Tweaked smooth shaded texture lighting properties.

[flightgear.git] / Main / GLUTmain.cxx

//
// GLUTmain.cxx -- top level sim routines
//
// Written by Curtis Olson for OpenGL, started May 1997.
//
// Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
//
// 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.
//
// $Id$
// (Log is kept at end of this file)


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

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

#include <GL/glut.h>
#include <XGL/xgl.h>
#include <stdio.h>
#include <string.h>

#ifdef HAVE_STDLIB_H
#   include <stdlib.h>
#endif

#include <Include/fg_constants.h>  // for VERSION
#include <Include/general.h>

#include <Aircraft/aircraft.h>
#include <Astro/moon.hxx>
#include <Astro/planets.hxx>
#include <Astro/sky.hxx>
#include <Astro/stars.hxx>
#include <Astro/sun.hxx>
#include <Cockpit/cockpit.hxx>
#include <Debug/fg_debug.h>
#include <Joystick/joystick.h>
#include <Math/fg_geodesy.h>
#include <Math/mat3.h>
#include <Math/polar3d.h>
#include <Scenery/scenery.hxx>
#include <Scenery/tilemgr.hxx>
#include <Time/event.hxx>
#include <Time/fg_time.hxx>
#include <Time/fg_timer.hxx>
#include <Time/sunpos.hxx>
#include <Weather/weather.h>

#include "GLUTkey.hxx"
#include "fg_init.hxx"
#include "options.hxx"
#include "views.hxx"


// This is a record containing global housekeeping information
fgGENERAL general;

// Another hack
int use_signals = 0;

// Yet another other hack. Used for my prototype instrument code. (Durk)
int displayInstruments; 

/*
// The following defines flight gear options. Because glutlib will also
// want to parse its own options, those options must not be included here
// or they will get parsed by the main program option parser. Hence case
// is significant for any option added that might be in conflict with
// glutlib's parser.
//
// glutlib parses for:
//    -display
//    -direct   (invalid in Win32)
//    -geometry
//    -gldebug
//    -iconized
//    -indirect (invalid in Win32)
//    -synce
//
// Note that glutlib depends upon strings while this program's
// option parser wants only initial characters followed by numbers
// or pathnames.
//
const char *fg_cmdargopts = "a:c:Hhp:r:v:x:?";
//
// Where
//   -a aircraftfilename    aircraft start over ride
//   -c0x0000 - 0xffffffff  debug class setting
//    H,h.? help on command line use (does not need Option struct)
//   -p  priority
//   -r flightgear          root path to program support files
//   -v0 -v1                initial view mode (hud/no_hud currently)
//   -xlogpathname          debug logfile name
//
// Defaults in arguments to indicate not set on command line.
// Program defaults set variables from constants if neither command
// options or environmental variables effect values.
//

char  acArgbuf          [ MAXPATH + 1] = "\0";
int   debugArgValue                    = -2;
int   priorityArgValue                 = -1;
char  rootArgbuf        [ MAXPATH + 1] = "\0";
int   viewArg                          = -1;
char  logArgbuf         [ MAXPATH + 1] = "\0";

// There is a reason for defining the option structs by name and then
// creating an array of pointers to options. C++ is unfriendly to
// initializing arrays of objects that are not built in types. Always
// look forward. (Besides, you can follow what is going on better and
// add or modify with greater security. -ch
//
Option aircraftOption = { 'a',
                          OPT_STRING,
                          acArgbuf,
                          "Startup aircraft pathname override"
                        };
Option debugOption    = { 'c',
                          OPT_LHEX,       // Long int (32 bits)
                          &debugArgValue,
                          "Debug trace level"
                        };
Option priorityOption = { 'p',
                          OPT_INTEGER,
                          &priorityArgValue,
                          "Debug priority Threshold"
                        };
Option rootOption     = { 'r',
                          OPT_STRING,
                          rootArgbuf,
                          "Root directory for execution"
                        };
Option hudOption      = { 'v',
                          OPT_INTEGER,
                          &viewArg,
                          "View mode start" // Naked,HUD,Panel,Chase,Tower...
                        };

// Only naked view and HUD are implemented at this time
Option logfileOption  = { 'x',
                          OPT_STRING,
                          logArgbuf,
                          "Debug log file name"
                        };

#define OptsDefined 6
Option *CmdLineOptions[ OptsDefined ] = {
  &aircraftOption,
  &debugOption,
  &hudOption,
  &priorityOption,
  &rootOption,
  &logfileOption
  };

const char *DefaultRootDir  = "\\Flightgear";
const char *DefaultAircraft = "Navion.acf";
const char *DefaultDebuglog = "fgdebug.log";
const int   DefaultViewMode = HUD_VIEW;
*/

