src/AIModel/AIBallistic.cxx

   1 // FGAIBallistic - FGAIBase-derived class creates a ballistic object
   2 //
   3 // Written by David Culp, started November 2003.
   4 // - davidculp2@comcast.net
   5 //
   6 // With major additions by Mathias Froehlich & Vivian Meazza 2004-2008
   7 //
   8 // This program is free software; you can redistribute it and/or
   9 // modify it under the terms of the GNU General Public License as
  10 // published by the Free Software Foundation; either version 2 of the
  11 // License, or (at your option) any later version.
  12 //
  13 // This program is distributed in the hope that it will be useful, but
  14 // WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 // General Public License for more details.
  17 //
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  21
  22 #ifdef HAVE_CONFIG_H
  23 #  include <config.h>
  24 #endif
  25
  26 #include <simgear/math/sg_random.h>
  27 #include <simgear/math/sg_geodesy.hxx>
  28 #include <simgear/scene/model/modellib.hxx>
  29
  30 #include <Scenery/scenery.hxx>
  31
  32 #include "AIModelData.hxx"
  33 #include "AIBallistic.hxx"
  34
  35 #include <Main/util.hxx>
  36
  37 using namespace simgear;
  38
  39 const double FGAIBallistic::slugs_to_kgs = 14.5939029372;
  40 const double FGAIBallistic::slugs_to_lbs = 32.1740485564;
  41
  42 FGAIBallistic::FGAIBallistic(object_type ot) :
  43 FGAIBase(ot),
  44     _elevation(0),
  45     _aero_stabilised(false),
  46     _drag_area(0.007),
  47     _life_timer(0.0),
  48 _gravity(32.1740485564),
  49     _buoyancy(0),
  50     _random(false),
  51     _ht_agl_ft(0),
  52     _load_resistance(0),
  53     _solid(false),
  54     _report_collision(false),
  55     _report_impact(false),
  56 _wind(true),
  57     _impact_report_node(fgGetNode("/ai/models/model-impact", true)),
  58     _force_stabilised(false),
  59 _external_force(false),
  60 _slave_to_ac(false),
  61 _slave_load_to_ac(false),
  62 _formate_to_ac(false),
  63 _contents_lb(0),
  64 _mass(0),
  65 _height(0),
  66 _old_height(0)
  67
  68 {
  69     no_roll = false;
  70 }
  71
  72 FGAIBallistic::~FGAIBallistic() {
  73 }
  74
  75 void FGAIBallistic::readFromScenario(SGPropertyNode* scFileNode) {
  76     if (!scFileNode){
  77         return;
  78     }
  79
  80     FGAIBase::readFromScenario(scFileNode);
  81
  82     //setPath(scFileNode->getStringValue("model", "Models/Geometry/rocket.ac"));
  83     setAzimuth(scFileNode->getDoubleValue("azimuth", 0.0));
  84     setElevation(scFileNode->getDoubleValue("elevation", 0));
  85     setDragArea(scFileNode->getDoubleValue("eda", 0.007));
  86     setLife(scFileNode->getDoubleValue("life", 900.0));
  87     setBuoyancy(scFileNode->getDoubleValue("buoyancy", 0));
  88     setWind_from_east(scFileNode->getDoubleValue("wind_from_east", 0));
  89     setWind_from_north(scFileNode->getDoubleValue("wind_from_north", 0));
  90     setWind(scFileNode->getBoolValue("wind", false));
  91     setRoll(scFileNode->getDoubleValue("roll", 0.0));
  92     setCd(scFileNode->getDoubleValue("cd", 0.029));
  93     //setMass(scFileNode->getDoubleValue("mass", 0.007));
  94     setWeight(scFileNode->getDoubleValue("weight", 0.25));
  95     setStabilisation(scFileNode->getBoolValue("aero-stabilized", false));
  96     setNoRoll(scFileNode->getBoolValue("no-roll", false));
  97     setRandom(scFileNode->getBoolValue("random", false));
  98     setImpact(scFileNode->getBoolValue("impact", false));
  99     setImpactReportNode(scFileNode->getStringValue("impact-reports"));
 100     setName(scFileNode->getStringValue("name", "Rocket"));
 101     setFuseRange(scFileNode->getDoubleValue("fuse-range", 0.0));
 102     setSMPath(scFileNode->getStringValue("submodel-path", ""));
 103     setSubID(scFileNode->getIntValue("SubID", 0));
 104     setExternalForce(scFileNode->getBoolValue("external-force", false));
 105     setForcePath(scFileNode->getStringValue("force-path", ""));
 106     setForceStabilisation(scFileNode->getBoolValue("force-stabilized", false));
 107     setXoffset(scFileNode->getDoubleValue("x-offset", 0.0));
 108     setYoffset(scFileNode->getDoubleValue("y-offset", 0.0));
 109     setZoffset(scFileNode->getDoubleValue("z-offset", 0.0));
 110     setPitchoffset(scFileNode->getDoubleValue("pitch-offset", 0.0));
 111     setRolloffset(scFileNode->getDoubleValue("roll-offset", 0.0));
 112     setYawoffset(scFileNode->getDoubleValue("yaw-offset", 0.0));
 113     setGroundOffset(scFileNode->getDoubleValue("ground-offset", 0.0));
 114     setLoadOffset(scFileNode->getDoubleValue("load-offset", 0.0));
 115     setSlaved(scFileNode->getBoolValue("slaved", false));
 116     setSlavedLoad(scFileNode->getBoolValue("slaved-load", false));
 117     setContentsNode(scFileNode->getStringValue("contents"));
 118     setRandom(scFileNode->getBoolValue("random", false));
 119 }
