1 // FGAIBase - abstract base class for AI objects
2 // Written by David Culp, started Nov 2003, based on
3 // David Luff's FGAIEntity class.
4 // - davidculp2@comcast.net
6 // With additions by Mathias Froehlich & Vivian Meazza 2004 -2007
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.
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.
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.
29 #include <simgear/compiler.h>
33 #include <osg/ref_ptr>
35 #include <osgDB/FileUtils>
37 #include <simgear/math/SGMath.hxx>
38 #include <simgear/misc/sg_path.hxx>
39 #include <simgear/scene/model/modellib.hxx>
40 #include <simgear/scene/util/SGNodeMasks.hxx>
41 #include <simgear/debug/logstream.hxx>
42 #include <simgear/props/props.hxx>
44 #include <Main/globals.hxx>
45 #include <Scenery/scenery.hxx>
46 #include <Scripting/NasalSys.hxx>
47 #include <Sound/fg_fx.hxx>
50 #include "AIManager.hxx"
52 const char *default_model = "Models/Geometry/glider.ac";
53 const double FGAIBase::e = 2.71828183;
54 const double FGAIBase::lbs_to_slugs = 0.031080950172; //conversion factor
56 using namespace simgear;
58 FGAIBase::FGAIBase(object_type ot, bool enableHot) :
63 model_removed( fgGetNode("/ai/models/model-removed", true) ),
74 _refID( _newAIModelID() ),
82 tgt_heading = hdg = tgt_altitude_ft = tgt_speed = 0.0;
83 tgt_roll = roll = tgt_pitch = tgt_yaw = tgt_vs = vs = pitch = 0.0;
84 bearing = elevation = range = rdot = 0.0;
85 x_shift = y_shift = rotation = 0.0;
91 _impact_reported = false;
92 _collision_reported = false;
93 _expiry_reported = false;
105 userpos = SGGeod::fromDeg(0, 0);
107 pos = SGGeod::fromDeg(0, 0);
110 speed_north_deg_sec = 0;
111 speed_east_deg_sec = 0;
131 // explicitly disable HOT for (most) AI models
133 aip.getSceneGraph()->setNodeMask(~SG_NODEMASK_TERRAIN_BIT);
136 FGAIBase::~FGAIBase() {
137 // Unregister that one at the scenery manager
141 SGPropertyNode* parent = props->getParent();
144 model_removed->setStringValue(props->getPath());
154 /** Cleanly remove the model
155 * and let the scenery database pager do the clean-up work.
158 FGAIBase::removeModel()
160 FGScenery* pSceneryManager = globals->get_scenery();
163 osg::ref_ptr<osg::Object> temp = _model.get();
164 pSceneryManager->get_scene_graph()->removeChild(aip.getSceneGraph());
165 // withdraw from SGModelPlacement and drop own reference (unref)
168 // pass it on to the pager, to be be deleted in the pager thread
169 pSceneryManager->getPagerSingleton()->queueDeleteRequest(temp);
173 SG_LOG(SG_AI, SG_ALERT, "AIBase: Could not unload model. Missing scenery manager!");
177 void FGAIBase::readFromScenario(SGPropertyNode* scFileNode)
182 setPath(scFileNode->getStringValue("model",
183 fgGetString("/sim/multiplay/default-model", default_model)));
185 setHeading(scFileNode->getDoubleValue("heading", 0.0));
186 setSpeed(scFileNode->getDoubleValue("speed", 0.0));
187 setAltitude(scFileNode->getDoubleValue("altitude", 0.0));
188 setLongitude(scFileNode->getDoubleValue("longitude", 0.0));
189 setLatitude(scFileNode->getDoubleValue("latitude", 0.0));
190 setBank(scFileNode->getDoubleValue("roll", 0.0));
192 SGPropertyNode* submodels = scFileNode->getChild("submodels");
195 setServiceable(submodels->getBoolValue("serviceable", false));
196 setSMPath(submodels->getStringValue("path", ""));
