// David Luff's FGAIEntity class.
// - davidculp2@comcast.net
//
+// With additions by Mathias Froehlich & Vivian Meazza 2004 -2007
+//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
-// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
-#include <plib/sg.h>
-#include <plib/ssg.h>
-#include <Main/globals.hxx>
-#include <Scenery/scenery.hxx>
-#include <simgear/math/point3d.hxx>
+#include <simgear/compiler.h>
+
+#include <string>
+
+#include <osg/ref_ptr>
+#include <osg/Node>
+#include <osgDB/FileUtils>
+
+#include <simgear/math/SGMath.hxx>
#include <simgear/misc/sg_path.hxx>
-#include <simgear/scene/model/location.hxx>
-#include <simgear/scene/model/model.hxx>
+#include <simgear/scene/model/modellib.hxx>
+#include <simgear/scene/util/SGNodeMasks.hxx>
#include <simgear/debug/logstream.hxx>
-#include <string>
+#include <simgear/props/props.hxx>
+
+#include <Main/globals.hxx>
+#include <Scenery/scenery.hxx>
+#include <Scripting/NasalSys.hxx>
#include "AIBase.hxx"
+#include "AIManager.hxx"
+
+const char *default_model = "Models/Geometry/glider.ac";
+const double FGAIBase::e = 2.71828183;
+const double FGAIBase::lbs_to_slugs = 0.031080950172; //conversion factor
+
+using namespace simgear;
+
+FGAIBase::FGAIBase(object_type ot) :
+ props( NULL ),
+ model_removed( fgGetNode("/ai/models/model-removed", true) ),
+ manager( NULL ),
+ fp( NULL ),
+
+ _impact_lat(0),
+ _impact_lon(0),
+ _impact_elev(0),
+ _impact_hdg(0),
+ _impact_pitch(0),
+ _impact_roll(0),
+ _impact_speed(0),
+
+ _refID( _newAIModelID() ),
+ _otype(ot),
+ _initialized(false)
+{
+ tgt_heading = hdg = tgt_altitude_ft = tgt_speed = 0.0;
+ tgt_roll = roll = tgt_pitch = tgt_yaw = tgt_vs = vs = pitch = 0.0;
+ bearing = elevation = range = rdot = 0.0;
+ x_shift = y_shift = rotation = 0.0;
+ in_range = false;
+ invisible = false;
+ no_roll = true;
+ life = 900;
+ delete_me = false;
+ _impact_reported = false;
+ _collision_reported = false;
+ _subID = 0;
+
+ _x_offset = 0;
+ _y_offset = 0;
+ _z_offset = 0;
+
+ _pitch_offset = 0;
+ _roll_offset = 0;
+ _yaw_offset = 0;
+
+ userpos = SGGeod::fromDeg(0, 0);
+
+ pos = SGGeod::fromDeg(0, 0);
+ speed = 0;
+ altitude_ft = 0;
+ speed_north_deg_sec = 0;
+ speed_east_deg_sec = 0;
+ turn_radius_ft = 0;
+
+ ft_per_deg_lon = 0;
+ ft_per_deg_lat = 0;
+
+ horiz_offset = 0;
+ vert_offset = 0;
+ ht_diff = 0;
+
+ serviceable = false;
+
+ fp = 0;
+
+ rho = 1;
+ T = 280;
+ p = 1e5;
+ a = 340;
+ Mach = 0;
+}
FGAIBase::~FGAIBase() {
+ // Unregister that one at the scenery manager
+ if (globals->get_scenery()) {
+ globals->get_scenery()->get_scene_graph()->removeChild(aip.getSceneGraph());
+ }
+
+ if (props) {
+ SGPropertyNode* parent = props->getParent();
+
+ if (parent)
+ model_removed->setStringValue(props->getPath());
+ }
+ delete fp;
+ fp = 0;
}
-void FGAIBase::update(double dt) {
+void FGAIBase::readFromScenario(SGPropertyNode* scFileNode)
+{
+ if (!scFileNode)
+ return;
+
+ setPath(scFileNode->getStringValue("model",
+ fgGetString("/sim/multiplay/default-model", default_model)));
+
+ setHeading(scFileNode->getDoubleValue("heading", 0.0));
+ setSpeed(scFileNode->getDoubleValue("speed", 0.0));
+ setAltitude(scFileNode->getDoubleValue("altitude", 0.0));
+ setLongitude(scFileNode->getDoubleValue("longitude", 0.0));
+ setLatitude(scFileNode->getDoubleValue("latitude", 0.0));
+ setBank(scFileNode->getDoubleValue("roll", 0.0));
+
+ SGPropertyNode* submodels = scFileNode->getChild("submodels");
+
+ if (submodels) {
+ setServiceable(submodels->getBoolValue("serviceable", false));
