ground_vehicle.cpp

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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 "train.h"
00014 #include "roadveh.h"
00015 
00019 template <class T, VehicleType Type>
00020 void GroundVehicle<T, Type>::PowerChanged()
00021 {
00022   assert(this->First() == this);
00023   const T *v = T::From(this);
00024 
00025   uint32 total_power = 0;
00026   uint32 max_te = 0;
00027   uint32 number_of_parts = 0;
00028   uint16 max_track_speed = v->GetDisplayMaxSpeed();
00029 
00030   for (const T *u = v; u != NULL; u = u->Next()) {
00031     uint32 current_power = u->GetPower() + u->GetPoweredPartPower(u);
00032     total_power += current_power;
00033 
00034     /* Only powered parts add tractive effort. */
00035     if (current_power > 0) max_te += u->GetWeight() * u->GetTractiveEffort();
00036     number_of_parts++;
00037 
00038     /* Get minimum max speed for this track. */
00039     uint16 track_speed = u->GetMaxTrackSpeed();
00040     if (track_speed > 0) max_track_speed = min(max_track_speed, track_speed);
00041   }
00042 
00043   byte air_drag;
00044   byte air_drag_value = v->GetAirDrag();
00045 
00046   /* If air drag is set to zero (default), the resulting air drag coefficient is dependent on max speed. */
00047   if (air_drag_value == 0) {
00048     uint16 max_speed = v->GetDisplayMaxSpeed();
00049     /* Simplification of the method used in TTDPatch. It uses <= 10 to change more steadily from 128 to 196. */
00050     air_drag = (max_speed <= 10) ? 192 : max(2048 / max_speed, 1);
00051   } else {
00052     /* According to the specs, a value of 0x01 in the air drag property means "no air drag". */
00053     air_drag = (air_drag_value == 1) ? 0 : air_drag_value;
00054   }
00055 
00056   this->gcache.cached_air_drag = air_drag + 3 * air_drag * number_of_parts / 20;
00057 
00058   max_te *= 10000; // Tractive effort in (tonnes * 1000 * 10 =) N.
00059   max_te /= 256;   // Tractive effort is a [0-255] coefficient.
00060   if (this->gcache.cached_power != total_power || this->gcache.cached_max_te != max_te) {
00061     /* Stop the vehicle if it has no power. */
00062     if (total_power == 0) this->vehstatus |= VS_STOPPED;
00063 
00064     this->gcache.cached_power = total_power;
00065     this->gcache.cached_max_te = max_te;
00066     SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
00067     SetWindowWidgetDirty(WC_VEHICLE_VIEW, this->index, WID_VV_START_STOP);
00068   }
00069 
00070   this->gcache.cached_max_track_speed = max_track_speed;
00071 }
00072 
00077 template <class T, VehicleType Type>
00078 void GroundVehicle<T, Type>::CargoChanged()
00079 {
00080   assert(this->First() == this);
00081   uint32 weight = 0;
00082 
00083   for (T *u = T::From(this); u != NULL; u = u->Next()) {
00084     uint32 current_weight = u->GetWeight();
00085     weight += current_weight;
00086     /* Slope steepness is in percent, result in N. */
00087     u->gcache.cached_slope_resistance = current_weight * u->GetSlopeSteepness() * 100;
00088   }
00089 
00090   /* Store consist weight in cache. */
00091   this->gcache.cached_weight = max<uint32>(1, weight);
00092   /* Friction in bearings and other mechanical parts is 0.1% of the weight (result in N). */
00093   this->gcache.cached_axle_resistance = 10 * weight;
00094 
00095   /* Now update vehicle power (tractive effort is dependent on weight). */
00096   this->PowerChanged();
00097 }
00098 
00103 template <class T, VehicleType Type>
00104 int GroundVehicle<T, Type>::GetAcceleration() const
00105 {
00106   /* Templated class used for function calls for performance reasons. */
00107   const T *v = T::From(this);
00108   int32 speed = v->GetCurrentSpeed(); // [km/h-ish]
00109 
00110   /* Weight is stored in tonnes. */
00111   int32 mass = this->gcache.cached_weight;
00112 
00113   /* Power is stored in HP, we need it in watts. */
00114   int32 power = this->gcache.cached_power * 746;
00115 
00116   int32 resistance = 0;
00117 
00118   bool maglev = v->GetAccelerationType() == 2;
00119 
00120   const int area = v->GetAirDragArea();
00121   if (!maglev) {
00122     /* Static resistance plus rolling friction. */
00123     resistance = this->gcache.cached_axle_resistance;
00124     resistance += mass * v->GetRollingFriction();
00125   }
00126   /* Air drag; the air drag coefficient is in an arbitrary NewGRF-unit,
00127    * so we need some magic conversion factor. */
00128   resistance += (area * this->gcache.cached_air_drag * speed * speed) / 1000;
00129 
00130   resistance += this->GetSlopeResistance();
00131 
00132   /* This value allows to know if the vehicle is accelerating or braking. */
00133   AccelStatus mode = v->GetAccelerationStatus();
00134 
00135   const int max_te = this->gcache.cached_max_te; // [N]
00136   int force;
00137   if (speed > 0) {
00138     if (!maglev) {
00139       /* Conversion factor from km/h to m/s is 5/18 to get [N] in the end. */
00140       force = power * 18 / (speed * 5);
00141       if (mode == AS_ACCEL && force > max_te) force = max_te;
00142     } else {
00143       force = power / 25;
00144     }
00145   } else {
00146     /* "Kickoff" acceleration. */
00147     force = (mode == AS_ACCEL && !maglev) ? min(max_te, power) : power;
00148     force = max(force, (mass * 8) + resistance);
00149   }
00150 
00151   if (mode == AS_ACCEL) {
00152     /* Easy way out when there is no acceleration. */
00153     if (force == resistance) return 0;
00154 
00155     /* When we accelerate, make sure we always keep doing that, even when
00156      * the excess force is more than the mass. Otherwise a vehicle going
00157      * down hill will never slow down enough, and a vehicle that came up
00158      * a hill will never speed up enough to (eventually) get back to the
00159      * same (maximum) speed. */
00160     int accel = (force - resistance) / (mass * 4);
00161     return force < resistance ? min(-1, accel) : max(1, accel);
00162   } else {
00163     return min(-force - resistance, -10000) / mass;
00164   }
00165 }
00166 
00167 /* Instantiation for Train */
00168 template struct GroundVehicle<Train, VEH_TRAIN>;
00169 /* Instantiation for RoadVehicle */
00170 template struct GroundVehicle<RoadVehicle, VEH_ROAD>;