 120
 121 osg::Node* FGAIBallistic::load3DModel(const string &path, SGPropertyNode *prop_root)
 122 {
 123   model = SGModelLib::loadModel(path, prop_root, new FGAIModelData(this, prop_root));
 124   return model.get();
 125 }
 126
 127 bool FGAIBallistic::init(bool search_in_AI_path) {
 128     FGAIBase::init(search_in_AI_path);
 129
 130     _impact_reported = false;
 131     _collision_reported = false;
 132     invisible = false;
 133
 134     _elapsed_time += (sg_random() * 100);
 135
 136     props->setStringValue("material/name", "");
 137     props->setStringValue("name", _name.c_str());
 138     props->setStringValue("submodels/path", _submodel.c_str());
 139
 140     // start with high value so that animations don't trigger yet
 141     _ht_agl_ft = 1e10;
 142     hdg = _azimuth;
 143     pitch = _elevation;
 144     roll = _rotation;
 145
 146     Transform();
 147
 148     return true;
 149 }
 150
 151 void FGAIBallistic::bind() {
 152     //    FGAIBase::bind();
 153
 154     props->tie("sim/time/elapsed-sec",
 155         SGRawValueMethods<FGAIBallistic,double>(*this,
 156         &FGAIBallistic::_getTime));
 157     props->tie("mass-slug",
 158         SGRawValueMethods<FGAIBallistic,double>(*this,
 159         &FGAIBallistic::getMass));
 160     props->tie("material/load-resistance",
 161                 SGRawValuePointer<double>(&_load_resistance));
 162     props->tie("material/solid",
 163                 SGRawValuePointer<bool>(&_solid));
 164     props->tie("altitude-agl-ft",
 165                 SGRawValuePointer<double>(&_ht_agl_ft));
 166     props->tie("controls/slave-to-ac",
 167         SGRawValueMethods<FGAIBallistic,bool>
 168         (*this, &FGAIBallistic::getSlaved, &FGAIBallistic::setSlaved));
 169     props->tie("controls/invisible",
 170         SGRawValuePointer<bool>(&invisible));
 171
 172     if(_external_force){
 173         props->tie("controls/force_stabilized",
 174             SGRawValuePointer<bool>(&_force_stabilised));
 175         props->tie("position/global-x",
 176             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosX, 0));
 177         props->tie("position/global-y",
 178             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosY, 0));
 179         props->tie("position/global-z",
 180             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosZ, 0));
 181         props->tie("velocities/vertical-speed-fps",
 182             SGRawValuePointer<double>(&vs));
 183         props->tie("velocities/true-airspeed-kt",
 184             SGRawValuePointer<double>(&speed));
 185         props->tie("velocities/horizontal-speed-fps",
 186             SGRawValuePointer<double>(&hs));
 187         props->tie("position/altitude-ft",
 188             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getAltitude, &FGAIBase::_setAltitude));
 189         props->tie("position/latitude-deg",
 190             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLatitude, &FGAIBase::_setLatitude));
 191         props->tie("position/longitude-deg",
 192             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLongitude, &FGAIBase::_setLongitude));
 193         props->tie("orientation/hdg-deg",
 194             SGRawValuePointer<double>(&hdg));
 195         props->tie("orientation/pitch-deg",
 196             SGRawValuePointer<double>(&pitch));
 197         props->tie("orientation/roll-deg",
 198             SGRawValuePointer<double>(&roll));
 199         props->tie("controls/slave-load-to-ac",
 200             SGRawValueMethods<FGAIBallistic,bool>
 201             (*this, &FGAIBallistic::getSlavedLoad, &FGAIBallistic::setSlavedLoad));
 202         props->tie("position/load-offset",
 203             SGRawValueMethods<FGAIBallistic,double>
 204             (*this, &FGAIBallistic::getLoadOffset, &FGAIBallistic::setLoadOffset));
 205         props->tie("load/distance-to-hitch-ft",
 206             SGRawValueMethods<FGAIBallistic,double>
 207             (*this, &FGAIBallistic::getDistanceLoadToHitch));
 208         props->tie("load/elevation-to-hitch-deg",
 209             SGRawValueMethods<FGAIBallistic,double>
 210             (*this, &FGAIBallistic::getElevLoadToHitch));
 211         props->tie("load/bearing-to-hitch-deg",
 212             SGRawValueMethods<FGAIBallistic,double>
 213             (*this, &FGAIBallistic::getBearingLoadToHitch));
 214     }
 215
 216 }
 217
 218 void FGAIBallistic::unbind() {
 219     //    FGAIBase::unbind();
 220
 221     props->untie("sim/time/elapsed-sec");
 222     props->untie("mass-slug");
 223     props->untie("material/load-resistance");
 224     props->untie("material/solid");
 225     props->untie("altitude-agl-ft");
 226     props->untie("controls/slave-to-ac");
 227     props->untie("controls/invisible");
 228
 229     if(_external_force){
 230         props->untie("position/global-y");
