fix a segmentation fault situation that is exposed at least on IRIX (but not Linux).

[flightgear.git] / src / AIModel / AIBallistic.cxx

diff --git a/src/AIModel/AIBallistic.cxx b/src/AIModel/AIBallistic.cxx
index 2d96b7c750014cd85ba84514920f2f443b13f8c5..d3ea25a1be4828b187902b1b96105e3f3e666923 100644 (file)
--- a/src/AIModel/AIBallistic.cxx
+++ b/src/AIModel/AIBallistic.cxx
@@ -27,7 +27,16 @@
 #include "AIBallistic.hxx"
 
 
-FGAIBallistic::FGAIBallistic() {
+
+FGAIBallistic::FGAIBallistic(FGAIManager* mgr) {
+    manager = mgr;
+    _type_str = "ballistic";
+    _otype = otBallistic;
+    drag_area = 0.007;
+    life_timer = 0.0;
+    gravity = 32;
+//  buoyancy = 64;
+    no_roll = false;
 }
 
 FGAIBallistic::~FGAIBallistic() {
@@ -36,82 +45,147 @@ FGAIBallistic::~FGAIBallistic() {
 
 bool FGAIBallistic::init() {
    FGAIBase::init();
-   vs = sin( elevation * 0.017453293 ) * speed;
-   hs = cos( elevation * 0.017453293 ) * speed;
-   aero_stabilized =  true;
+   aero_stabilized = true;
    hdg = azimuth;
    pitch = elevation;
+   roll = rotation;
+   Transform();
    return true;
 }
 
+void FGAIBallistic::bind() {
+//    FGAIBase::bind();
+   props->tie("sim/time/elapsed-sec",
+               SGRawValueMethods<FGAIBallistic,double>(*this,
+                                          &FGAIBallistic::_getTime));
+}
 
-void FGAIBallistic::update(double dt) {
+void FGAIBallistic::unbind() {
+//    FGAIBase::unbind();
+   props->untie("sim/time/elapsed-sec");
+}
 
+void FGAIBallistic::update(double dt) {
+   FGAIBase::update(dt);
    Run(dt);
    Transform();
-   FGAIBase::update(dt);
 }
 
 
 void FGAIBallistic::setAzimuth(double az) {
-   azimuth = az;
+   hdg = azimuth = az;
 }
 
 
 void FGAIBallistic::setElevation(double el) {
-   elevation = el;
+   pitch = elevation = el;
 }
 
+void FGAIBallistic::setRoll(double rl) {
+   rotation = rl;
+}
 
 void FGAIBallistic::setStabilization(bool val) {
    aero_stabilized = val;
 }
 
+void FGAIBallistic::setDragArea(double a) {
+   drag_area = a;
+}
+
+void FGAIBallistic::setLife(double seconds) {
+   life = seconds;
+}
+
+void FGAIBallistic::setBuoyancy(double fpss) {
+   buoyancy = fpss;
+}
+
+void FGAIBallistic::setWind_from_east(double fps) {
+   wind_from_east = fps;
+}
+
+void FGAIBallistic::setWind_from_north(double fps) {
+   wind_from_north = fps;
+}
+
+void FGAIBallistic::setWind(bool val) {
+   wind = val;
+}
+
+void FGAIBallistic::setCd(double c) {
+   Cd = c;
+}
+
+void FGAIBallistic::setWeight(double w) {
+   weight = w;
+}
 
 void FGAIBallistic::Run(double dt) {
+   life_timer += dt;
+   if (life_timer > life) setDie(true); 
 
    double speed_north_deg_sec;
    double speed_east_deg_sec;
-   double ft_per_deg_lon;
-   double ft_per_deg_lat;
-
-   // get size of a degree at this latitude
-   ft_per_deg_lat = 366468.96 - 3717.12 * cos(pos.lat() / 57.2958 );
-   ft_per_deg_lon = 365228.16 * cos(pos.lat() / 57.2958);
-
-   // the two drag calculations below assume sea-level density, 
-   // mass of 0.03 slugs,  drag coeff of 0.295, frontal area of 0.007 ft2 
-   // adjust horizontal speed due to drag 
-   hs -= 0.000082 * hs * hs * dt;
-   if ( hs < 0.0 ) hs = 0.0;
-
-   // adjust vertical speed due to drag
-   if (vs > 0.0) {
-     vs -= 0.000082 * vs * vs * dt;
-   } else {
-     vs += 0.000082 * vs * vs * dt;
-   }
+   double wind_speed_from_north_deg_sec;
+   double wind_speed_from_east_deg_sec;
+   double mass;
+      
+   // the drag calculations below assume sea-level density,
+   // rho = 0.023780  slugs/ft3
+   // calculate mass
+   mass = weight * lbs_to_slugs;
    
-   // convert horizontal speed (fps) to degrees per second
-   speed_north_deg_sec = cos( hdg / 57.29577951 ) * hs / ft_per_deg_lat;
-   speed_east_deg_sec  = sin( hdg / 57.29577951 ) * hs / ft_per_deg_lon;
+   // drag = Cd * 0.5 * rho * speed * speed * drag_area;
+   // acceleration = drag/mass;
+   // adjust speed by drag
+   speed -= (Cd * 0.5 * rho * speed * speed * drag_area/mass) * dt; 
 
+   // don't let speed become negative
+   if ( speed < 0.0 ) speed = 0.0;
+   
+   // calculate vertical and horizontal speed components
+   vs = sin( pitch * SG_DEGREES_TO_RADIANS ) * speed;
+   hs = cos( pitch * SG_DEGREES_TO_RADIANS ) * speed;
+
+   // convert horizontal speed (fps) to degrees per second
+   speed_north_deg_sec = cos(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lat;
+   speed_east_deg_sec  = sin(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lon;
+   
+   // if wind not required, set to zero
+   if (!wind){
+      wind_from_north = 0;
+      wind_from_east = 0;
+   }
+  
+   // convert wind speed (fps) to degrees per second
+   wind_speed_from_north_deg_sec = wind_from_north / ft_per_deg_lat;
+   wind_speed_from_east_deg_sec  = wind_from_east / ft_per_deg_lon;
+   
    // set new position
-   pos.setlat( pos.lat() + speed_north_deg_sec * dt);
-   pos.setlon( pos.lon() + speed_east_deg_sec * dt); 
+   pos.setlat( pos.lat() + (speed_north_deg_sec - wind_speed_from_north_deg_sec) * dt );
+   pos.setlon( pos.lon() + (speed_east_deg_sec - wind_speed_from_east_deg_sec) * dt ); 
 
-   // adjust vertical speed for acceleration of gravity
-   vs -= 32.17 * dt;
+   // adjust vertical speed for acceleration of gravity and buoyancy
+   vs -= (gravity - buoyancy) * dt;
+   
+   // adjust altitude (feet)
+   altitude += vs * dt;
+   pos.setelev(altitude * SG_FEET_TO_METER); 
 
-   // adjust altitude (meters)
-   altitude += vs * dt * 0.3048;
-   pos.setelev(altitude); 
+   // recalculate pitch (velocity vector) if aerostabilized
+   if (aero_stabilized) pitch = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
 
-   // adjust pitch if aerostabilized
-   if (aero_stabilized) pitch = atan2( vs, hs ) * 57.29577951;
+   // recalculate total speed
+   speed = sqrt( vs * vs + hs * hs);
 
    // set destruction flag if altitude less than sea level -1000
    if (altitude < -1000.0) setDie(true);
 
+}  // end Run
+
+double FGAIBallistic::_getTime() const {
+   return life_timer;
 }
 
+// end AIBallistic