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_map.h"
  16
  17 #include "safeguards.h"
  18
  19 /**
  20  * Recalculates the cached total power of a vehicle. Should be called when the consist is changed.
  21  */
  22 template <class T, VehicleType Type>
  23 void GroundVehicle<T, Type>::PowerChanged()
  24 {
  25         assert(this->First() == this);
  26         const T *v = T::From(this);
  27
  28         uint32 total_power = 0;
  29         uint32 max_te = 0;
  30         uint32 number_of_parts = 0;
  31         uint16 max_track_speed = v->GetDisplayMaxSpeed();
  32
  33         for (const T *u = v; u != NULL; u = u->Next()) {
  34                 uint32 current_power = u->GetPower() + u->GetPoweredPartPower(u);
  35                 total_power += current_power;
  36
  37                 /* Only powered parts add tractive effort. */
  38                 if (current_power > 0) max_te += u->GetWeight() * u->GetTractiveEffort();
  39                 number_of_parts++;
  40
  41                 /* Get minimum max speed for this track. */
  42                 uint16 track_speed = u->GetMaxTrackSpeed();
  43                 if (track_speed > 0) max_track_speed = min(max_track_speed, track_speed);
  44         }
  45
  46         byte air_drag;
  47         byte air_drag_value = v->GetAirDrag();
  48
  49         /* If air drag is set to zero (default), the resulting air drag coefficient is dependent on max speed. */
  50         if (air_drag_value == 0) {
  51                 uint16 max_speed = v->GetDisplayMaxSpeed();
  52                 /* Simplification of the method used in TTDPatch. It uses <= 10 to change more steadily from 128 to 196. */
  53                 air_drag = (max_speed <= 10) ? 192 : max(2048 / max_speed, 1);
  54         } else {
  55                 /* According to the specs, a value of 0x01 in the air drag property means "no air drag". */
  56                 air_drag = (air_drag_value == 1) ? 0 : air_drag_value;
  57         }
  58
  59         this->gcache.cached_air_drag = air_drag + 3 * air_drag * number_of_parts / 20;
  60
  61         max_te *= 10000; // Tractive effort in (tonnes * 1000 * 10 =) N.
  62         max_te /= 256;   // Tractive effort is a [0-255] coefficient.
  63         if (this->gcache.cached_power != total_power || this->gcache.cached_max_te != max_te) {
  64                 /* Stop the vehicle if it has no power. */
  65                 if (total_power == 0) this->vehstatus |= VS_STOPPED;
  66
  67                 this->gcache.cached_power = total_power;
  68                 this->gcache.cached_max_te = max_te;
  69                 SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
  70                 SetWindowWidgetDirty(WC_VEHICLE_VIEW, this->index, WID_VV_START_STOP);
  71         }
  72
  73         this->gcache.cached_max_track_speed = max_track_speed;
  74 }
  75
  76 /**
  77  * Recalculates the cached weight of a vehicle and its parts. Should be called each time the cargo on
  78  * the consist changes.
  79  */
  80 template <class T, VehicleType Type>
  81 void GroundVehicle<T, Type>::CargoChanged()
  82 {
  83         assert(this->First() == this);
  84         uint32 weight = 0;
  85
  86         for (T *u = T::From(this); u != NULL; u = u->Next()) {
  87                 uint32 current_weight = u->GetWeight();
  88                 weight += current_weight;
  89                 /* Slope steepness is in percent, result in N. */
  90                 u->gcache.cached_slope_resistance = current_weight * u->GetSlopeSteepness() * 100;
  91         }
  92
  93         /* Store consist weight in cache. */
  94         this->gcache.cached_weight = max<uint32>(1, weight);
  95         /* Friction in bearings and other mechanical parts is 0.1% of the weight (result in N). */
  96         this->gcache.cached_axle_resistance = 10 * weight;
  97
  98         /* Now update vehicle power (tractive effort is dependent on weight). */
  99         this->PowerChanged();
 100 }
 101
 102 /**
 103  * Calculates the acceleration of the vehicle under its current conditions.
 104  * @return Current acceleration of the vehicle.
 105  */
 106 template <class T, VehicleType Type>
 107 int GroundVehicle<T, Type>::GetAcceleration() const
 108 {
 109         /* Templated class used for function calls for performance reasons. */
 110         const T *v = T::From(this);
 111         /* Speed is used squared later on, so U16 * U16, and then multiplied by other values. */
 112         int64 speed = v->GetCurrentSpeed(); // [km/h-ish]
 113
 114         /* Weight is stored in tonnes. */
 115         int32 mass = this->gcache.cached_weight;
 116
 117         /* Power is stored in HP, we need it in watts.
