X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FFDM%2Fflight.cxx;h=0e4ff912a3948a99ffce66c9a298993d110eae60;hb=a99ea1c7b5fb0ba69810bbad9b6aca8b4cdc116b;hp=3f98f3bb715faf632ec63df65cdb183ad3985506;hpb=b86e6ddc11afe0578fff207e74a20abe8a053c23;p=flightgear.git

diff --git a/src/FDM/flight.cxx b/src/FDM/flight.cxx
index 3f98f3bb7..0e4ff912a 100644
--- a/src/FDM/flight.cxx
+++ b/src/FDM/flight.cxx
@@ -1,8 +1,8 @@
-// flight.c -- a general interface to the various flight models
+// flight.cxx -- a general interface to the various flight models
 //
 // Written by Curtis Olson, started May 1997.
 //
-// Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
+// Copyright (C) 1997  Curtis L. Olson  - http://www.flightgear.org/~curt
 //
 // This program is free software; you can redistribute it and/or
 // modify it under the terms of the GNU General Public License as
@@ -16,207 +16,916 @@
 //
 // 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.
 //
 // $Id$
 
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
 
-#include <stdio.h>
+#include "flight.hxx"
 
-#include <Debug/logstream.hxx>
-#include <FDM/External/external.hxx>
-#include <FDM/LaRCsim/ls_interface.h>
-#include <Include/fg_constants.h>
-#include <Main/options.hxx>
-#include <Math/fg_geodesy.hxx>
-#include <Time/timestamp.hxx>
+#include <simgear/constants.h>
+#include <simgear/debug/logstream.hxx>
+#include <simgear/math/SGMath.hxx>
+#include <simgear/timing/timestamp.hxx>
 
-#include "flight.hxx"
-#include "JSBsim.hxx"
-#include "LaRCsim.hxx"
+#include <Scenery/scenery.hxx>
+#include <Main/globals.hxx>
+#include <Main/fg_props.hxx>
+#include <FDM/groundcache.hxx>
 
 
+static inline void assign(double* ptr, const SGVec3d& vec)
+{
+  ptr[0] = vec[0];
+  ptr[1] = vec[1];
+  ptr[2] = vec[2];
+}
+
 // base_fdm_state is the internal state that is updated in integer
 // multiples of "dt".  This leads to "jitter" with respect to the real
 // world time, so we introduce cur_fdm_state which is extrapolated by
 // the difference between sim time and real world time
 
-FGInterface * cur_fdm_state;
+FGInterface *cur_fdm_state = 0;
 FGInterface base_fdm_state;
 
-
-int FGInterface::init( double dt ) {
-    cout << "dummy init() ... SHOULDN'T BE CALLED!" << endl;
-    return 0;
+// Constructor
+FGInterface::FGInterface()
+  : remainder(0)
+{
+    _setup();
 }
 
-int FGInterface::update( int multi_loop ) {
-    cout << "dummy update() ... SHOULDN'T BE CALLED!" << endl;
-    return 0;
+FGInterface::FGInterface( double dt )
+  : remainder(0)
+{
+    _setup();
 }
 
+// Destructor
 FGInterface::~FGInterface() {
+    // unbind();                   // FIXME: should be called explicitly
 }
 
-// Extrapolate fdm based on time_offset (in usec)
-void FGInterface::extrapolate( int time_offset ) {
-    double dt = time_offset / 1000000.0;
 
-    // -dw- metrowerks complains about ambiguous access, not critical
-    // to keep this ;)
-#ifndef __MWERKS__
-    cout << "extrapolating FDM by dt = " << dt << endl;
-#endif
+int
+FGInterface::_calc_multiloop (double dt)
+{
+  int hz = fgGetInt("/sim/model-hz");
+  int speedup = fgGetInt("/sim/speed-up");
+
+  dt += remainder;
+  remainder = 0;
+  double ml = dt * hz;
+  // Avoid roundoff problems by adding the roundoff itself.
+  // ... ok, two times the roundoff to have enough room.
+  int multiloop = int(floor(ml * (1.0 + 2.0*DBL_EPSILON)));
+  remainder = (ml - multiloop) / hz;
+
+  // If we artificially inflate ml above by a tiny amount to get the
+  // closest integer, then subtract the integer from the original
+  // slightly smaller value, we can get a negative remainder.
+  // Logically this should never happen, and we definitely don't want
+  // to carry a negative remainder over to the next iteration, so
+  // never let the remainder go below zero.
+  // 
+  // Note: this fixes a problem where we run 1, 3, 1, 3, 1, 3... loops
+  // of the FDM when in fact we want to run 2, 2, 2, 2, 2...
+  if ( remainder < 0 ) { remainder = 0; }
+
+  return (multiloop * speedup);
+}
 
-    double lat = geodetic_position_v[0] + geocentric_rates_v[0] * dt;
-    double lat_geoc = geocentric_position_v[0] + geocentric_rates_v[0] * dt;
 
