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 "AIBallistic.hxx"
  33
  34 #include <Main/util.hxx>
  35
  36 using namespace simgear;
  37
  38 const double FGAIBallistic::slugs_to_kgs = 14.5939029372;
  39 const double FGAIBallistic::slugs_to_lbs = 32.1740485564;
  40
  41 FGAIBallistic::FGAIBallistic(object_type ot) :
  42     FGAIBase(ot),
  43     _height(0.0),
  44     _ht_agl_ft(0.0),
  45     _azimuth(0.0),
  46     _elevation(0.0),
  47     _rotation(0.0),
  48     _formate_to_ac(false),
  49     _aero_stabilised(false),
  50     _drag_area(0.007),
  51     _life_timer(0.0),
  52     _gravity(32.1740485564),
  53     _buoyancy(0),
  54     _wind(true),
  55     _mass(0),
  56     _random(false),
  57     _load_resistance(0),
  58     _solid(false),
  59     _force_stabilised(false),
  60     _slave_to_ac(false),
  61     _slave_load_to_ac(false),
  62     _contents_lb(0),
  63     _report_collision(false),
  64     _report_impact(false),
  65     _external_force(false),
  66     _impact_report_node(fgGetNode("/ai/models/model-impact", true)),
  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 bool FGAIBallistic::init(bool search_in_AI_path) {
 123     FGAIBase::init(search_in_AI_path);
 124
 125     _impact_reported = false;
 126     _collision_reported = false;
 127     invisible = false;
 128
 129     _elapsed_time += (sg_random() * 100);
 130
 131     props->setStringValue("material/name", "");
 132     props->setStringValue("name", _name.c_str());
 133     props->setStringValue("submodels/path", _submodel.c_str());
 134
 135     // start with high value so that animations don't trigger yet
 136     _ht_agl_ft = 1e10;
 137     hdg = _azimuth;
 138     pitch = _elevation;
 139     roll = _rotation;
 140
 141     Transform();
 142
 143     return true;
 144 }
 145
 146 void FGAIBallistic::bind() {
 147     //    FGAIBase::bind();
 148
 149     props->tie("sim/time/elapsed-sec",
 150         SGRawValueMethods<FGAIBallistic,double>(*this,
 151         &FGAIBallistic::_getTime));
 152     props->tie("mass-slug",
 153         SGRawValueMethods<FGAIBallistic,double>(*this,
 154         &FGAIBallistic::getMass));
 155     props->tie("material/load-resistance",
 156                 SGRawValuePointer<double>(&_load_resistance));
 157     props->tie("material/solid",
 158                 SGRawValuePointer<bool>(&_solid));
 159     props->tie("altitude-agl-ft",
 160                 SGRawValuePointer<double>(&_ht_agl_ft));
 161     props->tie("controls/slave-to-ac",
 162         SGRawValueMethods<FGAIBallistic,bool>
 163         (*this, &FGAIBallistic::getSlaved, &FGAIBallistic::setSlaved));
 164     props->tie("controls/invisible",
 165         SGRawValuePointer<bool>(&invisible));
 166
 167     if(_external_force){
 168         props->tie("controls/force_stabilized",
 169             SGRawValuePointer<bool>(&_force_stabilised));
 170         props->tie("position/global-x",
 171             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosX, 0));
 172         props->tie("position/global-y",
 173             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosY, 0));
 174         props->tie("position/global-z",
 175             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosZ, 0));
 176         props->tie("velocities/vertical-speed-fps",
 177             SGRawValuePointer<double>(&vs));
 178         props->tie("velocities/true-airspeed-kt",
 179             SGRawValuePointer<double>(&speed));
 180         props->tie("velocities/horizontal-speed-fps",
 181             SGRawValuePointer<double>(&hs));
 182         props->tie("position/altitude-ft",
 183             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getAltitude, &FGAIBase::_setAltitude));
 184         props->tie("position/latitude-deg",
 185             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLatitude, &FGAIBase::_setLatitude));
 186         props->tie("position/longitude-deg",
 187             SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLongitude, &FGAIBase::_setLongitude));
 188         props->tie("orientation/hdg-deg",
 189             SGRawValuePointer<double>(&hdg));
 190         props->tie("orientation/pitch-deg",
 191             SGRawValuePointer<double>(&pitch));
 192         props->tie("orientation/roll-deg",
 193             SGRawValuePointer<double>(&roll));
 194         props->tie("controls/slave-load-to-ac",
 195             SGRawValueMethods<FGAIBallistic,bool>