// Debug defaults handled in fg_debug.c

// fgInitVisuals() -- Initialize various GL/view parameters
static void fgInitVisuals( void ) {
    fgLIGHT *l;
    fgOPTIONS *o;
    struct fgWEATHER *w;

    l = &cur_light_params;
    o = &current_options;
    w = &current_weather;

    // Go full screen if requested ...
    if ( o->fullscreen ) {
        glutFullScreen();
    }

    // If enabled, normal vectors specified with glNormal are scaled
    // to unit length after transformation.  See glNormal.
    xglEnable( GL_NORMALIZE );

    xglEnable( GL_LIGHTING );
    xglEnable( GL_LIGHT0 );
    xglLightfv( GL_LIGHT0, GL_POSITION, l->sun_vec );

    xglFogi (GL_FOG_MODE, GL_LINEAR);
    xglFogf (GL_FOG_START, w->visibility / 1000000.0 );
    xglFogf (GL_FOG_END, w->visibility);
    // xglFogf (GL_FOG_DENSITY, w->visibility);
    if ( o->shading ) {
        xglHint (GL_FOG_HINT, GL_NICEST );
    } else {
        xglHint (GL_FOG_HINT, GL_FASTEST );
    }
    if ( o->wireframe ) {
        // draw wire frame
        xglPolygonMode( GL_FRONT_AND_BACK, GL_LINE );
    }

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


// Update the view volume, position, and orientation
static void fgUpdateViewParams( void ) {
    fgFLIGHT *f;
    fgLIGHT *l;
    fgOPTIONS *o;
    fgVIEW *v;

    f = current_aircraft.flight;
    l = &cur_light_params;
    o = &current_options;
    v = &current_view;

    v->Update(f);
    v->UpdateWorldToEye(f);

    if (displayInstruments) {
        xglViewport( 0, (GLint)((v->winHeight) / 2 ) , 
                     (GLint)(v->winWidth), (GLint)(v->winHeight) / 2 );
        // Tell GL we are about to modify the projection parameters
        xglMatrixMode(GL_PROJECTION);
        xglLoadIdentity();
        gluPerspective(o->fov, v->win_ratio / 2.0, 1.0, 100000.0);
    } else {
        xglViewport(0, 0 , (GLint)(v->winWidth), (GLint)(v->winHeight) );
        // Tell GL we are about to modify the projection parameters
        xglMatrixMode(GL_PROJECTION);
        xglLoadIdentity();
        gluPerspective(o->fov, v->win_ratio, 10.0, 100000.0);
    }

    xglMatrixMode(GL_MODELVIEW);
    xglLoadIdentity();
    
    // set up our view volume (default)
    gluLookAt(v->view_pos.x, v->view_pos.y, v->view_pos.z,
               v->view_pos.x + v->view_forward[0], 
               v->view_pos.y + v->view_forward[1], 
               v->view_pos.z + v->view_forward[2],
               v->view_up[0], v->view_up[1], v->view_up[2]);

    // look almost straight up (testing and eclipse watching)
    /* gluLookAt(v->view_pos.x, v->view_pos.y, v->view_pos.z,
               v->view_pos.x + v->view_up[0] + .001, 
               v->view_pos.y + v->view_up[1] + .001, 
               v->view_pos.z + v->view_up[2] + .001,
               v->view_up[0], v->view_up[1], v->view_up[2]); */

    // lock view horizontally towards sun (testing)
    /* gluLookAt(v->view_pos.x, v->view_pos.y, v->view_pos.z,
               v->view_pos.x + v->surface_to_sun[0], 
               v->view_pos.y + v->surface_to_sun[1], 
               v->view_pos.z + v->surface_to_sun[2],
               v->view_up[0], v->view_up[1], v->view_up[2]); */

    // lock view horizontally towards south (testing)
    /* gluLookAt(v->view_pos.x, v->view_pos.y, v->view_pos.z,
               v->view_pos.x + v->surface_south[0], 
               v->view_pos.y + v->surface_south[1], 
               v->view_pos.z + v->surface_south[2],
               v->view_up[0], v->view_up[1], v->view_up[2]); */