-    double lon = geodetic_position_v[1] + geocentric_rates_v[1] * dt;
-    double lon_geoc = geocentric_position_v[1] + geocentric_rates_v[1] * dt;
+/**
+ * Set default values for the state of the FDM.
+ *
+ * This method is invoked by the constructors.
+ */
+void
+FGInterface::_setup ()
+{
+    inited = false;
+    bound = false;
+
+    d_cg_rp_body_v = SGVec3d::zeros();
+    v_dot_local_v = SGVec3d::zeros();
+    v_dot_body_v = SGVec3d::zeros();
+    a_cg_body_v = SGVec3d::zeros();
+    a_pilot_body_v = SGVec3d::zeros();
+    n_cg_body_v = SGVec3d::zeros();
+    v_local_v = SGVec3d::zeros();
+    v_local_rel_ground_v = SGVec3d::zeros();
+    v_local_airmass_v = SGVec3d::zeros();
+    v_wind_body_v = SGVec3d::zeros();
+    omega_body_v = SGVec3d::zeros();
+    euler_rates_v = SGVec3d::zeros();
+    geocentric_rates_v = SGVec3d::zeros();
+    geodetic_position_v = SGGeod::fromRadM(0, 0, 0);
+    cartesian_position_v = SGVec3d::fromGeod(geodetic_position_v);
+    geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);
+    euler_angles_v = SGVec3d::zeros();
+    
+    nlf=0;
+    v_rel_wind=v_true_kts=0;
+    v_ground_speed=v_equiv_kts=0;
+    v_calibrated_kts=0;
+    alpha=beta=0;
+    gamma_vert_rad=0;
+    density=mach_number=0;
+    static_pressure=total_pressure=0;
+    dynamic_pressure=0;
+    static_temperature=total_temperature=0;
+    sea_level_radius=earth_position_angle=0;
+    runway_altitude=0;
+    climb_rate=0;
+    altitude_agl=0;
+}
 
-    double alt = geodetic_position_v[2] + geocentric_rates_v[2] * dt;
-    double radius = geocentric_position_v[2] + geocentric_rates_v[2] * dt;
+void
+FGInterface::init () {}
+
+/**
+ * Initialize the state of the FDM.
+ *
+ * Subclasses of FGInterface may do their own, additional initialization,
+ * but there is some that is common to all.  Normally, they should call
+ * this before they begin their own init to make sure the basic structures
+ * are set up properly.
+ */
+void
+FGInterface::common_init ()
+{
+    SG_LOG( SG_FLIGHT, SG_INFO, "Start common FDM init" );
+
+    set_inited( true );
+
+    ground_cache.set_cache_time_offset(globals->get_sim_time_sec());
+
+//     stamp();
+//     set_remainder( 0 );
+
+    // Set initial position
+    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing position..." );
+    double lon = fgGetDouble("/sim/presets/longitude-deg")
+      * SGD_DEGREES_TO_RADIANS;
+    double lat = fgGetDouble("/sim/presets/latitude-deg")
+      * SGD_DEGREES_TO_RADIANS;
+    double alt_ft = fgGetDouble("/sim/presets/altitude-ft");
+    double alt_m = alt_ft * SG_FEET_TO_METER;
+    set_Longitude( lon );
+    set_Latitude( lat );
+    SG_LOG( SG_FLIGHT, SG_INFO, "Checking for lon = "
+            << lon*SGD_RADIANS_TO_DEGREES << "deg, lat = "
+            << lat*SGD_RADIANS_TO_DEGREES << "deg, alt = "
+            << alt_ft << "ft");
+
+    double ground_elev_m = get_groundlevel_m(lat, lon, alt_m);
+    double ground_elev_ft = ground_elev_m * SG_METER_TO_FEET;
+    _set_Runway_altitude ( ground_elev_ft );
+    if ( fgGetBool("/sim/presets/onground") || alt_ft < ground_elev_ft ) {
+        fgSetDouble("/position/altitude-ft", ground_elev_ft + 0.1);
+        set_Altitude( ground_elev_ft + 0.1);
+    } else {
+        set_Altitude( alt_ft );
+    }
 
-    geodetic_position_v[0] = lat;
-    geocentric_position_v[0] = lat_geoc;
+    // Set ground elevation
+    SG_LOG( SG_FLIGHT, SG_INFO,
+            "...initializing ground elevation to " << ground_elev_ft
+            << "ft..." );
+
+    // Set sea-level radius
+    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing sea-level radius..." );
+    SG_LOG( SG_FLIGHT, SG_INFO, " lat = "
+            << fgGetDouble("/sim/presets/latitude-deg")
+            << " alt = " << get_Altitude() );
+    double slr = SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v);
+    _set_Sea_level_radius( slr * SG_METER_TO_FEET );
+
+    // Set initial velocities
+    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing velocities..." );
+    if ( !fgHasNode("/sim/presets/speed-set") ) {
+        set_V_calibrated_kts(0.0);
+    } else {
+        const string speedset = fgGetString("/sim/presets/speed-set");
+        if ( speedset == "knots" || speedset == "KNOTS" ) {
+            set_V_calibrated_kts( fgGetDouble("/sim/presets/airspeed-kt") );
+        } else if ( speedset == "mach" || speedset == "MACH" ) {
+            set_Mach_number( fgGetDouble("/sim/presets/mach") );
+        } else if ( speedset == "UVW" || speedset == "uvw" ) {
+            set_Velocities_Wind_Body(
+                                     fgGetDouble("/sim/presets/uBody-fps"),
+                                     fgGetDouble("/sim/presets/vBody-fps"),
+                                     fgGetDouble("/sim/presets/wBody-fps") );
+        } else if ( speedset == "NED" || speedset == "ned" ) {
+            set_Velocities_Local(
+                                 fgGetDouble("/sim/presets/speed-north-fps"),
+                                 fgGetDouble("/sim/presets/speed-east-fps"),
+                                 fgGetDouble("/sim/presets/speed-down-fps") );
+        } else {
+            SG_LOG( SG_FLIGHT, SG_ALERT,
+                    "Unrecognized value for /sim/presets/speed-set: "
+                    << speedset);
+            set_V_calibrated_kts( 0.0 );
+        }
+    }
 
