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  1. /**
  2.  * Sets the new speed for an aircraft
  3.  * @param v The vehicle for which the speed should be obtained
  4.  * @param speed_limit The maximum speed the vehicle may have.
  5.  * @param hard_limit If true, the limit is directly enforced, otherwise the plane is slowed down gradually
  6.  * @return The number of position updates needed within the tick
  7.  */
  8. static int UpdateAircraftSpeed(Aircraft *v, uint speed_limit = SPEED_LIMIT_NONE, bool hard_limit = true)
  9. {
  10.     /**
  11.      * 'acceleration' has the unit 3/8 mph/tick. This function is called twice per tick.
  12.      * So the speed amount we need to accelerate is:
  13.      *     acceleration * 3 / 16 mph = acceleration * 3 / 16 * 16 / 10 km-ish/h
  14.      *                               = acceleration * 3 / 10 * 256 * (km-ish/h / 256)
  15.      *                               ~ acceleration * 77 (km-ish/h / 256)
  16.      */
  17.     uint spd = v->acceleration * 77;
  18.     byte t;
  19.  
  20.     /* Adjust speed limits by plane speed factor to prevent taxiing
  21.      * and take-off speeds being too low. */
  22.     speed_limit *= _settings_game.vehicle.plane_speed;
  23.  
  24.     /* adjust speed for broken vehicles */
  25.     if (v->vehstatus & VS_AIRCRAFT_BROKEN) {
  26.         speed_limit = min(speed_limit, SPEED_LIMIT_BROKEN);
  27.         hard_limit = false;
  28.     }
  29.  
  30.     if (v->vcache.cached_max_speed < speed_limit) {
  31.         if (v->cur_speed < speed_limit) hard_limit = false;
  32.         speed_limit = v->vcache.cached_max_speed;
  33.     }
  34.  
  35.     v->subspeed = (t = v->subspeed) + (byte)spd;
  36.  
  37.     /* Aircraft's current speed is used twice so that very fast planes are
  38.      * forced to slow down rapidly in the short distance needed. The magic
  39.      * value 16384 was determined to give similar results to the old speed/48
  40.      * method at slower speeds. This also results in less reduction at slow
  41.      * speeds to that aircraft do not get to taxi speed straight after
  42.      * touchdown. */
  43.     if (!hard_limit && v->cur_speed > speed_limit) {
  44.         speed_limit = v->cur_speed - max(1, ((v->cur_speed * v->cur_speed) / 16384) / _settings_game.vehicle.plane_speed);
  45.     }
  46.  
  47.     spd = min(v->cur_speed + (spd >> 8) + (v->subspeed < t), speed_limit);
  48.  
  49.  
  50.     /* updates statusbar only if speed have changed to save CPU time */
  51.     if (spd != v->cur_speed) {
  52.         v->cur_speed = spd;
  53.         SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
  54.     }
  55.  
  56.     /* Adjust distance moved by plane speed setting */
  57.     if (_settings_game.vehicle.plane_speed > 1) spd /= _settings_game.vehicle.plane_speed;
  58.  
  59.     /* Convert direction-independent speed into direction-dependent speed. (old movement method) */
  60.     spd = v->GetOldAdvanceSpeed(spd);
  61.  
  62.     spd += v->progress;
  63.     v->progress = (byte)spd;
  64.     return spd >> 8;
  65. }
Posted by Anonymous at 23 Oct 2017, 23:15:00 UTC
Language: cpp • Views: 548

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