201 void FGAIBase::update(double dt) {
203 if (_otype == otStatic)
206 if (_otype == otBallistic)
209 ft_per_deg_lat = 366468.96 - 3717.12 * cos(pos.getLatitudeRad());
210 ft_per_deg_lon = 365228.16 * cos(pos.getLatitudeRad());
214 // update model's audio sample values
215 _fx->set_position_geod( pos );
217 SGQuatd orient = SGQuatd::fromYawPitchRollDeg(hdg, pitch, roll);
218 _fx->set_orientation( orient );
221 velocity = SGVec3d( speed_north_deg_sec, speed_east_deg_sec, pitch*speed );
222 _fx->set_velocity( velocity );
226 string fxpath = _aimodel->get_sound_path();
230 props->setStringValue("sim/sound/path", _fxpath.c_str());
232 // initialize the sound configuration
233 SGSoundMgr *smgr = globals->get_soundmgr();
234 _fx = new FGFX(smgr, "aifx:"+_name+"-"+_callsign, props);
240 /** update LOD properties of the model */
241 void FGAIBase::updateLOD()
243 double maxRangeDetail = fgGetDouble("/sim/rendering/static-lod/ai-detailed", 10000.0);
244 double maxRangeBare = fgGetDouble("/sim/rendering/static-lod/ai-bare", 20000.0);
247 if( maxRangeDetail == 0.0 )
250 _model->setRange(0, 0.0, FLT_MAX);
251 _model->setRange(1, FLT_MAX, FLT_MAX);
255 _model->setRange(0, 0.0, maxRangeDetail);
256 _model->setRange(1, maxRangeDetail,maxRangeBare);
261 void FGAIBase::Transform() {
264 aip.setVisible(true);
265 aip.setPosition(pos);
268 aip.setOrientation(0.0, pitch, hdg);
270 aip.setOrientation(roll, pitch, hdg);
274 aip.setVisible(false);
280 bool FGAIBase::init(bool search_in_AI_path) {
283 if(search_in_AI_path)
285 // setup a modified Options structure, with only the $fg-root/AI defined;
286 // we'll check that first, then give the normal search logic a chance.
287 // this ensures that models in AI/ are preferred to normal models, where
289 osg::ref_ptr<osgDB::ReaderWriter::Options>
290 opt(osg::clone(osgDB::Registry::instance()->getOptions(), osg::CopyOp::SHALLOW_COPY));
292 SGPath ai_path(globals->get_fg_root(), "AI");
293 opt->setDatabasePath(ai_path.str());
295 f = osgDB::findDataFile(model_path, opt.get());
299 f = simgear::SGModelLib::findDataFile(model_path);
303 f = fgGetString("/sim/multiplay/default-model", default_model);
307 _aimodel = new FGAIModelData(props);
308 osg::Node * mdl = SGModelLib::loadDeferredModel(f, props, _aimodel);
312 // reinit, dump the old model
316 _model = new osg::LOD;
317 _model->setName("AI-model range animation node");
319 _model->addChild( mdl, 0, FLT_MAX );
320 _model->setCenterMode(osg::LOD::USE_BOUNDING_SPHERE_CENTER);
321 _model->setRangeMode(osg::LOD::DISTANCE_FROM_EYE_POINT);
322 // We really need low-resolution versions of AI/MP aircraft.
323 // Or at least dummy "stubs" with some default silhouette.
324 // _model->addChild( SGModelLib::loadPagedModel(fgGetString("/sim/multiplay/default-model", default_model),
325 // props, new FGNasalModelData(props)), FLT_MAX, FLT_MAX);
329 if (_model.valid() && _initialized == false) {
330 aip.init( _model.get() );
331 aip.setVisible(true);
333 globals->get_scenery()->get_scene_graph()->addChild(aip.getSceneGraph());
335 // Get the sound-path tag from the configuration file and store it
336 // in the property tree.
339 } else if (!model_path.empty()) {
340 SG_LOG(SG_AI, SG_WARN, "AIBase: Could not load model " << model_path);
341 // not properly installed...