 196             (*this, &FGAIBallistic::getSlavedLoad, &FGAIBallistic::setSlavedLoad));
 197         props->tie("position/load-offset",
 198             SGRawValueMethods<FGAIBallistic,double>
 199             (*this, &FGAIBallistic::getLoadOffset, &FGAIBallistic::setLoadOffset));
 200         props->tie("load/distance-to-hitch-ft",
 201             SGRawValueMethods<FGAIBallistic,double>
 202             (*this, &FGAIBallistic::getDistanceLoadToHitch));
 203         props->tie("load/elevation-to-hitch-deg",
 204             SGRawValueMethods<FGAIBallistic,double>
 205             (*this, &FGAIBallistic::getElevLoadToHitch));
 206         props->tie("load/bearing-to-hitch-deg",
 207             SGRawValueMethods<FGAIBallistic,double>
 208             (*this, &FGAIBallistic::getBearingLoadToHitch));
 209     }
 210
 211 }
 212
 213 void FGAIBallistic::unbind() {
 214     //    FGAIBase::unbind();
 215
 216     props->untie("sim/time/elapsed-sec");
 217     props->untie("mass-slug");
 218     props->untie("material/load-resistance");
 219     props->untie("material/solid");
 220     props->untie("altitude-agl-ft");
 221     props->untie("controls/slave-to-ac");
 222     props->untie("controls/invisible");
 223
 224     if(_external_force){
 225         props->untie("position/global-y");
 226         props->untie("position/global-x");
 227         props->untie("position/global-z");
 228         props->untie("velocities/vertical-speed-fps");
 229         props->untie("velocities/true-airspeed-kt");
 230         props->untie("velocities/horizontal-speed-fps");
 231         props->untie("position/altitude-ft");
 232         props->untie("position/latitude-deg");
 233         props->untie("position/longitude-deg");
 234         props->untie("position/ht-agl-ft");
 235         props->untie("orientation/hdg-deg");
 236         props->untie("orientation/pitch-deg");
 237         props->untie("orientation/roll-deg");
 238         props->untie("controls/force_stabilized");
 239         props->untie("position/load-offset");
 240         props->untie("load/distance-to-hitch-ft");
 241         props->untie("load/elevation-to-hitch-deg");
 242         props->untie("load/bearing-to-hitch-deg");
 243     }
 244 }
 245
 246 void FGAIBallistic::update(double dt) {
 247     FGAIBase::update(dt);
 248     _setUserPos();
 249
 250     if (_slave_to_ac){
 251         slaveToAC(dt);
 252         Transform();
 253         setHitchVelocity(dt);
 254     } else if (_formate_to_ac){
 255         formateToAC(dt);
 256         Transform();
 257         setHitchVelocity(dt);
 258     } else if (!invisible){
 259     Run(dt);
 260     Transform();
 261 }
 262
 263 }
 264
 265 void FGAIBallistic::setAzimuth(double az) {
 266     hdg = _azimuth = az;
 267 }
 268
 269 void FGAIBallistic::setElevation(double el) {
 270     pitch = _elevation = el;
 271 }
 272
 273 void FGAIBallistic::setRoll(double rl) {
 274     roll = _rotation = rl;
 275 }
 276
 277 void FGAIBallistic::setStabilisation(bool val) {
 278     _aero_stabilised = val;
 279 }
 280
 281 void FGAIBallistic::setForceStabilisation(bool val) {
 282     _force_stabilised = val;
 283 }
 284
 285 void FGAIBallistic::setNoRoll(bool nr) {
 286     no_roll = nr;
 287 }
 288
 289 void FGAIBallistic::setDragArea(double a) {
 290     _drag_area = a;
 291 }
 292
 293 void FGAIBallistic::setLife(double seconds) {
 294     life = seconds;
 295 }
 296
 297 void FGAIBallistic::setBuoyancy(double fpss) {
 298     _buoyancy = fpss;
 299 }
 300
 301 void FGAIBallistic::setWind_from_east(double fps) {
 302     _wind_from_east = fps;
 303 }
 304
 305 void FGAIBallistic::setWind_from_north(double fps) {
 306     _wind_from_north = fps;
 307 }
 308
 309 void FGAIBallistic::setWind(bool val) {
 310     _wind = val;
 311 }
 312
 313 void FGAIBallistic::setCd(double c) {
 314     _Cd = c;
 315 }
 316
 317 void FGAIBallistic::setMass(double m) {
 318     _mass = m;
 319 }
 320
 321 void FGAIBallistic::setWeight(double w) {
 322     _weight_lb = w;
 323 }
 324 void FGAIBallistic::setRandom(bool r) {
 325     _random = r;
 326 }
 327
 328 void FGAIBallistic::setImpact(bool i) {
 329     _report_impact = i;
 330 }
 331
 332 void FGAIBallistic::setCollision(bool c) {
 333     _report_collision = c;
 334 }
 335
 336 void FGAIBallistic::setExternalForce(bool f) {
 337     _external_force = f;
 338 }
 339
 340 void FGAIBallistic::setImpactReportNode(const string& path) {
 341
