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/point3d.hxx>
  27 #include <simgear/math/sg_random.h>
  28 #include <simgear/math/sg_geodesy.hxx>
  29 #include <simgear/scene/model/modellib.hxx>
  30
  31 #include <Scenery/scenery.hxx>
  32
  33 #include "AIModelData.hxx"
  34 #include "AIBallistic.hxx"
  35
  36 #include <Main/util.hxx>
  37
  38 using namespace simgear;
  39
  40 const double FGAIBallistic::slugs_to_kgs = 14.5939029372;
  41 const double FGAIBallistic::slugs_to_lbs = 32.1740485564;
  42
  43 FGAIBallistic::FGAIBallistic(object_type ot) :
  44 FGAIBase(ot),
  45     _elevation(0),
  46     _aero_stabilised(false),
  47     _drag_area(0.007),
  48     _life_timer(0.0),
  49 _gravity(32.1740485564),
  50     _buoyancy(0),
  51     _random(false),
  52     _ht_agl_ft(0),
  53     _load_resistance(0),
  54     _solid(false),
  55     _report_collision(false),
  56     _report_impact(false),
  57 _wind(true),
  58     _impact_report_node(fgGetNode("/ai/models/model-impact", true)),
  59     _force_stabilised(false),
  60 _external_force(false),
  61 _slave_to_ac(false),
  62 _slave_load_to_ac(false),
  63 _formate_to_ac(false),
  64 _contents_lb(0),
  65 _mass(0),
  66 _height(0),
  67 _old_height(0)
  68
  69 {
  70     no_roll = false;
  71 }
  72
  73 FGAIBallistic::~FGAIBallistic() {
  74 }
  75
  76 void FGAIBallistic::readFromScenario(SGPropertyNode* scFileNode) {
  77     if (!scFileNode){
  78         return;
  79     }
  80
  81     FGAIBase::readFromScenario(scFileNode);
  82
  83     //setPath(scFileNode->getStringValue("model", "Models/Geometry/rocket.ac"));
  84     setAzimuth(scFileNode->getDoubleValue("azimuth", 0.0));
  85     setElevation(scFileNode->getDoubleValue("elevation", 0));
  86     setDragArea(scFileNode->getDoubleValue("eda", 0.007));
  87     setLife(scFileNode->getDoubleValue("life", 900.0));
  88     setBuoyancy(scFileNode->getDoubleValue("buoyancy", 0));
  89     setWind_from_east(scFileNode->getDoubleValue("wind_from_east", 0));
  90     setWind_from_north(scFileNode->getDoubleValue("wind_from_north", 0));
  91     setWind(scFileNode->getBoolValue("wind", false));
  92     setRoll(scFileNode->getDoubleValue("roll", 0.0));
  93     setCd(scFileNode->getDoubleValue("cd", 0.029));
  94     //setMass(scFileNode->getDoubleValue("mass", 0.007));
  95     setWeight(scFileNode->getDoubleValue("weight", 0.25));
  96     setStabilisation(scFileNode->getBoolValue("aero-stabilized", false));
  97     setNoRoll(scFileNode->getBoolValue("no-roll", false));
  98     setRandom(scFileNode->getBoolValue("random", false));
  99     setImpact(scFileNode->getBoolValue("impact", false));
 100     setImpactReportNode(scFileNode->getStringValue("impact-reports"));
 101     setName(scFileNode->getStringValue("name", "Rocket"));
 102     setFuseRange(scFileNode->getDoubleValue("fuse-range", 0.0));
 103     setSMPath(scFileNode->getStringValue("submodel-path", ""));
 104     setSubID(scFileNode->getIntValue("SubID", 0));
 105     setExternalForce(scFileNode->getBoolValue("external-force", false));
 106     setForcePath(scFileNode->getStringValue("force-path", ""));
 107     setForceStabilisation(scFileNode->getBoolValue("force-stabilized", false));
 108     setXoffset(scFileNode->getDoubleValue("x-offset", 0.0));
 109     setYoffset(scFileNode->getDoubleValue("y-offset", 0.0));
 110     setZoffset(scFileNode->getDoubleValue("z-offset", 0.0));
 111     setPitchoffset(scFileNode->getDoubleValue("pitch-offset", 0.0));
 112     setRolloffset(scFileNode->getDoubleValue("roll-offset", 0.0));
 113     setYawoffset(scFileNode->getDoubleValue("yaw-offset", 0.0));
 114     setGroundOffset(scFileNode->getDoubleValue("ground-offset", 0.0));
 115     setLoadOffset(scFileNode->getDoubleValue("load-offset", 0.0));
 116     setSlaved(scFileNode->getBoolValue("slaved", false));
 117     setSlavedLoad(scFileNode->getBoolValue("slaved-load", false));
 118     setContentsNode(scFileNode->getStringValue("contents"));
 119     setRandom(scFileNode->getBoolValue("random", false));
 120 }
 121
 122 osg::Node* FGAIBallistic::load3DModel(const string &path, SGPropertyNode *prop_root)
 123 {
 124   model = SGModelLib::loadModel(path, prop_root, new FGAIModelData(this, prop_root));
 125   return model.get();
 126 }
 127
 128 bool FGAIBallistic::init(bool search_in_AI_path) {
 129     FGAIBase::init(search_in_AI_path);
 130
 131     _impact_reported = false;
 132     _collision_reported = false;
 133     invisible = false;
 134
 135     _elapsed_time += (sg_random() * 100);
 136
 137     props->setStringValue("material/name", "");
 138     props->setStringValue("name", _name.c_str());