    // set the sun position
    xglLightfv( GL_LIGHT0, GL_POSITION, l->sun_vec );
}


// Draw a basic instrument panel
static void fgUpdateInstrViewParams( void ) {
    fgVIEW *v;

    v = &current_view;

    xglViewport(0, 0 , (GLint)(v->winWidth), (GLint)(v->winHeight) / 2);
  
    xglMatrixMode(GL_PROJECTION);
    xglPushMatrix();
  
    xglLoadIdentity();
    gluOrtho2D(0, 640, 0, 480);
    xglMatrixMode(GL_MODELVIEW);
    xglPushMatrix();
    xglLoadIdentity();

    xglColor3f(1.0, 1.0, 1.0);
    xglIndexi(7);
  
    xglDisable(GL_DEPTH_TEST);
    xglDisable(GL_LIGHTING);
  
    xglLineWidth(1);
    xglColor3f (0.5, 0.5, 0.5);

    xglBegin(GL_QUADS);
    xglVertex2f(0.0, 0.00);
    xglVertex2f(0.0, 480.0);
    xglVertex2f(640.0,480.0);
    xglVertex2f(640.0, 0.0);
    xglEnd();

    xglRectf(0.0,0.0, 640, 480);
    xglEnable(GL_DEPTH_TEST);
    xglEnable(GL_LIGHTING);
    xglMatrixMode(GL_PROJECTION);
    xglPopMatrix();
    xglMatrixMode(GL_MODELVIEW);
    xglPopMatrix();
}


// Update all Visuals (redraws anything graphics related)
static void fgRenderFrame( void ) {
    fgLIGHT *l;
    fgOPTIONS *o;
    fgTIME *t;
    fgVIEW *v;
    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 gray90[4] = { 0.9, 0.9, 0.9, 1.0 };
    GLfloat terrain_color[4] = { 0.54, 0.44, 0.29, 1.0 };
        
    l = &cur_light_params;
    o = &current_options;
    t = &cur_time_params;
    v = &current_view;

    // update view volume parameters
    fgUpdateViewParams();

    if ( o->skyblend ) {
        glClearColor(black[0], black[1], black[2], black[3]);
    } else {
        glClearColor(l->sky_color[0], l->sky_color[1], 
                     l->sky_color[2], l->sky_color[3]);
    }
    xglClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT );

    // Tell GL we are switching to model view parameters
    xglMatrixMode(GL_MODELVIEW);
    // xglLoadIdentity();

    // draw sky
    xglDisable( GL_DEPTH_TEST );
    xglDisable( GL_LIGHTING );
    xglDisable( GL_CULL_FACE );
    xglDisable( GL_FOG );
    xglShadeModel( GL_SMOOTH );
    if ( o->skyblend ) {
        fgSkyRender();
    }

    // setup transformation for drawing astronomical objects
    xglPushMatrix();
    // Translate to view position
    xglTranslatef( v->view_pos.x, v->view_pos.y, v->view_pos.z );
    // Rotate based on gst (sidereal time)
    angle = t->gst * 15.041085; /* should be 15.041085, Curt thought it was 15*/
    // printf("Rotating astro objects by %.2f degrees\n",angle);
    xglRotatef( angle, 0.0, 0.0, -1.0 );

    // draw stars and planets
    fgStarsRender();
    fgPlanetsRender();

    // draw the sun
    fgSunRender();

    // render the moon
    xglEnable( GL_LIGHTING );
    // set lighting parameters
    xglLightfv(GL_LIGHT0, GL_AMBIENT, white );
    xglLightfv(GL_LIGHT0, GL_DIFFUSE, white );
    xglEnable( GL_CULL_FACE );
    
    // Let's try some blending technique's (Durk)
    glEnable(GL_BLEND);
    glBlendFunc(GL_ONE, GL_ONE);
    fgMoonRender();
    glDisable(GL_BLEND);

    xglPopMatrix();

    // draw scenery
    if ( o->shading ) {
        xglShadeModel( GL_SMOOTH ); 
    } else {
        xglShadeModel( GL_FLAT ); 
    }
    xglEnable( GL_DEPTH_TEST );
    if ( o->fog ) {
        xglEnable( GL_FOG );
        xglFogfv (GL_FOG_COLOR, l->fog_color);
    }
    // set lighting parameters
    xglLightfv(GL_LIGHT0, GL_AMBIENT, l->scene_ambient );
    xglLightfv(GL_LIGHT0, GL_DIFFUSE, l->scene_diffuse );

    if ( o->textures ) {
        // texture parameters
        xglEnable( GL_TEXTURE_2D );
        xglTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT ) ;
        xglTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT ) ;
        xglTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ) ;
        xglTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, 
                          GL_LINEAR /* GL_LINEAR_MIPMAP_LINEAR */ ) ;
        xglTexEnvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ) ;
        xglHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST ) ;
        // set base color (I don't think this is doing anything here)
        xglMaterialfv (GL_FRONT, GL_AMBIENT, gray90);
        xglMaterialfv (GL_FRONT, GL_DIFFUSE, white);
    } else {
        xglDisable( GL_TEXTURE_2D );
        xglMaterialfv (GL_FRONT, GL_AMBIENT, terrain_color);
        xglMaterialfv (GL_FRONT, GL_DIFFUSE, terrain_color);
    }

    fgTileMgrRender();

    xglDisable( GL_TEXTURE_2D );