349 void FGAIBase::initModel(osg::Node *node)
351 if (_model.valid()) {
354 props->setStringValue("submodels/path", _path.c_str());
355 SG_LOG(SG_AI, SG_DEBUG, "AIBase: submodels/path " << _path);
359 props->setStringValue("parent-name", _parent.c_str());
362 fgSetString("/ai/models/model-added", props->getPath().c_str());
363 } else if (!model_path.empty()) {
364 SG_LOG(SG_AI, SG_WARN, "AIBase: Could not load model " << model_path);
371 bool FGAIBase::isa( object_type otype ) {
372 return otype == _otype;
376 void FGAIBase::bind() {
377 props->tie("id", SGRawValueMethods<FGAIBase,int>(*this,
379 props->tie("velocities/true-airspeed-kt", SGRawValuePointer<double>(&speed));
380 props->tie("velocities/vertical-speed-fps",
381 SGRawValueMethods<FGAIBase,double>(*this,
382 &FGAIBase::_getVS_fps,
383 &FGAIBase::_setVS_fps));
385 props->tie("position/altitude-ft",
386 SGRawValueMethods<FGAIBase,double>(*this,
387 &FGAIBase::_getAltitude,
388 &FGAIBase::_setAltitude));
389 props->tie("position/latitude-deg",
390 SGRawValueMethods<FGAIBase,double>(*this,
391 &FGAIBase::_getLatitude,
392 &FGAIBase::_setLatitude));
393 props->tie("position/longitude-deg",
394 SGRawValueMethods<FGAIBase,double>(*this,
395 &FGAIBase::_getLongitude,
396 &FGAIBase::_setLongitude));
398 props->tie("position/global-x",
399 SGRawValueMethods<FGAIBase,double>(*this,
400 &FGAIBase::_getCartPosX,
402 props->tie("position/global-y",
403 SGRawValueMethods<FGAIBase,double>(*this,
404 &FGAIBase::_getCartPosY,
406 props->tie("position/global-z",
407 SGRawValueMethods<FGAIBase,double>(*this,
408 &FGAIBase::_getCartPosZ,
410 props->tie("callsign",
411 SGRawValueMethods<FGAIBase,const char*>(*this,
412 &FGAIBase::_getCallsign,
415 props->tie("orientation/pitch-deg", SGRawValuePointer<double>(&pitch));
416 props->tie("orientation/roll-deg", SGRawValuePointer<double>(&roll));
417 props->tie("orientation/true-heading-deg", SGRawValuePointer<double>(&hdg));
419 props->tie("radar/in-range", SGRawValuePointer<bool>(&in_range));
420 props->tie("radar/bearing-deg", SGRawValuePointer<double>(&bearing));
421 props->tie("radar/elevation-deg", SGRawValuePointer<double>(&elevation));
422 props->tie("radar/range-nm", SGRawValuePointer<double>(&range));
423 props->tie("radar/h-offset", SGRawValuePointer<double>(&horiz_offset));
424 props->tie("radar/v-offset", SGRawValuePointer<double>(&vert_offset));
425 props->tie("radar/x-shift", SGRawValuePointer<double>(&x_shift));
426 props->tie("radar/y-shift", SGRawValuePointer<double>(&y_shift));
427 props->tie("radar/rotation", SGRawValuePointer<double>(&rotation));
428 props->tie("radar/ht-diff-ft", SGRawValuePointer<double>(&ht_diff));
429 props->tie("subID", SGRawValuePointer<int>(&_subID));
430 props->tie("controls/lighting/nav-lights",
431 SGRawValueFunctions<bool>(_isNight));
432 props->setBoolValue("controls/lighting/beacon", true);
433 props->setBoolValue("controls/lighting/strobe", true);
434 props->setBoolValue("controls/glide-path", true);
436 props->setStringValue("controls/flight/lateral-mode", "roll");
437 props->setDoubleValue("controls/flight/target-hdg", hdg);
438 props->setDoubleValue("controls/flight/target-roll", roll);
440 props->setStringValue("controls/flight/longitude-mode", "alt");
441 props->setDoubleValue("controls/flight/target-alt", altitude_ft);
442 props->setDoubleValue("controls/flight/target-pitch", pitch);
444 props->setDoubleValue("controls/flight/target-spd", speed);
446 props->setBoolValue("sim/sound/avionics/enabled", false);
447 props->setDoubleValue("sim/sound/avionics/volume", 0.0);
448 props->setBoolValue("sim/sound/avionics/external-view", false);
449 props->setBoolValue("sim/current-view/internal", false);
453 void FGAIBase::unbind() {
455 props->untie("velocities/true-airspeed-kt");
456 props->untie("velocities/vertical-speed-fps");
458 props->untie("position/altitude-ft");
459 props->untie("position/latitude-deg");
460 props->untie("position/longitude-deg");
461 props->untie("position/global-x");
462 props->untie("position/global-y");
463 props->untie("position/global-z");
464 props->untie("callsign");
