flightgear/src/Main/main.cxx

// main.cxx -- top level sim routines
//
// Written by Curtis Olson, started May 1997.
//
// Copyright (C) 1997 - 2002  Curtis L. Olson  - curt@flightgear.org
//
// 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
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// 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.
//
// $Id$


#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <simgear/compiler.h>

#if defined(__linux__) && defined(__i386__)
#  include <fpu_control.h>
#  include <signal.h>
#endif

#ifdef SG_MATH_EXCEPTION_CLASH
#  include <math.h>
#endif

#ifdef HAVE_WINDOWS_H
#  include <windows.h>
#  include <float.h>
#endif

#include <plib/ssg.h>
#include <plib/netSocket.h>

#include <simgear/screen/extensions.hxx>
#include <simgear/scene/material/matlib.hxx>
#include <simgear/props/props.hxx>
#include <simgear/scene/sky/sky.hxx>
#include <simgear/timing/sg_time.hxx>
#include <simgear/scene/model/animation.hxx>
#include <simgear/ephemeris/ephemeris.hxx>
#include <simgear/scene/model/placement.hxx>
#include <simgear/math/sg_random.h>
#include <simgear/scene/model/modellib.hxx>

#ifdef FG_USE_CLOUDS_3D
#  include <simgear/scene/sky/clouds3d/SkySceneLoader.hpp>
#  include <simgear/scene/sky/clouds3d/SkyUtil.hpp>
#endif

#include <Include/general.hxx>
#include <Scenery/tileentry.hxx>
#include <Time/light.hxx>
#include <Time/light.hxx>
#include <Aircraft/aircraft.hxx>
#include <Cockpit/panel.hxx>
#include <Cockpit/cockpit.hxx>
#include <Cockpit/radiostack.hxx>
#include <Cockpit/hud.hxx>
#include <Model/panelnode.hxx>
#include <Model/modelmgr.hxx>
#include <Model/acmodel.hxx>
#include <Scenery/scenery.hxx>
#include <Scenery/tilemgr.hxx>
#include <FDM/flight.hxx>
#include <FDM/UIUCModel/uiuc_aircraftdir.h>
#include <FDM/ADA.hxx>
#include <ATC/ATCdisplay.hxx>
#include <ATC/ATCmgr.hxx>
#include <ATC/AIMgr.hxx>
#include <Replay/replay.hxx>
#include <Time/tmp.hxx>
#include <Time/fg_timer.hxx>
#include <Environment/environment_mgr.hxx>

#ifdef FG_MPLAYER_AS
#include <MultiPlayer/multiplaytxmgr.hxx>
#include <MultiPlayer/multiplayrxmgr.hxx>
#endif

#include "splash.hxx"
#include "fg_commands.hxx"
#include "fg_io.hxx"
#include "main.hxx"

float default_attenuation[3] = {1.0, 0.0, 0.0};
ssgSelector *ship_sel=NULL;
// upto 32 instances of a same object can be loaded.
ssgTransform *ship_pos[32];
double obj_lat[32],obj_lon[32],obj_alt[32],obj_pitch[32],obj_roll[32];
int objc=0;
ssgSelector *lightpoints_brightness = new ssgSelector;
ssgTransform *lightpoints_transform = new ssgTransform;
FGTileEntry *dummy_tile;
sgVec3 rway_ols;
// ADA
// Clip plane settings...
float scene_nearplane = 0.5f;
float scene_farplane = 120000.0f;

static double real_delta_time_sec = 0.0;
static double delta_time_sec = 0.0;

glPointParameterfProc glPointParameterfPtr = 0;
glPointParameterfvProc glPointParameterfvPtr = 0;
bool glPointParameterIsSupported = false;


#ifdef macintosh
#  include <console.h>		// -dw- for command line dialog
#endif

// This is a record containing a bit of global housekeeping information
FGGeneral general;

// Specify our current idle function state.  This is used to run all
// our initializations out of the idle callback so that we can get a
// splash screen up and running right away.
static int idle_state = 0;
static long global_multi_loop;

// fog constants.  I'm a little nervous about putting actual code out
// here but it seems to work (?)
static const double m_log01 = -log( 0.01 );
static const double sqrt_m_log01 = sqrt( m_log01 );
static GLfloat fog_exp_density;
static GLfloat fog_exp2_density;
static GLfloat rwy_exp2_punch_through;
static GLfloat taxi_exp2_punch_through;
static GLfloat ground_exp2_punch_through;

// Sky structures
SGSky *thesky;

#ifdef FG_USE_CLOUDS_3D
  SkySceneLoader *sgClouds3d;
  bool _bcloud_orig = true;
#endif

// hack
sgMat4 copy_of_ssgOpenGLAxisSwapMatrix =
{
  {  1.0f,  0.0f,  0.0f,  0.0f },
  {  0.0f,  0.0f, -1.0f,  0.0f },
  {  0.0f,  1.0f,  0.0f,  0.0f },
  {  0.0f,  0.0f,  0.0f,  1.0f }
};

ssgSimpleState *cloud3d_imposter_state;
ssgSimpleState *default_state;
ssgSimpleState *hud_and_panel;
ssgSimpleState *menus;

SGTimeStamp last_time_stamp;
SGTimeStamp current_time_stamp;


void fgBuildRenderStates( void ) {
    default_state = new ssgSimpleState;
    default_state->ref();
    default_state->disable( GL_TEXTURE_2D );
    default_state->enable( GL_CULL_FACE );
    default_state->enable( GL_COLOR_MATERIAL );
    default_state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
    default_state->setMaterial( GL_EMISSION, 0, 0, 0, 1 );
    default_state->setMaterial( GL_SPECULAR, 0, 0, 0, 1 );
    default_state->disable( GL_BLEND );
    default_state->disable( GL_ALPHA_TEST );
    default_state->disable( GL_LIGHTING );

    cloud3d_imposter_state = new ssgSimpleState;
    cloud3d_imposter_state->ref();
    cloud3d_imposter_state->enable( GL_TEXTURE_2D );
    cloud3d_imposter_state->enable( GL_CULL_FACE );
    cloud3d_imposter_state->enable( GL_COLOR_MATERIAL );
    cloud3d_imposter_state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
    cloud3d_imposter_state->setMaterial( GL_DIFFUSE, 1, 1, 1, 1 );
    cloud3d_imposter_state->setMaterial( GL_AMBIENT, 1, 1, 1, 1 );
    cloud3d_imposter_state->setMaterial( GL_EMISSION, 0, 0, 0, 1 );
    cloud3d_imposter_state->setMaterial( GL_SPECULAR, 0, 0, 0, 1 );
    cloud3d_imposter_state->enable( GL_BLEND );
    cloud3d_imposter_state->enable( GL_ALPHA_TEST );
    cloud3d_imposter_state->disable( GL_LIGHTING );

    hud_and_panel = new ssgSimpleState;
    hud_and_panel->ref();
    hud_and_panel->disable( GL_CULL_FACE );
    hud_and_panel->disable( GL_TEXTURE_2D );
    hud_and_panel->disable( GL_LIGHTING );
    hud_and_panel->enable( GL_BLEND );

    menus = new ssgSimpleState;
    menus->ref();
    menus->disable( GL_CULL_FACE );
    menus->disable( GL_TEXTURE_2D );
    menus->enable( GL_BLEND );
}


// fgInitVisuals() -- Initialize various GL/view parameters
void fgInitVisuals( void ) {

    FGLight *l = (FGLight *)(globals->get_subsystem("lighting"));

    // Go full screen if requested ...
    if ( fgGetBool("/sim/startup/fullscreen") ) {
        fgOSFullScreen();
    }

    // If enabled, normal vectors specified with glNormal are scaled
    // to unit length after transformation.  Enabling this has
    // performance implications.  See the docs for glNormal.
    // glEnable( GL_NORMALIZE );

    glEnable( GL_LIGHTING );
    glEnable( GL_LIGHT0 );
    // glLightfv( GL_LIGHT0, GL_POSITION, l->sun_vec );  // done later with ssg

    sgVec3 sunpos;
    sgSetVec3( sunpos, l->sun_vec()[0], l->sun_vec()[1], l->sun_vec()[2] );
    ssgGetLight( 0 ) -> setPosition( sunpos );

    glFogi (GL_FOG_MODE, GL_EXP2);
    if ( (!strcmp(fgGetString("/sim/rendering/fog"), "disabled")) || 
         (!fgGetBool("/sim/rendering/shading"))) {
        // if fastest fog requested, or if flat shading force fastest
        glHint ( GL_FOG_HINT, GL_FASTEST );
    } else if ( !strcmp(fgGetString("/sim/rendering/fog"), "nicest") ) {
        glHint ( GL_FOG_HINT, GL_NICEST );
    }
    if ( fgGetBool("/sim/rendering/wireframe") ) {
        // draw wire frame
        glPolygonMode( GL_FRONT_AND_BACK, GL_LINE );
    }