    // display HUD
    if( o->hud_status ) {
        fgCockpitUpdate();
    }

    // display instruments
    if (displayInstruments) {
        fgUpdateInstrViewParams();
    }

    xglutSwapBuffers();
}


// Update internal time dependent calculations (i.e. flight model)
void fgUpdateTimeDepCalcs(int multi_loop) {
    fgFLIGHT *f;
    fgTIME *t;
    fgVIEW *v;
    int i;

    f = current_aircraft.flight;
    t = &cur_time_params;
    v = &current_view;

    // update the flight model
    if ( multi_loop < 0 ) {
        multi_loop = DEFAULT_MULTILOOP;
    }

    // printf("updating flight model x %d\n", multi_loop);
    fgFlightModelUpdate(FG_LARCSIM, f, multi_loop);

    // update the view angle
    for ( i = 0; i < multi_loop; i++ ) {
        if ( fabs(v->goal_view_offset - v->view_offset) < 0.05 ) {
            v->view_offset = v->goal_view_offset;
            break;
        } else {
            // move v->view_offset towards v->goal_view_offset
            if ( v->goal_view_offset > v->view_offset ) {
                if ( v->goal_view_offset - v->view_offset < FG_PI ) {
                    v->view_offset += 0.01;
                } else {
                    v->view_offset -= 0.01;
                }
            } else {
                if ( v->view_offset - v->goal_view_offset < FG_PI ) {
                    v->view_offset -= 0.01;
                } else {
                    v->view_offset += 0.01;
                }
            }
            if ( v->view_offset > FG_2PI ) {
                v->view_offset -= FG_2PI;
            } else if ( v->view_offset < 0 ) {
                v->view_offset += FG_2PI;
            }
        }
    }
}


void fgInitTimeDepCalcs( void ) {
    // initialize timer

#ifdef HAVE_SETITIMER
    fgTimerInit( 1.0 / DEFAULT_TIMER_HZ, fgUpdateTimeDepCalcs );
#endif HAVE_SETITIMER

}


// 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 ) {
    fgAIRCRAFT *a;
    fgFLIGHT *f;
    fgGENERAL *g;
    fgTIME *t;
    static int remainder = 0;
    int elapsed, multi_loop;
    double cur_elev;
    int i;
    double accum;
    // double joy_x, joy_y;
    // int joy_b1, joy_b2;

    a = &current_aircraft;
    f = a->flight;
    g = &general;
    t = &cur_time_params;

    fgPrintf( FG_ALL, FG_DEBUG, "Running Main Loop\n");
    fgPrintf( FG_ALL, FG_DEBUG, "======= ==== ====\n");

    // update "time"
    fgTimeUpdate(f, t);

    // Read joystick
    /* fgJoystickRead( &joy_x, &joy_y, &joy_b1, &joy_b2 );
    printf( "Joystick X %f  Y %f  B1 %d  B2 %d\n",  
            joy_x, joy_y, joy_b1, joy_b2 );
    fgElevSet( -joy_y );
    fgAileronSet( joy_x ); */

    // Get elapsed time for this past frame
    elapsed = fgGetTimeInterval();
    fgPrintf( FG_ALL, FG_BULK, 
              "Time interval is = %d, previous remainder is = %d\n", 
              elapsed, remainder);

    // Calculate frame rate average
    if ( elapsed > 0.0 ) {
        accum = 0.0;
        for ( i = FG_FRAME_RATE_HISTORY - 2; i >= 0; i-- ) {
            accum += g->frames[i];
            // printf("frame[%d] = %.2f\n", i, g->frames[i]);
            g->frames[i+1] = g->frames[i];
        }
        g->frames[0] = 1000.0 / (float)elapsed;
        // printf("frame[0] = %.2f\n", g->frames[0]);
        accum += g->frames[0];
        g->frame_rate = accum / (float)FG_FRAME_RATE_HISTORY;
        // printf("ave = %.2f\n", g->frame_rate);
    }

    // Calculate model iterations needed for next frame
    fgPrintf( FG_ALL, FG_DEBUG, 
              "--> Frame rate is = %.2f\n", g->frame_rate);
    elapsed += remainder;

    multi_loop = (int)(((float)elapsed * 0.001) * DEFAULT_MODEL_HZ);
    remainder = elapsed - ((multi_loop*1000) / DEFAULT_MODEL_HZ);
    fgPrintf( FG_ALL, FG_BULK, 
              "Model iterations needed = %d, new remainder = %d\n", 
              multi_loop, remainder);
        