 342     if (!path.empty())
 343         _impact_report_node = fgGetNode(path.c_str(), true);
 344 }
 345
 346 void FGAIBallistic::setName(const string& n) {
 347     _name = n;
 348 }
 349
 350 void FGAIBallistic::setSMPath(const string& s) {
 351     _submodel = s;
 352 }
 353
 354 void FGAIBallistic::setFuseRange(double f) {
 355     _fuse_range = f;
 356 }
 357
 358 void FGAIBallistic::setSubID(int i) {
 359     _subID = i;
 360 }
 361
 362 void FGAIBallistic::setSubmodel(const string& s) {
 363     _submodel = s;
 364 }
 365
 366 void FGAIBallistic::setGroundOffset(double g) {
 367     _ground_offset = g;
 368 }
 369
 370 void FGAIBallistic::setLoadOffset(double l) {
 371     _load_offset = l;
 372 }
 373
 374 double FGAIBallistic::getLoadOffset() const {
 375     return _load_offset;
 376 }
 377
 378 void FGAIBallistic::setSlaved(bool s) {
 379     _slave_to_ac = s;
 380 }
 381
 382 void FGAIBallistic::setFormate(bool f) {
 383     _formate_to_ac = f;
 384 }
 385
 386 void FGAIBallistic::setContentsNode(const string& path) {
 387     if (!path.empty()) {
 388         _contents_node = fgGetNode(path.c_str(), true);
 389     }
 390 }
 391
 392 bool FGAIBallistic::getSlaved() const {
 393     return _slave_to_ac;
 394 }
 395
 396 double FGAIBallistic::getMass() const {
 397     return _mass;
 398 }
 399
 400 double FGAIBallistic::getContents() {
 401     if(_contents_node)
 402         _contents_lb = _contents_node->getChild("level-lbs",0,1)->getDoubleValue();
 403     return _contents_lb;
 404 }
 405
 406 void FGAIBallistic::setContents(double c) {
 407     if(_contents_node)
 408         _contents_lb = _contents_node->getChild("level-gal_us",0,1)->setDoubleValue(c);
 409 }
 410
 411 void FGAIBallistic::setSlavedLoad(bool l) {
 412     _slave_load_to_ac = l;
 413 }
 414
 415 bool FGAIBallistic::getSlavedLoad() const {
 416     return _slave_load_to_ac;
 417 }
 418
 419 void FGAIBallistic::setForcePath(const string& p) {
 420     _force_path = p;
 421     if (!_force_path.empty()) {
 422         SGPropertyNode *fnode = fgGetNode(_force_path.c_str(), 0, true );
 423         _force_node = fnode->getChild("force-lb", 0, true);
 424         _force_azimuth_node = fnode->getChild("force-azimuth-deg", 0, true);
 425         _force_elevation_node = fnode->getChild("force-elevation-deg", 0, true);
 426     }
 427 }
 428
 429 bool FGAIBallistic::getHtAGL(){
 430
 431     if (getGroundElevationM(SGGeod::fromGeodM(pos, 10000),
 432                             _elevation_m, &_material)) {
 433             _ht_agl_ft = pos.getElevationFt() - _elevation_m * SG_METER_TO_FEET;
 434             if (_material) {
 435                 const vector<string>& names = _material->get_names();
 436
 437                 _solid = _material->get_solid();
 438                 _load_resistance = _material->get_load_resistance();
 439                 _frictionFactor =_material->get_friction_factor();
 440                 if (!names.empty())
 441                     props->setStringValue("material/name", names[0].c_str());
 442                 else
 443                     props->setStringValue("material/name", "");
 444                 /*cout << "material " << mat_name
 445                 << " solid " << _solid
 446                 << " load " << _load_resistance
 447                 << " frictionFactor " << frictionFactor
 448                 << endl;*/
 449             }
 450             return true;
 451     } else {
 452         return false;
 453     }
 454
 455 }
 456
 457 double FGAIBallistic::getRecip(double az){
 458     // calculate the reciprocal of the input azimuth
 459     if(az - 180 < 0){
 460         return az + 180;
 461     } else {
 462         return az - 180;
 463     }
 464 }
 465
 466 void FGAIBallistic::setPch(double e, double dt, double coeff){
 467     double c = dt / (coeff + dt);
 468     pitch = (e * c) + (pitch * (1 - c));
 469 }
 470
 471 void FGAIBallistic::setBnk(double r, double dt, double coeff){
 472     double c = dt / (coeff + dt);
 473     roll = (r * c) + (roll * (1 - c));
 474 }
 475
 476 void FGAIBallistic::setHt(double h, double dt, double coeff){
 477     double c = dt / (coeff + dt);
 478     _height = (h * c) + (_height * (1 - c));
 479 }
 480
 481 void FGAIBallistic::setHdg(double az, double dt, double coeff){
 482     double recip = getRecip(hdg);
 483     double c = dt / (coeff + dt);
 484     //we need to ensure that we turn the short way to the new hdg