    // This is the default anyways, but it can't hurt
    glFrontFace ( GL_CCW );

    // Just testing ...
    // glEnable(GL_POINT_SMOOTH);
    // glEnable(GL_LINE_SMOOTH);
    // glEnable(GL_POLYGON_SMOOTH);      
}


// For HiRes screen Dumps using Brian Pauls TR Library
void trRenderFrame( void ) {
#ifdef FG_ENABLE_MULTIPASS_CLOUDS
    bool multi_pass_clouds = fgGetBool("/sim/rendering/multi-pass-clouds");
#else
    bool multi_pass_clouds = false;
#endif
    bool draw_clouds = fgGetBool("/environment/clouds/status");

    if ( fgPanelVisible() ) {
        GLfloat height = fgGetInt("/sim/startup/ysize");
        GLfloat view_h =
            (globals->get_current_panel()->getViewHeight() - globals->get_current_panel()->getYOffset())
            * (height / 768.0) + 1;
        glTranslatef( 0.0, view_h, 0.0 );
    }

    static GLfloat black[4] = { 0.0, 0.0, 0.0, 1.0 };
    static GLfloat white[4] = { 1.0, 1.0, 1.0, 1.0 };

    FGLight *l = (FGLight *)(globals->get_subsystem("lighting"));

    glClearColor(l->adj_fog_color()[0], l->adj_fog_color()[1], 
                 l->adj_fog_color()[2], l->adj_fog_color()[3]);

    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

    // set the opengl state to known default values
    default_state->force();

    glEnable( GL_FOG );
    glFogf  ( GL_FOG_DENSITY, fog_exp2_density);
    glFogi  ( GL_FOG_MODE,    GL_EXP2 );
    glFogfv ( GL_FOG_COLOR,   l->adj_fog_color() );

    // GL_LIGHT_MODEL_AMBIENT has a default non-zero value so if
    // we only update GL_AMBIENT for our lights we will never get
    // a completely dark scene.  So, we set GL_LIGHT_MODEL_AMBIENT
    // explicitely to black.
    glLightModelfv( GL_LIGHT_MODEL_AMBIENT, black );
    glLightModeli( GL_LIGHT_MODEL_LOCAL_VIEWER, GL_FALSE );

    ssgGetLight( 0 ) -> setColour( GL_AMBIENT, l->scene_ambient() );

    // texture parameters
    glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ) ;
    glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST ) ;

    // we need a white diffuse light for the phase of the moon
    ssgGetLight( 0 ) -> setColour( GL_DIFFUSE, white );
    thesky->preDraw( cur_fdm_state->get_Altitude() * SG_FEET_TO_METER,
                     fog_exp2_density );

    // draw the ssg scene
    // return to the desired diffuse color
    ssgGetLight( 0 ) -> setColour( GL_DIFFUSE, l->scene_diffuse() );
    glEnable( GL_DEPTH_TEST );
    ssgSetNearFar( scene_nearplane, scene_farplane );
    if ( draw_clouds ) {
        // Draw the terrain
        FGTileMgr::set_tile_filter( true );
        sgSetModelFilter( false );
        globals->get_aircraft_model()->select( false );
        ssgCullAndDraw( globals->get_scenery()->get_scene_graph() );
        // Disable depth buffer update, draw the clouds
        glDepthMask( GL_FALSE );
        thesky->drawUpperClouds();
        if ( multi_pass_clouds ) {
            thesky->drawLowerClouds();
        }
        glDepthMask( GL_TRUE );
        if ( multi_pass_clouds ) {
            // Draw the objects except the aircraft
            //  and update the stencil buffer with 1
            glEnable( GL_STENCIL_TEST );
            glStencilFunc( GL_ALWAYS, 1, 1 );
            glStencilOp( GL_KEEP, GL_KEEP, GL_REPLACE );
        }
        FGTileMgr::set_tile_filter( false );
        sgSetModelFilter( true );
        ssgCullAndDraw( globals->get_scenery()->get_scene_graph() );
    } else {
        FGTileMgr::set_tile_filter( true );
        sgSetModelFilter( true );
        globals->get_aircraft_model()->select( false );
        ssgCullAndDraw( globals->get_scenery()->get_scene_graph() );
    }

    // draw the lights
    glFogf (GL_FOG_DENSITY, rwy_exp2_punch_through);
    ssgSetNearFar( scene_nearplane, scene_farplane );
    ssgCullAndDraw( globals->get_scenery()->get_vasi_lights_root() );
    ssgCullAndDraw( globals->get_scenery()->get_rwy_lights_root() );

    ssgCullAndDraw( globals->get_scenery()->get_gnd_lights_root() );

    if ( draw_clouds ) {
        if ( multi_pass_clouds ) {
            // Disable depth buffer update, draw the clouds where the
            //  objects overwrite the already drawn clouds, by testing
            //  the stencil buffer against 1
            glDepthMask( GL_FALSE );
            glStencilFunc( GL_EQUAL, 1, 1 );
            glStencilOp( GL_KEEP, GL_KEEP, GL_KEEP );
            thesky->drawUpperClouds();
            thesky->drawLowerClouds();
            glDepthMask( GL_TRUE );
            glDisable( GL_STENCIL_TEST );
        } else {
            glDepthMask( GL_FALSE );
            thesky->drawLowerClouds();
            glDepthMask( GL_TRUE );
        }
    }

    globals->get_aircraft_model()->select( true );
    globals->get_model_mgr()->draw();
    globals->get_aircraft_model()->draw();
}


// Update all Visuals (redraws anything graphics related)
void fgRenderFrame() {
    bool draw_otw = fgGetBool("/sim/rendering/draw-otw");
    bool skyblend = fgGetBool("/sim/rendering/skyblend");
    bool enhanced_lighting = fgGetBool("/sim/rendering/enhanced-lighting");
    bool distance_attenuation = fgGetBool("/sim/rendering/distance-attenuation");
#ifdef FG_ENABLE_MULTIPASS_CLOUDS
    bool multi_pass_clouds = fgGetBool("/sim/rendering/multi-pass-clouds");
#else
    bool multi_pass_clouds = false;
#endif
    bool draw_clouds = fgGetBool("/environment/clouds/status");

    GLfloat black[4] = { 0.0, 0.0, 0.0, 1.0 };
    GLfloat white[4] = { 1.0, 1.0, 1.0, 1.0 };

    // static const SGPropertyNode *longitude
    //     = fgGetNode("/position/longitude-deg");
    // static const SGPropertyNode *latitude
    //     = fgGetNode("/position/latitude-deg");
    // static const SGPropertyNode *altitude
    //     = fgGetNode("/position/altitude-ft");
    static const SGPropertyNode *groundlevel_nearplane
        = fgGetNode("/sim/current-view/ground-level-nearplane-m");

    FGLight *l = (FGLight *)(globals->get_subsystem("lighting"));
    static double last_visibility = -9999;

    // update fog params
    double actual_visibility;
    if (fgGetBool("/environment/clouds/status"))
        actual_visibility = thesky->get_visibility();
    else
        actual_visibility = fgGetDouble("/environment/visibility-m");
    if ( actual_visibility != last_visibility ) {
        last_visibility = actual_visibility;

        fog_exp_density = m_log01 / actual_visibility;
        fog_exp2_density = sqrt_m_log01 / actual_visibility;
        ground_exp2_punch_through = sqrt_m_log01 / (actual_visibility * 1.5);
        if ( actual_visibility < 8000 ) {
            rwy_exp2_punch_through = sqrt_m_log01 / (actual_visibility * 2.5);
            taxi_exp2_punch_through = sqrt_m_log01 / (actual_visibility * 1.5);
        } else {
            rwy_exp2_punch_through = sqrt_m_log01 / ( 8000 * 2.5 );
            taxi_exp2_punch_through = sqrt_m_log01 / ( 8000 * 1.5 );
        }
    }

    // double angle;
    // GLfloat black[4] = { 0.0, 0.0, 0.0, 1.0 };
    // GLfloat white[4] = { 1.0, 1.0, 1.0, 1.0 };
    // GLfloat terrain_color[4] = { 0.54, 0.44, 0.29, 1.0 };
    // GLfloat mat_shininess[] = { 10.0 };
    GLbitfield clear_mask;

    if ( idle_state != 1000 ) {
        // still initializing, draw the splash screen
        if ( fgGetBool("/sim/startup/splash-screen") ) {
            fgSplashUpdate(0.0, 1.0);
        }
        // Keep resetting sim time while the sim is initializing
        globals->set_sim_time_sec( 0.0 );
        SGAnimation::set_sim_time_sec( 0.0 );
    } else {
        // idle_state is now 1000 meaning we've finished all our
        // initializations and are running the main loop, so this will
        // now work without seg faulting the system.