466 props->untie("orientation/pitch-deg");
467 props->untie("orientation/roll-deg");
468 props->untie("orientation/true-heading-deg");
470 props->untie("radar/in-range");
471 props->untie("radar/bearing-deg");
472 props->untie("radar/elevation-deg");
473 props->untie("radar/range-nm");
474 props->untie("radar/h-offset");
475 props->untie("radar/v-offset");
476 props->untie("radar/x-shift");
477 props->untie("radar/y-shift");
478 props->untie("radar/rotation");
479 props->untie("radar/ht-diff-ft");
481 props->untie("controls/lighting/nav-lights");
483 props->setBoolValue("/sim/controls/radar/", true);
487 double FGAIBase::UpdateRadar(FGAIManager* manager) {
488 bool control = fgGetBool("/sim/controls/radar", true);
490 if(!control) return 0;
492 double radar_range_ft2 = fgGetDouble("/instrumentation/radar/range");
493 bool force_on = fgGetBool("/instrumentation/radar/debug-mode", false);
494 radar_range_ft2 *= SG_NM_TO_METER * SG_METER_TO_FEET * 1.1; // + 10%
495 radar_range_ft2 *= radar_range_ft2;
497 double user_latitude = manager->get_user_latitude();
498 double user_longitude = manager->get_user_longitude();
499 double lat_range = fabs(pos.getLatitudeDeg() - user_latitude) * ft_per_deg_lat;
500 double lon_range = fabs(pos.getLongitudeDeg() - user_longitude) * ft_per_deg_lon;
501 double range_ft2 = lat_range*lat_range + lon_range*lon_range;
504 // Test whether the target is within radar range.
506 in_range = (range_ft2 && (range_ft2 <= radar_range_ft2));
508 if ( in_range || force_on ) {
509 props->setBoolValue("radar/in-range", true);
511 // copy values from the AIManager
512 double user_altitude = manager->get_user_altitude();
513 double user_heading = manager->get_user_heading();
514 double user_pitch = manager->get_user_pitch();
515 //double user_yaw = manager->get_user_yaw();
516 //double user_speed = manager->get_user_speed();
518 // calculate range to target in feet and nautical miles
519 double range_ft = sqrt( range_ft2 );
520 range = range_ft / 6076.11549;
522 // calculate bearing to target
523 if (pos.getLatitudeDeg() >= user_latitude) {
524 bearing = atan2(lat_range, lon_range) * SG_RADIANS_TO_DEGREES;
525 if (pos.getLongitudeDeg() >= user_longitude) {
526 bearing = 90.0 - bearing;
528 bearing = 270.0 + bearing;
531 bearing = atan2(lon_range, lat_range) * SG_RADIANS_TO_DEGREES;
532 if (pos.getLongitudeDeg() >= user_longitude) {
533 bearing = 180.0 - bearing;
535 bearing = 180.0 + bearing;
539 // This is an alternate way to compute bearing and distance which
540 // agrees with the original scheme within about 0.1 degrees.
542 // Point3D start( user_longitude * SGD_DEGREES_TO_RADIANS,
543 // user_latitude * SGD_DEGREES_TO_RADIANS, 0 );
544 // Point3D dest( pos.getLongitudeRad(), pos.getLatitudeRad(), 0 );
545 // double gc_bearing, gc_range;
546 // calc_gc_course_dist( start, dest, &gc_bearing, &gc_range );
547 // gc_range *= SG_METER_TO_NM;
548 // gc_bearing *= SGD_RADIANS_TO_DEGREES;
549 // printf("orig b = %.3f %.2f gc b= %.3f, %.2f\n",
550 // bearing, range, gc_bearing, gc_range);
552 // calculate look left/right to target, without yaw correction
553 horiz_offset = bearing - user_heading;
554 if (horiz_offset > 180.0) horiz_offset -= 360.0;
555 if (horiz_offset < -180.0) horiz_offset += 360.0;
557 // calculate elevation to target
558 elevation = atan2( altitude_ft - user_altitude, range_ft ) * SG_RADIANS_TO_DEGREES;
560 // calculate look up/down to target
561 vert_offset = elevation - user_pitch;
563 /* this calculation needs to be fixed, but it isn't important anyway
564 // calculate range rate
565 double recip_bearing = bearing + 180.0;
566 if (recip_bearing > 360.0) recip_bearing -= 360.0;
567 double my_horiz_offset = recip_bearing - hdg;
568 if (my_horiz_offset > 180.0) my_horiz_offset -= 360.0;
569 if (my_horiz_offset < -180.0) my_horiz_offset += 360.0;
570 rdot = (-user_speed * cos( horiz_offset * SG_DEGREES_TO_RADIANS ))
571 +(-speed * 1.686 * cos( my_horiz_offset * SG_DEGREES_TO_RADIANS ));
574 // now correct look left/right for yaw
575 // horiz_offset += user_yaw; // FIXME: WHY WOULD WE WANT TO ADD IN SIDE-SLIP HERE?