-    geodetic_position_v[1] = lon;
-    geocentric_position_v[1] = lon_geoc;
+    // Set initial Euler angles
+    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing Euler angles..." );
+    set_Euler_Angles( fgGetDouble("/sim/presets/roll-deg")
+                        * SGD_DEGREES_TO_RADIANS,
+                      fgGetDouble("/sim/presets/pitch-deg")
+                        * SGD_DEGREES_TO_RADIANS,
+                      fgGetDouble("/sim/presets/heading-deg")
+                        * SGD_DEGREES_TO_RADIANS );
 
-    geodetic_position_v[2] = alt;
-    geocentric_position_v[2] = radius;
+    SG_LOG( SG_FLIGHT, SG_INFO, "End common FDM init" );
 }
 
 
-#if 0
-// Initialize the flight model parameters
-int fgFDMInit(int model, FGInterface& f, double dt) {
-    double save_alt = 0.0;
+/**
+ * Bind getters and setters to properties.
+ *
+ * The bind() method will be invoked after init().  Note that unlike
+ * the usual implementations of FGSubsystem::bind(), this method does
+ * not automatically pick up existing values for the properties at
+ * bind time; instead, all values are set explicitly in the init()
+ * method.
+ */
+void
+FGInterface::bind ()
+{
+  bound = true;
+
+                                // Time management (read-only)
+//   fgTie("/fdm/time/delta_t", this,
+//         &FGInterface::get_delta_t); // read-only
+//   fgTie("/fdm/time/elapsed", this,
+//         &FGInterface::get_elapsed); // read-only
+//   fgTie("/fdm/time/remainder", this,
+//         &FGInterface::get_remainder); // read-only
+//   fgTie("/fdm/time/multi_loop", this,
+//         &FGInterface::get_multi_loop); // read-only
+
+			// Aircraft position
+  fgTie("/position/latitude-deg", this,
+        &FGInterface::get_Latitude_deg,
+        &FGInterface::set_Latitude_deg,
+        false);
+  fgSetArchivable("/position/latitude-deg");
+  fgTie("/position/longitude-deg", this,
+        &FGInterface::get_Longitude_deg,
+        &FGInterface::set_Longitude_deg,
+        false);
+  fgSetArchivable("/position/longitude-deg");
+  fgTie("/position/altitude-ft", this,
+        &FGInterface::get_Altitude,
+        &FGInterface::set_Altitude,
+        false);
+  fgSetArchivable("/position/altitude-ft");
+  fgTie("/position/altitude-agl-ft", this,
+        &FGInterface::get_Altitude_AGL); // read-only
+  fgSetArchivable("/position/ground-elev-ft");
+  fgTie("/position/ground-elev-ft", this,
+        &FGInterface::get_Runway_altitude); // read-only
+  fgSetArchivable("/position/ground-elev-m");
+  fgTie("/position/ground-elev-m", this,
+        &FGInterface::get_Runway_altitude_m); // read-only
+  fgTie("/environment/ground-elevation-m", this,
+        &FGInterface::get_Runway_altitude_m); // read-only
+  fgSetArchivable("/position/sea-level-radius-ft");
+  fgTie("/position/sea-level-radius-ft", this,
+        &FGInterface::get_Sea_level_radius); // read-only
+
+				// Orientation
+  fgTie("/orientation/roll-deg", this,
+	&FGInterface::get_Phi_deg,
+	&FGInterface::set_Phi_deg);
+  fgSetArchivable("/orientation/roll-deg");
+  fgTie("/orientation/pitch-deg", this,
+	&FGInterface::get_Theta_deg,
+	&FGInterface::set_Theta_deg);
+  fgSetArchivable("/orientation/pitch-deg");
+  fgTie("/orientation/heading-deg", this,
+	&FGInterface::get_Psi_deg,
+	&FGInterface::set_Psi_deg);
+  fgSetArchivable("/orientation/heading-deg");
+
+  // Body-axis "euler rates" (rotation speed, but in a funny
+  // representation).
+  fgTie("/orientation/roll-rate-degps", this,
+	&FGInterface::get_Phi_dot_degps);
+  fgTie("/orientation/pitch-rate-degps", this,
+	&FGInterface::get_Theta_dot_degps);
+  fgTie("/orientation/yaw-rate-degps", this,
+	&FGInterface::get_Psi_dot_degps);
+
+                                // Ground speed knots
+  fgTie("/velocities/groundspeed-kt", this,
+        &FGInterface::get_V_ground_speed_kt);
+
+				// Calibrated airspeed
+  fgTie("/velocities/airspeed-kt", this,
+	&FGInterface::get_V_calibrated_kts,
+	&FGInterface::set_V_calibrated_kts,
+	false);
+
+				// Mach number
+  fgTie("/velocities/mach", this,
+	&FGInterface::get_Mach_number,
+	&FGInterface::set_Mach_number,
+	false);
+
+				// Local velocities
+//   fgTie("/velocities/speed-north-fps", this,
+// 	&FGInterface::get_V_north,
+// 	&FGInterface::set_V_north);
+//   fgSetArchivable("/velocities/speed-north-fps");
+//   fgTie("/velocities/speed-east-fps", this,
+// 	&FGInterface::get_V_east,
+// 	&FGInterface::set_V_east);
+//   fgSetArchivable("/velocities/speed-east-fps");
+//   fgTie("/velocities/speed-down-fps", this,
+// 	&FGInterface::get_V_down,
+// 	&FGInterface::set_V_down);
+//   fgSetArchivable("/velocities/speed-down-fps");
+				// FIXME: Temporarily read-only, until the
+				// incompatibilities between JSBSim and
+				// LaRCSim are fixed (LaRCSim adds the
+				// earth's rotation to the east velocity).
+  fgTie("/velocities/speed-north-fps", this,
+	&FGInterface::get_V_north);
+  fgTie("/velocities/speed-east-fps", this,
+	&FGInterface::get_V_east);
+  fgTie("/velocities/speed-down-fps", this,
+	&FGInterface::get_V_down);
+
+				// Relative wind
+				// FIXME: temporarily archivable, until
+				// the NED problem is fixed.
+  fgTie("/velocities/uBody-fps", this,
+	&FGInterface::get_uBody,
+	&FGInterface::set_uBody,
+	false);
+  fgSetArchivable("/velocities/uBody-fps");
+  fgTie("/velocities/vBody-fps", this,
+	&FGInterface::get_vBody,
+	&FGInterface::set_vBody,
+	false);
+  fgSetArchivable("/velocities/vBody-fps");
+  fgTie("/velocities/wBody-fps", this,
+	&FGInterface::get_wBody,
+	&FGInterface::set_wBody,
+	false);
+  fgSetArchivable("/velocities/wBody-fps");
+
+				// Climb and slip (read-only)
+  fgTie("/velocities/vertical-speed-fps", this,
+	&FGInterface::get_Climb_Rate,
+  &FGInterface::set_Climb_Rate ); 
+  fgTie("/velocities/glideslope", this,
+  &FGInterface::get_Gamma_vert_rad,
+  &FGInterface::set_Gamma_vert_rad );
+  fgTie("/orientation/side-slip-rad", this,
+	&FGInterface::get_Beta); // read-only
+  fgTie("/orientation/side-slip-deg", this,
+  &FGInterface::get_Beta_deg); // read-only
+  fgTie("/orientation/alpha-deg", this,
+  &FGInterface::get_Alpha_deg); // read-only
+  fgTie("/accelerations/nlf", this,
+  &FGInterface::get_Nlf); // read-only
+
+                                // NED accelerations
+  fgTie("/accelerations/ned/north-accel-fps_sec",
+        this, &FGInterface::get_V_dot_north);
+  fgTie("/accelerations/ned/east-accel-fps_sec",
+        this, &FGInterface::get_V_dot_east);
+  fgTie("/accelerations/ned/down-accel-fps_sec",
+        this, &FGInterface::get_V_dot_down);
+
+                                // Pilot accelerations
+  fgTie("/accelerations/pilot/x-accel-fps_sec",
+        this, &FGInterface::get_A_X_pilot);
+  fgTie("/accelerations/pilot/y-accel-fps_sec",
+        this, &FGInterface::get_A_Y_pilot);
+  fgTie("/accelerations/pilot/z-accel-fps_sec",
+        this, &FGInterface::get_A_Z_pilot);
 