        FGViewer *current__view = globals->get_current_view();

        // calculate our current position in cartesian space
        globals->get_scenery()->set_center( globals->get_scenery()->get_next_center() );

        // update view port
        fgReshape( fgGetInt("/sim/startup/xsize"),
                   fgGetInt("/sim/startup/ysize") );

        if ( fgGetBool("/sim/rendering/clouds3d") ) {
            glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT );
            cloud3d_imposter_state->force();
            glDisable( GL_FOG );
            glColor4f( 1.0, 1.0, 1.0, 1.0 );
            glEnable(GL_DEPTH_TEST);
            glEnable(GL_BLEND);
            glBlendFunc( GL_ONE, GL_ONE_MINUS_SRC_ALPHA ) ;

#ifdef FG_USE_CLOUDS_3D
            if ( _bcloud_orig ) {
                Point3D c = globals->get_scenery()->get_center();
                sgClouds3d->Set_Cloud_Orig( &c );
                _bcloud_orig = false;
            }
            sgClouds3d->Update( current__view->get_absolute_view_pos() );
#endif
            glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
            glDisable(GL_DEPTH_TEST);
        }

        clear_mask = GL_DEPTH_BUFFER_BIT;
        if ( fgGetBool("/sim/rendering/wireframe") ) {
            clear_mask |= GL_COLOR_BUFFER_BIT;
        }

        if ( skyblend ) {
            if ( fgGetBool("/sim/rendering/textures") ) {
            // glClearColor(black[0], black[1], black[2], black[3]);
            glClearColor(l->adj_fog_color()[0], l->adj_fog_color()[1],
                         l->adj_fog_color()[2], l->adj_fog_color()[3]);
            clear_mask |= GL_COLOR_BUFFER_BIT;
            }
        } else {
            glClearColor(l->sky_color()[0], l->sky_color()[1],
                         l->sky_color()[2], l->sky_color()[3]);
            clear_mask |= GL_COLOR_BUFFER_BIT;
        }
        if ( multi_pass_clouds && draw_clouds ) {
            glClearStencil( 0 );
            clear_mask |= GL_STENCIL_BUFFER_BIT;
        }
        glClear( clear_mask );

        // Tell GL we are switching to model view parameters

        // I really should create a derived ssg node or use a call
        // back or something so that I can draw the sky within the
        // ssgCullAndDraw() function, but for now I just mimic what
        // ssg does to set up the model view matrix
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        ssgSetCamera( (sgVec4 *)current__view->get_VIEW() );

        // set the opengl state to known default values
        default_state->force();

        // update fog params if visibility has changed
        double visibility_meters = fgGetDouble("/environment/visibility-m");
        thesky->set_visibility(visibility_meters);

        thesky->modify_vis( cur_fdm_state->get_Altitude() * SG_FEET_TO_METER,
                            ( global_multi_loop * fgGetInt("/sim/speed-up") )
                            / (double)fgGetInt("/sim/model-hz") );

        // Set correct opengl fog density
        glFogf (GL_FOG_DENSITY, fog_exp2_density);

        // update the sky dome
        if ( skyblend ) {
            /*
             SG_LOG( SG_GENERAL, SG_BULK, "thesky->repaint() sky_color = "
             << l->sky_color()[0] << " "
             << l->sky_color()[1] << " "
             << l->sky_color()[2] << " "
             << l->sky_color()[3] );
            SG_LOG( SG_GENERAL, SG_BULK, "    fog = "
             << l->fog_color()[0] << " "
             << l->fog_color()[1] << " "
             << l->fog_color()[2] << " "
             << l->fog_color()[3] ); 
            SG_LOG( SG_GENERAL, SG_BULK,
                    "    sun_angle = " << l->sun_angle
             << "    moon_angle = " << l->moon_angle );
            */

            static SGSkyColor scolor;
            FGLight *l = (FGLight *)(globals->get_subsystem("lighting"));

            scolor.sky_color   = l->sky_color();
            scolor.fog_color   = l->adj_fog_color();
            scolor.cloud_color = l->cloud_color();
            scolor.sun_angle   = l->get_sun_angle();
            scolor.moon_angle  = l->get_moon_angle();
            scolor.nplanets    = globals->get_ephem()->getNumPlanets();
            scolor.nstars      = globals->get_ephem()->getNumStars();
            scolor.planet_data = globals->get_ephem()->getPlanets();
            scolor.star_data   = globals->get_ephem()->getStars();

            thesky->repaint( scolor );

            /*
            SG_LOG( SG_GENERAL, SG_BULK,
                    "thesky->reposition( view_pos = " << view_pos[0] << " "
             << view_pos[1] << " " << view_pos[2] );
            SG_LOG( SG_GENERAL, SG_BULK,
                    "    zero_elev = " << zero_elev[0] << " "
             << zero_elev[1] << " " << zero_elev[2]
             << " lon = " << cur_fdm_state->get_Longitude()
             << " lat = " << cur_fdm_state->get_Latitude() );
            SG_LOG( SG_GENERAL, SG_BULK,
                    "    sun_rot = " << l->get_sun_rotation
             << " gst = " << SGTime::cur_time_params->getGst() );
            SG_LOG( SG_GENERAL, SG_BULK,
                 "    sun ra = " << globals->get_ephem()->getSunRightAscension()
              << " sun dec = " << globals->get_ephem()->getSunDeclination()
              << " moon ra = " << globals->get_ephem()->getMoonRightAscension()
              << " moon dec = " << globals->get_ephem()->getMoonDeclination() );
            */

            // The sun and moon distances are scaled down versions
            // of the actual distance to get both the moon and the sun
            // within the range of the far clip plane.
            // Moon distance:    384,467 kilometers
            // Sun distance: 150,000,000 kilometers
            double sun_horiz_eff, moon_horiz_eff;
            if (fgGetBool("/sim/rendering/horizon-effect")) {
            sun_horiz_eff = 0.67+pow(0.5+cos(l->get_sun_angle())*2/2, 0.33)/3;
            moon_horiz_eff = 0.67+pow(0.5+cos(l->get_moon_angle())*2/2, 0.33)/3;
            } else {
               sun_horiz_eff = moon_horiz_eff = 1.0;
            }

            static SGSkyState sstate;

            sstate.view_pos  = current__view->get_view_pos();
            sstate.zero_elev = current__view->get_zero_elev();
            sstate.view_up   = current__view->get_world_up();
            sstate.lon       = current__view->getLongitude_deg()
                                * SGD_DEGREES_TO_RADIANS;
            sstate.lat       = current__view->getLatitude_deg()
                                * SGD_DEGREES_TO_RADIANS;
            sstate.alt       = current__view->getAltitudeASL_ft()
                                * SG_FEET_TO_METER;
            sstate.spin      = l->get_sun_rotation();
            sstate.gst       = globals->get_time_params()->getGst();
            sstate.sun_ra    = globals->get_ephem()->getSunRightAscension();
            sstate.sun_dec   = globals->get_ephem()->getSunDeclination();
            sstate.sun_dist  = 50000.0 * sun_horiz_eff;
            sstate.moon_ra   = globals->get_ephem()->getMoonRightAscension();
            sstate.moon_dec  = globals->get_ephem()->getMoonDeclination();
            sstate.moon_dist = 40000.0 * moon_horiz_eff;

            thesky->reposition( sstate, delta_time_sec );
        }

        glEnable( GL_DEPTH_TEST );
        if ( strcmp(fgGetString("/sim/rendering/fog"), "disabled") ) {
            glEnable( GL_FOG );
            glFogi( GL_FOG_MODE, GL_EXP2 );
            glFogfv( GL_FOG_COLOR, l->adj_fog_color() );
        }