 118          * Each vehicle can have U16 power, 128 vehicles, HP -> watt
 119          * and km/h to m/s conversion below result in a maxium of
 120          * about 1.1E11, way more than 4.3E9 of int32. */
 121         int64 power = this->gcache.cached_power * 746ll;
 122
 123         /* This is constructed from:
 124          *  - axle resistance:  U16 power * 10 for 128 vehicles.
 125          *     * 8.3E7
 126          *  - rolling friction: U16 power * 144 for 128 vehicles.
 127          *     * 1.2E9
 128          *  - slope resistance: U16 weight * 100 * 10 (steepness) for 128 vehicles.
 129          *     * 8.4E9
 130          *  - air drag: 28 * (U8 drag + 3 * U8 drag * 128 vehicles / 20) * U16 speed * U16 speed
 131          *     * 6.2E14 before dividing by 1000
 132          * Sum is 6.3E11, more than 4.3E9 of int32, so int64 is needed.
 133          */
 134         int64 resistance = 0;
 135
 136         bool maglev = v->GetAccelerationType() == 2;
 137
 138         const int area = v->GetAirDragArea();
 139         if (!maglev) {
 140                 /* Static resistance plus rolling friction. */
 141                 resistance = this->gcache.cached_axle_resistance;
 142                 resistance += mass * v->GetRollingFriction();
 143         }
 144         /* Air drag; the air drag coefficient is in an arbitrary NewGRF-unit,
 145          * so we need some magic conversion factor. */
 146         resistance += (area * this->gcache.cached_air_drag * speed * speed) / 1000;
 147
 148         resistance += this->GetSlopeResistance();
 149
 150         /* This value allows to know if the vehicle is accelerating or braking. */
 151         AccelStatus mode = v->GetAccelerationStatus();
 152
 153         const int max_te = this->gcache.cached_max_te; // [N]
 154         /* Constructued from power, with need to multiply by 18 and assuming
 155          * low speed, it needs to be a 64 bit integer too. */
 156         int64 force;
 157         if (speed > 0) {
 158                 if (!maglev) {
 159                         /* Conversion factor from km/h to m/s is 5/18 to get [N] in the end. */
 160                         force = power * 18 / (speed * 5);
 161                         if (mode == AS_ACCEL && force > max_te) force = max_te;
 162                 } else {
 163                         force = power / 25;
 164                 }
 165         } else {
 166                 /* "Kickoff" acceleration. */
 167                 force = (mode == AS_ACCEL && !maglev) ? min(max_te, power) : power;
 168                 force = max(force, (mass * 8) + resistance);
 169         }
 170
 171         if (mode == AS_ACCEL) {
 172                 /* Easy way out when there is no acceleration. */
 173                 if (force == resistance) return 0;
 174
 175                 /* When we accelerate, make sure we always keep doing that, even when
 176                  * the excess force is more than the mass. Otherwise a vehicle going
 177                  * down hill will never slow down enough, and a vehicle that came up
 178                  * a hill will never speed up enough to (eventually) get back to the
 179                  * same (maximum) speed. */
 180                 int accel = ClampToI32((force - resistance) / (mass * 4));
 181                 return force < resistance ? min(-1, accel) : max(1, accel);
 182         } else {
 183                 return ClampToI32(min(-force - resistance, -10000) / mass);
 184         }
 185 }
 186
 187 /**
 188  * Check whether the whole vehicle chain is in the depot.
 189  * @return true if and only if the whole chain is in the depot.
 190  */
 191 template <class T, VehicleType Type>
 192 bool GroundVehicle<T, Type>::IsChainInDepot() const
 193 {
 194         const T *v = this->First();
 195         /* Is the front engine stationary in the depot? */
 196         assert_compile((int)TRANSPORT_RAIL == (int)VEH_TRAIN);
 197         assert_compile((int)TRANSPORT_ROAD == (int)VEH_ROAD);
 198         if (!IsDepotTypeTile(v->tile, (TransportType)Type) || v->cur_speed != 0) return false;
 199
 200         /* Check whether the rest is also already trying to enter the depot. */
 201         for (; v != NULL; v = v->Next()) {
 202                 if (!v->T::IsInDepot() || v->tile != this->tile) return false;
 203         }
 204
 205         return true;
 206 }
 207
 208 /* Instantiation for Train */
 209 template struct GroundVehicle<Train, VEH_TRAIN>;
 210 /* Instantiation for RoadVehicle */
 211 template struct GroundVehicle<RoadVehicle, VEH_ROAD>;