 231         props->untie("position/global-x");
 232         props->untie("position/global-z");
 233         props->untie("velocities/vertical-speed-fps");
 234         props->untie("velocities/true-airspeed-kt");
 235         props->untie("velocities/horizontal-speed-fps");
 236         props->untie("position/altitude-ft");
 237         props->untie("position/latitude-deg");
 238         props->untie("position/longitude-deg");
 239         props->untie("position/ht-agl-ft");
 240         props->untie("orientation/hdg-deg");
 241         props->untie("orientation/pitch-deg");
 242         props->untie("orientation/roll-deg");
 243         props->untie("controls/force_stabilized");
 244         props->untie("position/load-offset");
 245         props->untie("load/distance-to-hitch-ft");
 246         props->untie("load/elevation-to-hitch-deg");
 247         props->untie("load/bearing-to-hitch-deg");
 248     }
 249 }
 250
 251 void FGAIBallistic::update(double dt) {
 252     FGAIBase::update(dt);
 253     _setUserPos();
 254
 255     if (_slave_to_ac){
 256         slaveToAC(dt);
 257         Transform();
 258         setHitchVelocity(dt);
 259     } else if (_formate_to_ac){
 260         formateToAC(dt);
 261         Transform();
 262         setHitchVelocity(dt);
 263     } else if (!invisible){
 264     Run(dt);
 265     Transform();
 266 }
 267
 268 }
 269
 270 void FGAIBallistic::setAzimuth(double az) {
 271     hdg = _azimuth = az;
 272 }
 273
 274 void FGAIBallistic::setElevation(double el) {
 275     pitch = _elevation = el;
 276 }
 277
 278 void FGAIBallistic::setRoll(double rl) {
 279     roll = _rotation = rl;
 280 }
 281
 282 void FGAIBallistic::setStabilisation(bool val) {
 283     _aero_stabilised = val;
 284 }
 285
 286 void FGAIBallistic::setForceStabilisation(bool val) {
 287     _force_stabilised = val;
 288 }
 289
 290 void FGAIBallistic::setNoRoll(bool nr) {
 291     no_roll = nr;
 292 }
 293
 294 void FGAIBallistic::setDragArea(double a) {
 295     _drag_area = a;
 296 }
 297
 298 void FGAIBallistic::setLife(double seconds) {
 299     life = seconds;
 300 }
 301
 302 void FGAIBallistic::setBuoyancy(double fpss) {
 303     _buoyancy = fpss;
 304 }
 305
 306 void FGAIBallistic::setWind_from_east(double fps) {
 307     _wind_from_east = fps;
 308 }
 309
 310 void FGAIBallistic::setWind_from_north(double fps) {
 311     _wind_from_north = fps;
 312 }
 313
 314 void FGAIBallistic::setWind(bool val) {
 315     _wind = val;
 316 }
 317
 318 void FGAIBallistic::setCd(double c) {
 319     _Cd = c;
 320 }
 321
 322 void FGAIBallistic::setMass(double m) {
 323     _mass = m;
 324 }
 325
 326 void FGAIBallistic::setWeight(double w) {
 327     _weight_lb = w;
 328 }
 329 void FGAIBallistic::setRandom(bool r) {
 330     _random = r;
 331 }
 332
 333 void FGAIBallistic::setImpact(bool i) {
 334     _report_impact = i;
 335 }
 336
 337 void FGAIBallistic::setCollision(bool c) {
 338     _report_collision = c;
 339 }
 340
 341 void FGAIBallistic::setExternalForce(bool f) {
 342     _external_force = f;
 343 }
 344
 345 void FGAIBallistic::setImpactReportNode(const string& path) {
 346
 347     if (!path.empty())
 348         _impact_report_node = fgGetNode(path.c_str(), true);
 349 }
 350
 351 void FGAIBallistic::setName(const string& n) {
 352     _name = n;
 353 }
 354
 355 void FGAIBallistic::setSMPath(const string& s) {
 356     _submodel = s;
 357 }
 358
 359 void FGAIBallistic::setFuseRange(double f) {
 360     _fuse_range = f;
 361 }
 362
 363 void FGAIBallistic::setSubID(int i) {
 364     _subID = i;
 365 }
 366
 367 void FGAIBallistic::setSubmodel(const string& s) {
 368     _submodel = s;
 369 }
 370
 371 void FGAIBallistic::setGroundOffset(double g) {
 372     _ground_offset = g;
 373 }
 374
 375 void FGAIBallistic::setLoadOffset(double l) {
 376     _load_offset = l;
 377 }
 378
 379 double FGAIBallistic::getLoadOffset() const {
 380     return _load_offset;
 381 }
 382
 383 void FGAIBallistic::setSlaved(bool s) {
 384     _slave_to_ac = s;
 385 }
 386
 387 void FGAIBallistic::setFormate(bool f) {
 388     _formate_to_ac = f;
 389 }
 390
 391 void FGAIBallistic::setContentsNode(const string& path) {
 392     if (!path.empty()) {
 393         _contents_node = fgGetNode(path.c_str(), true);
 394     }
 395 }
 396
 397 bool FGAIBallistic::getSlaved() const {
 398     return _slave_to_ac;
 399 }
 400
 401 double FGAIBallistic::getMass() const {
 402     return _mass;
 403 }
 404
 405 double FGAIBallistic::getContents() {
 406     if(_contents_node)
 407         _contents_lb = _contents_node->getChild("level-lbs",0,1)->getDoubleValue();
 408     return _contents_lb;
 409 }
 410
 411 void FGAIBallistic::setContents(double c) {
 412     if(_contents_node)
 413         _contents_lb = _contents_node->getChild("level-gal_us",0,1)->setDoubleValue(c);
 414 }
 415
 416 void FGAIBallistic::setSlavedLoad(bool l) {