        // set sun/lighting parameters
        ssgGetLight( 0 ) -> setPosition( l->sun_vec() );

        // GL_LIGHT_MODEL_AMBIENT has a default non-zero value so if
        // we only update GL_AMBIENT for our lights we will never get
        // a completely dark scene.  So, we set GL_LIGHT_MODEL_AMBIENT
        // explicitely to black.
        glLightModelfv( GL_LIGHT_MODEL_AMBIENT, black );

        ssgGetLight( 0 ) -> setColour( GL_AMBIENT, l->scene_ambient() );
        ssgGetLight( 0 ) -> setColour( GL_DIFFUSE, l->scene_diffuse() );
        ssgGetLight( 0 ) -> setColour( GL_SPECULAR, l->scene_specular() );

        // texture parameters
        // glEnable( GL_TEXTURE_2D );
        glTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ) ;
        glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST ) ;

        // glMatrixMode( GL_PROJECTION );
        // glLoadIdentity();
        ssgSetFOV( current__view->get_h_fov(),
                   current__view->get_v_fov() );

        double agl =
            current_aircraft.fdm_state->get_Altitude() * SG_FEET_TO_METER
            - globals->get_scenery()->get_cur_elev();

        if ( agl > 10.0 ) {
            scene_nearplane = 10.0f;
            scene_farplane = 120000.0f;
        } else {
            scene_nearplane = groundlevel_nearplane->getDoubleValue();
            scene_farplane = 120000.0f;
        }

        ssgSetNearFar( scene_nearplane, scene_farplane );

#ifdef FG_MPLAYER_AS
        // Update any multiplayer models
        globals->get_multiplayer_rx_mgr()->Update();
#endif

        if ( draw_otw && skyblend ) {
            // draw the sky backdrop

            // we need a white diffuse light for the phase of the moon
            ssgGetLight( 0 ) -> setColour( GL_DIFFUSE, white );
            thesky->preDraw( cur_fdm_state->get_Altitude() * SG_FEET_TO_METER,
                             fog_exp2_density );
            // return to the desired diffuse color
            ssgGetLight( 0 ) -> setColour( GL_DIFFUSE, l->scene_diffuse() );
        }

        // draw the ssg scene
        glEnable( GL_DEPTH_TEST );

        ssgSetNearFar( scene_nearplane, scene_farplane );

        if ( fgGetBool("/sim/rendering/wireframe") ) {
            // draw wire frame
            glPolygonMode( GL_FRONT_AND_BACK, GL_LINE );
        }
        if ( draw_otw ) {
            if ( draw_clouds ) {

                // Draw the terrain
                FGTileMgr::set_tile_filter( true );
                sgSetModelFilter( false );
                globals->get_aircraft_model()->select( false );
                ssgCullAndDraw( globals->get_scenery()->get_scene_graph() );

                // Disable depth buffer update, draw the clouds
                glDepthMask( GL_FALSE );
                thesky->drawUpperClouds();
                if ( multi_pass_clouds ) {
                    thesky->drawLowerClouds();
                }
                glDepthMask( GL_TRUE );

                if ( multi_pass_clouds ) {
                    // Draw the objects except the aircraft
                    //  and update the stencil buffer with 1
                    glEnable( GL_STENCIL_TEST );
                    glStencilFunc( GL_ALWAYS, 1, 1 );
                    glStencilOp( GL_KEEP, GL_KEEP, GL_REPLACE );
                }
                FGTileMgr::set_tile_filter( false );
                sgSetModelFilter( true );
                ssgCullAndDraw( globals->get_scenery()->get_scene_graph() );
            } else {
                FGTileMgr::set_tile_filter( true );
                sgSetModelFilter( true );
                globals->get_aircraft_model()->select( false );
                ssgCullAndDraw( globals->get_scenery()->get_scene_graph() );
            }
        }

        // This is a bit kludgy.  Every 200 frames, do an extra
        // traversal of the scene graph without drawing anything, but
        // with the field-of-view set to 360x360 degrees.  This
        // ensures that out-of-range random objects that are not in
        // the current view frustum will still be freed properly.
        static int counter = 0;
        counter++;
        if (counter == 200) {
            sgFrustum f;
            f.setFOV(360, 360);
                    // No need to put the near plane too close;
                    // this way, at least the aircraft can be
                    // culled.
            f.setNearFar(1000, 1000000);
            sgMat4 m;
            ssgGetModelviewMatrix(m);
            FGTileMgr::set_tile_filter( true );
            sgSetModelFilter( true );
            globals->get_scenery()->get_scene_graph()->cull(&f, m, true);
            counter = 0;
        }

        // change state for lighting here

        // draw runway lighting
        glFogf (GL_FOG_DENSITY, rwy_exp2_punch_through);
        ssgSetNearFar( scene_nearplane, scene_farplane );

        if ( enhanced_lighting ) {

            // Enable states for drawing points with GL_extension
            glEnable(GL_POINT_SMOOTH);

            if ( distance_attenuation && glPointParameterIsSupported )
            {
                // Enable states for drawing points with GL_extension
                glEnable(GL_POINT_SMOOTH);

                float quadratic[3] = {1.0, 0.001, 0.0000001};
                // makes the points fade as they move away
                glPointParameterfvPtr(GL_DISTANCE_ATTENUATION_EXT, quadratic);
                glPointParameterfPtr(GL_POINT_SIZE_MIN_EXT, 1.0); 
            }

            glPointSize(4.0);

            // blending function for runway lights
            glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) ;
        }

        glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
        glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
        glEnable(GL_TEXTURE_GEN_S);
        glEnable(GL_TEXTURE_GEN_T);
        glPolygonMode(GL_FRONT, GL_POINT);

        // draw runway lighting
        if ( draw_otw ) {
            ssgCullAndDraw( globals->get_scenery()->get_vasi_lights_root() );
            ssgCullAndDraw( globals->get_scenery()->get_rwy_lights_root() );
        }

        // change punch through and then draw taxi lighting
        glFogf ( GL_FOG_DENSITY, fog_exp2_density );
        // sgVec3 taxi_fog;
        // sgSetVec3( taxi_fog, 0.0, 0.0, 0.0 );
        // glFogfv ( GL_FOG_COLOR, taxi_fog );
        if ( draw_otw ) {
            ssgCullAndDraw( globals->get_scenery()->get_taxi_lights_root() );
        }

        // clean up lighting
        glPolygonMode(GL_FRONT, GL_FILL);
        glDisable(GL_TEXTURE_GEN_S);
        glDisable(GL_TEXTURE_GEN_T);

        //static int _frame_count = 0;
        //if (_frame_count % 30 == 0) {
        //  printf("SSG: %s\n", ssgShowStats());
        //}
        //else {
        //  ssgShowStats();
        //}
        //_frame_count++;


        if ( enhanced_lighting ) {
            if ( distance_attenuation && glPointParameterIsSupported ) {
                glPointParameterfvPtr(GL_DISTANCE_ATTENUATION_EXT,
                                      default_attenuation);
            }

            glPointSize(1.0);
            glDisable(GL_POINT_SMOOTH);
        }

        // draw ground lighting
        glFogf (GL_FOG_DENSITY, ground_exp2_punch_through);
        if ( draw_otw ) {
            ssgCullAndDraw( globals->get_scenery()->get_gnd_lights_root() );
        }

        if ( draw_otw && fgGetBool("/sim/rendering/clouds3d") ) {
            glDisable( GL_FOG );
            glDisable( GL_LIGHTING );
            // cout << "drawing new clouds" << endl;

            glEnable(GL_DEPTH_TEST);
            glEnable(GL_BLEND);
            glBlendFunc( GL_ONE, GL_ONE_MINUS_SRC_ALPHA ) ;

            /*
            glEnable( GL_TEXTURE_2D );
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
            */

