src/Environment/ridge_lift.cxx

   1 // simulates ridge lift
   2 //
   3 // Written by Patrice Poly
   4 // Copyright (C) 2009 Patrice Poly - p.polypa@gmail.com
   5 //
   6 //
   7 // Entirely based  on the paper :
   8 // http://carrier.csi.cam.ac.uk/forsterlewis/soaring/sim/fsx/dev/sim_probe/sim_probe_paper.html
   9 // by Ian Forster-Lewis, University of Cambridge, 26th December 2007
  10 //
  11 //
  12 // This program is free software; you can redistribute it and/or
  13 // modify it under the terms of the GNU General Public License as
  14 // published by the Free Software Foundation; either version 2 of the
  15 // License, or (at your option) any later version.
  16 //
  17 // This program is distributed in the hope that it will be useful, but
  18 // WITHOUT ANY WARRANTY; without even the implied warranty of
  19 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20 // General Public License for more details.
  21 //
  22 // You should have received a copy of the GNU General Public License
  23 // along with this program; if not, write to the Free Software
  24 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  25 //
  26 //
  27
  28
  29 #ifdef HAVE_CONFIG_H
  30 #  include <config.h>
  31 #endif
  32
  33 #include <Main/fg_props.hxx>
  34 #include <Main/globals.hxx>
  35 #include <Main/util.hxx>
  36 #include <Scenery/scenery.hxx>
  37 #include <string>
  38 #include <math.h>
  39
  40
  41 using std::string;
  42
  43 #include "ridge_lift.hxx"
  44
  45 static string CreateIndexedPropertyName(string Property, int index)
  46 {
  47         std::stringstream str;
  48         str << index;
  49         string tmp;
  50         str >> tmp;
  51         return Property + "[" + tmp + "]";
  52 }
  53
  54 static inline double sign(double x) {
  55         return x == 0 ? 0 : x > 0 ? 1.0 : -1.0;
  56 }
  57
  58 static const double BOUNDARY1_m = 40.0;
  59
  60 const double FGRidgeLift::dist_probe_m[] = { // in meters
  61      0.0,
  62    250.0,
  63    750.0,
  64   2000.0,
  65   -100.0
  66 };
  67
  68 //constructor
  69 FGRidgeLift::FGRidgeLift ()
  70 {
  71         strength = 0.0;
  72         timer = 0.0;
  73         for( int i = 0; i < 5; i++ )
  74                 probe_elev_m[i] = probe_lat_deg[i] = probe_lon_deg[i] = 0.0;
  75
  76         for( int i = 0; i < 4; i++ )
  77                 slope[i] = 0.0;
  78 }
  79
  80 //destructor
  81 FGRidgeLift::~FGRidgeLift()
  82 {
  83
  84 }
  85
  86 void FGRidgeLift::init(void)
  87 {
  88         _enabled_node = fgGetNode( "/environment/ridge-lift/enabled", false );
  89
  90         _ridge_lift_fps_node = fgGetNode("/environment/ridge-lift-fps", true);
  91         _surface_wind_from_deg_node =
  92                         fgGetNode("/environment/config/boundary/entry[0]/wind-from-heading-deg"
  93                         , true);
  94         _surface_wind_speed_node =
  95                         fgGetNode("/environment/config/boundary/entry[0]/wind-speed-kt"
  96                         , true);
  97         _user_longitude_node = fgGetNode("/position/longitude-deg", true);
  98         _user_latitude_node = fgGetNode("/position/latitude-deg", true);
  99         _user_altitude_agl_ft_node = fgGetNode("/position/altitude-agl-ft", true);
 100         _ground_elev_node = fgGetNode("/position/ground-elev-ft", true );
 101 }
 102
 103 void FGRidgeLift::bind() {
 104         string prop;
 105
 106         _tiedProperties.setRoot( fgGetNode("/environment/ridge-lift",true));
 107         for( int i = 0; i < 5; i++ ) {
 108                 _tiedProperties.Tie( "probe-elev-m", i, this, i, &FGRidgeLift::get_probe_elev_m );
 109                 _tiedProperties.Tie( "probe-lat-deg", i, this, i, &FGRidgeLift::get_probe_lat_deg );
 110                 _tiedProperties.Tie( "probe-lon-deg", i, this, i, &FGRidgeLift::get_probe_lon_deg );
 111         }
 112
 113         for( int i = 0; i < 4; i++ ) {
 114                 _tiedProperties.Tie( "slope", i, this, i, &FGRidgeLift::get_slope );
 115         }
 116 }
 117
 118 void FGRidgeLift::unbind() {
 119         _tiedProperties.Untie();
 120 }
 121
 122 void FGRidgeLift::update(double dt) {
 123
 124         if( dt <= SGLimitsd::min() ) // paused, do nothing but keep current lift
 125                 return;
 126
 127         if( _enabled_node && false == _enabled_node->getBoolValue() ) {
 128                 // do nothing if lift has been zeroed
 129                 if( strength != 0.0 ) {
 130                         if( strength > 0.1 ) {
 131                                 // slowly fade out strong lifts
 132                                 strength = fgGetLowPass( strength, 0, dt );
 133                         } else {
