OpenTTD: src/ground_vehicle.cpp Source File

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ground_vehicle.cpp
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1 /* $Id: ground_vehicle.cpp 26702 2014-07-22 19:46:10Z rubidium $ */
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
12 #include "stdafx.h"
13 #include "train.h"
14 #include "roadveh.h"
15 #include "depot_map.h"
16
17 #include "safeguards.h"
18
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
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
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
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>;