 485     if (az < recip && az < hdg && hdg > 180) {
 486         hdg = ((az + 360) * c) + (hdg * (1 - c));
 487     } else if (az > recip && az > hdg && hdg <= 180){
 488         hdg = ((az - 360) * c) + (hdg * (1 - c));
 489     } else {
 490         hdg = (az * c) + (hdg * (1 - c));
 491     }
 492     }
 493
 494 double  FGAIBallistic::getTgtXOffset() const {
 495     return _tgt_x_offset;
 496 }
 497
 498 double  FGAIBallistic::getTgtYOffset() const {
 499     return _tgt_y_offset;
 500 }
 501
 502 double  FGAIBallistic::getTgtZOffset() const {
 503     return _tgt_z_offset;
 504 }
 505
 506 void FGAIBallistic::setTgtXOffset(double x){
 507     _tgt_x_offset = x;
 508 }
 509
 510 void FGAIBallistic::setTgtYOffset(double y){
 511     _tgt_y_offset = y;
 512 }
 513
 514 void FGAIBallistic::setTgtZOffset(double z){
 515     _tgt_z_offset = z;
 516 }
 517
 518 void FGAIBallistic::slaveToAC(double dt){
 519
 520     setHitchPos();
 521     pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
 522     pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
 523     pos.setElevationFt(hitchpos.getElevationFt());
 524     setHeading(manager->get_user_heading());
 525     setPitch(manager->get_user_pitch() + _pitch_offset);
 526     setBank(manager->get_user_roll() + _roll_offset);
 527     setSpeed(manager->get_user_speed());
 528     //update the mass (slugs)
 529     _mass = (_weight_lb + getContents()) / slugs_to_lbs;
 530
 531     /*cout <<"_mass "<<_mass <<" " << getContents()
 532     <<" " << getContents() / slugs_to_lbs << endl;*/
 533 }
 534
 535 void FGAIBallistic::Run(double dt) {
 536     _life_timer += dt;
 537
 538     // if life = -1 the object does not die
 539     if (_life_timer > life && life != -1)
 540         setDie(true);
 541
 542     //set the contents in the appropriate tank or other property in the parent to zero
 543     setContents(0);
 544
 545     //randomise Cd by +- 5%
 546     if (_random)
 547         _Cd = _Cd * 0.95 + (0.05 * sg_random());
 548
 549     // Adjust Cd by Mach number. The equations are based on curves
 550     // for a conventional shell/bullet (no boat-tail).
 551     double Cdm;
 552
 553     if (Mach < 0.7)
 554         Cdm = 0.0125 * Mach + _Cd;
 555     else if (Mach < 1.2 )
 556         Cdm = 0.3742 * pow(Mach, 2) - 0.252 * Mach + 0.0021 + _Cd;
 557     else
 558         Cdm = 0.2965 * pow(Mach, -1.1506) + _Cd;
 559
 560     //cout << "Mach " << Mach << " Cdm " << Cdm << "// ballistic speed kts "<< speed <<  endl;
 561
 562     // drag = Cd * 0.5 * rho * speed * speed * drag_area;
 563     // rho is adjusted for altitude in void FGAIBase::update,
 564     // using Standard Atmosphere (sealevel temperature 15C)
 565     // acceleration = drag/mass;
 566     // adjust speed by drag
 567     speed -= (Cdm * 0.5 * rho * speed * speed * _drag_area/_mass) * dt;
 568
 569     // don't let speed become negative
 570     if ( speed < 0.0 )
 571         speed = 0.0;
 572
 573     double speed_fps = speed * SG_KT_TO_FPS;
 574     //double hs;
 575
 576     // calculate vertical and horizontal speed components
 577     if (speed == 0.0) {
 578         hs = vs = 0.0;
 579     } else {
 580         vs = sin( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
 581         hs = cos( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
 582     }
 583
 584     //resolve horizontal speed into north and east components:
 585     double speed_north_fps = cos(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
 586     double speed_east_fps = sin(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
 587
 588     // convert horizontal speed (fps) to degrees per second
 589     double speed_north_deg_sec = speed_north_fps / ft_per_deg_lat;
 590     double speed_east_deg_sec  = speed_east_fps / ft_per_deg_lon;
 591
 592     // if wind not required, set to zero
 593     if (!_wind) {
 594         _wind_from_north = 0;
 595         _wind_from_east = 0;
 596     } else {
 597         _wind_from_north = manager->get_wind_from_north();
 598         _wind_from_east = manager->get_wind_from_east();
 599     }
 600
 601     //calculate velocity due to external force
 602     double force_speed_north_deg_sec = 0;
 603     double force_speed_east_deg_sec = 0;
 604 //    double vs_force_fps = 0;
 605     double hs_force_fps = 0;
 606     double v_force_acc_fpss = 0;
 607     double force_speed_north_fps = 0;
 608     double force_speed_east_fps = 0;
 609     double h_force_lbs = 0;