-    FG_LOG( FG_FLIGHT ,FG_INFO, "Initializing flight model" );
+}
 
-    base_fdm_state = f;
 
-    if ( model == FGInterface::FG_SLEW ) {
-	// fgSlewInit(dt);
-#ifndef __MWERKS__   // -dw- 04/22/99 JSB sim not ported yet
-    } else if ( model == FGInterface::FG_JSBSIM ) {
-	fgJSBsimInit(dt, f);
-	fgJSBsim_2_FGInterface(base_fdm_state);
-#endif
-    } else if ( model == FGInterface::FG_LARCSIM ) {
-	// lets try to avoid really screwing up the LaRCsim model
-	if ( base_fdm_state.get_Altitude() < -9000.0 ) {
-	    save_alt = base_fdm_state.get_Altitude();
-	    base_fdm_state.set_Altitude( 0.0 );
-	}
-
-	// translate FG to LaRCsim structure
-	FGInterface_2_LaRCsim(base_fdm_state);
-
-	// initialize LaRCsim
-	fgLaRCsimInit(dt);
-
-	FG_LOG( FG_FLIGHT, FG_INFO, "FG pos = " << 
-		base_fdm_state.get_Latitude() );
-
-	// translate LaRCsim back to FG structure
-	fgLaRCsim_2_FGInterface(base_fdm_state);
-
-	// but lets restore our original bogus altitude when we are done
-	if ( save_alt < -9000.0 ) {
-	    base_fdm_state.set_Altitude( save_alt );
-	}
-    } else if ( model == FGInterface::FG_EXTERNAL ) {
-	fgExternalInit(base_fdm_state);
-    } else {
-	FG_LOG( FG_FLIGHT, FG_WARN,
-		"Unimplemented flight model == " << model );
-    }
+/**
+ * Unbind any properties bound to this FDM.
+ *
+ * This method allows the FDM to release properties so that a new
+ * FDM can bind them instead.
+ */
+void
+FGInterface::unbind ()
+{
+  bound = false;
+
+  // fgUntie("/fdm/time/delta_t");
+  // fgUntie("/fdm/time/elapsed");
+  // fgUntie("/fdm/time/remainder");
+  // fgUntie("/fdm/time/multi_loop");
+  fgUntie("/position/latitude-deg");
+  fgUntie("/position/longitude-deg");
+  fgUntie("/position/altitude-ft");
+  fgUntie("/position/altitude-agl-ft");
+  fgUntie("/position/ground-elev-ft");
+  fgUntie("/position/ground-elev-m");
+  fgUntie("/environment/ground-elevation-m");
+  fgUntie("/position/sea-level-radius-ft");
+  fgUntie("/orientation/roll-deg");
+  fgUntie("/orientation/pitch-deg");
+  fgUntie("/orientation/heading-deg");
+  fgUntie("/orientation/roll-rate-degps");
+  fgUntie("/orientation/pitch-rate-degps");
+  fgUntie("/orientation/yaw-rate-degps");
+  fgUntie("/orientation/side-slip-rad");
+  fgUntie("/orientation/side-slip-deg");
+  fgUntie("/orientation/alpha-deg");
+  fgUntie("/velocities/airspeed-kt");
+  fgUntie("/velocities/groundspeed-kt");
+  fgUntie("/velocities/mach");
+  fgUntie("/velocities/speed-north-fps");
+  fgUntie("/velocities/speed-east-fps");
+  fgUntie("/velocities/speed-down-fps");
+  fgUntie("/velocities/uBody-fps");
+  fgUntie("/velocities/vBody-fps");
+  fgUntie("/velocities/wBody-fps");
+  fgUntie("/velocities/vertical-speed-fps");
+  fgUntie("/velocities/glideslope");
+  fgUntie("/accelerations/nlf");
+  fgUntie("/accelerations/pilot/x-accel-fps_sec");
+  fgUntie("/accelerations/pilot/y-accel-fps_sec");
+  fgUntie("/accelerations/pilot/z-accel-fps_sec");
+  fgUntie("/accelerations/ned/north-accel-fps_sec");
+  fgUntie("/accelerations/ned/east-accel-fps_sec");
+  fgUntie("/accelerations/ned/down-accel-fps_sec");
+}
 