 139     props->setStringValue("submodels/path", _submodel.c_str());
 140
 141     // start with high value so that animations don't trigger yet
 142     _ht_agl_ft = 1e10;
 143     hdg = _azimuth;
 144     pitch = _elevation;
 145     roll = _rotation;
 146
 147     Transform();
 148
 149     return true;
 150 }
 151
 152 void FGAIBallistic::bind() {
 153     //    FGAIBase::bind();
 154
 155     props->tie("sim/time/elapsed-sec",
 156         SGRawValueMethods<FGAIBallistic,double>(*this,
 157         &FGAIBallistic::_getTime));
 158     props->tie("mass-slug",
 159         SGRawValueMethods<FGAIBallistic,double>(*this,
 160         &FGAIBallistic::getMass));
 161     props->tie("material/load-resistance",
 162                 SGRawValuePointer<double>(&_load_resistance));
 163     props->tie("material/solid",
 164                 SGRawValuePointer<bool>(&_solid));
 165     props->tie("altitude-agl-ft",
 166                 SGRawValuePointer<double>(&_ht_agl_ft));
 167     props->tie("controls/slave-to-ac",
 168         SGRawValueMethods<FGAIBallistic,bool>
 169         (*this, &FGAIBallistic::getSlaved, &FGAIBallistic::setSlaved));
 170     props->tie("controls/invisible",
 171         SGRawValuePointer<bool>(&invisible));
 172
 173     if(_external_force){
 174         props->tie("controls/force_stabilized",
 175             SGRawValuePointer<bool>(&_force_stabilised));
 176         props->tie("position/global-x",
 177             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosX, 0));
 178         props->tie("position/global-y",
 179             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosY, 0));
 180         props->tie("position/global-z",
 181             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosZ, 0));
 182         props->tie("velocities/vertical-speed-fps",
 183             SGRawValuePointer<double>(&vs));
 184         props->tie("velocities/true-airspeed-kt",
 185             SGRawValuePointer<double>(&speed));
 186         props->tie("velocities/horizontal-speed-fps",
 187             SGRawValuePointer<double>(&hs));
 188         props->tie("position/altitude-ft",
 189             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getAltitude, &FGAIBase::_setAltitude));
 190         props->tie("position/latitude-deg",
 191             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLatitude, &FGAIBase::_setLatitude));
 192         props->tie("position/longitude-deg",
 193             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLongitude, &FGAIBase::_setLongitude));
 194         props->tie("orientation/hdg-deg",
 195             SGRawValuePointer<double>(&hdg));
 196         props->tie("orientation/pitch-deg",
 197             SGRawValuePointer<double>(&pitch));
 198         props->tie("orientation/roll-deg",
 199             SGRawValuePointer<double>(&roll));
 200         props->tie("controls/slave-load-to-ac",
 201             SGRawValueMethods<FGAIBallistic,bool>
 202             (*this, &FGAIBallistic::getSlavedLoad, &FGAIBallistic::setSlavedLoad));
 203         props->tie("position/load-offset",
 204             SGRawValueMethods<FGAIBallistic,double>
 205             (*this, &FGAIBallistic::getLoadOffset, &FGAIBallistic::setLoadOffset));
 206         props->tie("load/distance-to-hitch-ft",
 207             SGRawValueMethods<FGAIBallistic,double>
 208             (*this, &FGAIBallistic::getDistanceLoadToHitch));
 209         props->tie("load/elevation-to-hitch-deg",
 210             SGRawValueMethods<FGAIBallistic,double>
 211             (*this, &FGAIBallistic::getElevLoadToHitch));
 212         props->tie("load/bearing-to-hitch-deg",
 213             SGRawValueMethods<FGAIBallistic,double>
 214             (*this, &FGAIBallistic::getBearingLoadToHitch));
 215     }
 216
 217 }
 218
 219 void FGAIBallistic::unbind() {
 220     //    FGAIBase::unbind();
 221
 222     props->untie("sim/time/elapsed-sec");
 223     props->untie("mass-slug");
 224     props->untie("material/load-resistance");
 225     props->untie("material/solid");
 226     props->untie("altitude-agl-ft");
 227     props->untie("controls/slave-to-ac");
 228     props->untie("controls/invisible");
 229
 230     if(_external_force){
 231         props->untie("position/global-y");
 232         props->untie("position/global-x");
 233         props->untie("position/global-z");
 234         props->untie("velocities/vertical-speed-fps");
 235         props->untie("velocities/true-airspeed-kt");
 236         props->untie("velocities/horizontal-speed-fps");
 237         props->untie("position/altitude-ft");
 238         props->untie("position/latitude-deg");
 239         props->untie("position/longitude-deg");