 610     double normal_force_lbs = 0;
 611     double normal_force_fpss = 0;
 612     double static_friction_force_lbs = 0;
 613     double dynamic_friction_force_lbs = 0;
 614     double friction_force_speed_north_fps = 0;
 615     double friction_force_speed_east_fps = 0;
 616     double friction_force_speed_north_deg_sec = 0;
 617     double friction_force_speed_east_deg_sec = 0;
 618     double force_elevation_deg = 0;
 619
 620     if (_external_force) {
 621         SGPropertyNode *n = fgGetNode(_force_path.c_str(), true);
 622         double force_lbs            = n->getChild("force-lb", 0, true)->getDoubleValue();
 623         force_elevation_deg         = n->getChild("force-elevation-deg", 0, true)->getDoubleValue();
 624         double force_azimuth_deg    = n->getChild("force-azimuth-deg", 0, true)->getDoubleValue();
 625
 626         //resolve force into vertical and horizontal components:
 627         double v_force_lbs = force_lbs * sin( force_elevation_deg * SG_DEGREES_TO_RADIANS );
 628         h_force_lbs = force_lbs * cos( force_elevation_deg * SG_DEGREES_TO_RADIANS );
 629
 630         //ground interaction
 631
 632         if (getHtAGL()){
 633             double deadzone = 0.1;
 634
 635             if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
 636                 normal_force_lbs = (_mass * slugs_to_lbs) - v_force_lbs;
 637
 638                 if ( normal_force_lbs < 0 )
 639                     normal_force_lbs = 0;
 640
 641                 pos.setElevationFt(0 + _ground_offset);
 642                 if (vs < 0)
 643                     vs = -vs * 0.5;
 644
 645                 // calculate friction
 646                 // we assume a static Coefficient of Friction (mu) of 0.62 (wood on concrete)
 647                 double mu = 0.62;
 648
 649                 static_friction_force_lbs = mu * normal_force_lbs * _frictionFactor;
 650
 651                 //adjust horizontal force. We assume that a speed of <= 5 fps is static
 652                 if (h_force_lbs <= static_friction_force_lbs && hs <= 5){
 653                     h_force_lbs = hs = 0;
 654                     speed_north_fps = speed_east_fps = 0;
 655                 } else
 656                     dynamic_friction_force_lbs = (static_friction_force_lbs * 0.95);
 657
 658                 //ignore wind when on the ground for now
 659                 //TODO fix this
 660                 _wind_from_north = 0;
 661                 _wind_from_east = 0;
 662
 663             }
 664
 665         }
 666
 667         //acceleration = (force(lbsf)/mass(slugs))
 668         v_force_acc_fpss = v_force_lbs/_mass;
 669         normal_force_fpss = normal_force_lbs/_mass;
 670         double h_force_acc_fpss = h_force_lbs/_mass;
 671         double dynamic_friction_acc_fpss = dynamic_friction_force_lbs/_mass;
 672
 673         // velocity = acceleration * dt
 674         hs_force_fps = h_force_acc_fpss * dt;
 675         double friction_force_fps = dynamic_friction_acc_fpss * dt;
 676
 677         //resolve horizontal speeds into north and east components:
 678         force_speed_north_fps   = cos(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
 679         force_speed_east_fps    = sin(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
 680
 681         friction_force_speed_north_fps = cos(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
 682         friction_force_speed_east_fps  = sin(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
 683
 684         // convert horizontal speed (fps) to degrees per second
 685         force_speed_north_deg_sec = force_speed_north_fps / ft_per_deg_lat;
 686         force_speed_east_deg_sec  = force_speed_east_fps / ft_per_deg_lon;
 687
 688         friction_force_speed_north_deg_sec = friction_force_speed_north_fps / ft_per_deg_lat;
 689         friction_force_speed_east_deg_sec  = friction_force_speed_east_fps / ft_per_deg_lon;
 690     }
 691
 692     // convert wind speed (fps) to degrees lat/lon per second
 693     double wind_speed_from_north_deg_sec = _wind_from_north / ft_per_deg_lat;
 694     double wind_speed_from_east_deg_sec  = _wind_from_east / ft_per_deg_lon;
 695
 696     //recombine the horizontal velocity components
 697     hs = sqrt(((speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps)
 698         * (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
 699         + ((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)