-    // set valid time for this record
-    base_fdm_state.stamp_time();
-	
-    f = base_fdm_state;
+/**
+ * Update the state of the FDM (i.e. run the equations of motion).
+ */
+void
+FGInterface::update (double dt)
+{
+    SG_LOG(SG_FLIGHT, SG_ALERT, "dummy update() ... SHOULDN'T BE CALLED!");
+}
 
-    return 1;
+
+void FGInterface::_updatePositionM(const SGVec3d& cartPos)
+{
+    cartesian_position_v = cartPos;
+    geodetic_position_v = SGGeod::fromCart(cartesian_position_v);
+    geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);
+    _set_Sea_level_radius( SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v)*SG_METER_TO_FEET );
+    _update_ground_elev_at_pos();
 }
-#endif
 
 
-#if 0
-// Run multiloop iterations of the flight model
-int fgFDMUpdate(int model, FGInterface& f, int multiloop, int time_offset) {
-    double time_step, start_elev, end_elev;
+void FGInterface::_updatePosition(const SGGeod& geod)
+{
+    geodetic_position_v = geod;
+    cartesian_position_v = SGVec3d::fromGeod(geodetic_position_v);
+    geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);
 
-    // printf("Altitude = %.2f\n", FG_Altitude * 0.3048);
+    _set_Sea_level_radius( SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v)*SG_METER_TO_FEET );
+    _update_ground_elev_at_pos();
+}
 
-    // set valid time for this record
-    base_fdm_state.stamp_time();
 
-    time_step = (1.0 / current_options.get_model_hz()) * multiloop;
-    start_elev = base_fdm_state.get_Altitude();
+void FGInterface::_updatePosition(const SGGeoc& geoc)
+{
+    geocentric_position_v = geoc;
+    cartesian_position_v = SGVec3d::fromGeoc(geocentric_position_v);
+    geodetic_position_v = SGGeod::fromCart(cartesian_position_v);
 
-    if ( model == FGInterface::FG_SLEW ) {
-	// fgSlewUpdate(f, multiloop);
-#ifndef __MWERKS__   // -dw- 04/22/99 JSB sim not ported yet
-    } else if ( model == FGInterface::FG_JSBSIM ) {
-	fgJSBsimUpdate(base_fdm_state, multiloop);
-	f = base_fdm_state;
-#endif
-    } else if ( model == FGInterface::FG_LARCSIM ) {
-	fgLaRCsimUpdate(base_fdm_state, multiloop);
-	// extrapolate position based on actual time
-	// f = extrapolate_fdm( base_fdm_state, time_offset );
-	f = base_fdm_state;
-    } else if ( model == FGInterface::FG_EXTERNAL ) {
-	// fgExternalUpdate(f, multiloop);
-	FGTimeStamp current;
-	current.stamp();
-	f = base_fdm_state;
-	f.extrapolate( current - base_fdm_state.get_time_stamp() );
-    } else {
-	FG_LOG( FG_FLIGHT, FG_WARN,
-		"Unimplemented flight model == " <<  model );
-    }
+    _set_Sea_level_radius( SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v)*SG_METER_TO_FEET );
+    _update_ground_elev_at_pos();
+}
 
-    end_elev = base_fdm_state.get_Altitude();
 
-    if ( time_step > 0.0 ) {
-	// feet per second
-	base_fdm_state.set_Climb_Rate( (end_elev - start_elev) / time_step );
-    }
+void FGInterface::_updateGeodeticPosition( double lat, double lon, double alt )
+{
+    _updatePosition(SGGeod::fromRadFt(lon, lat, alt));
+}
+
 
-    return 1;
+void FGInterface::_updateGeocentricPosition( double lat, double lon,
+					     double alt )
+{
+    _updatePosition(SGGeoc::fromRadFt(lon, lat, get_Sea_level_radius() + alt));
+}
+
+void FGInterface::_update_ground_elev_at_pos( void ) {
+    double groundlevel_m = get_groundlevel_m(geodetic_position_v);
+    _set_Runway_altitude( groundlevel_m * SG_METER_TO_FEET );
+}
+
+// Positions
+void FGInterface::set_Latitude(double lat) {
+    geodetic_position_v.setLatitudeRad(lat);
+}
+
+void FGInterface::set_Longitude(double lon) {
+    geodetic_position_v.setLongitudeRad(lon);
+}
+
+void FGInterface::set_Altitude(double alt) {
+    geodetic_position_v.setElevationFt(alt);
+}
+
+void FGInterface::set_AltitudeAGL(double altagl) {
+    altitude_agl=altagl;
+}
+
+// Velocities
+void FGInterface::set_V_calibrated_kts(double vc) {
+    v_calibrated_kts = vc;
 }
-#endif
 