 240         props->untie("position/ht-agl-ft");
 241         props->untie("orientation/hdg-deg");
 242         props->untie("orientation/pitch-deg");
 243         props->untie("orientation/roll-deg");
 244         props->untie("controls/force_stabilized");
 245         props->untie("position/load-offset");
 246         props->untie("load/distance-to-hitch-ft");
 247         props->untie("load/elevation-to-hitch-deg");
 248         props->untie("load/bearing-to-hitch-deg");
 249     }
 250 }
 251
 252 void FGAIBallistic::update(double dt) {
 253     FGAIBase::update(dt);
 254     _setUserPos();
 255
 256     if (_slave_to_ac){
 257         slaveToAC(dt);
 258         Transform();
 259         setHitchVelocity(dt);
 260     } else if (_formate_to_ac){
 261         formateToAC(dt);
 262         Transform();
 263         setHitchVelocity(dt);
 264     } else if (!invisible){
 265     Run(dt);
 266     Transform();
 267 }
 268
 269 }
 270
 271 void FGAIBallistic::setAzimuth(double az) {
 272     hdg = _azimuth = az;
 273 }
 274
 275 void FGAIBallistic::setElevation(double el) {
 276     pitch = _elevation = el;
 277 }
 278
 279 void FGAIBallistic::setRoll(double rl) {
 280     roll = _rotation = rl;
 281 }
 282
 283 void FGAIBallistic::setStabilisation(bool val) {
 284     _aero_stabilised = val;
 285 }
 286
 287 void FGAIBallistic::setForceStabilisation(bool val) {
 288     _force_stabilised = val;
 289 }
 290
 291 void FGAIBallistic::setNoRoll(bool nr) {
 292     no_roll = nr;
 293 }
 294
 295 void FGAIBallistic::setDragArea(double a) {
 296     _drag_area = a;
 297 }
 298
 299 void FGAIBallistic::setLife(double seconds) {
 300     life = seconds;
 301 }
 302
 303 void FGAIBallistic::setBuoyancy(double fpss) {
 304     _buoyancy = fpss;
 305 }
 306
 307 void FGAIBallistic::setWind_from_east(double fps) {
 308     _wind_from_east = fps;
 309 }
 310
 311 void FGAIBallistic::setWind_from_north(double fps) {
 312     _wind_from_north = fps;
 313 }
 314
 315 void FGAIBallistic::setWind(bool val) {
 316     _wind = val;
 317 }
 318
 319 void FGAIBallistic::setCd(double c) {
 320     _Cd = c;
 321 }
 322
 323 void FGAIBallistic::setMass(double m) {
 324     _mass = m;
 325 }
 326
 327 void FGAIBallistic::setWeight(double w) {
 328     _weight_lb = w;
 329 }
 330 void FGAIBallistic::setRandom(bool r) {
 331     _random = r;
 332 }
 333
 334 void FGAIBallistic::setImpact(bool i) {
 335     _report_impact = i;
 336 }
 337
 338 void FGAIBallistic::setCollision(bool c) {
 339     _report_collision = c;
 340 }
 341
 342 void FGAIBallistic::setExternalForce(bool f) {
 343     _external_force = f;
 344 }
 345
 346 void FGAIBallistic::setImpactReportNode(const string& path) {
 347
 348     if (!path.empty())
 349         _impact_report_node = fgGetNode(path.c_str(), true);
 350 }
 351
 352 void FGAIBallistic::setName(const string& n) {
 353     _name = n;
 354 }
 355
 356 void FGAIBallistic::setSMPath(const string& s) {
 357     _submodel = s;
 358 }
 359
 360 void FGAIBallistic::setFuseRange(double f) {
 361     _fuse_range = f;
 362 }
 363
 364 void FGAIBallistic::setSubID(int i) {
 365     _subID = i;
 366 }
 367
 368 void FGAIBallistic::setSubmodel(const string& s) {
 369     _submodel = s;
 370 }
 371
 372 void FGAIBallistic::setGroundOffset(double g) {
 373     _ground_offset = g;
 374 }
 375
 376 void FGAIBallistic::setLoadOffset(double l) {
 377     _load_offset = l;
 378 }
 379
 380 double FGAIBallistic::getLoadOffset() const {
 381     return _load_offset;
 382 }
 383
 384 void FGAIBallistic::setSlaved(bool s) {
 385     _slave_to_ac = s;
 386 }
 387
 388 void FGAIBallistic::setFormate(bool f) {
 389     _formate_to_ac = f;
 390 }
 391
 392 void FGAIBallistic::setContentsNode(const string& path) {
 393     if (!path.empty()) {
 394         _contents_node = fgGetNode(path.c_str(), true);
 395     }
 396 }
 397
 398 bool FGAIBallistic::getSlaved() const {
 399     return _slave_to_ac;
 400 }
 401
 402 double FGAIBallistic::getMass() const {
 403     return _mass;
 404 }
 405
 406 double FGAIBallistic::getContents() {
 407     if(_contents_node)
 408         _contents_lb = _contents_node->getChild("level-lbs",0,1)->getDoubleValue();
 409     return _contents_lb;
 410 }
 411
 412 void FGAIBallistic::setContents(double c) {
 413     if(_contents_node)
 414         _contents_lb = _contents_node->getChild("level-gal_us",0,1)->setDoubleValue(c);
 415 }
 416
 417 void FGAIBallistic::setSlavedLoad(bool l) {
 418     _slave_load_to_ac = l;
 419 }
 420
 421 bool FGAIBallistic::getSlavedLoad() const {
 422     return _slave_load_to_ac;
 423 }
 424
 425 void FGAIBallistic::setForcePath(const string& p) {