#ifdef FG_USE_CLOUDS_3D
            sgClouds3d->Draw((sgVec4 *)current__view->get_VIEW());
#endif
            glEnable( GL_FOG );
            glEnable( GL_LIGHTING );
            glEnable( GL_DEPTH_TEST );
            glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
        }

        if ( draw_otw && draw_clouds ) {
            if ( multi_pass_clouds ) {
                // Disable depth buffer update, draw the clouds where the
                //  objects overwrite the already drawn clouds, by testing
                //  the stencil buffer against 1
                glDepthMask( GL_FALSE );
                glStencilFunc( GL_EQUAL, 1, 1 );
                glStencilOp( GL_KEEP, GL_KEEP, GL_KEEP );
                thesky->drawUpperClouds();
                thesky->drawLowerClouds();
                glDepthMask( GL_TRUE );
                glDisable( GL_STENCIL_TEST );
            } else {
                glDepthMask( GL_FALSE );
                thesky->drawLowerClouds();
                glDepthMask( GL_TRUE );
            }
        }

        if ( draw_otw ) {
            FGTileMgr::set_tile_filter( false );
            sgSetModelFilter( false );
            globals->get_aircraft_model()->select( true );
            globals->get_model_mgr()->draw();
            globals->get_aircraft_model()->draw();
            // If the view is internal, the previous line draw the 
            //  cockpit with modified near/far clip planes and deselect
            //  the aircraft in the global scenegraph
            // Otherwise, it just enables the aircraft: The scenegraph
            //  must be drawn again to see the plane.
            ssgCullAndDraw( globals->get_scenery()->get_scene_graph() );
            FGTileMgr::set_tile_filter( true );
            sgSetModelFilter( true );
            globals->get_aircraft_model()->select( true );
        }

        // display HUD && Panel
        glDisable( GL_FOG );
        glDisable( GL_DEPTH_TEST );
        // glDisable( GL_CULL_FACE );
        // glDisable( GL_TEXTURE_2D );

        // update the controls subsystem
        globals->get_controls()->update(delta_time_sec);

        hud_and_panel->apply();
        fgCockpitUpdate();

        // Use the hud_and_panel ssgSimpleState for rendering the ATC output
        // This only works properly if called before the panel call
        if((fgGetBool("/sim/ATC/enabled")) || (fgGetBool("/sim/ai-traffic/enabled")))
            globals->get_ATC_display()->update(delta_time_sec);

        // update the panel subsystem
        if ( globals->get_current_panel() != NULL ) {
            globals->get_current_panel()->update(delta_time_sec);
        }
        fgUpdate3DPanels();

        // We can do translucent menus, so why not. :-)
        menus->apply();
        glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
        puDisplay();
        // glDisable ( GL_BLEND ) ;

        glEnable( GL_DEPTH_TEST );
        glEnable( GL_FOG );

        // Fade out the splash screen over the first three seconds.
        double t = globals->get_sim_time_sec();
        if ( t <= 1.0 ) {
            fgSplashUpdate(0.0, 1.0);
        } else if ( t <= 3.0) {
            fgSplashUpdate(0.0, (3.0 - t) / 2.0);
        }
    }
}


// Update internal time dependent calculations (i.e. flight model)
// FIXME: this distinction is obsolete; all subsystems now get delta
// time on update.
void fgUpdateTimeDepCalcs() {
    static bool inited = false;

    static const SGPropertyNode *replay_master
        = fgGetNode( "/sim/freeze/replay", true );
    static SGPropertyNode *replay_time
        = fgGetNode( "/sim/replay/time", true );
    // static const SGPropertyNode *replay_end_time
    //     = fgGetNode( "/sim/replay/end-time", true );

    //SG_LOG(SG_FLIGHT,SG_INFO, "Updating time dep calcs()");

    // Initialize the FDM here if it hasn't been and if we have a
    // scenery elevation hit.

    // cout << "cur_fdm_state->get_inited() = " << cur_fdm_state->get_inited() 
    //      << " cur_elev = " << scenery.get_cur_elev() << endl;

    if ( !cur_fdm_state->get_inited() &&
         globals->get_scenery()->get_cur_elev() > -9990 )
    {
        SG_LOG(SG_FLIGHT,SG_INFO, "Finally initializing fdm");  
        cur_fdm_state->init();
        if ( cur_fdm_state->get_bound() ) {
            cur_fdm_state->unbind();
        }
        cur_fdm_state->bind();
    }

    // conceptually, the following block could be done for each fdm
    // instance ...
    if ( cur_fdm_state->get_inited() ) {
        // we have been inited, and  we are good to go ...

        if ( !inited ) {
            inited = true;
        }

        if ( ! replay_master->getBoolValue() ) {
            cur_fdm_state->update( delta_time_sec );
        } else {
            FGReplay *r = (FGReplay *)(globals->get_subsystem( "replay" ));
            r->replay( replay_time->getDoubleValue() );
            replay_time->setDoubleValue( replay_time->getDoubleValue()
                                         + ( delta_time_sec
                                             * fgGetInt("/sim/speed-up") ) );
        }
    } else {
        // do nothing, fdm isn't inited yet
    }

    globals->get_model_mgr()->update(delta_time_sec);
    globals->get_aircraft_model()->update(delta_time_sec);

    // update the view angle
    globals->get_viewmgr()->update(delta_time_sec);

    // Update solar system
    globals->get_ephem()->update( globals->get_time_params()->getMjd(),
                                  globals->get_time_params()->getLst(),
                                  cur_fdm_state->get_Latitude() );

    // Update radio stack model
    current_radiostack->update(delta_time_sec);
}


void fgInitTimeDepCalcs( void ) {
    // noop for now
}


static const double alt_adjust_ft = 3.758099;
static const double alt_adjust_m = alt_adjust_ft * SG_FEET_TO_METER;


// What should we do when we have nothing else to do?  Let's get ready
// for the next move and update the display?
static void fgMainLoop( void ) {
    int model_hz = fgGetInt("/sim/model-hz");

    static const SGPropertyNode *longitude
        = fgGetNode("/position/longitude-deg");
    static const SGPropertyNode *latitude
        = fgGetNode("/position/latitude-deg");
    static const SGPropertyNode *altitude
        = fgGetNode("/position/altitude-ft");
    static const SGPropertyNode *clock_freeze
        = fgGetNode("/sim/freeze/clock", true);
    static const SGPropertyNode *cur_time_override
        = fgGetNode("/sim/time/cur-time-override", true);
    // static const SGPropertyNode *replay_master
    //     = fgGetNode("/sim/freeze/replay", true);

    SGCloudLayer::enable_bump_mapping = fgGetBool("/sim/rendering/bump-mapping",true);

    // Update the elapsed time.
    static bool first_time = true;
    if ( first_time ) {
        last_time_stamp.stamp();
        first_time = false;
    }

    double throttle_hz = fgGetDouble("/sim/frame-rate-throttle-hz", 0.0);
    if ( throttle_hz > 0.0 ) {
        // simple frame rate throttle
        double dt = 1000000.0 / throttle_hz;
        current_time_stamp.stamp();
        while ( current_time_stamp - last_time_stamp < dt ) {
            current_time_stamp.stamp();
        }
    } else {
        // run as fast as the app will go
        current_time_stamp.stamp();
    }

    real_delta_time_sec
        = double(current_time_stamp - last_time_stamp) / 1000000.0;
    if ( clock_freeze->getBoolValue() ) {
        delta_time_sec = 0;
    } else {
        delta_time_sec = real_delta_time_sec;
    }
    last_time_stamp = current_time_stamp;
    globals->inc_sim_time_sec( delta_time_sec );
    SGAnimation::set_sim_time_sec( globals->get_sim_time_sec() );

    // These are useful, especially for Nasal scripts.
    fgSetDouble("/sim/time/delta-realtime-sec", real_delta_time_sec);
    fgSetDouble("/sim/time/delta-sec", delta_time_sec);

    static long remainder = 0;
    long elapsed;
#ifdef FANCY_FRAME_COUNTER
    int i;
    double accum;
#else
    static time_t last_time = 0;
    static int frames = 0;
#endif // FANCY_FRAME_COUNTER

    SGTime *t = globals->get_time_params();

    globals->get_event_mgr()->update(delta_time_sec);

    SG_LOG( SG_ALL, SG_DEBUG, "Running Main Loop");
    SG_LOG( SG_ALL, SG_DEBUG, "======= ==== ====");

#if defined( ENABLE_PLIB_JOYSTICK )
    // Read joystick and update control settings
    // if ( fgGetString("/sim/control-mode") == "joystick" )
    // {
    //    fgJoystickRead();
    // }
#endif

    // Fix elevation.  I'm just sticking this here for now, it should
    // probably move eventually

    /* printf("Before - ground = %.2f  runway = %.2f  alt = %.2f\n",
           scenery.get_cur_elev(),
           cur_fdm_state->get_Runway_altitude() * SG_FEET_TO_METER,
           cur_fdm_state->get_Altitude() * SG_FEET_TO_METER); */