    // Run flight model
    if ( ! use_signals ) {
        // flight model
        fgUpdateTimeDepCalcs(multi_loop);
    }

    // I'm just sticking this here for now, it should probably move
    // eventually
    /* cur_elev = mesh_altitude(FG_Longitude * RAD_TO_ARCSEC, 
                               FG_Latitude  * RAD_TO_ARCSEC); */
    // there is no ground collision detection really, so for now I
    // just hard code the ground elevation to be 0 */
    cur_elev = 0;

    // printf("Ground elevation is %.2f meters here.\n", cur_elev);
    // FG_Runway_altitude = cur_elev * METER_TO_FEET;

    if ( FG_Altitude * FEET_TO_METER < cur_elev + 3.758099) {
        // set this here, otherwise if we set runway height above our
        // current height we get a really nasty bounce.
        FG_Runway_altitude = FG_Altitude - 3.758099;

        // now set aircraft altitude above ground
        FG_Altitude = cur_elev * METER_TO_FEET + 3.758099;
        fgPrintf( FG_ALL, FG_BULK, "<*> resetting altitude to %.0f meters\n", 
               FG_Altitude * FEET_TO_METER);
    }

    fgAircraftOutputCurrent(a);

    // see if we need to load any new scenery tiles
    fgTileMgrUpdate();

    // Process/manage pending events
    fgEventProcess();

    // redraw display
    fgRenderFrame();

    fgPrintf( FG_ALL, FG_DEBUG, "\n");
}


// Handle new window size or exposure
static void fgReshape( int width, int height ) {
    fgVIEW *v;

    v = &current_view;

    // Do this so we can call fgReshape(0,0) ourselves without having
    // to know what the values of width & height are.
    if ( (height > 0) && (width > 0) ) {
        v->win_ratio = (GLfloat) width / (GLfloat) height;
    }

    v->winWidth = width;
    v->winHeight = height;

    // Inform gl of our view window size (now handled elsewhere)
    // xglViewport(0, 0, (GLint)width, (GLint)height);
    fgUpdateViewParams();
    
    // xglClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
}


// Initialize GLUT and define a main window
int fgGlutInit( int *argc, char **argv ) {
    // GLUT will extract all glut specific options so later on we only
    // need wory about our own.
    xglutInit(argc, argv);

    // Define Display Parameters
    xglutInitDisplayMode( GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE );

    // Define initial window size
    xglutInitWindowSize(640, 480);

    // Initialize windows
    xglutCreateWindow("Flight Gear");

    return(1);
}


// Initialize GLUT event handlers
int fgGlutInitEvents( void ) {
    // call fgReshape() on window resizes
    xglutReshapeFunc( fgReshape );

    // call GLUTkey() on keyboard event
    xglutKeyboardFunc( GLUTkey );
    glutSpecialFunc( GLUTspecialkey );

    // call fgMainLoop() whenever there is
    // nothing else to do
    xglutIdleFunc( fgMainLoop );

    // draw the scene
    xglutDisplayFunc( fgRenderFrame );

    return(1);
}


// Main ...
int main( int argc, char **argv ) {
    fgFLIGHT *f;
    fgOPTIONS *o;
    char config[256];
    int result;  // Used in command line argument.

    f = current_aircraft.flight;
    o = &current_options;

#ifdef HAVE_BC5PLUS
    _control87(MCW_EM, MCW_EM);  /* defined in float.h */
#endif

    // Initialize the debugging output system
    fgInitDebug();

    fgPrintf(FG_GENERAL, FG_INFO, "Flight Gear:  Version %s\n\n", VERSION);

    // Initialize the Window/Graphics environment.
    if( !fgGlutInit(&argc, argv) ) {
        fgPrintf( FG_GENERAL, FG_EXIT, "GLUT initialization failed ...\n" );
    }

    // Attempt to locate and parse a config file
    // First check fg_root
    strcpy(config, o->fg_root);
    strcat(config, "/system.fgfsrc");
    result = o->parse_config_file(config);

    // Next check home directory
    if ( getenv("HOME") != NULL ) {
        strcpy(config, getenv("HOME"));
        strcat(config, "/.fgfsrc");
        result = o->parse_config_file(config);
    }

    // Parse remaining command line options
    // These will override anything specified in a config file
    result = o->parse_command_line(argc, argv);
    if ( result != FG_OPTIONS_OK ) {
        // Something must have gone horribly wrong with the command
        // line parsing or maybe the user just requested help ... :-)
        o->usage();
        fgPrintf( FG_GENERAL, FG_EXIT, "\nExiting ...\n");
    }