 426     _force_path = p;
 427     if (!_force_path.empty()) {
 428         SGPropertyNode *fnode = fgGetNode(_force_path.c_str(), 0, true );
 429         _force_node = fnode->getChild("force-lb", 0, true);
 430         _force_azimuth_node = fnode->getChild("force-azimuth-deg", 0, true);
 431         _force_elevation_node = fnode->getChild("force-elevation-deg", 0, true);
 432     }
 433 }
 434
 435 bool FGAIBallistic::getHtAGL(){
 436
 437     if (globals->get_scenery()->get_elevation_m(pos.getLatitudeDeg(), pos.getLongitudeDeg(),
 438         10000.0, _elevation_m, &_material)){
 439             _ht_agl_ft = pos.getElevationFt() - _elevation_m * SG_METER_TO_FEET;
 440             if (_material) {
 441                 const vector<string>& names = _material->get_names();
 442
 443                 _solid = _material->get_solid();
 444                 _load_resistance = _material->get_load_resistance();
 445                 _frictionFactor =_material->get_friction_factor();
 446                 if (!names.empty())
 447                     props->setStringValue("material/name", names[0].c_str());
 448                 else
 449                     props->setStringValue("material/name", "");
 450                 /*cout << "material " << mat_name
 451                 << " solid " << _solid
 452                 << " load " << _load_resistance
 453                 << " frictionFactor " << frictionFactor
 454                 << endl;*/
 455             }
 456             return true;
 457     } else {
 458         return false;
 459     }
 460
 461 }
 462
 463 double FGAIBallistic::getRecip(double az){
 464     // calculate the reciprocal of the input azimuth
 465     if(az - 180 < 0){
 466         return az + 180;
 467     } else {
 468         return az - 180;
 469     }
 470 }
 471
 472 void FGAIBallistic::setPch(double e, double dt, double coeff){
 473     double c = dt / (coeff + dt);
 474     pitch = (e * c) + (pitch * (1 - c));
 475 }
 476
 477 void FGAIBallistic::setBnk(double r, double dt, double coeff){
 478     double c = dt / (coeff + dt);
 479     roll = (r * c) + (roll * (1 - c));
 480 }
 481
 482 void FGAIBallistic::setHt(double h, double dt, double coeff){
 483     double c = dt / (coeff + dt);
 484     _height = (h * c) + (_height * (1 - c));
 485 }
 486
 487 void FGAIBallistic::setHdg(double az, double dt, double coeff){
 488     double recip = getRecip(hdg);
 489     double c = dt / (coeff + dt);
 490     //we need to ensure that we turn the short way to the new hdg
 491     if (az < recip && az < hdg && hdg > 180) {
 492         hdg = ((az + 360) * c) + (hdg * (1 - c));
 493     } else if (az > recip && az > hdg && hdg <= 180){
 494         hdg = ((az - 360) * c) + (hdg * (1 - c));
 495     } else {
 496         hdg = (az * c) + (hdg * (1 - c));
 497     }
 498     }
 499
 500 double  FGAIBallistic::getTgtXOffset() const {
 501     return _tgt_x_offset;
 502 }
 503
 504 double  FGAIBallistic::getTgtYOffset() const {
 505     return _tgt_y_offset;
 506 }
 507
 508 double  FGAIBallistic::getTgtZOffset() const {
 509     return _tgt_z_offset;
 510 }
 511
 512 void FGAIBallistic::setTgtXOffset(double x){
 513     _tgt_x_offset = x;
 514 }
 515
 516 void FGAIBallistic::setTgtYOffset(double y){
 517     _tgt_y_offset = y;
 518 }
 519
 520 void FGAIBallistic::setTgtZOffset(double z){
 521     _tgt_z_offset = z;
 522 }
 523
 524 void FGAIBallistic::slaveToAC(double dt){
 525
 526     setHitchPos();
 527     pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
 528     pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
 529     pos.setElevationFt(hitchpos.getElevationFt());
 530     setHeading(manager->get_user_heading());
 531     setPitch(manager->get_user_pitch() + _pitch_offset);
 532     setBank(manager->get_user_roll() + _roll_offset);
 533     setSpeed(manager->get_user_speed());
 534     //update the mass (slugs)
 535     _mass = (_weight_lb + getContents()) / slugs_to_lbs;
 536
 537     /*cout <<"_mass "<<_mass <<" " << getContents()
 538     <<" " << getContents() / slugs_to_lbs << endl;*/
 539 }
 540
 541 void FGAIBallistic::Run(double dt) {
 542     _life_timer += dt;
 543
 544     // if life = -1 the object does not die
 545     if (_life_timer > life && life != -1)
 546         setDie(true);
 547
 548     //set the contents in the appropriate tank or other property in the parent to zero
 549     setContents(0);
 550
 551     //randomise Cd by +- 5%
 552     if (_random)
 553         _Cd = _Cd * 0.95 + (0.05 * sg_random());
 554
 555     // Adjust Cd by Mach number. The equations are based on curves
 556     // for a conventional shell/bullet (no boat-tail).