    /* printf("Adjustment - ground = %.2f  runway = %.2f  alt = %.2f\n",
           scenery.get_cur_elev(),
           cur_fdm_state->get_Runway_altitude() * SG_FEET_TO_METER,
           cur_fdm_state->get_Altitude() * SG_FEET_TO_METER); */

    // cout << "Warp = " << globals->get_warp() << endl;

    // update "time"
    static bool last_clock_freeze = false;

    if ( clock_freeze->getBoolValue() ) {
        // clock freeze requested
        if ( cur_time_override->getLongValue() == 0 ) {
            fgSetLong( "/sim/time/cur-time-override", t->get_cur_time() );
            globals->set_warp( 0 );
        }
    } else {
        // no clock freeze requested
        if ( last_clock_freeze == true ) {
            // clock just unfroze, let's set warp as the difference
            // between frozen time and current time so we don't get a
            // time jump (and corresponding sky object and lighting
            // jump.)
            globals->set_warp( cur_time_override->getLongValue() - time(NULL) );
            fgSetLong( "/sim/time/cur-time-override", 0 );
        }
        if ( globals->get_warp_delta() != 0 ) {
            globals->inc_warp( globals->get_warp_delta() );
        }
    }

    last_clock_freeze = clock_freeze->getBoolValue();

    t->update( longitude->getDoubleValue() * SGD_DEGREES_TO_RADIANS,
               latitude->getDoubleValue() * SGD_DEGREES_TO_RADIANS,
               cur_time_override->getLongValue(),
               globals->get_warp() );

    if (globals->get_warp_delta() != 0) {
	FGLight *l = (FGLight *)(globals->get_subsystem("lighting"));
	l->update( 0.5 );
    }

    // update magvar model
    globals->get_mag()->update( longitude->getDoubleValue()
                              * SGD_DEGREES_TO_RADIANS,
                            latitude->getDoubleValue()
                              * SGD_DEGREES_TO_RADIANS,
                            altitude->getDoubleValue() * SG_FEET_TO_METER,
                            globals->get_time_params()->getJD() );

    // Get elapsed time (in usec) for this past frame
    elapsed = fgGetTimeInterval();
    SG_LOG( SG_ALL, SG_DEBUG, 
            "Elapsed time interval is = " << elapsed 
            << ", previous remainder is = " << remainder );

    // Calculate frame rate average
#ifdef FANCY_FRAME_COUNTER
    /* old fps calculation */
    if ( elapsed > 0 ) {
        double tmp;
        accum = 0.0;
        for ( i = FG_FRAME_RATE_HISTORY - 2; i >= 0; i-- ) {
            tmp = general.get_frame(i);
            accum += tmp;
            // printf("frame[%d] = %.2f\n", i, g->frames[i]);
            general.set_frame(i+1,tmp);
        }
        tmp = 1000000.0 / (float)elapsed;
        general.set_frame(0,tmp);
        // printf("frame[0] = %.2f\n", general.frames[0]);
        accum += tmp;
        general.set_frame_rate(accum / (float)FG_FRAME_RATE_HISTORY);
        // printf("ave = %.2f\n", general.frame_rate);
    }
#else
    if ( (t->get_cur_time() != last_time) && (last_time > 0) ) {
        general.set_frame_rate( frames );
        fgSetInt("/sim/frame-rate", frames);
        SG_LOG( SG_ALL, SG_DEBUG, 
            "--> Frame rate is = " << general.get_frame_rate() );
        frames = 0;
    }
    last_time = t->get_cur_time();
    ++frames;
#endif

    // Run ATC subsystem
    if (fgGetBool("/sim/ATC/enabled"))
        globals->get_ATC_mgr()->update(delta_time_sec);

    // Run the AI subsystem
    if (fgGetBool("/sim/ai-traffic/enabled"))
        globals->get_AI_mgr()->update(delta_time_sec);

    // Run flight model

    // Calculate model iterations needed for next frame
    elapsed += remainder;

    global_multi_loop = (long)(((double)elapsed * 0.000001) * model_hz );
    remainder = elapsed - ( (global_multi_loop*1000000) / model_hz );
    SG_LOG( SG_ALL, SG_DEBUG, 
            "Model iterations needed = " << global_multi_loop
            << ", new remainder = " << remainder );
        
    // chop max interations to something reasonable if the sim was
    // delayed for an excesive amount of time
    if ( global_multi_loop > 2.0 * model_hz ) {
        global_multi_loop = (int)(2.0 * model_hz );
        remainder = 0;
    }

    // flight model
    if ( global_multi_loop > 0 ) {
        fgUpdateTimeDepCalcs();
    } else {
        SG_LOG( SG_ALL, SG_DEBUG, 
            "Elapsed time is zero ... we're zinging" );
    }

    // Do any I/O channel work that might need to be done
    globals->get_io()->update( real_delta_time_sec );

    // see if we need to load any deferred-load textures
    globals->get_matlib()->load_next_deferred();

    // Run audio scheduler
#ifdef ENABLE_AUDIO_SUPPORT
    if ( globals->get_soundmgr()->is_working() ) {
        globals->get_soundmgr()->update( delta_time_sec );
    }
#endif

    globals->get_subsystem_mgr()->update(delta_time_sec);

    //
    // Tile Manager updates - see if we need to load any new scenery tiles.
    //   this code ties together the fdm, viewer and scenery classes...
    //   we may want to move this to it's own class at some point
    //
    double visibility_meters = fgGetDouble("/environment/visibility-m");
    FGViewer *current_view = globals->get_current_view();

    // get the location data for the primary FDM (now hardcoded to ac model)...
    SGLocation *acmodel_loc = NULL;
    acmodel_loc = (SGLocation *)globals->
        get_aircraft_model()->get3DModel()->getSGLocation();

    // update tile manager for FDM...
    // ...only if location is different than the current-view location
    // (to avoid duplicating effort)
    if( !fgGetBool("/sim/current-view/config/from-model") ) {
        if( acmodel_loc != NULL ) {
            globals->get_tile_mgr()->prep_ssg_nodes( acmodel_loc,
                                                     visibility_meters );
            globals->get_tile_mgr()->
                update( acmodel_loc, visibility_meters,
                        acmodel_loc->
                        get_absolute_view_pos(globals->
                                              get_scenery()->get_center()) );
            // save results of update in SGLocation for fdm...
            if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
                acmodel_loc->
                    set_cur_elev_m( globals->get_scenery()->get_cur_elev() );
                fgSetDouble("/position/ground-elev-m",
                            globals->get_scenery()->get_cur_elev());
            }
            acmodel_loc->
                set_tile_center( globals->get_scenery()->get_next_center() );
        }
    }

    globals->get_tile_mgr()->prep_ssg_nodes( current_view->getSGLocation(),
                                             visibility_meters );
    // update tile manager for view...
    // IMPORTANT!!! the tilemgr update for view location _must_ be
    // done last after the FDM's until all of Flight Gear code
    // references the viewer's location for elevation instead of the
    // "scenery's" current elevation.
    SGLocation *view_location = globals->get_current_view()->getSGLocation();
    globals->get_tile_mgr()->update( view_location, visibility_meters,
                                     current_view->get_absolute_view_pos() );
    // save results of update in SGLocation for fdm...
    if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
        current_view->getSGLocation()->
            set_cur_elev_m( globals->get_scenery()->get_cur_elev() );
    }
    current_view->getSGLocation()->
        set_tile_center( globals->get_scenery()->get_next_center() );

#ifdef ENABLE_AUDIO_SUPPORT
    // Right now we make a simplifying assumption that the primary
    // aircraft is the source of all sounds and that all sounds are
    // positioned relative to the current view position.

    static sgVec3 last_pos_offset;

    // set positional offset for sources
    sgVec3 source_pos_offset;
    sgSubVec3( source_pos_offset,
               view_location->get_view_pos(), acmodel_loc->get_view_pos() );
    // cout << "pos all = " << source_pos_offset[0] << " " << source_pos_offset[1] << " " << source_pos_offset[2] << endl;
    globals->get_soundmgr()->set_source_pos_all( source_pos_offset );

    // set the velocity
    sgVec3 source_vel;
    sgSubVec3( source_vel, source_pos_offset, last_pos_offset );
    sgScaleVec3( source_vel, delta_time_sec );
    sgCopyVec3( last_pos_offset, source_pos_offset );
    // cout << "vel = " << source_vel[0] << " " << source_vel[1] << " " << source_vel[2] << endl;
    globals->get_soundmgr()->set_source_vel_all( source_vel );