 417     _slave_load_to_ac = l;
 418 }
 419
 420 bool FGAIBallistic::getSlavedLoad() const {
 421     return _slave_load_to_ac;
 422 }
 423
 424 void FGAIBallistic::setForcePath(const string& p) {
 425     _force_path = p;
 426     if (!_force_path.empty()) {
 427         SGPropertyNode *fnode = fgGetNode(_force_path.c_str(), 0, true );
 428         _force_node = fnode->getChild("force-lb", 0, true);
 429         _force_azimuth_node = fnode->getChild("force-azimuth-deg", 0, true);
 430         _force_elevation_node = fnode->getChild("force-elevation-deg", 0, true);
 431     }
 432 }
 433
 434 bool FGAIBallistic::getHtAGL(){
 435
 436     if (globals->get_scenery()->get_elevation_m(pos.getLatitudeDeg(), pos.getLongitudeDeg(),
 437         10000.0, _elevation_m, &_material)){
 438             _ht_agl_ft = pos.getElevationFt() - _elevation_m * SG_METER_TO_FEET;
 439             if (_material) {
 440                 const vector<string>& names = _material->get_names();
 441
 442                 _solid = _material->get_solid();
 443                 _load_resistance = _material->get_load_resistance();
 444                 _frictionFactor =_material->get_friction_factor();
 445                 if (!names.empty())
 446                     props->setStringValue("material/name", names[0].c_str());
 447                 else
 448                     props->setStringValue("material/name", "");
 449                 /*cout << "material " << mat_name
 450                 << " solid " << _solid
 451                 << " load " << _load_resistance
 452                 << " frictionFactor " << frictionFactor
 453                 << endl;*/
 454             }
 455             return true;
 456     } else {
 457         return false;
 458     }
 459
 460 }
 461
 462 double FGAIBallistic::getRecip(double az){
 463     // calculate the reciprocal of the input azimuth
 464     if(az - 180 < 0){
 465         return az + 180;
 466     } else {
 467         return az - 180;
 468     }
 469 }
 470
 471 void FGAIBallistic::setPch(double e, double dt, double coeff){
 472     double c = dt / (coeff + dt);
 473     pitch = (e * c) + (pitch * (1 - c));
 474 }
 475
 476 void FGAIBallistic::setBnk(double r, double dt, double coeff){
 477     double c = dt / (coeff + dt);
 478     roll = (r * c) + (roll * (1 - c));
 479 }
 480
 481 void FGAIBallistic::setHt(double h, double dt, double coeff){
 482     double c = dt / (coeff + dt);
 483     _height = (h * c) + (_height * (1 - c));
 484 }
 485
 486 void FGAIBallistic::setHdg(double az, double dt, double coeff){
 487     double recip = getRecip(hdg);
 488     double c = dt / (coeff + dt);
 489     //we need to ensure that we turn the short way to the new hdg
 490     if (az < recip && az < hdg && hdg > 180) {
 491         hdg = ((az + 360) * c) + (hdg * (1 - c));
 492     } else if (az > recip && az > hdg && hdg <= 180){
 493         hdg = ((az - 360) * c) + (hdg * (1 - c));
 494     } else {
 495         hdg = (az * c) + (hdg * (1 - c));
 496     }
 497     }
 498
 499 double  FGAIBallistic::getTgtXOffset() const {
 500     return _tgt_x_offset;
 501 }
 502
 503 double  FGAIBallistic::getTgtYOffset() const {
 504     return _tgt_y_offset;
 505 }
 506
 507 double  FGAIBallistic::getTgtZOffset() const {
 508     return _tgt_z_offset;
 509 }
 510
 511 void FGAIBallistic::setTgtXOffset(double x){
 512     _tgt_x_offset = x;
 513 }
 514
 515 void FGAIBallistic::setTgtYOffset(double y){
 516     _tgt_y_offset = y;
 517 }
 518
 519 void FGAIBallistic::setTgtZOffset(double z){
 520     _tgt_z_offset = z;
 521 }
 522
 523 void FGAIBallistic::slaveToAC(double dt){
 524
 525     setHitchPos();
 526     pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
 527     pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
 528     pos.setElevationFt(hitchpos.getElevationFt());
 529     setHeading(manager->get_user_heading());
 530     setPitch(manager->get_user_pitch() + _pitch_offset);
 531     setBank(manager->get_user_roll() + _roll_offset);
 532     setSpeed(manager->get_user_speed());
 533     //update the mass (slugs)
 534     _mass = (_weight_lb + getContents()) / slugs_to_lbs;
 535
 536     /*cout <<"_mass "<<_mass <<" " << getContents()
 537     <<" " << getContents() / slugs_to_lbs << endl;*/
 538 }
 539
 540 void FGAIBallistic::Run(double dt) {
 541     _life_timer += dt;
 542
 543     // if life = -1 the object does not die
 544     if (_life_timer > life && life != -1)
 545         setDie(true);
 546
 547     //set the contents in the appropriate tank or other property in the parent to zero
 548     setContents(0);
 549
 550     //randomise Cd by +- 5%
 551     if (_random)
 552         _Cd = _Cd * 0.95 + (0.05 * sg_random());
 553
 554     // Adjust Cd by Mach number. The equations are based on curves
 555     // for a conventional shell/bullet (no boat-tail).