 557     double Cdm;
 558
 559     if (Mach < 0.7)
 560         Cdm = 0.0125 * Mach + _Cd;
 561     else if (Mach < 1.2 )
 562         Cdm = 0.3742 * pow(Mach, 2) - 0.252 * Mach + 0.0021 + _Cd;
 563     else
 564         Cdm = 0.2965 * pow(Mach, -1.1506) + _Cd;
 565
 566     //cout << "Mach " << Mach << " Cdm " << Cdm << "// ballistic speed kts "<< speed <<  endl;
 567
 568     // drag = Cd * 0.5 * rho * speed * speed * drag_area;
 569     // rho is adjusted for altitude in void FGAIBase::update,
 570     // using Standard Atmosphere (sealevel temperature 15C)
 571     // acceleration = drag/mass;
 572     // adjust speed by drag
 573     speed -= (Cdm * 0.5 * rho * speed * speed * _drag_area/_mass) * dt;
 574
 575     // don't let speed become negative
 576     if ( speed < 0.0 )
 577         speed = 0.0;
 578
 579     double speed_fps = speed * SG_KT_TO_FPS;
 580     //double hs;
 581
 582     // calculate vertical and horizontal speed components
 583     if (speed == 0.0) {
 584         hs = vs = 0.0;
 585     } else {
 586         vs = sin( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
 587         hs = cos( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
 588     }
 589
 590     //resolve horizontal speed into north and east components:
 591     double speed_north_fps = cos(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
 592     double speed_east_fps = sin(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
 593
 594     // convert horizontal speed (fps) to degrees per second
 595     double speed_north_deg_sec = speed_north_fps / ft_per_deg_lat;
 596     double speed_east_deg_sec  = speed_east_fps / ft_per_deg_lon;
 597
 598     // if wind not required, set to zero
 599     if (!_wind) {
 600         _wind_from_north = 0;
 601         _wind_from_east = 0;
 602     } else {
 603         _wind_from_north = manager->get_wind_from_north();
 604         _wind_from_east = manager->get_wind_from_east();
 605     }
 606
 607     //calculate velocity due to external force
 608     double force_speed_north_deg_sec = 0;
 609     double force_speed_east_deg_sec = 0;
 610     double vs_force_fps = 0;
 611     double hs_force_fps = 0;
 612     double v_force_acc_fpss = 0;
 613     double force_speed_north_fps = 0;
 614     double force_speed_east_fps = 0;
 615     double h_force_lbs = 0;
 616     double normal_force_lbs = 0;
 617     double normal_force_fpss = 0;
 618     double static_friction_force_lbs = 0;
 619     double dynamic_friction_force_lbs = 0;
 620     double friction_force_speed_north_fps = 0;
 621     double friction_force_speed_east_fps = 0;
 622     double friction_force_speed_north_deg_sec = 0;
 623     double friction_force_speed_east_deg_sec = 0;
 624     double force_elevation_deg = 0;
 625
 626     if (_external_force) {
 627         SGPropertyNode *n = fgGetNode(_force_path.c_str(), true);
 628         double force_lbs            = n->getChild("force-lb", 0, true)->getDoubleValue();
 629         force_elevation_deg         = n->getChild("force-elevation-deg", 0, true)->getDoubleValue();
 630         double force_azimuth_deg    = n->getChild("force-azimuth-deg", 0, true)->getDoubleValue();
 631
 632         //resolve force into vertical and horizontal components:
 633         double v_force_lbs = force_lbs * sin( force_elevation_deg * SG_DEGREES_TO_RADIANS );
 634         h_force_lbs = force_lbs * cos( force_elevation_deg * SG_DEGREES_TO_RADIANS );
 635
 636         //ground interaction
 637
 638         if (getHtAGL()){
 639             double deadzone = 0.1;
 640
 641             if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
 642                 normal_force_lbs = (_mass * slugs_to_lbs) - v_force_lbs;
 643
 644                 if ( normal_force_lbs < 0 )
 645                     normal_force_lbs = 0;
 646
 647                 pos.setElevationFt(0 + _ground_offset);
 648                 if (vs < 0)
 649                     vs = -vs * 0.5;
 650
 651                 // calculate friction
 652                 // we assume a static Coefficient of Friction (mu) of 0.62 (wood on concrete)
 653                 double mu = 0.62;
 654
 655                 static_friction_force_lbs = mu * normal_force_lbs * _frictionFactor;
 656
 657                 //adjust horizontal force. We assume that a speed of <= 5 fps is static
 658                 if (h_force_lbs <= static_friction_force_lbs && hs <= 5){
 659                     h_force_lbs = hs = 0;
 660                     speed_north_fps = speed_east_fps = 0;
 661                 } else
 662                     dynamic_friction_force_lbs = (static_friction_force_lbs * 0.95);
 663
 664                 //ignore wind when on the ground for now
 665                 //TODO fix this
 666                 _wind_from_north = 0;
 667                 _wind_from_east = 0;
 668
 669             }
 670
 671         }
 672
 673         //acceleration = (force(lbsf)/mass(slugs))
 674         v_force_acc_fpss = v_force_lbs/_mass;
 675         normal_force_fpss = normal_force_lbs/_mass;