577 // calculate values for radar display
578 y_shift = range * cos( horiz_offset * SG_DEGREES_TO_RADIANS);
579 x_shift = range * sin( horiz_offset * SG_DEGREES_TO_RADIANS);
580 rotation = hdg - user_heading;
581 if (rotation < 0.0) rotation += 360.0;
582 ht_diff = altitude_ft - user_altitude;
590 * Getters and Setters
593 SGVec3d FGAIBase::getCartPosAt(const SGVec3d& _off) const {
594 // Transform that one to the horizontal local coordinate system.
595 SGQuatd hlTrans = SGQuatd::fromLonLat(pos);
597 // and postrotate the orientation of the AIModel wrt the horizontal
599 hlTrans *= SGQuatd::fromYawPitchRollDeg(hdg, pitch, roll);
601 // The offset converted to the usual body fixed coordinate system
602 // rotated to the earth fixed coordinates axis
603 SGVec3d off = hlTrans.backTransform(_off);
605 // Add the position offset of the AIModel to gain the earth centered position
606 SGVec3d cartPos = SGVec3d::fromGeod(pos);
608 return cartPos + off;
611 SGVec3d FGAIBase::getCartPos() const {
612 SGVec3d cartPos = SGVec3d::fromGeod(pos);
616 bool FGAIBase::getGroundElevationM(const SGGeod& pos, double& elev,
617 const SGMaterial** material) const {
618 return globals->get_scenery()->get_elevation_m(pos, elev, material,
622 double FGAIBase::_getCartPosX() const {
623 SGVec3d cartPos = getCartPos();
627 double FGAIBase::_getCartPosY() const {
628 SGVec3d cartPos = getCartPos();
632 double FGAIBase::_getCartPosZ() const {
633 SGVec3d cartPos = getCartPos();
637 void FGAIBase::_setLongitude( double longitude ) {
638 pos.setLongitudeDeg(longitude);
641 void FGAIBase::_setLatitude ( double latitude ) {
642 pos.setLatitudeDeg(latitude);
645 void FGAIBase::_setUserPos(){
646 userpos.setLatitudeDeg(manager->get_user_latitude());
647 userpos.setLongitudeDeg(manager->get_user_longitude());
648 userpos.setElevationM(manager->get_user_altitude() * SG_FEET_TO_METER);
651 void FGAIBase::_setSubID( int s ) {
655 bool FGAIBase::setParentNode() {
658 SG_LOG(SG_AI, SG_ALERT, "AIBase: " << _name
659 << " parent not set ");
663 const SGPropertyNode_ptr ai = fgGetNode("/ai/models", true);
665 for (int i = ai->nChildren() - 1; i >= -1; i--) {
666 SGPropertyNode_ptr model;
668 if (i < 0) { // last iteration: selected model
669 model = _selected_ac;
671 model = ai->getChild(i);
672 string path = ai->getPath();
673 const string name = model->getStringValue("name");
675 if (!model->nChildren()){
678 if (name == _parent) {
679 _selected_ac = model; // save selected model for last iteration
689 if (_selected_ac != 0){
690 const string name = _selected_ac->getStringValue("name");
693 SG_LOG(SG_AI, SG_ALERT, "AIBase: " << _name
694 << " parent not found: dying ");
701 double FGAIBase::_getLongitude() const {
702 return pos.getLongitudeDeg();
705 double FGAIBase::_getLatitude() const {
706 return pos.getLatitudeDeg();
709 double FGAIBase::_getElevationFt() const {
710 return pos.getElevationFt();
713 double FGAIBase::_getRdot() const {
717 double FGAIBase::_getVS_fps() const {
721 double FGAIBase::_get_speed_east_fps() const {
722 return speed_east_deg_sec * ft_per_deg_lon;
725 double FGAIBase::_get_speed_north_fps() const {
726 return speed_north_deg_sec * ft_per_deg_lat;
729 void FGAIBase::_setVS_fps( double _vs ) {