 556     double Cdm;
 557
 558     if (Mach < 0.7)
 559         Cdm = 0.0125 * Mach + _Cd;
 560     else if (Mach < 1.2 )
 561         Cdm = 0.3742 * pow(Mach, 2) - 0.252 * Mach + 0.0021 + _Cd;
 562     else
 563         Cdm = 0.2965 * pow(Mach, -1.1506) + _Cd;
 564
 565     //cout << "Mach " << Mach << " Cdm " << Cdm << "// ballistic speed kts "<< speed <<  endl;
 566
 567     // drag = Cd * 0.5 * rho * speed * speed * drag_area;
 568     // rho is adjusted for altitude in void FGAIBase::update,
 569     // using Standard Atmosphere (sealevel temperature 15C)
 570     // acceleration = drag/mass;
 571     // adjust speed by drag
 572     speed -= (Cdm * 0.5 * rho * speed * speed * _drag_area/_mass) * dt;
 573
 574     // don't let speed become negative
 575     if ( speed < 0.0 )
 576         speed = 0.0;
 577
 578     double speed_fps = speed * SG_KT_TO_FPS;
 579     //double hs;
 580
 581     // calculate vertical and horizontal speed components
 582     if (speed == 0.0) {
 583         hs = vs = 0.0;
 584     } else {
 585         vs = sin( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
 586         hs = cos( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
 587     }
 588
 589     //resolve horizontal speed into north and east components:
 590     double speed_north_fps = cos(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
 591     double speed_east_fps = sin(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
 592
 593     // convert horizontal speed (fps) to degrees per second
 594     double speed_north_deg_sec = speed_north_fps / ft_per_deg_lat;
 595     double speed_east_deg_sec  = speed_east_fps / ft_per_deg_lon;
 596
 597     // if wind not required, set to zero
 598     if (!_wind) {
 599         _wind_from_north = 0;
 600         _wind_from_east = 0;
 601     } else {
 602         _wind_from_north = manager->get_wind_from_north();
 603         _wind_from_east = manager->get_wind_from_east();
 604     }
 605
 606     //calculate velocity due to external force
 607     double force_speed_north_deg_sec = 0;
 608     double force_speed_east_deg_sec = 0;
 609     double vs_force_fps = 0;
 610     double hs_force_fps = 0;
 611     double v_force_acc_fpss = 0;
 612     double force_speed_north_fps = 0;
 613     double force_speed_east_fps = 0;
 614     double h_force_lbs = 0;
 615     double normal_force_lbs = 0;
 616     double normal_force_fpss = 0;
 617     double static_friction_force_lbs = 0;
 618     double dynamic_friction_force_lbs = 0;
 619     double friction_force_speed_north_fps = 0;
 620     double friction_force_speed_east_fps = 0;
 621     double friction_force_speed_north_deg_sec = 0;
 622     double friction_force_speed_east_deg_sec = 0;
 623     double force_elevation_deg = 0;
 624
 625     if (_external_force) {
 626         SGPropertyNode *n = fgGetNode(_force_path.c_str(), true);
 627         double force_lbs            = n->getChild("force-lb", 0, true)->getDoubleValue();
 628         force_elevation_deg         = n->getChild("force-elevation-deg", 0, true)->getDoubleValue();
 629         double force_azimuth_deg    = n->getChild("force-azimuth-deg", 0, true)->getDoubleValue();
 630
 631         //resolve force into vertical and horizontal components:
 632         double v_force_lbs = force_lbs * sin( force_elevation_deg * SG_DEGREES_TO_RADIANS );
 633         h_force_lbs = force_lbs * cos( force_elevation_deg * SG_DEGREES_TO_RADIANS );
 634
 635         //ground interaction
 636
 637         if (getHtAGL()){
 638             double deadzone = 0.1;
 639
 640             if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
 641                 normal_force_lbs = (_mass * slugs_to_lbs) - v_force_lbs;
 642
 643                 if ( normal_force_lbs < 0 )
 644                     normal_force_lbs = 0;
 645
 646                 pos.setElevationFt(0 + _ground_offset);
 647                 if (vs < 0)
 648                     vs = -vs * 0.5;
 649
 650                 // calculate friction
 651                 // we assume a static Coefficient of Friction (mu) of 0.62 (wood on concrete)
 652                 double mu = 0.62;
 653
 654                 static_friction_force_lbs = mu * normal_force_lbs * _frictionFactor;
 655
 656                 //adjust horizontal force. We assume that a speed of <= 5 fps is static
 657                 if (h_force_lbs <= static_friction_force_lbs && hs <= 5){
 658                     h_force_lbs = hs = 0;
 659                     speed_north_fps = speed_east_fps = 0;
 660                 } else
 661                     dynamic_friction_force_lbs = (static_friction_force_lbs * 0.95);
 662
 663                 //ignore wind when on the ground for now
 664                 //TODO fix this
 665                 _wind_from_north = 0;
 666                 _wind_from_east = 0;
 667
 668             }
 669
 670         }
 671
 672         //acceleration = (force(lbsf)/mass(slugs))
 673         v_force_acc_fpss = v_force_lbs/_mass;
 674         normal_force_fpss = normal_force_lbs/_mass;