 676         double h_force_acc_fpss = h_force_lbs/_mass;
 677         double dynamic_friction_acc_fpss = dynamic_friction_force_lbs/_mass;
 678
 679         // velocity = acceleration * dt
 680         hs_force_fps = h_force_acc_fpss * dt;
 681         double friction_force_fps = dynamic_friction_acc_fpss * dt;
 682
 683         //resolve horizontal speeds into north and east components:
 684         force_speed_north_fps   = cos(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
 685         force_speed_east_fps    = sin(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
 686
 687         friction_force_speed_north_fps = cos(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
 688         friction_force_speed_east_fps  = sin(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
 689
 690         // convert horizontal speed (fps) to degrees per second
 691         force_speed_north_deg_sec = force_speed_north_fps / ft_per_deg_lat;
 692         force_speed_east_deg_sec  = force_speed_east_fps / ft_per_deg_lon;
 693
 694         friction_force_speed_north_deg_sec = friction_force_speed_north_fps / ft_per_deg_lat;
 695         friction_force_speed_east_deg_sec  = friction_force_speed_east_fps / ft_per_deg_lon;
 696     }
 697
 698     // convert wind speed (fps) to degrees lat/lon per second
 699     double wind_speed_from_north_deg_sec = _wind_from_north / ft_per_deg_lat;
 700     double wind_speed_from_east_deg_sec  = _wind_from_east / ft_per_deg_lon;
 701
 702     //recombine the horizontal velocity components
 703     hs = sqrt(((speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps)
 704         * (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
 705         + ((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)
 706         * (speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)));
 707
 708     if (hs <= 0.00001)
 709         hs = 0;
 710
 711     // adjust vertical speed for acceleration of gravity, buoyancy, and vertical force
 712     vs -= (_gravity - _buoyancy - v_force_acc_fpss - normal_force_fpss) * dt;
 713
 714     if (vs <= 0.00001 && vs >= -0.00001)
 715         vs = 0;
 716
 717     // set new position
 718     if(_slave_load_to_ac) {
 719         setHitchPos();
 720         pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
 721         pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
 722         pos.setElevationFt(hitchpos.getElevationFt());
 723
 724         if (getHtAGL()){
 725             double deadzone = 0.1;
 726
 727             if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
 728                 pos.setElevationFt(0 + _ground_offset);
 729             } else {
 730                 pos.setElevationFt(hitchpos.getElevationFt() + _load_offset);
 731             }
 732
 733         }
 734     } else {
 735         pos.setLatitudeDeg( pos.getLatitudeDeg()
 736             + (speed_north_deg_sec - wind_speed_from_north_deg_sec
 737             + force_speed_north_deg_sec + friction_force_speed_north_deg_sec) * dt );
 738         pos.setLongitudeDeg( pos.getLongitudeDeg()
 739             + (speed_east_deg_sec - wind_speed_from_east_deg_sec
 740             + force_speed_east_deg_sec + friction_force_speed_east_deg_sec) * dt );
 741         pos.setElevationFt(pos.getElevationFt() + vs * dt);
 742     }
 743
 744     // recalculate total speed
 745     if ( vs == 0 && hs == 0)
 746         speed = 0;
 747     else
 748         speed = sqrt( vs * vs + hs * hs) / SG_KT_TO_FPS;
 749
 750     // recalculate elevation and azimuth (velocity vectors)
 751     _elevation = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
 752     _azimuth =  atan2((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps),
 753         (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
 754         * SG_RADIANS_TO_DEGREES;
 755
 756     // rationalise azimuth
 757     if (_azimuth < 0)
 758         _azimuth += 360;
 759
 760     if (_aero_stabilised) { // we simulate rotational moment of inertia by using a filter
 761         const double coeff = 0.9;
 762
 763         // we assume a symetrical MI about the pitch and yaw axis
 764         setPch(_elevation, dt, coeff);
 765         setHdg(_azimuth, dt, coeff);
 766     } else if (_force_stabilised) { // we simulate rotational moment of inertia by using a filter
 767         const double coeff = 0.9;
 768         double ratio = h_force_lbs/(_mass * slugs_to_lbs);
 769
 770         if (ratio >  1) ratio =  1;
 771         if (ratio < -1) ratio = -1;
 772
 773         double force_pitch = acos(ratio) * SG_RADIANS_TO_DEGREES;
 774
 775         if (force_pitch <= force_elevation_deg)
 776             force_pitch = force_elevation_deg;
 777
 778         // we assume a symetrical MI about the pitch and yaw axis
 779         setPch(force_pitch,dt, coeff);
 780         setHdg(_azimuth, dt, coeff);
 781     }
 782
 783     //do impacts and collisions
 784     if (_report_impact && !_impact_reported)
 785         handle_impact();
 786
 787     if (_report_collision && !_collision_reported)