 700         * (speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)));
 701
 702     if (hs <= 0.00001)
 703         hs = 0;
 704
 705     // adjust vertical speed for acceleration of gravity, buoyancy, and vertical force
 706     vs -= (_gravity - _buoyancy - v_force_acc_fpss - normal_force_fpss) * dt;
 707
 708     if (vs <= 0.00001 && vs >= -0.00001)
 709         vs = 0;
 710
 711     // set new position
 712     if(_slave_load_to_ac) {
 713         setHitchPos();
 714         pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
 715         pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
 716         pos.setElevationFt(hitchpos.getElevationFt());
 717
 718         if (getHtAGL()){
 719             double deadzone = 0.1;
 720
 721             if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
 722                 pos.setElevationFt(0 + _ground_offset);
 723             } else {
 724                 pos.setElevationFt(hitchpos.getElevationFt() + _load_offset);
 725             }
 726
 727         }
 728     } else {
 729         pos.setLatitudeDeg( pos.getLatitudeDeg()
 730             + (speed_north_deg_sec - wind_speed_from_north_deg_sec
 731             + force_speed_north_deg_sec + friction_force_speed_north_deg_sec) * dt );
 732         pos.setLongitudeDeg( pos.getLongitudeDeg()
 733             + (speed_east_deg_sec - wind_speed_from_east_deg_sec
 734             + force_speed_east_deg_sec + friction_force_speed_east_deg_sec) * dt );
 735         pos.setElevationFt(pos.getElevationFt() + vs * dt);
 736     }
 737
 738     // recalculate total speed
 739     if ( vs == 0 && hs == 0)
 740         speed = 0;
 741     else
 742         speed = sqrt( vs * vs + hs * hs) / SG_KT_TO_FPS;
 743
 744     // recalculate elevation and azimuth (velocity vectors)
 745     _elevation = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
 746     _azimuth =  atan2((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps),
 747         (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
 748         * SG_RADIANS_TO_DEGREES;
 749
 750     // rationalise azimuth
 751     if (_azimuth < 0)
 752         _azimuth += 360;
 753
 754     if (_aero_stabilised) { // we simulate rotational moment of inertia by using a filter
 755         const double coeff = 0.9;
 756
 757         // we assume a symetrical MI about the pitch and yaw axis
 758         setPch(_elevation, dt, coeff);
 759         setHdg(_azimuth, dt, coeff);
 760     } else if (_force_stabilised) { // we simulate rotational moment of inertia by using a filter
 761         const double coeff = 0.9;
 762         double ratio = h_force_lbs/(_mass * slugs_to_lbs);
 763
 764         if (ratio >  1) ratio =  1;
 765         if (ratio < -1) ratio = -1;
 766
 767         double force_pitch = acos(ratio) * SG_RADIANS_TO_DEGREES;
 768
 769         if (force_pitch <= force_elevation_deg)
 770             force_pitch = force_elevation_deg;
 771
 772         // we assume a symetrical MI about the pitch and yaw axis
 773         setPch(force_pitch,dt, coeff);
 774         setHdg(_azimuth, dt, coeff);
 775     }
 776
 777     //do impacts and collisions
 778     if (_report_impact && !_impact_reported)
 779         handle_impact();
 780
 781     if (_report_collision && !_collision_reported)
 782         handle_collision();
 783
 784     // set destruction flag if altitude less than sea level -1000
 785     if (altitude_ft < -1000.0 && life != -1)
 786         setDie(true);
 787
 788 }  // end Run
 789
 790 double FGAIBallistic::_getTime() const {
 791     return _life_timer;
 792 }
 793
 794 void FGAIBallistic::handle_impact() {
 795
 796     // try terrain intersection
 797     if(!getHtAGL())
 798         return;
 799
 800     if (_ht_agl_ft <= 0) {
 801         SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: terrain impact");
 802         report_impact(_elevation_m);
 803         _impact_reported = true;
 804
 805         if (life == -1){
 806             invisible = true;
 807         } else if (_subID == 0)  // kill the AIObject if there is no subsubmodel
 808             setDie(true);
 809     }
 810 }
 811
 812 void FGAIBallistic::handle_collision()
 813 {
 814     const FGAIBase *object = manager->calcCollision(pos.getElevationFt(),
 815             pos.getLatitudeDeg(),pos.getLongitudeDeg(), _fuse_range);
 816
 817     if (object) {
 818         SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: object hit");