+ setSMPath(submodels->getStringValue("path", ""));
+ }
+
}
+void FGAIBase::update(double dt) {
+
+ if (_otype == otStatic)
+ return;
+
+ if (_otype == otBallistic)
+ CalculateMach();
+
+ ft_per_deg_lat = 366468.96 - 3717.12 * cos(pos.getLatitudeRad());
+ ft_per_deg_lon = 365228.16 * cos(pos.getLatitudeRad());
+}
void FGAIBase::Transform() {
- aip.setPosition(pos.lon(), pos.lat(), pos.elev() * SG_METER_TO_FEET);
- aip.setOrientation(roll, pitch, hdg);
- aip.update( globals->get_scenery()->get_center() );
+
+ if (!invisible) {
+ aip.setVisible(true);
+ aip.setPosition(pos);
+
+ if (no_roll)
+ aip.setOrientation(0.0, pitch, hdg);
+ else
+ aip.setOrientation(roll, pitch, hdg);
+
+ aip.update();
+ } else {
+ aip.setVisible(false);
+ aip.update();
+ }
+
}
+bool FGAIBase::init(bool search_in_AI_path) {
+ osg::ref_ptr<osgDB::ReaderWriter::Options> opt=
+ new osgDB::ReaderWriter::Options(*osgDB::Registry::instance()->getOptions());
+
+ if(search_in_AI_path)
+ {
+ SGPath ai_path(globals->get_fg_root());
+ ai_path.append("AI");
+ opt->getDatabasePathList().push_front(ai_path.str());
+ }
+
+ string f = osgDB::findDataFile(model_path, opt.get());
+
+ if(f.empty())
+ f = fgGetString("/sim/multiplay/default-model", default_model);
+
+ model = load3DModel(f, props);
+
+ if (model.valid() && _initialized == false) {
+ aip.init( model.get() );
+ aip.setVisible(true);
+ invisible = false;
+ globals->get_scenery()->get_scene_graph()->addChild(aip.getSceneGraph());
+ _initialized = true;
-bool FGAIBase::init() {
- ssgBranch *model = sgLoad3DModel( globals->get_fg_root(),
- model_path.c_str(),
- globals->get_props(),
- globals->get_sim_time_sec() );
- if (model) {
- aip.init( model );
- aip.setVisible(true);
- globals->get_scenery()->get_scene_graph()->addKid(aip.getSceneGraph());
- } else {
- SG_LOG(SG_INPUT, SG_WARN, "AIBase: Could not load aircraft model.");
- }
+ } else if (!model_path.empty()) {
+ SG_LOG(SG_INPUT, SG_WARN, "AIBase: Could not load model " << model_path);
+ }
- tgt_roll = tgt_pitch = tgt_yaw = tgt_vs = vs = roll = pitch = 0.0;
+ setDie(false);
+ return true;
}
+void FGAIBase::initModel(osg::Node *node)
+{
+ if (model.valid()) {
-void FGAIBase::setPath( const char* model ) {
- model_path.append(model);
+ fgSetString("/ai/models/model-added", props->getPath().c_str());
+
+ } else if (!model_path.empty()) {
+ SG_LOG(SG_INPUT, SG_WARN, "AIBase: Could not load model " << model_path);
+ }
+
+ props->setStringValue("submodels/path", _path.c_str());
+ setDie(false);
}
-void FGAIBase::setSpeed( double speed_KTAS ) {
- speed = tgt_speed = speed_KTAS;
+
+osg::Node* FGAIBase::load3DModel(const string &path, SGPropertyNode *prop_root)
+{
+ model = SGModelLib::loadPagedModel(path, prop_root, new FGNasalModelData(prop_root));
+ initModel(model.get());
+ return model.get();
}
-void FGAIBase::setAltitude( double altitude_ft ) {
- altitude = tgt_altitude = altitude_ft;
- pos.setelev(altitude * 0.3048);
+bool FGAIBase::isa( object_type otype ) {
+ return otype == _otype;
}
-void FGAIBase::setLongitude( double longitude ) {
- pos.setlon(longitude);
+
+void FGAIBase::bind() {
+ props->tie("id", SGRawValueMethods<FGAIBase,int>(*this,
+ &FGAIBase::getID));
+ props->tie("velocities/true-airspeed-kt", SGRawValuePointer<double>(&speed));
+ props->tie("velocities/vertical-speed-fps",
+ SGRawValueMethods<FGAIBase,double>(*this,
+ &FGAIBase::_getVS_fps,
+ &FGAIBase::_setVS_fps));
+
+ props->tie("position/altitude-ft",
+ SGRawValueMethods<FGAIBase,double>(*this,
+ &FGAIBase::_getAltitude,