    // These are a few miscellaneous things that aren't really
    // "subsystems" but still need to be initialized.
    if( !fgInitGeneral()) {
        fgPrintf( FG_GENERAL, FG_EXIT, "General initializations failed ...\n" );
    }

    // This is the top level init routine which calls all the other
    // subsystem initialization routines.  If you are adding a
    // subsystem to flight gear, its initialization call should
    // located in this routine.
    if( !fgInitSubsystems()) {
        fgPrintf( FG_GENERAL, FG_EXIT,
                  "Subsystem initializations failed ...\n" );
    }

    // setup OpenGL view parameters
    fgInitVisuals();

    if ( use_signals ) {
        // init timer routines, signals, etc.  Arrange for an alarm
        // signal to be generated, etc.
        fgInitTimeDepCalcs();
    }

    // Initialize the various GLUT Event Handlers.
    if( !fgGlutInitEvents() ) {
        fgPrintf( FG_GENERAL, FG_EXIT, 
                  "GLUT event handler initialization failed ...\n" );
    }

    // pass control off to the master GLUT event handler
    glutMainLoop();

    // we never actually get here ... but just in case ... :-)
    return(0);
}


#ifdef __SUNPRO_CC
extern "C" {
    void __eprintf( void ) {
    }
}
#endif


// $Log$
// Revision 1.16  1998/05/20 20:51:33  curt
// Tweaked smooth shaded texture lighting properties.
// Converted fgLIGHT to a C++ class.
//
// Revision 1.15  1998/05/16 13:08:34  curt
// C++ - ified views.[ch]xx
// Shuffled some additional view parameters into the fgVIEW class.
// Changed tile-radius to tile-diameter because it is a much better
//   name.
// Added a WORLD_TO_EYE transformation to views.cxx.  This allows us
//  to transform world space to eye space for view frustum culling.
//
// Revision 1.14  1998/05/13 18:29:57  curt
// Added a keyboard binding to dynamically adjust field of view.
// Added a command line option to specify fov.
// Adjusted terrain color.
// Root path info moved to fgOPTIONS.
// Added ability to parse options out of a config file.
//
// Revision 1.13  1998/05/11 18:18:15  curt
// For flat shading use "glHint (GL_FOG_HINT, GL_FASTEST )"
//
// Revision 1.12  1998/05/07 23:14:15  curt
// Added "D" key binding to set autopilot heading.
// Made frame rate calculation average out over last 10 frames.
// Borland C++ floating point exception workaround.
// Added a --tile-radius=n option.
//
// Revision 1.11  1998/05/06 03:16:23  curt
// Added an averaged global frame rate counter.
// Added an option to control tile radius.
//
// Revision 1.10  1998/05/03 00:47:31  curt
// Added an option to enable/disable full-screen mode.
//
// Revision 1.9  1998/04/30 12:34:17  curt
// Added command line rendering options:
//   enable/disable fog/haze
//   specify smooth/flat shading
//   disable sky blending and just use a solid color
//   enable wireframe drawing mode
//
// Revision 1.8  1998/04/28 01:20:21  curt
// Type-ified fgTIME and fgVIEW.
// Added a command line option to disable textures.
//
// Revision 1.7  1998/04/26 05:10:02  curt
// "struct fgLIGHT" -> "fgLIGHT" because fgLIGHT is typedef'd.
//
// Revision 1.6  1998/04/25 22:06:30  curt
// Edited cvs log messages in source files ... bad bad bad!
//
// Revision 1.5  1998/04/25 20:24:01  curt
// Cleaned up initialization sequence to eliminate interdependencies
// between sun position, lighting, and view position.  This creates a
// valid single pass initialization path.
//
// Revision 1.4  1998/04/24 14:19:30  curt
// Fog tweaks.
//
// Revision 1.3  1998/04/24 00:49:18  curt
// Wrapped "#include <config.h>" in "#ifdef HAVE_CONFIG_H"
// Trying out some different option parsing code.
// Some code reorganization.
//
// Revision 1.2  1998/04/22 13:25:41  curt
// C++ - ifing the code.
// Starting a bit of reorganization of lighting code.
//
// Revision 1.1  1998/04/21 17:02:39  curt
// Prepairing for C++ integration.
//
// Revision 1.71  1998/04/18 04:11:26  curt
// Moved fg_debug to it's own library, added zlib support.
//
// Revision 1.70  1998/04/14 02:21:02  curt
// Incorporated autopilot heading hold contributed by:  Jeff Goeke-Smith