    // Right now we make a simplifying assumption that the listener is
    // always positioned at the origin.
    sgVec3 listener_pos;
    sgSetVec3( listener_pos, 0.0, 0.0, 0.0 );
    // cout << "listener = " << listener_pos[0] << " " << listener_pos[1] << " " << listener_pos[2] << endl;
    globals->get_soundmgr()->set_listener_pos( listener_pos );
#endif

    // If fdm location is same as viewer's then we didn't do the
    // update for fdm location above so we need to save the viewer
    // results in the fdm SGLocation as well...
    if( fgGetBool("/sim/current-view/config/from-model") ) {
        if( acmodel_loc != 0 ) {
            if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
                acmodel_loc->set_cur_elev_m( globals->get_scenery()->
                                             get_cur_elev() );
                fgSetDouble("/position/ground-elev-m",
                            globals->get_scenery()->get_cur_elev());
            }
            acmodel_loc->set_tile_center( globals->get_scenery()->
                                          get_next_center() );
        }
    }

    // END Tile Manager udpates

    if (fgGetBool("/sim/rendering/specular-highlight")) {
        glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SEPARATE_SPECULAR_COLOR);
	// glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE);
    } else {
        glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
        // glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, GL_FALSE);
    }

    fgRequestRedraw();

    SG_LOG( SG_ALL, SG_DEBUG, "" );
}


// This is the top level master main function that is registered as
// our idle funciton

// The first few passes take care of initialization things (a couple
// per pass) and once everything has been initialized fgMainLoop from
// then on.

static void fgIdleFunction ( void ) {
    // printf("idle state == %d\n", idle_state);

    if ( idle_state == 0 ) {
        fgSetBool("sim/initialised", false);

        // Initialize the splash screen right away
        if ( fgGetBool("/sim/startup/splash-screen") ) {
            fgSplashInit(fgGetString("/sim/startup/splash-texture"));
        }
        
        idle_state++;
    } else if ( idle_state == 1 ) {
        // Initialize audio support
#ifdef ENABLE_AUDIO_SUPPORT

        // Start the intro music
        if ( fgGetBool("/sim/startup/intro-music") ) {
            SGPath mp3file( globals->get_fg_root() );
            mp3file.append( "Sounds/intro.mp3" );

            SG_LOG( SG_GENERAL, SG_INFO, 
                "Starting intro music: " << mp3file.str() );

#if defined( __CYGWIN__ )
            string command = "start /m `cygpath -w " + mp3file.str() + "`";
#elif defined( WIN32 )
            string command = "start /m " + mp3file.str();
#else
            string command = "mpg123 " + mp3file.str() + "> /dev/null 2>&1";
#endif

            system ( command.c_str() );
        }
#endif

        idle_state++;
    } else if ( idle_state == 2 ) {
        // These are a few miscellaneous things that aren't really
        // "subsystems" but still need to be initialized.

#ifdef USE_GLIDE
        if ( strstr ( general.get_glRenderer(), "Glide" ) ) {
            grTexLodBiasValue ( GR_TMU0, 1.0 ) ;
        }
#endif

        idle_state++;
    } else if ( idle_state == 3 ) {
        // This is the top level init routine which calls all the
        // other subsystem initialization routines.  If you are adding
        // a subsystem to flightgear, its initialization call should
        // located in this routine.
        if( !fgInitSubsystems()) {
            SG_LOG( SG_GENERAL, SG_ALERT,
                "Subsystem initializations failed ..." );
            exit(-1);
        }

        idle_state++;
    } else if ( idle_state == 4 ) {
        // Initialize the time offset (warp) after fgInitSubsystem
        // (which initializes the lighting interpolation tables.)
        fgInitTimeOffset();

        // setup OpenGL view parameters
        fgInitVisuals();

        // Read the list of available aircrafts
        fgReadAircraft();

        idle_state++;
    } else if ( idle_state == 5 ) {

        idle_state++;
    } else if ( idle_state == 6 ) {
        // sleep(1);

        idle_state = 1000;

        SG_LOG( SG_GENERAL, SG_INFO, "Panel visible = " << fgPanelVisible() );
        fgReshape( fgGetInt("/sim/startup/xsize"),
               fgGetInt("/sim/startup/ysize") );

    } 

    if ( idle_state == 1000 ) {
        // We've finished all our initialization steps, from now on we
        // run the main loop.
        fgSetBool("sim/initialised",true);

        fgRegisterIdleHandler(fgMainLoop);
    } else {
        if ( fgGetBool("/sim/startup/splash-screen") ) {
            fgSplashUpdate(0.0, 1.0);
        }
    }
}

// options.cxx needs to see this for toggle_panel()
// Handle new window size or exposure
void fgReshape( int width, int height ) {
    int view_h;

    if ( (!fgGetBool("/sim/virtual-cockpit"))
         && fgPanelVisible() && idle_state == 1000 ) {
        view_h = (int)(height * (globals->get_current_panel()->getViewHeight() -
                             globals->get_current_panel()->getYOffset()) / 768.0);
    } else {
        view_h = height;
    }

    glViewport( 0, (GLint)(height - view_h), (GLint)(width), (GLint)(view_h) );

    fgSetInt("/sim/startup/xsize", width);
    fgSetInt("/sim/startup/ysize", height);
    guiInitMouse(width, height);

    // for all views
    FGViewMgr *viewmgr = globals->get_viewmgr();
    if (viewmgr) {
      for ( int i = 0; i < viewmgr->size(); ++i ) {
        viewmgr->get_view(i)->
          set_aspect_ratio((float)view_h / (float)width);
      }

      ssgSetFOV( viewmgr->get_current_view()->get_h_fov(),
               viewmgr->get_current_view()->get_v_fov() );

#ifdef FG_USE_CLOUDS_3D
      sgClouds3d->Resize( viewmgr->get_current_view()->get_h_fov(),
               viewmgr->get_current_view()->get_v_fov() );
#endif
    }

    fgHUDReshape();

}


// do some clean up on exit.  Specifically we want to call alutExit()
// which happens in the sound manager destructor.
void fgExitCleanup() {
    delete globals;
    fgOSExit(0);
}


// Main top level initialization
bool fgMainInit( int argc, char **argv ) {

#if defined( macintosh )
    freopen ("stdout.txt", "w", stdout );
    freopen ("stderr.txt", "w", stderr );
    argc = ccommand( &argv );
#endif

    // set default log levels
    sglog().setLogLevels( SG_ALL, SG_ALERT );

    atexit(fgExitCleanup);

    string version;
#ifdef FLIGHTGEAR_VERSION
    version = FLIGHTGEAR_VERSION;
#else
    version = "unknown version";
#endif
    SG_LOG( SG_GENERAL, SG_INFO, "FlightGear:  Version "
            << version );
    SG_LOG( SG_GENERAL, SG_INFO, "Built with " << SG_COMPILER_STR << endl );

    // Allocate global data structures.  This needs to happen before
    // we parse command line options

    globals = new FGGlobals;

    // seed the random number generater
    sg_srandom_time();

    FGControls *controls = new FGControls;
    globals->set_controls( controls );

    string_list *col = new string_list;
    globals->set_channel_options_list( col );

    // Scan the config file(s) and command line options to see if
    // fg_root was specified (ignore all other options for now)
    fgInitFGRoot(argc, argv);

    // Check for the correct base package version
    static char required_version[] = "0.9.4";
    string base_version = fgBasePackageVersion();
    if ( !(base_version == required_version) ) {
        // tell the operator how to use this application

        SG_LOG( SG_GENERAL, SG_ALERT, "" ); // To popup the console on windows
        cerr << endl << "Base package check failed ... " \
             << "Found version " << base_version << " at: " \
             << globals->get_fg_root() << endl;
        cerr << "Please upgrade to version: " << required_version << endl;
#ifdef _MSC_VER
        cerr << "Hit a key to continue..." << endl;
        cin.get();
#endif
        exit(-1);
    }

    // Initialize the Aircraft directory to "" (UIUC)
    aircraft_dir = "";

    // Load the configuration parameters.  (Command line options
    // overrides config file options.  Config file options override
    // defaults.)
    if ( !fgInitConfig(argc, argv) ) {
        SG_LOG( SG_GENERAL, SG_ALERT, "Config option parsing failed ..." );
        exit(-1);
    }