+void FGInterface::set_Mach_number(double mach) {
+    mach_number = mach;
+}
+
+void FGInterface::set_Velocities_Local( double north, 
+					double east, 
+					double down ){
+    v_local_v[0] = north;
+    v_local_v[1] = east;
+    v_local_v[2] = down;
+}
+
+void FGInterface::set_Velocities_Wind_Body( double u, 
+					    double v, 
+					    double w){
+    v_wind_body_v[0] = u;
+    v_wind_body_v[1] = v;
+    v_wind_body_v[2] = w;
+}
+
+// Euler angles 
+void FGInterface::set_Euler_Angles( double phi, 
+				    double theta, 
+				    double psi ) {
+    euler_angles_v[0] = phi;
+    euler_angles_v[1] = theta;
+    euler_angles_v[2] = psi;                                            
+}  
+
+// Flight Path
+void FGInterface::set_Climb_Rate( double roc) {
+    climb_rate = roc;
+}
+
+void FGInterface::set_Gamma_vert_rad( double gamma) {
+    gamma_vert_rad = gamma;
+}
+
+void FGInterface::set_Static_pressure(double p) { static_pressure = p; }
+void FGInterface::set_Static_temperature(double T) { static_temperature = T; }
+void FGInterface::set_Density(double rho) { density = rho; }
+
+void FGInterface::set_Velocities_Local_Airmass (double wnorth, 
+						double weast, 
+						double wdown ) {
+    v_local_airmass_v[0] = wnorth;
+    v_local_airmass_v[1] = weast;
+    v_local_airmass_v[2] = wdown;
+}
+
+
+void FGInterface::_busdump(void) {
+
+    SG_LOG(SG_FLIGHT,SG_INFO,"d_cg_rp_body_v: " << d_cg_rp_body_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_dot_local_v: " << v_dot_local_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_dot_body_v: " << v_dot_body_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"a_cg_body_v: " << a_cg_body_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"a_pilot_body_v: " << a_pilot_body_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"n_cg_body_v: " << n_cg_body_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_local_v: " << v_local_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_local_rel_ground_v: " << v_local_rel_ground_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_local_airmass_v: " << v_local_airmass_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_wind_body_v: " << v_wind_body_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"omega_body_v: " << omega_body_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"euler_rates_v: " << euler_rates_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"geocentric_rates_v: " << geocentric_rates_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"geocentric_position_v: " << geocentric_position_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"geodetic_position_v: " << geodetic_position_v);
+    SG_LOG(SG_FLIGHT,SG_INFO,"euler_angles_v: " << euler_angles_v);
+
+    SG_LOG(SG_FLIGHT,SG_INFO,"nlf: " << nlf );
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_rel_wind: " << v_rel_wind );
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_true_kts: " << v_true_kts );
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_ground_speed: " << v_ground_speed );
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_equiv_kts: " << v_equiv_kts );
+    SG_LOG(SG_FLIGHT,SG_INFO,"v_calibrated_kts: " << v_calibrated_kts );
+    SG_LOG(SG_FLIGHT,SG_INFO,"alpha: " << alpha );
+    SG_LOG(SG_FLIGHT,SG_INFO,"beta: " << beta );
+    SG_LOG(SG_FLIGHT,SG_INFO,"gamma_vert_rad: " << gamma_vert_rad );
+    SG_LOG(SG_FLIGHT,SG_INFO,"density: " << density );
+    SG_LOG(SG_FLIGHT,SG_INFO,"mach_number: " << mach_number );
+    SG_LOG(SG_FLIGHT,SG_INFO,"static_pressure: " << static_pressure );
+    SG_LOG(SG_FLIGHT,SG_INFO,"total_pressure: " << total_pressure );
+    SG_LOG(SG_FLIGHT,SG_INFO,"dynamic_pressure: " << dynamic_pressure );
+    SG_LOG(SG_FLIGHT,SG_INFO,"static_temperature: " << static_temperature );
+    SG_LOG(SG_FLIGHT,SG_INFO,"total_temperature: " << total_temperature );
+    SG_LOG(SG_FLIGHT,SG_INFO,"sea_level_radius: " << sea_level_radius );
+    SG_LOG(SG_FLIGHT,SG_INFO,"earth_position_angle: " << earth_position_angle );
+    SG_LOG(SG_FLIGHT,SG_INFO,"runway_altitude: " << runway_altitude );
+    SG_LOG(SG_FLIGHT,SG_INFO,"climb_rate: " << climb_rate );
+    SG_LOG(SG_FLIGHT,SG_INFO,"altitude_agl: " << altitude_agl );
+}
+
+bool
+FGInterface::prepare_ground_cache_m(double startSimTime, double endSimTime,
+                                    const double pt[3], double rad)
+{
+  return ground_cache.prepare_ground_cache(startSimTime, endSimTime,
+                                           SGVec3d(pt), rad);
+}
+
+bool
+FGInterface::prepare_ground_cache_ft(double startSimTime, double endSimTime,
+                                     const double pt[3], double rad)
+{
+  // Convert units and do the real work.
+  SGVec3d pt_ft = SG_FEET_TO_METER*SGVec3d(pt);
+  return ground_cache.prepare_ground_cache(startSimTime, endSimTime,
+                                           pt_ft, rad*SG_FEET_TO_METER);
+}
+
+bool
+FGInterface::is_valid_m(double *ref_time, double pt[3], double *rad)
+{
+  SGVec3d _pt;
+  bool valid = ground_cache.is_valid(*ref_time, _pt, *rad);
+  assign(pt, _pt);
+  return valid;
+}
 
