src/ground_vehicle.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 ground_vehicle.cpp Implementation of GroundVehicle. */
   9
  10 #include "stdafx.h"
  11 #include "train.h"
  12 #include "roadveh.h"
  13 #include "depot_map.h"
  14
  15 #include "safeguards.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 = this->vcache.cached_max_speed; // Max track speed in internal units.
  30
  31         for (const T *u = v; u != nullptr; 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 *= GROUND_ACCELERATION; // Tractive effort in (tonnes * 1000 * 9.8 =) 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 != nullptr; 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         /* Speed is used squared later on, so U16 * U16, and then multiplied by other values. */
 110         int64 speed = v->GetCurrentSpeed(); // [km/h-ish]
 111
 112         /* Weight is stored in tonnes. */
 113         int32 mass = this->gcache.cached_weight;
 114
 115         /* Power is stored in HP, we need it in watts.
 116          * Each vehicle can have U16 power, 128 vehicles, HP -> watt
 117          * and km/h to m/s conversion below result in a maximum of
 118          * about 1.1E11, way more than 4.3E9 of int32. */
 119         int64 power = this->gcache.cached_power * 746ll;
 120
 121         /* This is constructed from:
 122          *  - axle resistance:  U16 power * 10 for 128 vehicles.
 123          *     * 8.3E7
 124          *  - rolling friction: U16 power * 144 for 128 vehicles.
 125          *     * 1.2E9
 126          *  - slope resistance: U16 weight * 100 * 10 (steepness) for 128 vehicles.
 127          *     * 8.4E9
 128          *  - air drag: 28 * (U8 drag + 3 * U8 drag * 128 vehicles / 20) * U16 speed * U16 speed
 129          *     * 6.2E14 before dividing by 1000
 130          * Sum is 6.3E11, more than 4.3E9 of int32, so int64 is needed.
 131          */
 132         int64 resistance = 0;
 133
 134         bool maglev = v->GetAccelerationType() == 2;
 135
 136         const int area = v->GetAirDragArea();
 137         if (!maglev) {
 138                 /* Static resistance plus rolling friction. */
 139                 resistance = this->gcache.cached_axle_resistance;
 140                 resistance += mass * v->GetRollingFriction();
 141         }
 142         /* Air drag; the air drag coefficient is in an arbitrary NewGRF-unit,
 143          * so we need some magic conversion factor. */
 144         resistance += (area * this->gcache.cached_air_drag * speed * speed) / 1000;
 145
 146         resistance += this->GetSlopeResistance();
 147
 148         /* This value allows to know if the vehicle is accelerating or braking. */
 149         AccelStatus mode = v->GetAccelerationStatus();
 150
 151         const int max_te = this->gcache.cached_max_te; // [N]
 152         /* Constructued from power, with need to multiply by 18 and assuming
 153          * low speed, it needs to be a 64 bit integer too. */
 154         int64 force;
 155         if (speed > 0) {
 156                 if (!maglev) {
 157                         /* Conversion factor from km/h to m/s is 5/18 to get [N] in the end. */
 158                         force = power * 18 / (speed * 5);
 159                         if (mode == AS_ACCEL && force > max_te) force = max_te;
 160                 } else {
 161                         force = power / 25;
 162                 }
 163         } else {
 164                 /* "Kickoff" acceleration. */
 165                 force = (mode == AS_ACCEL && !maglev) ? min(max_te, power) : power;
 166                 force = max(force, (mass * 8) + resistance);
 167         }
 168
 169         if (mode == AS_ACCEL) {
 170                 /* Easy way out when there is no acceleration. */
 171                 if (force == resistance) return 0;
 172
 173                 /* When we accelerate, make sure we always keep doing that, even when
 174                  * the excess force is more than the mass. Otherwise a vehicle going
 175                  * down hill will never slow down enough, and a vehicle that came up
 176                  * a hill will never speed up enough to (eventually) get back to the
 177                  * same (maximum) speed. */
 178                 int accel = ClampToI32((force - resistance) / (mass * 4));
 179                 return force < resistance ? min(-1, accel) : max(1, accel);
 180         } else {
 181                 return ClampToI32(min(-force - resistance, -10000) / mass);
 182         }
 183 }
 184
 185 /**
 186  * Check whether the whole vehicle chain is in the depot.
 187  * @return true if and only if the whole chain is in the depot.
 188  */
 189 template <class T, VehicleType Type>
 190 bool GroundVehicle<T, Type>::IsChainInDepot() const
 191 {
 192         const T *v = this->First();
 193         /* Is the front engine stationary in the depot? */
 194         assert_compile((int)TRANSPORT_RAIL == (int)VEH_TRAIN);
 195         assert_compile((int)TRANSPORT_ROAD == (int)VEH_ROAD);
 196         if (!IsDepotTypeTile(v->tile, (TransportType)Type) || v->cur_speed != 0) return false;
 197
 198         /* Check whether the rest is also already trying to enter the depot. */
 199         for (; v != nullptr; v = v->Next()) {
 200                 if (!v->T::IsInDepot() || v->tile != this->tile) return false;
 201         }
 202
 203         return true;
 204 }
 205
 206 /* Instantiation for Train */
 207 template struct GroundVehicle<Train, VEH_TRAIN>;
 208 /* Instantiation for RoadVehicle */
 209 template struct GroundVehicle<RoadVehicle, VEH_ROAD>;