// <jgoeke@voyager.net>
//
// Revision 1.69  1998/04/08 23:35:34  curt
// Tweaks to Gnu automake/autoconf system.
//
// Revision 1.68  1998/04/03 22:09:03  curt
// Converting to Gnu autoconf system.
//
// Revision 1.67  1998/03/23 21:24:37  curt
// Source code formating tweaks.
//
// Revision 1.66  1998/03/14 00:31:20  curt
// Beginning initial terrain texturing experiments.
//
// Revision 1.65  1998/03/09 22:45:57  curt
// Minor tweaks for building on sparc platform.
//
// Revision 1.64  1998/02/20 00:16:23  curt
// Thursday's tweaks.
//
// Revision 1.63  1998/02/16 16:17:39  curt
// Minor tweaks.
//
// Revision 1.62  1998/02/16 13:39:42  curt
// Miscellaneous weekend tweaks.  Fixed? a cache problem that caused whole
// tiles to occasionally be missing.
//
// Revision 1.61  1998/02/12 21:59:46  curt
// Incorporated code changes contributed by Charlie Hotchkiss
// <chotchkiss@namg.us.anritsu.com>
//
// Revision 1.60  1998/02/11 02:50:40  curt
// Minor changes.
//
// Revision 1.59  1998/02/09 22:56:54  curt
// Removed "depend" files from cvs control.  Other minor make tweaks.
//
// Revision 1.58  1998/02/09 15:07:49  curt
// Minor tweaks.
//
// Revision 1.57  1998/02/07 15:29:40  curt
// Incorporated HUD changes and struct/typedef changes from Charlie Hotchkiss
// <chotchkiss@namg.us.anritsu.com>
//
// Revision 1.56  1998/02/03 23:20:23  curt
// Lots of little tweaks to fix various consistency problems discovered by
// Solaris' CC.  Fixed a bug in fg_debug.c with how the fgPrintf() wrapper
// passed arguments along to the real printf().  Also incorporated HUD changes
// by Michele America.
//
// Revision 1.55  1998/02/02 20:53:58  curt
// Incorporated Durk's changes.
//
// Revision 1.54  1998/01/31 00:43:10  curt
// Added MetroWorks patches from Carmen Volpe.
//
// Revision 1.53  1998/01/27 18:35:54  curt
// Minor tweaks.
//
// Revision 1.52  1998/01/27 00:47:56  curt
// Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
// system and commandline/config file processing code.
//
// Revision 1.51  1998/01/26 15:57:05  curt
// Tweaks for dynamic scenery development.
//
// Revision 1.50  1998/01/19 19:27:07  curt
// Merged in make system changes from Bob Kuehne <rpk@sgi.com>
// This should simplify things tremendously.
//
// Revision 1.49  1998/01/19 18:40:31  curt
// Tons of little changes to clean up the code and to remove fatal errors
// when building with the c++ compiler.
//
// Revision 1.48  1998/01/19 18:35:46  curt
// Minor tweaks and fixes for cygwin32.
//
// Revision 1.47  1998/01/13 00:23:08  curt
// Initial changes to support loading and management of scenery tiles.  Note,
// there's still a fair amount of work left to be done.
//
// Revision 1.46  1998/01/08 02:22:06  curt
// Beginning to integrate Tile management subsystem.
//
// Revision 1.45  1998/01/07 03:18:55  curt
// Moved astronomical stuff from .../Src/Scenery to .../Src/Astro/
//
// Revision 1.44  1997/12/30 22:22:31  curt
// Further integration of event manager.
//
// Revision 1.43  1997/12/30 20:47:43  curt
// Integrated new event manager with subsystem initializations.
//
// Revision 1.42  1997/12/30 16:36:47  curt
// Merged in Durk's changes ...
//
// Revision 1.41  1997/12/30 13:06:56  curt
// A couple lighting tweaks ...
//
// Revision 1.40  1997/12/30 01:38:37  curt
// Switched back to per vertex normals and smooth shading for terrain.
//
// Revision 1.39  1997/12/22 23:45:45  curt
// First stab at sunset/sunrise sky glow effects.
//
// Revision 1.38  1997/12/22 04:14:28  curt
// Aligned sky with sun so dusk/dawn effects can be correct relative to the sun.
//
// Revision 1.37  1997/12/19 23:34:03  curt
// Lot's of tweaking with sky rendering and lighting.
//
// Revision 1.36  1997/12/19 16:44:57  curt
// Working on scene rendering order and options.
//
// Revision 1.35  1997/12/18 23:32:32  curt
// First stab at sky dome actually starting to look reasonable. :-)
//
// Revision 1.34  1997/12/17 23:13:34  curt
// Began working on rendering a sky.
//
// Revision 1.33  1997/12/15 23:54:45  curt
// Add xgl wrappers for debugging.