+ &FGAIBase::_setAltitude));
+ props->tie("position/latitude-deg",
+ SGRawValueMethods<FGAIBase,double>(*this,
+ &FGAIBase::_getLatitude,
+ &FGAIBase::_setLatitude));
+ props->tie("position/longitude-deg",
+ SGRawValueMethods<FGAIBase,double>(*this,
+ &FGAIBase::_getLongitude,
+ &FGAIBase::_setLongitude));
+
+ props->tie("position/global-x",
+ SGRawValueMethods<FGAIBase,double>(*this,
+ &FGAIBase::_getCartPosX,
+ 0));
+ props->tie("position/global-y",
+ SGRawValueMethods<FGAIBase,double>(*this,
+ &FGAIBase::_getCartPosY,
+ 0));
+ props->tie("position/global-z",
+ SGRawValueMethods<FGAIBase,double>(*this,
+ &FGAIBase::_getCartPosZ,
+ 0));
+ props->tie("callsign",
+ SGRawValueMethods<FGAIBase,const char*>(*this,
+ &FGAIBase::_getCallsign,
+ 0));
+
+ props->tie("orientation/pitch-deg", SGRawValuePointer<double>(&pitch));
+ props->tie("orientation/roll-deg", SGRawValuePointer<double>(&roll));
+ props->tie("orientation/true-heading-deg", SGRawValuePointer<double>(&hdg));
+
+ props->tie("radar/in-range", SGRawValuePointer<bool>(&in_range));
+ props->tie("radar/bearing-deg", SGRawValuePointer<double>(&bearing));
+ props->tie("radar/elevation-deg", SGRawValuePointer<double>(&elevation));
+ props->tie("radar/range-nm", SGRawValuePointer<double>(&range));
+ props->tie("radar/h-offset", SGRawValuePointer<double>(&horiz_offset));
+ props->tie("radar/v-offset", SGRawValuePointer<double>(&vert_offset));
+ props->tie("radar/x-shift", SGRawValuePointer<double>(&x_shift));
+ props->tie("radar/y-shift", SGRawValuePointer<double>(&y_shift));
+ props->tie("radar/rotation", SGRawValuePointer<double>(&rotation));
+ props->tie("radar/ht-diff-ft", SGRawValuePointer<double>(&ht_diff));
+ props->tie("subID", SGRawValuePointer<int>(&_subID));
+ props->tie("controls/lighting/nav-lights",
+ SGRawValueFunctions<bool>(_isNight));
+ props->setBoolValue("controls/lighting/beacon", true);
+ props->setBoolValue("controls/lighting/strobe", true);
+ props->setBoolValue("controls/glide-path", true);
+
+ props->setStringValue("controls/flight/lateral-mode", "roll");
+ props->setDoubleValue("controls/flight/target-hdg", hdg);
+ props->setDoubleValue("controls/flight/target-roll", roll);
+
+ props->setStringValue("controls/flight/longitude-mode", "alt");
+ props->setDoubleValue("controls/flight/target-alt", altitude_ft);
+ props->setDoubleValue("controls/flight/target-pitch", pitch);
+
+ props->setDoubleValue("controls/flight/target-spd", speed);
+
}
-void FGAIBase::setLatitude( double latitude ) {
- pos.setlat(latitude);
+void FGAIBase::unbind() {
+ props->untie("id");
+ props->untie("velocities/true-airspeed-kt");
+ props->untie("velocities/vertical-speed-fps");
+
+ props->untie("position/altitude-ft");
+ props->untie("position/latitude-deg");
+ props->untie("position/longitude-deg");
+ props->untie("position/global-x");
+ props->untie("position/global-y");
+ props->untie("position/global-z");
+ props->untie("callsign");
+
+ props->untie("orientation/pitch-deg");
+ props->untie("orientation/roll-deg");
+ props->untie("orientation/true-heading-deg");
+
+ props->untie("radar/in-range");
+ props->untie("radar/bearing-deg");
+ props->untie("radar/elevation-deg");
+ props->untie("radar/range-nm");
+ props->untie("radar/h-offset");
+ props->untie("radar/v-offset");
+ props->untie("radar/x-shift");
+ props->untie("radar/y-shift");
+ props->untie("radar/rotation");
+ props->untie("radar/ht-diff-ft");
+
+ props->untie("controls/lighting/nav-lights");
+
+ props->setBoolValue("/sim/controls/radar/", true);
+
}
