OpenTTD Source  20241108-master-g80f628063a
ground_vehicle.cpp
Go to the documentation of this file.
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 
10 #include "stdafx.h"
11 #include "train.h"
12 #include "roadveh.h"
13 #include "depot_map.h"
14 
15 #include "safeguards.h"
16 
20 template <class T, VehicleType Type>
22 {
23  assert(this->First() == this);
24  const T *v = T::From(this);
25 
26  uint32_t total_power = 0;
27  uint32_t max_te = 0;
28  uint32_t number_of_parts = 0;
29  uint16_t 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_t 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_t track_speed = u->GetMaxTrackSpeed();
41  if (track_speed > 0) max_track_speed = std::min(max_track_speed, track_speed);
42  }
43 
44  uint8_t air_drag;
45  uint8_t 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_t 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 : std::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);
69  }
70 
71  this->gcache.cached_max_track_speed = max_track_speed;
72 }
73 
78 template <class T, VehicleType Type>
80 {
81  assert(this->First() == this);
82  uint32_t weight = 0;
83 
84  for (T *u = T::From(this); u != nullptr; u = u->Next()) {
85  uint32_t 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 = std::max(1u, 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 
104 template <class T, VehicleType Type>
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_t speed = v->GetCurrentSpeed(); // [km/h-ish]
111 
112  /* Weight is stored in tonnes. */
113  int32_t 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_t 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_t, so int64_t is needed.
131  */
132  int64_t 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 += static_cast<int64_t>(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_t 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) ? std::min<int>(max_te, power) : power;
166  force = std::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 = ClampTo<int32_t>((force - resistance) / (mass * 4));
179  return force < resistance ? std::min(-1, accel) : std::max(1, accel);
180  } else {
181  return ClampTo<int32_t>(std::min<int64_t>(-force - resistance, -10000) / mass);
182  }
183 }
184 
189 template <class T, VehicleType Type>
191 {
192  const T *v = this->First();
193  /* Is the front engine stationary in the depot? */
194  static_assert((int)TRANSPORT_RAIL == (int)VEH_TRAIN);
195  static_assert((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 */
Map related accessors for depots.
bool IsDepotTypeTile(Tile tile, TransportType type)
Check if a tile is a depot and it is a depot of the given type.
Definition: depot_map.h:18
AccelStatus
What is the status of our acceleration?
@ AS_ACCEL
We want to go faster, if possible of course.
Road vehicle states.
A number of safeguards to prevent using unsafe methods.
Definition of base types and functions in a cross-platform compatible way.
bool IsChainInDepot() const override
Check whether the whole vehicle chain is in the depot.
void CargoChanged()
Recalculates the cached weight of a vehicle and its parts.
void PowerChanged()
Recalculates the cached total power of a vehicle.
int GetAcceleration() const
Calculates the acceleration of the vehicle under its current conditions.
Base for the train class.
TransportType
Available types of transport.
@ TRANSPORT_RAIL
Transport by train.
@ TRANSPORT_ROAD
Transport by road vehicle.
@ VS_STOPPED
Vehicle is stopped by the player.
Definition: vehicle_base.h:34
@ VEH_ROAD
Road vehicle type.
Definition: vehicle_type.h:25
@ VEH_TRAIN
Train vehicle type.
Definition: vehicle_type.h:24
static const int GROUND_ACCELERATION
Acceleration due to gravity, 9.8 m/s^2.
Definition: vehicle_type.h:18
@ WID_VV_START_STOP
Start or stop this vehicle, and show information about the current state.
void SetWindowWidgetDirty(WindowClass cls, WindowNumber number, WidgetID widget_index)
Mark a particular widget in a particular window as dirty (in need of repainting)
Definition: window.cpp:3106
void SetWindowDirty(WindowClass cls, WindowNumber number)
Mark window as dirty (in need of repainting)
Definition: window.cpp:3093
@ WC_VEHICLE_DETAILS
Vehicle details; Window numbers:
Definition: window_type.h:200
@ WC_VEHICLE_VIEW
Vehicle view; Window numbers:
Definition: window_type.h:339