 819         report_impact(pos.getElevationM(), object);
 820         _collision_reported = true;
 821     }
 822 }
 823
 824 void FGAIBallistic::report_impact(double elevation, const FGAIBase *object)
 825 {
 826     _impact_lat    = pos.getLatitudeDeg();
 827     _impact_lon    = pos.getLongitudeDeg();
 828     _impact_elev   = elevation;
 829     _impact_speed  = speed * SG_KT_TO_MPS;
 830     _impact_hdg    = hdg;
 831     _impact_pitch  = pitch;
 832     _impact_roll   = roll;
 833
 834     SGPropertyNode *n = props->getNode("impact", true);
 835     if (object)
 836         n->setStringValue("type", object->getTypeString());
 837     else
 838         n->setStringValue("type", "terrain");
 839
 840     n->setDoubleValue("longitude-deg", _impact_lon);
 841     n->setDoubleValue("latitude-deg", _impact_lat);
 842     n->setDoubleValue("elevation-m", _impact_elev);
 843     n->setDoubleValue("heading-deg", _impact_hdg);
 844     n->setDoubleValue("pitch-deg", _impact_pitch);
 845     n->setDoubleValue("roll-deg", _impact_roll);
 846     n->setDoubleValue("speed-mps", _impact_speed);
 847
 848     _impact_report_node->setStringValue(props->getPath());
 849 }
 850
 851 SGVec3d FGAIBallistic::getCartUserPos() const {
 852     SGVec3d cartUserPos = SGVec3d::fromGeod(userpos);
 853     return cartUserPos;
 854 }
 855
 856 SGVec3d FGAIBallistic::getCartHitchPos() const{
 857
 858     // convert geodetic positions to geocentered
 859     SGVec3d cartuserPos = getCartUserPos();
 860     SGVec3d cartPos = getCartPos();
 861
 862     // Transform to the right coordinate frame, configuration is done in
 863     // the x-forward, y-right, z-up coordinates (feet), computation
 864     // in the simulation usual body x-forward, y-right, z-down coordinates
 865     // (meters) )
 866     SGVec3d _off(_x_offset * SG_FEET_TO_METER,
 867         _y_offset * SG_FEET_TO_METER,
 868         -_z_offset * SG_FEET_TO_METER);
 869
 870     // Transform the user position to the horizontal local coordinate system.
 871     SGQuatd hlTrans = SGQuatd::fromLonLat(userpos);
 872
 873     // and postrotate the orientation of the user model wrt the horizontal
 874     // local frame
 875     hlTrans *= SGQuatd::fromYawPitchRollDeg(
 876         manager->get_user_heading(),
 877         manager->get_user_pitch(),
 878         manager->get_user_roll());
 879
 880     // The offset converted to the usual body fixed coordinate system
 881     // rotated to the earth-fixed coordinates axis
 882     SGVec3d off = hlTrans.backTransform(_off);
 883
 884     // Add the position offset of the user model to get the geocentered position
 885     SGVec3d offsetPos = cartuserPos + off;
 886
 887     return offsetPos;
 888 }
 889
 890 void FGAIBallistic::setHitchPos(){
 891     // convert the hitch geocentered position to geodetic
 892     SGVec3d carthitchPos = getCartHitchPos();
 893
 894     SGGeodesy::SGCartToGeod(carthitchPos, hitchpos);
 895 }
 896
 897 double FGAIBallistic::getDistanceLoadToHitch() const {
 898     //calculate the distance load to hitch
 899     SGVec3d carthitchPos = getCartHitchPos();
 900     SGVec3d cartPos = getCartPos();
 901
 902     SGVec3d diff = carthitchPos - cartPos;
 903     double distance = norm(diff);
 904     return distance * SG_METER_TO_FEET;
 905 }
 906
 907 void FGAIBallistic::setHitchVelocity(double dt) {
 908     //calculate the distance from the previous hitch position
 909     SGVec3d carthitchPos = getCartHitchPos();
 910     SGVec3d diff = carthitchPos - _oldcarthitchPos;
 911
 912     double distance = norm(diff);
 913
 914     //calculate speed knots
 915     speed = (distance/dt) * SG_MPS_TO_KT;
 916
 917     //now calulate the angle between the old and current hitch positions (degrees)
 918     double angle = 0;
 919     double daltM = hitchpos.getElevationM() - oldhitchpos.getElevationM();
 920
 921     if (fabs(distance) < SGLimits<float>::min()) {
 922         angle = 0;
 923     } else {
 924         double sAngle = daltM/distance;
 925         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
 926         angle = SGMiscd::rad2deg(asin(sAngle));
 927     }
 928
 929     _elevation = angle;
 930
 931     //calculate the bearing of the new hitch position from the old
 932     double az1, az2, dist;
 933
 934     geo_inverse_wgs_84(oldhitchpos, hitchpos, &az1, &az2, &dist);
 935
 936     _azimuth = az1;
 937
 938     // and finally store the new values