-void FGAIBase::setHeading( double heading ) {
- hdg = tgt_heading = heading;
+double FGAIBase::UpdateRadar(FGAIManager* manager) {
+ bool control = fgGetBool("/sim/controls/radar", true);
+
+ if(!control) return 0;
+
+ double radar_range_ft2 = fgGetDouble("/instrumentation/radar/range");
+ bool force_on = fgGetBool("/instrumentation/radar/debug-mode", false);
+ radar_range_ft2 *= SG_NM_TO_METER * SG_METER_TO_FEET * 1.1; // + 10%
+ radar_range_ft2 *= radar_range_ft2;
+
+ double user_latitude = manager->get_user_latitude();
+ double user_longitude = manager->get_user_longitude();
+ double lat_range = fabs(pos.getLatitudeDeg() - user_latitude) * ft_per_deg_lat;
+ double lon_range = fabs(pos.getLongitudeDeg() - user_longitude) * ft_per_deg_lon;
+ double range_ft2 = lat_range*lat_range + lon_range*lon_range;
+
+ //
+ // Test whether the target is within radar range.
+ //
+ in_range = (range_ft2 && (range_ft2 <= radar_range_ft2));
+
+ if ( in_range || force_on ) {
+ props->setBoolValue("radar/in-range", true);
+
+ // copy values from the AIManager
+ double user_altitude = manager->get_user_altitude();
+ double user_heading = manager->get_user_heading();
+ double user_pitch = manager->get_user_pitch();
+ //double user_yaw = manager->get_user_yaw();
+ //double user_speed = manager->get_user_speed();
+
+ // calculate range to target in feet and nautical miles
+ double range_ft = sqrt( range_ft2 );
+ range = range_ft / 6076.11549;
+
+ // calculate bearing to target
+ if (pos.getLatitudeDeg() >= user_latitude) {
+ bearing = atan2(lat_range, lon_range) * SG_RADIANS_TO_DEGREES;
+ if (pos.getLongitudeDeg() >= user_longitude) {
+ bearing = 90.0 - bearing;
+ } else {
+ bearing = 270.0 + bearing;
+ }
+ } else {
+ bearing = atan2(lon_range, lat_range) * SG_RADIANS_TO_DEGREES;
+ if (pos.getLongitudeDeg() >= user_longitude) {
+ bearing = 180.0 - bearing;
+ } else {
+ bearing = 180.0 + bearing;
+ }
+ }
+
+ // This is an alternate way to compute bearing and distance which
+ // agrees with the original scheme within about 0.1 degrees.
+ //
+ // Point3D start( user_longitude * SGD_DEGREES_TO_RADIANS,
+ // user_latitude * SGD_DEGREES_TO_RADIANS, 0 );
+ // Point3D dest( pos.getLongitudeRad(), pos.getLatitudeRad(), 0 );
+ // double gc_bearing, gc_range;
+ // calc_gc_course_dist( start, dest, &gc_bearing, &gc_range );
+ // gc_range *= SG_METER_TO_NM;
+ // gc_bearing *= SGD_RADIANS_TO_DEGREES;
+ // printf("orig b = %.3f %.2f gc b= %.3f, %.2f\n",
+ // bearing, range, gc_bearing, gc_range);
+
+ // calculate look left/right to target, without yaw correction
+ horiz_offset = bearing - user_heading;
+ if (horiz_offset > 180.0) horiz_offset -= 360.0;
+ if (horiz_offset < -180.0) horiz_offset += 360.0;
+
+ // calculate elevation to target
+ elevation = atan2( altitude_ft - user_altitude, range_ft ) * SG_RADIANS_TO_DEGREES;
+
+ // calculate look up/down to target
+ vert_offset = elevation - user_pitch;
+
+ /* this calculation needs to be fixed, but it isn't important anyway
+ // calculate range rate
+ double recip_bearing = bearing + 180.0;
+ if (recip_bearing > 360.0) recip_bearing -= 360.0;
+ double my_horiz_offset = recip_bearing - hdg;
+ if (my_horiz_offset > 180.0) my_horiz_offset -= 360.0;
+ if (my_horiz_offset < -180.0) my_horiz_offset += 360.0;
+ rdot = (-user_speed * cos( horiz_offset * SG_DEGREES_TO_RADIANS ))
+ +(-speed * 1.686 * cos( my_horiz_offset * SG_DEGREES_TO_RADIANS ));
+ */
+
+ // now correct look left/right for yaw
+ // horiz_offset += user_yaw; // FIXME: WHY WOULD WE WANT TO ADD IN SIDE-SLIP HERE?