-// Set the altitude (force)
-void fgFDMForceAltitude(int model, double alt_meters) {
-    double sea_level_radius_meters;
-    double lat_geoc;
+bool FGInterface::is_valid_ft(double *ref_time, double pt[3], double *rad)
+{
+  // Convert units and do the real work.
+  SGVec3d _pt;
+  bool found_ground = ground_cache.is_valid(*ref_time, _pt, *rad);
+  assign(pt, SG_METER_TO_FEET*_pt);
+  *rad *= SG_METER_TO_FEET;
+  return found_ground;
+}
+
+double
+FGInterface::get_cat_m(double t, const double pt[3],
+                       double end[2][3], double vel[2][3])
+{
+  SGVec3d _end[2], _vel[2];
+  double dist = ground_cache.get_cat(t, SGVec3d(pt), _end, _vel);
+  for (int k=0; k<2; ++k) {
+    assign( end[k], _end[k] );
+    assign( vel[k], _vel[k] );
+  }
+  return dist;
+}
 
-    // Set the FG variables first
-    fgGeodToGeoc( base_fdm_state.get_Latitude(), alt_meters, 
-		  &sea_level_radius_meters, &lat_geoc);
+double
+FGInterface::get_cat_ft(double t, const double pt[3],
+                        double end[2][3], double vel[2][3])
+{
+  // Convert units and do the real work.
+  SGVec3d pt_m = SG_FEET_TO_METER*SGVec3d(pt);
+  SGVec3d _end[2], _vel[2];
+  double dist = ground_cache.get_cat(t, pt_m, _end, _vel);
+  for (int k=0; k<2; ++k) {
+    assign( end[k], SG_METER_TO_FEET*_end[k] );
+    assign( vel[k], SG_METER_TO_FEET*_vel[k] );
+  }
+  return dist*SG_METER_TO_FEET;
+}
+
+bool
+FGInterface::get_body_m(double t, simgear::BVHNode::Id id,
+                        double bodyToWorld[16], double linearVel[3],
+                        double angularVel[3])
+{
+  SGMatrixd _bodyToWorld;
+  SGVec3d _linearVel, _angularVel;
+  if (!ground_cache.get_body(t, _bodyToWorld, _linearVel, _angularVel, id))
+    return false;
+
+  assign(linearVel, _linearVel);
+  assign(angularVel, _angularVel);
+  for (unsigned i = 0; i < 16; ++i)
+      bodyToWorld[i] = _bodyToWorld.data()[i];
+
+  return true;
+}
 
-    base_fdm_state.set_Altitude( alt_meters * METER_TO_FEET );
-    base_fdm_state.set_Radius_to_vehicle( base_fdm_state.get_Altitude() + 
-					  (sea_level_radius_meters * 
-					   METER_TO_FEET) );
+bool
+FGInterface::get_agl_m(double t, const double pt[3], double max_altoff,
+                       double contact[3], double normal[3],
+                       double linearVel[3], double angularVel[3],
+                       SGMaterial const*& material, simgear::BVHNode::Id& id)
+{
+  SGVec3d pt_m = SGVec3d(pt) - max_altoff*ground_cache.get_down();
+  SGVec3d _contact, _normal, _linearVel, _angularVel;
+  material = 0;
+  bool ret = ground_cache.get_agl(t, pt_m, _contact, _normal, _linearVel,
+                                  _angularVel, id, material);
+  // correct the linear velocity, since the line intersector delivers
+  // values for the start point and the get_agl function should
+  // traditionally deliver for the contact point
+  _linearVel += cross(_angularVel, _contact - pt_m);
+
+  assign(contact, _contact);
+  assign(normal, _normal);
+  assign(linearVel, _linearVel);
+  assign(angularVel, _angularVel);
+  return ret;
+}
+
+bool
+FGInterface::get_agl_ft(double t, const double pt[3], double max_altoff,
+                        double contact[3], double normal[3],
+                        double linearVel[3], double angularVel[3],
+                        SGMaterial const*& material, simgear::BVHNode::Id& id)
+{
+  // Convert units and do the real work.
+  SGVec3d pt_m = SGVec3d(pt) - max_altoff*ground_cache.get_down();
+  pt_m *= SG_FEET_TO_METER;
+  SGVec3d _contact, _normal, _linearVel, _angularVel;
+  material = 0;
+  bool ret = ground_cache.get_agl(t, pt_m, _contact, _normal, _linearVel,
+                                  _angularVel, id, material);
+  // correct the linear velocity, since the line intersector delivers
+  // values for the start point and the get_agl function should
+  // traditionally deliver for the contact point
+  _linearVel += cross(_angularVel, _contact - pt_m);
+
+  // Convert units back ...
+  assign( contact, SG_METER_TO_FEET*_contact );
+  assign( normal, _normal );
+  assign( linearVel, SG_METER_TO_FEET*_linearVel );
+  assign( angularVel, _angularVel );
+  return ret;
+}
+
+bool
+FGInterface::get_nearest_m(double t, const double pt[3], double maxDist,
+                           double contact[3], double normal[3],
+                           double linearVel[3], double angularVel[3],
+                           SGMaterial const*& material,
+                           simgear::BVHNode::Id& id)
+{
+  SGVec3d _contact, _linearVel, _angularVel;
+  if (!ground_cache.get_nearest(t, SGVec3d(pt), maxDist, _contact, _linearVel,
+                                _angularVel, id, material))
+      return false;
+
+  assign(contact, _contact);
+  assign(linearVel, _linearVel);
+  assign(angularVel, _angularVel);
+  return true;
+}
 