 939     _oldcarthitchPos = carthitchPos;
 940     oldhitchpos = hitchpos;
 941 }
 942
 943 double FGAIBallistic::getElevLoadToHitch() const {
 944     // now the angle, positive angles are upwards
 945     double distance = getDistanceLoadToHitch() * SG_FEET_TO_METER;
 946     double angle = 0;
 947     double daltM = hitchpos.getElevationM() - pos.getElevationM();
 948
 949     if (fabs(distance) < SGLimits<float>::min()) {
 950         angle = 0;
 951     } else {
 952         double sAngle = daltM/distance;
 953         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
 954         angle = SGMiscd::rad2deg(asin(sAngle));
 955     }
 956
 957     return angle;
 958 }
 959
 960 double FGAIBallistic::getBearingLoadToHitch() const {
 961     //calculate the bearing and range of the second pos from the first
 962     double az1, az2, distance;
 963
 964     geo_inverse_wgs_84(pos, hitchpos, &az1, &az2, &distance);
 965
 966     return az1;
 967 }
 968
 969 double FGAIBallistic::getRelBrgHitchToUser() const {
 970     //calculate the relative bearing
 971     double az1, az2, distance;
 972
 973     geo_inverse_wgs_84(hitchpos, userpos, &az1, &az2, &distance);
 974
 975     double rel_brg = az1 - hdg;
 976
 977     if (rel_brg > 180)
 978         rel_brg -= 360;
 979
 980     return rel_brg;
 981 }
 982
 983 double FGAIBallistic::getElevHitchToUser() const {
 984
 985     //calculate the distance from the user position
 986     SGVec3d carthitchPos = getCartHitchPos();
 987     SGVec3d cartuserPos = getCartUserPos();
 988
 989     SGVec3d diff = cartuserPos - carthitchPos;
 990
 991     double distance = norm(diff);
 992     double angle = 0;
 993
 994     double daltM = userpos.getElevationM() - hitchpos.getElevationM();
 995
 996     // now the angle, positive angles are upwards
 997     if (fabs(distance) < SGLimits<float>::min()) {
 998         angle = 0;
 999     } else {
1000         double sAngle = daltM/distance;
1001         sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
1002         angle = SGMiscd::rad2deg(asin(sAngle));
1003     }
1004
1005     return angle;
1006 }
1007
1008 void FGAIBallistic::setTgtOffsets(double dt, double coeff){
1009     double c = dt / (coeff + dt);
1010
1011     _x_offset = (_tgt_x_offset * c) + (_x_offset * (1 - c));
1012     _y_offset = (_tgt_y_offset * c) + (_y_offset * (1 - c));
1013     _z_offset = (_tgt_z_offset * c) + (_z_offset * (1 - c));
1014 }
1015
1016 void FGAIBallistic::formateToAC(double dt){
1017
1018     setTgtOffsets(dt, 25);
1019     setHitchPos();
1020     setHitchVelocity(dt);
1021
1022     // elapsed time has a random initialisation so that each
1023     // wingman moves differently
1024     _elapsed_time += dt;
1025
1026     // we derive a sine based factor to give us smoothly
1027     // varying error between -1 and 1
1028     double factor  = sin(SGMiscd::deg2rad(_elapsed_time * 10));
1029     double r_angle = 5 * factor;
1030     double p_angle = 2.5 * factor;
1031     double h_angle = 5 * factor;
1032     double h_feet  = 3 * factor;
1033
1034     pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
1035     pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
1036
1037     if (getHtAGL()){
1038
1039         if(_ht_agl_ft <= 10) {
1040             _height = userpos.getElevationFt();
1041         } else if (_ht_agl_ft > 10 && _ht_agl_ft <= 150 ) {
1042             setHt(userpos.getElevationFt(), dt, 1.0);
1043         } else if (_ht_agl_ft > 150 && _ht_agl_ft <= 250) {
1044             setHt(hitchpos.getElevationFt()+ h_feet, dt, 0.75);
1045         } else
1046             setHt(hitchpos.getElevationFt()+ h_feet, dt, 0.5);
1047
1048         pos.setElevationFt(_height);
1049     }
1050
1051     // these calculations are unreliable at slow speeds
1052     if(speed >= 10) {
1053         setHdg(_azimuth + h_angle, dt, 0.9);
1054         setPch(_elevation + p_angle + _pitch_offset, dt, 0.9);
1055
1056         if (roll <= 115 && roll >= -115)
1057             setBnk(manager->get_user_roll() + r_angle + _roll_offset, dt, 0.5);
1058         else
1059             roll = manager->get_user_roll() + r_angle + _roll_offset;
1060
1061     } else {
1062         setHdg(manager->get_user_heading(), dt, 0.9);
1063         setPch(manager->get_user_pitch() + _pitch_offset, dt, 0.9);
1064         setBnk(manager->get_user_roll() + _roll_offset, dt, 0.9);
1065     }
1066
1067     setSpeed(speed);
1068 }
1069 // end AIBallistic