 675         double h_force_acc_fpss = h_force_lbs/_mass;
 676         double dynamic_friction_acc_fpss = dynamic_friction_force_lbs/_mass;
 677
 678         // velocity = acceleration * dt
 679         hs_force_fps = h_force_acc_fpss * dt;
 680         double friction_force_fps = dynamic_friction_acc_fpss * dt;
 681
 682         //resolve horizontal speeds into north and east components:
 683         force_speed_north_fps   = cos(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
 684         force_speed_east_fps    = sin(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
 685
 686         friction_force_speed_north_fps = cos(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
 687         friction_force_speed_east_fps  = sin(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
 688
 689         // convert horizontal speed (fps) to degrees per second
 690         force_speed_north_deg_sec = force_speed_north_fps / ft_per_deg_lat;
 691         force_speed_east_deg_sec  = force_speed_east_fps / ft_per_deg_lon;
 692
 693         friction_force_speed_north_deg_sec = friction_force_speed_north_fps / ft_per_deg_lat;
 694         friction_force_speed_east_deg_sec  = friction_force_speed_east_fps / ft_per_deg_lon;
 695     }
 696
 697     // convert wind speed (fps) to degrees lat/lon per second
 698     double wind_speed_from_north_deg_sec = _wind_from_north / ft_per_deg_lat;
 699     double wind_speed_from_east_deg_sec  = _wind_from_east / ft_per_deg_lon;
 700
 701     //recombine the horizontal velocity components
 702     hs = sqrt(((speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps)
 703         * (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
 704         + ((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)
 705         * (speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)));
 706
 707     if (hs <= 0.00001)
 708         hs = 0;
 709
 710     // adjust vertical speed for acceleration of gravity, buoyancy, and vertical force
 711     vs -= (_gravity - _buoyancy - v_force_acc_fpss - normal_force_fpss) * dt;
 712
 713     if (vs <= 0.00001 && vs >= -0.00001)
 714         vs = 0;
 715
 716     // set new position
 717     if(_slave_load_to_ac) {
 718         setHitchPos();
 719         pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
 720         pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
 721         pos.setElevationFt(hitchpos.getElevationFt());
 722
 723         if (getHtAGL()){
 724             double deadzone = 0.1;
 725
 726             if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
 727                 pos.setElevationFt(0 + _ground_offset);
 728             } else {
 729                 pos.setElevationFt(hitchpos.getElevationFt() + _load_offset);
 730             }
 731
 732         }
 733     } else {
 734         pos.setLatitudeDeg( pos.getLatitudeDeg()
 735             + (speed_north_deg_sec - wind_speed_from_north_deg_sec
 736             + force_speed_north_deg_sec + friction_force_speed_north_deg_sec) * dt );
 737         pos.setLongitudeDeg( pos.getLongitudeDeg()
 738             + (speed_east_deg_sec - wind_speed_from_east_deg_sec
 739             + force_speed_east_deg_sec + friction_force_speed_east_deg_sec) * dt );
 740         pos.setElevationFt(pos.getElevationFt() + vs * dt);
 741     }
 742
 743     // recalculate total speed
 744     if ( vs == 0 && hs == 0)
 745         speed = 0;
 746     else
 747         speed = sqrt( vs * vs + hs * hs) / SG_KT_TO_FPS;
 748
 749     // recalculate elevation and azimuth (velocity vectors)
 750     _elevation = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
 751     _azimuth =  atan2((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps),
 752         (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
 753         * SG_RADIANS_TO_DEGREES;
 754
 755     // rationalise azimuth
 756     if (_azimuth < 0)
 757         _azimuth += 360;
 758
 759     if (_aero_stabilised) { // we simulate rotational moment of inertia by using a filter
 760         const double coeff = 0.9;
 761
 762         // we assume a symetrical MI about the pitch and yaw axis
 763         setPch(_elevation, dt, coeff);
 764         setHdg(_azimuth, dt, coeff);
 765     } else if (_force_stabilised) { // we simulate rotational moment of inertia by using a filter
 766         const double coeff = 0.9;
 767         double ratio = h_force_lbs/(_mass * slugs_to_lbs);
 768
 769         if (ratio >  1) ratio =  1;
 770         if (ratio < -1) ratio = -1;
 771
 772         double force_pitch = acos(ratio) * SG_RADIANS_TO_DEGREES;
 773
 774         if (force_pitch <= force_elevation_deg)
 775             force_pitch = force_elevation_deg;
 776
 777         // we assume a symetrical MI about the pitch and yaw axis
 778         setPch(force_pitch,dt, coeff);
 779         setHdg(_azimuth, dt, coeff);
 780     }
 781
 782     //do impacts and collisions
 783     if (_report_impact && !_impact_reported)
 784         handle_impact();
 785
 786     if (_report_collision && !_collision_reported)