 134                                 strength = 0.0;
 135                         }
 136                         _ridge_lift_fps_node->setDoubleValue( strength );
 137                 }
 138                 return;
 139         }
 140
 141         timer -= dt;
 142         if (timer <= 0.0 ) {
 143
 144                 // probe0 is current position
 145                 probe_lat_deg[0] = _user_latitude_node->getDoubleValue();
 146                 probe_lon_deg[0] = _user_longitude_node->getDoubleValue();
 147                 probe_elev_m[0]  = _ground_elev_node->getDoubleValue() * SG_FEET_TO_METER;
 148
 149                 // position is geodetic, need geocentric for advanceRadM
 150                 SGGeod myGeodPos = SGGeod::fromDegM( probe_lon_deg[0], probe_lat_deg[0], 20000.0 );
 151                 SGGeoc myGeocPos = SGGeoc::fromGeod( myGeodPos );
 152                 double ground_wind_from_rad = _surface_wind_from_deg_node->getDoubleValue() * SG_DEGREES_TO_RADIANS;
 153
 154                 // compute the remaining probes
 155                 for (unsigned i = 1; i < sizeof(probe_elev_m)/sizeof(probe_elev_m[0]); i++) {
 156                         SGGeoc probe = myGeocPos.advanceRadM( ground_wind_from_rad, dist_probe_m[i] );
 157                         // convert to geodetic position for ground level computation
 158                         SGGeod probeGeod = SGGeod::fromGeoc( probe );
 159                         probe_lat_deg[i] = probeGeod.getLatitudeDeg();
 160                         probe_lon_deg[i] = probeGeod.getLongitudeDeg();
 161                         if (!globals->get_scenery()->get_elevation_m( probeGeod, probe_elev_m[i], NULL )) {
 162                                 // no ground found? use elevation of previous probe :-(
 163                                 probe_elev_m[i] = probe_elev_m[i-1];
 164                         }
 165                 }
 166
 167                 // slopes
 168                 double adj_slope[sizeof(slope)];
 169                 slope[0] = (probe_elev_m[0] - probe_elev_m[1]) / dist_probe_m[1];
 170                 slope[1] = (probe_elev_m[1] - probe_elev_m[2]) / dist_probe_m[2];
 171                 slope[2] = (probe_elev_m[2] - probe_elev_m[3]) / dist_probe_m[3];
 172                 slope[3] = (probe_elev_m[4] - probe_elev_m[0]) / -dist_probe_m[4];
 173
 174                 for (unsigned i = 0; i < sizeof(slope)/sizeof(slope[0]); i++)
 175                         adj_slope[i] = sin(atan(5.0 * pow ( (fabs(slope[i])),1.7) ) ) *sign(slope[i]);
 176
 177                 //adjustment
 178                 adj_slope[0] *= 0.2;
 179                 adj_slope[1] *= 0.2;
 180                 if ( adj_slope [2] < 0.0 ) {
 181                         adj_slope[2] *= 0.5;
 182                 } else {
 183                         adj_slope[2] = 0.0 ;
 184                 }
 185
 186                 if ( ( adj_slope [0] >= 0.0 ) && ( adj_slope [3] < 0.0 ) ) {
 187                         adj_slope[3] = 0.0;
 188                 } else {
 189                         adj_slope[3] *= 0.2;
 190                 }
 191                 lift_factor = adj_slope[0]+adj_slope[1]+adj_slope[2]+adj_slope[3];
 192
 193                 // restart the timer
 194                 timer = 1.0;
 195         }
 196
 197         //user altitude above ground
 198         double user_altitude_agl_m = _user_altitude_agl_ft_node->getDoubleValue() * SG_FEET_TO_METER;
 199
 200         //boundaries
 201         double boundary2_m = 130.0; // in the lift
 202         if (lift_factor < 0.0) { // in the sink
 203                 double highest_probe_temp= max ( probe_elev_m[1], probe_elev_m[2] );
 204                 double highest_probe_downwind_m= max ( highest_probe_temp, probe_elev_m[3] );
 205                 boundary2_m = highest_probe_downwind_m - probe_elev_m[0];
 206         }
 207
 208         double agl_factor;
 209         if ( user_altitude_agl_m < BOUNDARY1_m ) {
 210                 agl_factor = 0.5+0.5*user_altitude_agl_m /BOUNDARY1_m ;
 211         } else if ( user_altitude_agl_m < boundary2_m ) {
 212                 agl_factor = 1.0;
 213         } else {
 214                 agl_factor = exp(-(2 + probe_elev_m[0] / 2000) *
 215                                 (user_altitude_agl_m - boundary2_m) / max(probe_elev_m[0],200.0));
 216         }
 217
 218         double ground_wind_speed_mps = _surface_wind_speed_node->getDoubleValue() * SG_NM_TO_METER / 3600;
 219         double lift_mps = lift_factor* ground_wind_speed_mps * agl_factor;
 220
 221         //the updraft, finally, in ft per second
 222         strength = fgGetLowPass( strength, lift_mps * SG_METER_TO_FEET, dt );
 223         _ridge_lift_fps_node->setDoubleValue( strength );
 224 }