friction. */
 124                 resistance = this->gcache.cached_axle_resistance;
 125                 resistance += mass * v->GetRollingFriction();
 126         }
 127         /* Air drag; the air drag coefficient is in an arbitrary NewGRF-unit,
 128          * so we need some magic conversion factor. */
 129         resistance += (area * this->gcache.cached_air_drag * speed * speed) / 1000;
 130
 131         resistance += this->GetSlopeResistance();
 132
 133         /* This value allows to know if the vehicle is accelerating or braking. */
 134         AccelStatus mode = v->GetAccelerationStatus();
 135
 136         const int max_te = this->gcache.cached_max_te; // [N]
 137         int force;
 138         if (speed > 0) {
 139                 if (!maglev) {
 140                         /* Conversion factor from km/h to m/s is 5/18 to get [N] in the end. */
 141                         force = power * 18 / (speed * 5);
 142                         if (mode == AS_ACCEL && force > max_te) force = max_te;
 143                 } else {
 144                         force = power / 25;
 145                 }
 146         } else {
 147                 /* "Kickoff" acceleration. */
 148                 force = (mode == AS_ACCEL && !maglev) ? min(max_te, power) : power;
 149                 force = max(force, (mass * 8) + resistance);
 150         }
 151
 152         if (mode == AS_ACCEL) {
 153                 /* Easy way out when there is no acceleration. */
 154                 if (force == resistance) return 0;
 155
 156                 /* When we accelerate, make sure we always keep doing that, even when
 157                  * the excess force is more than the mass. Otherwise a vehicle going
 158                  * down hill will never slow down enough, and a vehicle that came up
 159                  * a hill will never speed up enough to (eventually) get back to the
 160                  * same (maximum) speed. */
 161                 int accel = (force - resistance) / (mass * 4);
 162                 return force < resistance ? min(-1, accel) : max(1, accel);
 163         } else {
 164                 return min(-force - resistance, -10000) / mass;
 165         }
 166 }
 167
 168 /**
 169  * Check whether the whole vehicle chain is in the depot.
 170  * @return true if and only if the whole chain is in the depot.
 171  */
 172 template <class T, VehicleType Type>
 173 bool GroundVehicle<T, Type>::IsChainInDepot() const
 174 {
 175         const T *v = this->First();
 176         /* Is the front engine stationary in the depot? */
 177         assert_compile((int)TRANSPORT_RAIL == (int)VEH_TRAIN);
 178         assert_compile((int)TRANSPORT_ROAD == (int)VEH_ROAD);
 179         if (!IsDepotTypeTile(v->tile, (TransportType)Type) || v->cur_speed != 0) return false;
 180
 181         /* Check whether the rest is also already trying to enter the depot. */
 182         for (; v != NULL; v = v->Next()) {
 183                 if (!v->T::IsInDepot() || v->tile != this->tile) return false;
 184         }
 185
 186         return true;
 187 }
 188
 189 /* Instantiation for Train */
 190 template struct GroundVehicle<Train, VEH_TRAIN>;
 191 /* Instantiation for RoadVehicle */
 192 template struct GroundVehicle<RoadVehicle, VEH_ROAD>;