+
+ // calculate values for radar display
+ y_shift = range * cos( horiz_offset * SG_DEGREES_TO_RADIANS);
+ x_shift = range * sin( horiz_offset * SG_DEGREES_TO_RADIANS);
+ rotation = hdg - user_heading;
+ if (rotation < 0.0) rotation += 360.0;
+ ht_diff = altitude_ft - user_altitude;
+
+ }
+
+ return range_ft2;
}
-void FGAIBase::setDie( bool die ) {
- delete_me = die;
+/*
+* Getters and Setters
+*/
+
+SGVec3d FGAIBase::getCartPosAt(const SGVec3d& _off) const {
+ // Transform that one to the horizontal local coordinate system.
+ SGQuatd hlTrans = SGQuatd::fromLonLat(pos);
+
+ // and postrotate the orientation of the AIModel wrt the horizontal
+ // local frame
+ hlTrans *= SGQuatd::fromYawPitchRollDeg(hdg, pitch, roll);
+
+ // The offset converted to the usual body fixed coordinate system
+ // rotated to the earth fiexed coordinates axis
+ SGVec3d off = hlTrans.backTransform(_off);
+
+ // Add the position offset of the AIModel to gain the earth centered position
+ SGVec3d cartPos = SGVec3d::fromGeod(pos);
+
+ return cartPos + off;
+}
+
+SGVec3d FGAIBase::getCartPos() const {
+ SGVec3d cartPos = SGVec3d::fromGeod(pos);
+ return cartPos;
+}
+
+bool FGAIBase::getGroundElevationM(const SGGeod& pos, double& elev,
+ const SGMaterial** material) const {
+ return globals->get_scenery()->get_elevation_m(pos, elev, material,
+ model.get());
+}
+
+double FGAIBase::_getCartPosX() const {
+ SGVec3d cartPos = getCartPos();
+ return cartPos.x();
+}
+
+double FGAIBase::_getCartPosY() const {
+ SGVec3d cartPos = getCartPos();
+ return cartPos.y();
+}
+
+double FGAIBase::_getCartPosZ() const {
+ SGVec3d cartPos = getCartPos();
+ return cartPos.z();
+}
+
+void FGAIBase::_setLongitude( double longitude ) {
+ pos.setLongitudeDeg(longitude);
+}
+
+void FGAIBase::_setLatitude ( double latitude ) {
+ pos.setLatitudeDeg(latitude);
+}
+
+void FGAIBase::_setUserPos(){
+ userpos.setLatitudeDeg(manager->get_user_latitude());
+ userpos.setLongitudeDeg(manager->get_user_longitude());
+ userpos.setElevationM(manager->get_user_altitude() * SG_FEET_TO_METER);
+}
+
+void FGAIBase::_setSubID( int s ) {
+ _subID = s;
+}
+
+double FGAIBase::_getLongitude() const {
+ return pos.getLongitudeDeg();
+}
+
+double FGAIBase::_getLatitude() const {
+ return pos.getLatitudeDeg();
+}
+
+double FGAIBase::_getElevationFt () const {
+ return pos.getElevationFt();
+}
+
+double FGAIBase::_getRdot() const {
+ return rdot;
+}
+
+double FGAIBase::_getVS_fps() const {
+ return vs*60.0;
+}
+
+double FGAIBase::_get_speed_east_fps() const {
+ return speed_east_deg_sec * ft_per_deg_lon;
+}
+
+double FGAIBase::_get_speed_north_fps() const {
+ return speed_north_deg_sec * ft_per_deg_lat;
+}
+
+void FGAIBase::_setVS_fps( double _vs ) {
+ vs = _vs/60.0;
+}
+
+double FGAIBase::_getAltitude() const {
+ return altitude_ft;
+}
+
+bool FGAIBase::_getServiceable() const {
+ return serviceable;
+}
+
+SGPropertyNode* FGAIBase::_getProps() const {