-    // additional work needed for some flight models
-    if ( model == FGInterface::FG_LARCSIM ) {
-	ls_ForceAltitude( base_fdm_state.get_Altitude() );
+bool
+FGInterface::get_nearest_ft(double t, const double pt[3], double maxDist,
+                            double contact[3], double normal[3],
+                            double linearVel[3], double angularVel[3],
+                            SGMaterial const*& material,
+                            simgear::BVHNode::Id& id)
+{
+  SGVec3d _contact, _linearVel, _angularVel;
+  if (!ground_cache.get_nearest(t, SG_FEET_TO_METER*SGVec3d(pt),
+                                SG_FEET_TO_METER*maxDist, _contact, _linearVel,
+                                _angularVel, id, material))
+      return false;
+
+  assign(contact, SG_METER_TO_FEET*_contact);
+  assign(linearVel, SG_METER_TO_FEET*_linearVel);
+  assign(angularVel, _angularVel);
+  return true;
+}
+
+double
+FGInterface::get_groundlevel_m(double lat, double lon, double alt)
+{
+  return get_groundlevel_m(SGGeod::fromRadM(lon, lat, alt));
+}
+
+double
+FGInterface::get_groundlevel_m(const SGGeod& geod)
+{
+  // Compute the cartesian position of the given lat/lon/alt.
+  SGVec3d pos = SGVec3d::fromGeod(geod);
+
+  // FIXME: how to handle t - ref_time differences ???
+  SGVec3d cpos;
+  double ref_time = 0, radius;
+  // Prepare the ground cache for that position.
+  if (!is_valid_m(&ref_time, cpos.data(), &radius)) {
+    double startTime = ref_time;
+    double endTime = startTime + 1;
+    bool ok = prepare_ground_cache_m(startTime, endTime, pos.data(), 10);
+    /// This is most likely the case when the given altitude is
+    /// too low, try with a new altitude of 10000m, that should be
+    /// sufficient to find a ground level below everywhere on our planet
+    if (!ok) {
+      pos = SGVec3d::fromGeod(SGGeod::fromGeodM(geod, 10000));
+      /// If there is still no ground, return sea level radius
+      if (!prepare_ground_cache_m(startTime, endTime, pos.data(), 10))
+        return 0;
+    }
+  } else if (radius*radius <= distSqr(pos, cpos)) {
+    double startTime = ref_time;
+    double endTime = startTime + 1;
+
+    /// We reuse the old radius value, but only if it is at least 10 Meters ..
+    if (!(10 < radius)) // Well this strange compare is nan safe
+      radius = 10;
+
+    bool ok = prepare_ground_cache_m(startTime, endTime, pos.data(), radius);
+    /// This is most likely the case when the given altitude is
+    /// too low, try with a new altitude of 10000m, that should be
+    /// sufficient to find a ground level below everywhere on our planet
+    if (!ok) {
+      pos = SGVec3d::fromGeod(SGGeod::fromGeodM(geod, 10000));
+      /// If there is still no ground, return sea level radius
+      if (!prepare_ground_cache_m(startTime, endTime, pos.data(), radius))
+        return 0;
     }
+  }
+  
+  double contact[3], normal[3], vel[3], angvel[3];
+  const SGMaterial* material;
+  simgear::BVHNode::Id id;
+  // Ignore the return value here, since it just tells us if
+  // the returns stem from the groundcache or from the coarse
+  // computations below the groundcache. The contact point is still something
+  // valid, the normals and the other returns just contain some defaults.
+  get_agl_m(ref_time, pos.data(), 2.0, contact, normal, vel, angvel,
+            material, id);
+  return SGGeod::fromCart(SGVec3d(contact)).getElevationM();
+}
+  
+bool
+FGInterface::caught_wire_m(double t, const double pt[4][3])
+{
+  SGVec3d pt_m[4];
+  for (int i=0; i<4; ++i)
+    pt_m[i] = SGVec3d(pt[i]);
+  
+  return ground_cache.caught_wire(t, pt_m);
 }
 
+bool
+FGInterface::caught_wire_ft(double t, const double pt[4][3])
+{
+  // Convert units and do the real work.
+  SGVec3d pt_m[4];
+  for (int i=0; i<4; ++i)
+    pt_m[i] = SG_FEET_TO_METER*SGVec3d(pt[i]);
+    
+  return ground_cache.caught_wire(t, pt_m);
+}
+  
+bool
+FGInterface::get_wire_ends_m(double t, double end[2][3], double vel[2][3])
+{
+  SGVec3d _end[2], _vel[2];
+  bool ret = ground_cache.get_wire_ends(t, _end, _vel);
+  for (int k=0; k<2; ++k) {
+    assign( end[k], _end[k] );
+    assign( vel[k], _vel[k] );
+  }
+  return ret;
+}
 
-// Set the local ground elevation
-void fgFDMSetGroundElevation(int model, double ground_meters) {
-    base_fdm_state.set_Runway_altitude( ground_meters * METER_TO_FEET );
-    cur_fdm_state->set_Runway_altitude( ground_meters * METER_TO_FEET );
+bool
+FGInterface::get_wire_ends_ft(double t, double end[2][3], double vel[2][3])
+{
+  // Convert units and do the real work.
+  SGVec3d _end[2], _vel[2];
+  bool ret = ground_cache.get_wire_ends(t, _end, _vel);
+  for (int k=0; k<2; ++k) {
+    assign( end[k], SG_METER_TO_FEET*_end[k] );
+    assign( vel[k], SG_METER_TO_FEET*_vel[k] );
+  }
+  return ret;
 }
 
+void
+FGInterface::release_wire(void)
+{
+  ground_cache.release_wire();
+}
 
+void fgToggleFDMdataLogging(void) {
+  cur_fdm_state->ToggleDataLogging();
+}