 788         handle_collision();
 789
 790     // set destruction flag if altitude less than sea level -1000
 791     if (altitude_ft < -1000.0 && life != -1)
 792         setDie(true);
 793
 794 }  // end Run
 795
 796 double FGAIBallistic::_getTime() const {
 797     return _life_timer;
 798 }
 799
 800 void FGAIBallistic::handle_impact() {
 801
 802     // try terrain intersection
 803     if(!getHtAGL())
 804         return;
 805
 806     if (_ht_agl_ft <= 0) {
 807         SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: terrain impact");
 808         report_impact(_elevation_m);
 809         _impact_reported = true;
 810
 811         if (life == -1){
 812             invisible = true;
 813         } else if (_subID == 0)  // kill the AIObject if there is no subsubmodel
 814             setDie(true);
 815     }
 816 }
 817
 818 void FGAIBallistic::handle_collision()
 819 {
 820     const FGAIBase *object = manager->calcCollision(pos.getElevationFt(),
 821             pos.getLatitudeDeg(),pos.getLongitudeDeg(), _fuse_range);
 822
 823     if (object) {
 824         SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: object hit");
 825         report_impact(pos.getElevationM(), object);
 826         _collision_reported = true;
 827     }
 828 }
 829
 830 void FGAIBallistic::report_impact(double elevation, const FGAIBase *object)
 831 {
 832     _impact_lat    = pos.getLatitudeDeg();
 833     _impact_lon    = pos.getLongitudeDeg();
 834     _impact_elev   = elevation;
 835     _impact_speed  = speed * SG_KT_TO_MPS;
 836     _impact_hdg    = hdg;
 837     _impact_pitch  = pitch;
 838     _impact_roll   = roll;
 839
 840     SGPropertyNode *n = props->getNode("impact", true);
 841     if (object)
 842         n->setStringValue("type", object->getTypeString());
 843     else
 844         n->setStringValue("type", "terrain");
 845
 846     n->setDoubleValue("longitude-deg", _impact_lon);
 847     n->setDoubleValue("latitude-deg", _impact_lat);
 848     n->setDoubleValue("elevation-m", _impact_elev);
 849     n->setDoubleValue("heading-deg", _impact_hdg);
 850     n->setDoubleValue("pitch-deg", _impact_pitch);
 851     n->setDoubleValue("roll-deg", _impact_roll);
 852     n->setDoubleValue("speed-mps", _impact_speed);
 853
 854     _impact_report_node->setStringValue(props->getPath());
 855 }
 856
 857 SGVec3d FGAIBallistic::getCartUserPos() const {
 858     SGVec3d cartUserPos = SGVec3d::fromGeod(userpos);
 859     return cartUserPos;
 860 }
 861
 862 SGVec3d FGAIBallistic::getCartHitchPos() const{
 863
 864     // convert geodetic positions to geocentered
 865     SGVec3d cartuserPos = getCartUserPos();
 866     SGVec3d cartPos = getCartPos();
 867
 868     // Transform to the right coordinate frame, configuration is done in
 869     // the x-forward, y-right, z-up coordinates (feet), computation
 870     // in the simulation usual body x-forward, y-right, z-down coordinates
 871     // (meters) )
 872     SGVec3d _off(_x_offset * SG_FEET_TO_METER,
 873         _y_offset * SG_FEET_TO_METER,
 874         -_z_offset * SG_FEET_TO_METER);
 875
 876     // Transform the user position to the horizontal local coordinate system.
 877     SGQuatd hlTrans = SGQuatd::fromLonLat(userpos);
 878
 879     // and postrotate the orientation of the user model wrt the horizontal
 880     // local frame
 881     hlTrans *= SGQuatd::fromYawPitchRollDeg(
 882         manager->get_user_heading(),
 883         manager->get_user_pitch(),
 884         manager->get_user_roll());
 885
 886     // The offset converted to the usual body fixed coordinate system
 887     // rotated to the earth-fixed coordinates axis
 888     SGVec3d off = hlTrans.backTransform(_off);
 889
 890     // Add the position offset of the user model to get the geocentered position
 891     SGVec3d offsetPos = cartuserPos + off;
 892
 893     return offsetPos;
 894 }
 895
 896 void FGAIBallistic::setHitchPos(){
 897     // convert the hitch geocentered position to geodetic
 898     SGVec3d carthitchPos = getCartHitchPos();
 899
 900     SGGeodesy::SGCartToGeod(carthitchPos, hitchpos);
 901 }
 902
 903 double FGAIBallistic::getDistanceLoadToHitch() const {
 904     //calculate the distance load to hitch
 905     SGVec3d carthitchPos = getCartHitchPos();
 906     SGVec3d cartPos = getCartPos();
 907
 908     SGVec3d diff = carthitchPos - cartPos;
 909     double distance = norm(diff);
 910     return distance * SG_METER_TO_FEET;
 911 }
 912
 913 void FGAIBallistic::setHitchVelocity(double dt) {
 914     //calculate the distance from the previous hitch position
 915     SGVec3d carthitchPos = getCartHitchPos();
 916     SGVec3d diff = carthitchPos - _oldcarthitchPos;
 917
 918     double distance = norm(diff);
 919
 920     //calculate speed knots
 921     speed = (distance/dt) * SG_MPS_TO_KT;
 922
 923     //now calulate the angle between the old and current hitch positions (degrees)
 924     double angle = 0;
 925     double daltM = hitchpos.getElevationM() - oldhitchpos.getElevationM();