    // Initialize the Window/Graphics environment.
#if !defined(__APPLE__) || defined(OSX_BUNDLE)
    // Mac OS X command line ("non-bundle") applications call this
    // from main(), in bootstrap.cxx.  Andy doesn't know why, someone
    // feel free to add comments...
    fgOSInit(&argc, argv);
#endif

    fgRegisterWindowResizeHandler( fgReshape );
    fgRegisterIdleHandler( fgIdleFunction );
    fgRegisterDrawHandler( fgRenderFrame );

#ifdef FG_ENABLE_MULTIPASS_CLOUDS
    bool get_stencil_buffer = true;
#else
    bool get_stencil_buffer = false;
#endif

    // Clouds3D requires an alpha channel
    // clouds may require stencil buffer
    fgOSOpenWindow( fgGetInt("/sim/startup/xsize"),
                    fgGetInt("/sim/startup/ysize"),
                    fgGetInt("/sim/rendering/bits-per-pixel"),
                    fgGetBool("/sim/rendering/clouds3d"),
                    get_stencil_buffer,
                    fgGetBool("/sim/startup/fullscreen") );

    // This seems to be the absolute earliest in the init sequence
    // that these calls will return valid info.  Too bad it's after
    // we've already created and sized out window. :-(
    general.set_glVendor( (char *)glGetString ( GL_VENDOR ) );
    general.set_glRenderer( (char *)glGetString ( GL_RENDERER ) );
    general.set_glVersion( (char *)glGetString ( GL_VERSION ) );
    SG_LOG( SG_GENERAL, SG_INFO, general.get_glRenderer() );

    GLint tmp;
    glGetIntegerv( GL_MAX_TEXTURE_SIZE, &tmp );
    general.set_glMaxTexSize( tmp );
    SG_LOG ( SG_GENERAL, SG_INFO, "Max texture size = " << tmp );

    glGetIntegerv( GL_DEPTH_BITS, &tmp );
    general.set_glDepthBits( tmp );
    SG_LOG ( SG_GENERAL, SG_INFO, "Depth buffer bits = " << tmp );

    // Initialize plib net interface
    netInit( &argc, argv );

    // Initialize ssg (from plib).  Needs to come before we do any
    // other ssg stuff, but after opengl has been initialized.
    ssgInit();

    // Initialize the user interface (we need to do this before
    // passing off control to the OS main loop and before
    // fgInitGeneral to get our fonts !!!
    guiInit();

    // Read the list of available aircrafts
    fgReadAircraft();

#ifdef GL_EXT_texture_lod_bias
    glTexEnvf( GL_TEXTURE_FILTER_CONTROL_EXT, GL_TEXTURE_LOD_BIAS_EXT, -0.5 ) ;
#endif

            // get the address of our OpenGL extensions
    if ( fgGetBool("/sim/rendering/distance-attenuation") )
    {
        if (SGIsOpenGLExtensionSupported("GL_EXT_point_parameters") ) {
            glPointParameterIsSupported = true;
            glPointParameterfPtr = (glPointParameterfProc)
                                   SGLookupFunction("glPointParameterfEXT");
            glPointParameterfvPtr = (glPointParameterfvProc)
                                    SGLookupFunction("glPointParameterfvEXT");

        } else if ( SGIsOpenGLExtensionSupported("GL_ARB_point_parameters") ) {
            glPointParameterIsSupported = true;
            glPointParameterfPtr = (glPointParameterfProc)
                                   SGLookupFunction("glPointParameterfARB");
            glPointParameterfvPtr = (glPointParameterfvProc)
                                    SGLookupFunction("glPointParameterfvARB");
        } else
            glPointParameterIsSupported = false;
   }

    // based on the requested presets, calculate the true starting
    // lon, lat
    fgInitNav();
    fgInitPosition();

    SGTime *t = fgInitTime();
    globals->set_time_params( t );

    // Do some quick general initializations
    if( !fgInitGeneral()) {
        SG_LOG( SG_GENERAL, SG_ALERT, 
            "General initializations failed ..." );
        exit(-1);
    }

    ////////////////////////////////////////////////////////////////////
    // Initialize the property-based built-in commands
    ////////////////////////////////////////////////////////////////////
    fgInitCommands();

    ////////////////////////////////////////////////////////////////////
    // Initialize the material manager
    ////////////////////////////////////////////////////////////////////
    globals->set_matlib( new SGMaterialLib );

    globals->set_model_lib(new SGModelLib);

    ////////////////////////////////////////////////////////////////////
    // Initialize the TG scenery subsystem.
    ////////////////////////////////////////////////////////////////////
    globals->set_scenery( new FGScenery );
    globals->get_scenery()->init();
    globals->get_scenery()->bind();
    globals->set_tile_mgr( new FGTileMgr );

    ////////////////////////////////////////////////////////////////////
    // Initialize the general model subsystem.
    ////////////////////////////////////////////////////////////////////
    globals->set_model_mgr(new FGModelMgr);
    globals->get_model_mgr()->init();
    globals->get_model_mgr()->bind();

    ////////////////////////////////////////////////////////////////////
    // Initialize the 3D aircraft model subsystem (has a dependency on
    // the scenery subsystem.)
    ////////////////////////////////////////////////////////////////////
    globals->set_aircraft_model(new FGAircraftModel);
    globals->get_aircraft_model()->init();
    globals->get_aircraft_model()->bind();

    ////////////////////////////////////////////////////////////////////
    // Initialize the view manager subsystem.
    ////////////////////////////////////////////////////////////////////
    FGViewMgr *viewmgr = new FGViewMgr;
    globals->set_viewmgr( viewmgr );
    viewmgr->init();
    viewmgr->bind();


    // Initialize the sky
    SGPath ephem_data_path( globals->get_fg_root() );
    ephem_data_path.append( "Astro" );
    SGEphemeris *ephem = new SGEphemeris( ephem_data_path.c_str() );
    ephem->update( globals->get_time_params()->getMjd(),
                   globals->get_time_params()->getLst(),
                   0.0 );
    globals->set_ephem( ephem );

    // TODO: move to environment mgr
    thesky = new SGSky;
    SGPath texture_path(globals->get_fg_root());
    texture_path.append("Textures");
    texture_path.append("Sky");
    for (int i = 0; i < FGEnvironmentMgr::MAX_CLOUD_LAYERS; i++) {
        SGCloudLayer * layer = new SGCloudLayer(texture_path.str());
        thesky->add_cloud_layer(layer);
    }

    SGPath sky_tex_path( globals->get_fg_root() );
    sky_tex_path.append( "Textures" );
    sky_tex_path.append( "Sky" );
    thesky->texture_path( sky_tex_path.str() );

    // The sun and moon diameters are scaled down numbers of the
    // actual diameters. This was needed to fit bot the sun and the
    // moon within the distance to the far clip plane.
    // Moon diameter:    3,476 kilometers
    // Sun diameter: 1,390,000 kilometers
    thesky->build( 80000.0, 80000.0,
                   463.3, 361.8,
                   globals->get_ephem()->getNumPlanets(), 
                   globals->get_ephem()->getPlanets(),
                   globals->get_ephem()->getNumStars(),
                   globals->get_ephem()->getStars() );

    // Initialize MagVar model
    SGMagVar *magvar = new SGMagVar();
    globals->set_mag( magvar );


                                // kludge to initialize mag compass
                                // (should only be done for in-flight
                                // startup)
    // update magvar model
    globals->get_mag()->update( fgGetDouble("/position/longitude-deg")
                                * SGD_DEGREES_TO_RADIANS,
                                fgGetDouble("/position/latitude-deg")
                                * SGD_DEGREES_TO_RADIANS,
                                fgGetDouble("/position/altitude-ft")
                                * SG_FEET_TO_METER,
                                globals->get_time_params()->getJD() );
    double var = globals->get_mag()->get_magvar() * SGD_RADIANS_TO_DEGREES;
    fgSetDouble("/instrumentation/heading-indicator/offset-deg", -var);

    // airport = new ssgBranch;
    // airport->setName( "Airport Lighting" );
    // lighting->addKid( airport );

    // build our custom render states
    fgBuildRenderStates();

    try {
        // pass control off to the master event handler
        fgOSMainLoop();
    } catch (...) {
        SG_LOG( SG_ALL, SG_ALERT,
            "Unknown exception in the main loop. Aborting..." );
    }

    // we never actually get here ... but to avoid compiler warnings,
    // etc.
    return false;
}


// end of main.cxx