+ return props;
+}
+
+void FGAIBase::_setAltitude( double _alt ) {
+ setAltitude( _alt );
+}
+
+bool FGAIBase::_isNight() {
+ return (fgGetFloat("/sim/time/sun-angle-rad") > 1.57);
+}
+
+bool FGAIBase::_getCollisionData() {
+ return _collision_reported;
+}
+
+bool FGAIBase::_getImpactData() {
+ return _impact_reported;
+}
+
+double FGAIBase::_getImpactLat() const {
+ return _impact_lat;
+}
+
+double FGAIBase::_getImpactLon() const {
+ return _impact_lon;
+}
+
+double FGAIBase::_getImpactElevFt() const {
+ return _impact_elev * SG_METER_TO_FEET;
+}
+
+double FGAIBase::_getImpactPitch() const {
+ return _impact_pitch;
+}
+
+double FGAIBase::_getImpactRoll() const {
+ return _impact_roll;
+}
+
+double FGAIBase::_getImpactHdg() const {
+ return _impact_hdg;
+}
+
+double FGAIBase::_getImpactSpeed() const {
+ return _impact_speed;
+}
+
+int FGAIBase::getID() const {
+ return _refID;
+}
+
+int FGAIBase::_getSubID() const {
+ return _subID;
+}
+
+double FGAIBase::_getSpeed() const {
+ return speed;
+}
+
+double FGAIBase::_getRoll() const {
+ return roll;
+}
+
+double FGAIBase::_getPitch() const {
+ return pitch;
+}
+
+double FGAIBase::_getHeading() const {
+ return hdg;
+}
+
+double FGAIBase::_getXOffset() const {
+ return _x_offset;
+}
+
+double FGAIBase::_getYOffset() const {
+ return _y_offset;
+}
+
+double FGAIBase::_getZOffset() const {
+ return _z_offset;
+}
+
+const char* FGAIBase::_getPath() const {
+ return model_path.c_str();
+}
+
+const char* FGAIBase::_getSMPath() const {
+ return _path.c_str();
+}
+
+const char* FGAIBase::_getName() const {
+ return _name.c_str();
+}
+
+const char* FGAIBase::_getCallsign() const {
+ return _callsign.c_str();
+}
+
+const char* FGAIBase::_getSubmodel() const {
+ return _submodel.c_str();
+}
+
+void FGAIBase::CalculateMach() {
+ // Calculate rho at altitude, using standard atmosphere
+ // For the temperature T and the pressure p,
+ double altitude = altitude_ft;
+
+ if (altitude < 36152) { // curve fits for the troposphere
+ T = 59 - 0.00356 * altitude;
+ p = 2116 * pow( ((T + 459.7) / 518.6) , 5.256);
+ } else if ( 36152 < altitude && altitude < 82345 ) { // lower stratosphere
+ T = -70;
+ p = 473.1 * pow( e , 1.73 - (0.000048 * altitude) );
+ } else { // upper stratosphere
+ T = -205.05 + (0.00164 * altitude);
+ p = 51.97 * pow( ((T + 459.7) / 389.98) , -11.388);
+ }
+
+ rho = p / (1718 * (T + 459.7));
+
+ // calculate the speed of sound at altitude
+ // a = sqrt ( g * R * (T + 459.7))
+ // where:
+ // a = speed of sound [ft/s]
+ // g = specific heat ratio, which is usually equal to 1.4
+ // R = specific gas constant, which equals 1716 ft-lb/slug/R
+ a = sqrt ( 1.4 * 1716 * (T + 459.7));
+
+ // calculate Mach number
+ Mach = speed/a;
+
+ // cout << "Speed(ft/s) "<< speed <<" Altitude(ft) "<< altitude << " Mach " << Mach << endl;
+}
+
+int FGAIBase::_newAIModelID() {
+ static int id = 0;
+
+ if (!++id)
+ id++; // id = 0 is not allowed.
+
+ return id;
}