 787         handle_collision();
 788
 789     // set destruction flag if altitude less than sea level -1000
 790     if (altitude_ft < -1000.0 && life != -1)
 791         setDie(true);
 792
 793 }  // end Run
 794
 795 double FGAIBallistic::_getTime() const {
 796     return _life_timer;
 797 }
 798
 799 void FGAIBallistic::handle_impact() {
 800
 801     // try terrain intersection
 802     if(!getHtAGL())
 803         return;
 804
 805     if (_ht_agl_ft <= 0) {
 806         SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: terrain impact");
 807         report_impact(_elevation_m);
 808         _impact_reported = true;
 809
 810         if (life == -1){
 811             invisible = true;
 812         } else if (_subID == 0)  // kill the AIObject if there is no subsubmodel
 813             setDie(true);
 814     }
 815 }
 816
 817 void FGAIBallistic::handle_collision()
 818 {
 819     const FGAIBase *object = manager->calcCollision(pos.getElevationFt(),
 820             pos.getLatitudeDeg(),pos.getLongitudeDeg(), _fuse_range);
 821
 822     if (object) {
 823         SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: object hit");
 824         report_impact(pos.getElevationM(), object);
 825         _collision_reported = true;
 826     }
 827 }
 828
 829 void FGAIBallistic::report_impact(double elevation, const FGAIBase *object)
 830 {
 831     _impact_lat    = pos.getLatitudeDeg();
 832     _impact_lon    = pos.getLongitudeDeg();
 833     _impact_elev   = elevation;
 834     _impact_speed  = speed * SG_KT_TO_MPS;
 835     _impact_hdg    = hdg;
 836     _impact_pitch  = pitch;
 837     _impact_roll   = roll;
 838
 839     SGPropertyNode *n = props->getNode("impact", true);
 840     if (object)
 841         n->setStringValue("type", object->getTypeString());
 842     else
 843         n->setStringValue("type", "terrain");
 844
 845     n->setDoubleValue("longitude-deg", _impact_lon);
 846     n->setDoubleValue("latitude-deg", _impact_lat);
 847     n->setDoubleValue("elevation-m", _impact_elev);
 848     n->setDoubleValue("heading-deg", _impact_hdg);
 849     n->setDoubleValue("pitch-deg", _impact_pitch);
 850     n->setDoubleValue("roll-deg", _impact_roll);
 851     n->setDoubleValue("speed-mps", _impact_speed);
 852
 853     _impact_report_node->setStringValue(props->getPath());
 854 }
 855
 856 SGVec3d FGAIBallistic::getCartUserPos() const {
 857     SGVec3d cartUserPos = SGVec3d::fromGeod(userpos);
 858     return cartUserPos;
 859 }
 860
 861 SGVec3d FGAIBallistic::getCartHitchPos() const{
 862
 863     // convert geodetic positions to geocentered
 864     SGVec3d cartuserPos = getCartUserPos();
 865     SGVec3d cartPos = getCartPos();
 866
 867     // Transform to the right coordinate frame, configuration is done in
 868     // the x-forward, y-right, z-up coordinates (feet), computation
 869     // in the simulation usual body x-forward, y-right, z-down coordinates
 870     // (meters) )
 871     SGVec3d _off(_x_offset * SG_FEET_TO_METER,
 872         _y_offset * SG_FEET_TO_METER,
 873         -_z_offset * SG_FEET_TO_METER);
 874
 875     // Transform the user position to the horizontal local coordinate system.
 876     SGQuatd hlTrans = SGQuatd::fromLonLat(userpos);
 877
 878     // and postrotate the orientation of the user model wrt the horizontal
 879     // local frame
 880     hlTrans *= SGQuatd::fromYawPitchRollDeg(
 881         manager->get_user_heading(),
 882         manager->get_user_pitch(),
 883         manager->get_user_roll());
 884
 885     // The offset converted to the usual body fixed coordinate system
 886     // rotated to the earth-fixed coordinates axis
 887     SGVec3d off = hlTrans.backTransform(_off);
 888
 889     // Add the position offset of the user model to get the geocentered position
 890     SGVec3d offsetPos = cartuserPos + off;
 891
 892     return offsetPos;
 893 }
 894
 895 void FGAIBallistic::setHitchPos(){
 896     // convert the hitch geocentered position to geodetic
 897     SGVec3d carthitchPos = getCartHitchPos();
 898
 899     SGGeodesy::SGCartToGeod(carthitchPos, hitchpos);
 900 }
 901
 902 double FGAIBallistic::getDistanceLoadToHitch() const {
 903     //calculate the distance load to hitch
 904     SGVec3d carthitchPos = getCartHitchPos();
 905     SGVec3d cartPos = getCartPos();
 906
 907     SGVec3d diff = carthitchPos - cartPos;
 908     double distance = norm(diff);
 909     return distance * SG_METER_TO_FEET;
 910 }
 911
 912 void FGAIBallistic::setHitchVelocity(double dt) {
 913     //calculate the distance from the previous hitch position
 914     SGVec3d carthitchPos = getCartHitchPos();
 915     SGVec3d diff = carthitchPos - _oldcarthitchPos;
 916
 917     double distance = norm(diff);
 918
 919     //calculate speed knots
 920     speed = (distance/dt) * SG_MPS_TO_KT;
 921
 922     //now calulate the angle between the old and current hitch positions (degrees)
 923     double angle = 0;
 924     double daltM = hitchpos.getElevationM() - oldhitchpos.getElevationM();
