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 "vehicle_gui.h"
  16 #include "window_func.h"
  17
  18 /**
  19  * Recalculates the cached total power of a vehicle. Should be called when the consist is changed.
  20  */
  21 template <class T, VehicleType Type>
  22 void GroundVehicle<T, Type>::PowerChanged()
  23 {
  24         assert(this->First() == this);
  25         const T *v = T::From(this);
  26
  27         uint32 total_power = 0;
  28         uint32 max_te = 0;
  29         uint32 number_of_parts = 0;
  30         uint16 max_track_speed = v->GetDisplayMaxSpeed();
  31
  32         for (const T *u = v; u != NULL; u = u->Next()) {
  33                 uint32 current_power = u->GetPower() + u->GetPoweredPartPower(u);
  34                 total_power += current_power;
  35
  36                 /* Only powered parts add tractive effort. */
  37                 if (current_power > 0) max_te += u->GetWeight() * u->GetTractiveEffort();
  38                 number_of_parts++;
  39
  40                 /* Get minimum max speed for this track. */
  41                 uint16 track_speed = u->GetMaxTrackSpeed();
  42                 if (track_speed > 0) max_track_speed = min(max_track_speed, track_speed);
  43         }
  44
  45         byte air_drag;
  46         byte air_drag_value = v->GetAirDrag();
  47
  48         /* If air drag is set to zero (default), the resulting air drag coefficient is dependent on max speed. */
  49         if (air_drag_value == 0) {
  50                 uint16 max_speed = v->GetDisplayMaxSpeed();
  51                 /* Simplification of the method used in TTDPatch. It uses <= 10 to change more steadily from 128 to 196. */
  52                 air_drag = (max_speed <= 10) ? 192 : max(2048 / max_speed, 1);
  53         } else {
  54                 /* According to the specs, a value of 0x01 in the air drag property means "no air drag". */
  55                 air_drag = (air_drag_value == 1) ? 0 : air_drag_value;
  56         }
  57
  58         this->gcache.cached_air_drag = air_drag + 3 * air_drag * number_of_parts / 20;
  59
  60         max_te *= 10000; // Tractive effort in (tonnes * 1000 * 10 =) N.
  61         max_te /= 256;   // Tractive effort is a [0-255] coefficient.
  62         if (this->gcache.cached_power != total_power || this->gcache.cached_max_te != max_te) {
  63                 /* Stop the vehicle if it has no power. */
  64                 if (total_power == 0) this->vehstatus |= VS_STOPPED;
  65
  66                 this->gcache.cached_power = total_power;
  67                 this->gcache.cached_max_te = max_te;
  68                 SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
  69                 SetWindowWidgetDirty(WC_VEHICLE_VIEW, this->index, VVW_WIDGET_START_STOP_VEH);
  70         }
  71
  72         this->gcache.cached_max_track_speed = max_track_speed;
  73 }
  74
  75 /**
  76  * Recalculates the cached weight of a vehicle and its parts. Should be called each time the cargo on
  77  * the consist changes.
  78  */
  79 template <class T, VehicleType Type>
  80 void GroundVehicle<T, Type>::CargoChanged()
  81 {
  82         assert(this->First() == this);
  83         uint32 weight = 0;
  84
  85         for (T *u = T::From(this); u != NULL; u = u->Next()) {
  86                 uint32 current_weight = u->GetWeight();
  87                 weight += current_weight;
  88                 /* Slope steepness is in percent, result in N. */
  89                 u->gcache.cached_slope_resistance = current_weight * u->GetSlopeSteepness() * 100;
  90         }
  91
  92         /* Store consist weight in cache. */
  93         this->gcache.cached_weight = max<uint32>(1, weight);
  94         /* Friction in bearings and other mechanical parts is 0.1% of the weight (result in N). */
  95         this->gcache.cached_axle_resistance = 10 * weight;
  96
  97         /* Now update vehicle power (tractive effort is dependent on weight). */
  98         this->PowerChanged();
  99 }
 100
 101 /**
 102  * Calculates the acceleration of the vehicle under its current conditions.
 103  * @return Current acceleration of the vehicle.
 104  */
 105 template <class T, VehicleType Type>
 106 int GroundVehicle<T, Type>::GetAcceleration() const
 107 {
 108         /* Templated class used for function calls for performance reasons. */
 109         const T *v = T::From(this);
 110         int32 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         int32 power = this->gcache.cached_power * 746;
 117
 118         int32 resistance = 0;
 119
 120         bool maglev = v->GetAccelerationType() == 2;
 121
 122         const int area = v->GetAirDragArea();
 123         if (!maglev) {
 124                 /* Static resistance plus rolling friction. */
 125                 resistance = this->gcache.cached_axle_resistance;
 126                 resistance += mass * v->GetRollingFriction();
 127         }
 128         /* Air drag; the air drag coefficient is in an arbitrary NewGRF-unit,
 129          * so we need some magic conversion factor. */
 130         resistance += (area * this->gcache.cached_air_drag * speed * speed) / 1000;
 131
 132         resistance += this->GetSlopeResistance();
 133
 134         /* This value allows to know if the vehicle is accelerating or braking. */
 135         AccelStatus mode = v->GetAccelerationStatus();
 136
 137         const int max_te = this->gcache.cached_max_te; // [N]
 138         int force;
 139         if (speed > 0) {
 140                 if (!maglev) {
 141                         /* Conversion factor from km/h to m/s is 5/18 to get [N] in the end. */
 142                         force = power * 18 / (speed * 5);
 143                         if (mode == AS_ACCEL && force > max_te) force = max_te;
 144                 } else {
 145                         force = power / 25;
 146                 }
 147         } else {
 148                 /* "Kickoff" acceleration. */
 149                 force = (mode == AS_ACCEL && !maglev) ? min(max_te, power) : power;
 150                 force = max(force, (mass * 8) + resistance);
 151         }
 152
 153         if (mode == AS_ACCEL) {
 154                 /* Easy way out when there is no acceleration. */
 155                 if (force == resistance) return 0;
 156
 157                 /* When we accelerate, make sure we always keep doing that, even when
 158                  * the excess force is more than the mass. Otherwise a vehicle going
 159                  * down hill will never slow down enough, and a vehicle that came up
 160                  * a hill will never speed up enough to (eventually) get back to the
 161                  * same (maximum) speed. */
 162                 int accel = (force - resistance) / (mass * 4);
 163                 return force < resistance ? min(-1, accel) : max(1, accel);
 164         } else {
 165                 return min(-force - resistance, -10000) / mass;
 166         }
 167 }
 168
 169 /* Instantiation for Train */
 170 template struct GroundVehicle<Train, VEH_TRAIN>;
 171 /* Instantiation for RoadVehicle */
 172 template struct GroundVehicle<RoadVehicle, VEH_ROAD>;