733 double FGAIBase::_getAltitude() const {
737 double FGAIBase::_getAltitudeAGL(SGGeod inpos, double start){
738 getGroundElevationM(SGGeod::fromGeodM(inpos, start),
739 _elevation_m, &_material);
740 return inpos.getElevationFt() - _elevation_m * SG_METER_TO_FEET;
743 bool FGAIBase::_getServiceable() const {
747 SGPropertyNode* FGAIBase::_getProps() const {
751 void FGAIBase::_setAltitude( double _alt ) {
755 bool FGAIBase::_isNight() {
756 return (fgGetFloat("/sim/time/sun-angle-rad") > 1.57);
759 bool FGAIBase::_getCollisionData() {
760 return _collision_reported;
763 bool FGAIBase::_getExpiryData() {
764 return _expiry_reported;
767 bool FGAIBase::_getImpactData() {
768 return _impact_reported;
771 double FGAIBase::_getImpactLat() const {
775 double FGAIBase::_getImpactLon() const {
779 double FGAIBase::_getImpactElevFt() const {
780 return _impact_elev * SG_METER_TO_FEET;
783 double FGAIBase::_getImpactPitch() const {
784 return _impact_pitch;
787 double FGAIBase::_getImpactRoll() const {
791 double FGAIBase::_getImpactHdg() const {
795 double FGAIBase::_getImpactSpeed() const {
796 return _impact_speed;
799 int FGAIBase::getID() const {
803 int FGAIBase::_getSubID() const {
807 double FGAIBase::_getSpeed() const {
811 double FGAIBase::_getRoll() const {
815 double FGAIBase::_getPitch() const {
819 double FGAIBase::_getHeading() const {
823 double FGAIBase::_getXOffset() const {
827 double FGAIBase::_getYOffset() const {
831 double FGAIBase::_getZOffset() const {
835 const char* FGAIBase::_getPath() const {
836 return model_path.c_str();
839 const char* FGAIBase::_getSMPath() const {
840 return _path.c_str();
843 const char* FGAIBase::_getName() const {
844 return _name.c_str();
847 const char* FGAIBase::_getCallsign() const {
848 return _callsign.c_str();
851 const char* FGAIBase::_getSubmodel() const {
852 return _submodel.c_str();
855 void FGAIBase::CalculateMach() {
856 // Calculate rho at altitude, using standard atmosphere
857 // For the temperature T and the pressure p,
858 double altitude = altitude_ft;
860 if (altitude < 36152) { // curve fits for the troposphere
861 T = 59 - 0.00356 * altitude;
862 p = 2116 * pow( ((T + 459.7) / 518.6) , 5.256);
863 } else if ( 36152 < altitude && altitude < 82345 ) { // lower stratosphere
865 p = 473.1 * pow( e , 1.73 - (0.000048 * altitude) );
866 } else { // upper stratosphere
867 T = -205.05 + (0.00164 * altitude);
868 p = 51.97 * pow( ((T + 459.7) / 389.98) , -11.388);
871 rho = p / (1718 * (T + 459.7));
873 // calculate the speed of sound at altitude
874 // a = sqrt ( g * R * (T + 459.7))
876 // a = speed of sound [ft/s]
877 // g = specific heat ratio, which is usually equal to 1.4
878 // R = specific gas constant, which equals 1716 ft-lb/slug/R
879 a = sqrt ( 1.4 * 1716 * (T + 459.7));
881 // calculate Mach number
884 // cout << "Speed(ft/s) "<< speed <<" Altitude(ft) "<< altitude << " Mach " << Mach << endl;
887 int FGAIBase::_newAIModelID() {
891 id++; // id = 0 is not allowed.
897 void FGAIModelData::modelLoaded(const string& path, SGPropertyNode *prop, osg::Node *n)
899 const char* fxpath = prop->getStringValue("sound/path");
901 string sound_path = string(fxpath);
902 if (sound_path != "") {
903 _path = "/AI/"+sound_path;
906 _nasal->modelLoaded(path, prop, n);