 926
 927     if (fabs(distance) < SGLimits<float>::min()) {
 928         angle = 0;
 929     } else {
 930         double sAngle = daltM/distance;
 931         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
 932         angle = SGMiscd::rad2deg(asin(sAngle));
 933     }
 934
 935     _elevation = angle;
 936
 937     //calculate the bearing of the new hitch position from the old
 938     double az1, az2, dist;
 939
 940     geo_inverse_wgs_84(oldhitchpos, hitchpos, &az1, &az2, &dist);
 941
 942     _azimuth = az1;
 943
 944     // and finally store the new values
 945     _oldcarthitchPos = carthitchPos;
 946     oldhitchpos = hitchpos;
 947 }
 948
 949 double FGAIBallistic::getElevLoadToHitch() const {
 950     // now the angle, positive angles are upwards
 951     double distance = getDistanceLoadToHitch() * SG_FEET_TO_METER;
 952     double angle = 0;
 953     double daltM = hitchpos.getElevationM() - pos.getElevationM();
 954
 955     if (fabs(distance) < SGLimits<float>::min()) {
 956         angle = 0;
 957     } else {
 958         double sAngle = daltM/distance;
 959         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
 960         angle = SGMiscd::rad2deg(asin(sAngle));
 961     }
 962
 963     return angle;
 964 }
 965
 966 double FGAIBallistic::getBearingLoadToHitch() const {
 967     //calculate the bearing and range of the second pos from the first
 968     double az1, az2, distance;
 969
 970     geo_inverse_wgs_84(pos, hitchpos, &az1, &az2, &distance);
 971
 972     return az1;
 973 }
 974
 975 double FGAIBallistic::getRelBrgHitchToUser() const {
 976     //calculate the relative bearing
 977     double az1, az2, distance;
 978
 979     geo_inverse_wgs_84(hitchpos, userpos, &az1, &az2, &distance);
 980
 981     double rel_brg = az1 - hdg;
 982
 983     if (rel_brg > 180)
 984         rel_brg -= 360;
 985
 986     return rel_brg;
 987 }
 988
 989 double FGAIBallistic::getElevHitchToUser() const {
 990
 991     //calculate the distance from the user position
 992     SGVec3d carthitchPos = getCartHitchPos();
 993     SGVec3d cartuserPos = getCartUserPos();
 994
 995     SGVec3d diff = cartuserPos - carthitchPos;
 996
 997     double distance = norm(diff);
 998     double angle = 0;
 999
1000     double daltM = userpos.getElevationM() - hitchpos.getElevationM();
1001
1002     // now the angle, positive angles are upwards
1003     if (fabs(distance) < SGLimits<float>::min()) {
1004         angle = 0;
1005     } else {
1006         double sAngle = daltM/distance;
1007         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
1008         angle = SGMiscd::rad2deg(asin(sAngle));
1009     }
1010
1011     return angle;
1012 }
1013
1014 void FGAIBallistic::setTgtOffsets(double dt, double coeff){
1015     double c = dt / (coeff + dt);
1016
1017     _x_offset = (_tgt_x_offset * c) + (_x_offset * (1 - c));
1018     _y_offset = (_tgt_y_offset * c) + (_y_offset * (1 - c));
1019     _z_offset = (_tgt_z_offset * c) + (_z_offset * (1 - c));
1020 }
1021
1022 void FGAIBallistic::formateToAC(double dt){
1023
1024     setTgtOffsets(dt, 25);
1025     setHitchPos();
1026     setHitchVelocity(dt);
1027
1028     // elapsed time has a random initialisation so that each
1029     // wingman moves differently
1030     _elapsed_time += dt;
1031
1032     // we derive a sine based factor to give us smoothly
1033     // varying error between -1 and 1
1034     double factor  = sin(SGMiscd::deg2rad(_elapsed_time * 10));
1035     double r_angle = 5 * factor;
1036     double p_angle = 2.5 * factor;
1037     double h_angle = 5 * factor;
1038     double h_feet  = 3 * factor;
1039
1040     pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
1041     pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
1042
1043     if (getHtAGL()){
1044
1045         if(_ht_agl_ft <= 10) {
1046             _height = userpos.getElevationFt();
1047         } else if (_ht_agl_ft > 10 && _ht_agl_ft <= 150 ) {
1048             setHt(userpos.getElevationFt(), dt, 1.0);
1049         } else if (_ht_agl_ft > 150 && _ht_agl_ft <= 250) {
1050             setHt(hitchpos.getElevationFt()+ h_feet, dt, 0.75);
1051         } else
1052             setHt(hitchpos.getElevationFt()+ h_feet, dt, 0.5);
1053
1054         pos.setElevationFt(_height);
1055     }
1056
1057     // these calculations are unreliable at slow speeds
1058     if(speed >= 10) {
1059         setHdg(_azimuth + h_angle, dt, 0.9);
1060         setPch(_elevation + p_angle + _pitch_offset, dt, 0.9);
1061
1062         if (roll <= 115 && roll >= -115)
1063             setBnk(manager->get_user_roll() + r_angle + _roll_offset, dt, 0.5);
1064         else
1065             roll = manager->get_user_roll() + r_angle + _roll_offset;
1066
1067     } else {
1068         setHdg(manager->get_user_heading(), dt, 0.9);
1069         setPch(manager->get_user_pitch() + _pitch_offset, dt, 0.9);
1070         setBnk(manager->get_user_roll() + _roll_offset, dt, 0.9);
1071     }
1072
1073     setSpeed(speed);
1074 }
1075 // end AIBallistic