 925
 926     if (fabs(distance) < SGLimits<float>::min()) {
 927         angle = 0;
 928     } else {
 929         double sAngle = daltM/distance;
 930         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
 931         angle = SGMiscd::rad2deg(asin(sAngle));
 932     }
 933
 934     _elevation = angle;
 935
 936     //calculate the bearing of the new hitch position from the old
 937     double az1, az2, dist;
 938
 939     geo_inverse_wgs_84(oldhitchpos, hitchpos, &az1, &az2, &dist);
 940
 941     _azimuth = az1;
 942
 943     // and finally store the new values
 944     _oldcarthitchPos = carthitchPos;
 945     oldhitchpos = hitchpos;
 946 }
 947
 948 double FGAIBallistic::getElevLoadToHitch() const {
 949     // now the angle, positive angles are upwards
 950     double distance = getDistanceLoadToHitch() * SG_FEET_TO_METER;
 951     double angle = 0;
 952     double daltM = hitchpos.getElevationM() - pos.getElevationM();
 953
 954     if (fabs(distance) < SGLimits<float>::min()) {
 955         angle = 0;
 956     } else {
 957         double sAngle = daltM/distance;
 958         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
 959         angle = SGMiscd::rad2deg(asin(sAngle));
 960     }
 961
 962     return angle;
 963 }
 964
 965 double FGAIBallistic::getBearingLoadToHitch() const {
 966     //calculate the bearing and range of the second pos from the first
 967     double az1, az2, distance;
 968
 969     geo_inverse_wgs_84(pos, hitchpos, &az1, &az2, &distance);
 970
 971     return az1;
 972 }
 973
 974 double FGAIBallistic::getRelBrgHitchToUser() const {
 975     //calculate the relative bearing
 976     double az1, az2, distance;
 977
 978     geo_inverse_wgs_84(hitchpos, userpos, &az1, &az2, &distance);
 979
 980     double rel_brg = az1 - hdg;
 981
 982     if (rel_brg > 180)
 983         rel_brg -= 360;
 984
 985     return rel_brg;
 986 }
 987
 988 double FGAIBallistic::getElevHitchToUser() const {
 989
 990     //calculate the distance from the user position
 991     SGVec3d carthitchPos = getCartHitchPos();
 992     SGVec3d cartuserPos = getCartUserPos();
 993
 994     SGVec3d diff = cartuserPos - carthitchPos;
 995
 996     double distance = norm(diff);
 997     double angle = 0;
 998
 999     double daltM = userpos.getElevationM() - hitchpos.getElevationM();
1000
1001     // now the angle, positive angles are upwards
1002     if (fabs(distance) < SGLimits<float>::min()) {
1003         angle = 0;
1004     } else {
1005         double sAngle = daltM/distance;
1006         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
1007         angle = SGMiscd::rad2deg(asin(sAngle));
1008     }
1009
1010     return angle;
1011 }
1012
1013 void FGAIBallistic::setTgtOffsets(double dt, double coeff){
1014     double c = dt / (coeff + dt);
1015
1016     _x_offset = (_tgt_x_offset * c) + (_x_offset * (1 - c));
1017     _y_offset = (_tgt_y_offset * c) + (_y_offset * (1 - c));
1018     _z_offset = (_tgt_z_offset * c) + (_z_offset * (1 - c));
1019 }
1020
1021 void FGAIBallistic::formateToAC(double dt){
1022
1023     setTgtOffsets(dt, 25);
1024     setHitchPos();
1025     setHitchVelocity(dt);
1026
1027     // elapsed time has a random initialisation so that each
1028     // wingman moves differently
1029     _elapsed_time += dt;
1030
1031     // we derive a sine based factor to give us smoothly
1032     // varying error between -1 and 1
1033     double factor  = sin(SGMiscd::deg2rad(_elapsed_time * 10));
1034     double r_angle = 5 * factor;
1035     double p_angle = 2.5 * factor;
1036     double h_angle = 5 * factor;
1037     double h_feet  = 3 * factor;
1038
1039     pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
1040     pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
1041
1042     if (getHtAGL()){
1043
1044         if(_ht_agl_ft <= 10) {
1045             _height = userpos.getElevationFt();
1046         } else if (_ht_agl_ft > 10 && _ht_agl_ft <= 150 ) {
1047             setHt(userpos.getElevationFt(), dt, 1.0);
1048         } else if (_ht_agl_ft > 150 && _ht_agl_ft <= 250) {
1049             setHt(hitchpos.getElevationFt()+ h_feet, dt, 0.75);
1050         } else
1051             setHt(hitchpos.getElevationFt()+ h_feet, dt, 0.5);
1052
1053         pos.setElevationFt(_height);
1054     }
1055
1056     // these calculations are unreliable at slow speeds
1057     if(speed >= 10) {
1058         setHdg(_azimuth + h_angle, dt, 0.9);
1059         setPch(_elevation + p_angle + _pitch_offset, dt, 0.9);
1060
1061         if (roll <= 115 && roll >= -115)
1062             setBnk(manager->get_user_roll() + r_angle + _roll_offset, dt, 0.5);
1063         else
1064             roll = manager->get_user_roll() + r_angle + _roll_offset;
1065
1066     } else {
1067         setHdg(manager->get_user_heading(), dt, 0.9);
1068         setPch(manager->get_user_pitch() + _pitch_offset, dt, 0.9);
1069         setBnk(manager->get_user_roll() + _roll_offset, dt, 0.9);
1070     }
1071
1072     setSpeed(speed);
1073 }
1074 // end AIBallistic