// Generate terrain normals on the fly.
//
// Revision 1.32  1997/12/15 20:59:08  curt
// Misc. tweaks.
//
// Revision 1.31  1997/12/12 21:41:25  curt
// More light/material property tweaking ... still a ways off.
//
// Revision 1.30  1997/12/12 19:52:47  curt
// Working on lightling and material properties.
//
// Revision 1.29  1997/12/11 04:43:54  curt
// Fixed sun vector and lighting problems.  I thing the moon is now lit
// correctly.
//
// Revision 1.28  1997/12/10 22:37:45  curt
// Prepended "fg" on the name of all global structures that didn't have it yet.
// i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
//
// Revision 1.27  1997/12/09 05:11:54  curt
// Working on tweaking lighting.
//
// Revision 1.26  1997/12/09 04:25:29  curt
// Working on adding a global lighting params structure.
//
// Revision 1.25  1997/12/08 22:54:09  curt
// Enabled GL_CULL_FACE.
//
// Revision 1.24  1997/11/25 19:25:32  curt
// Changes to integrate Durk's moon/sun code updates + clean up.
//
// Revision 1.23  1997/11/15 18:16:34  curt
// minor tweaks.
//
// Revision 1.22  1997/10/30 12:38:41  curt
// Working on new scenery subsystem.
//
// Revision 1.21  1997/09/23 00:29:38  curt
// Tweaks to get things to compile with gcc-win32.
//
// Revision 1.20  1997/09/22 14:44:19  curt
// Continuing to try to align stars correctly.
//
// Revision 1.19  1997/09/18 16:20:08  curt
// At dusk/dawn add/remove stars in stages.
//
// Revision 1.18  1997/09/16 22:14:51  curt
// Tweaked time of day lighting equations.  Don't draw stars during the day.
//
// Revision 1.17  1997/09/16 15:50:29  curt
// Working on star alignment and time issues.
//
// Revision 1.16  1997/09/13 02:00:06  curt
// Mostly working on stars and generating sidereal time for accurate star
// placement.
//
// Revision 1.15  1997/09/05 14:17:27  curt
// More tweaking with stars.
//
// Revision 1.14  1997/09/05 01:35:53  curt
// Working on getting stars right.
//
// Revision 1.13  1997/09/04 02:17:34  curt
// Shufflin' stuff.
//
// Revision 1.12  1997/08/27 21:32:24  curt
// Restructured view calculation code.  Added stars.
//
// Revision 1.11  1997/08/27 03:30:16  curt
// Changed naming scheme of basic shared structures.
//
// Revision 1.10  1997/08/25 20:27:22  curt
// Merged in initial HUD and Joystick code.
//
// Revision 1.9  1997/08/22 21:34:39  curt
// Doing a bit of reorganizing and house cleaning.
//
// Revision 1.8  1997/08/19 23:55:03  curt
// Worked on better simulating real lighting.
//
// Revision 1.7  1997/08/16 12:22:38  curt
// Working on improving the lighting/shading.
//
// Revision 1.6  1997/08/13 20:24:56  curt
// Changes due to changing sunpos interface.
//
// Revision 1.5  1997/08/06 21:08:32  curt
// Sun position now really* works (I think) ... I still have sun time warping
// code in place, probably should remove it soon.
//
// Revision 1.4  1997/08/06 15:41:26  curt
// Working on correct sun position.
//
// Revision 1.3  1997/08/06 00:24:22  curt
// Working on correct real time sun lighting.
//
// Revision 1.2  1997/08/04 20:25:15  curt
// Organizational tweaking.
//
// Revision 1.1  1997/08/02 18:45:00  curt
// Renamed GLmain.c GLUTmain.c
//
// Revision 1.43  1997/08/02 16:23:47  curt
// Misc. tweaks.
//
// Revision 1.42  1997/08/01 19:43:33  curt
// Making progress with coordinate system overhaul.
//
// Revision 1.41  1997/07/31 22:52:37  curt
// Working on redoing internal coordinate systems & scenery transformations.
//
// Revision 1.40  1997/07/30 16:12:42  curt
// Moved fg_random routines from Util/ to Math/
//
// Revision 1.39  1997/07/21 14:45:01  curt
// Minor tweaks.
//
// Revision 1.38  1997/07/19 23:04:47  curt
// Added an initial weather section.
//
// Revision 1.37  1997/07/19 22:34:02  curt
// Moved PI definitions to ../constants.h
// Moved random() stuff to ../Utils/ and renamed fg_random()
//
// Revision 1.36  1997/07/18 23:41:25  curt
// Tweaks for building with Cygnus Win32 compiler.
//
// Revision 1.35  1997/07/18 14:28:34  curt
// Hacked in some support for wind/turbulence.
//
// Revision 1.34  1997/07/16 20:04:48  curt
// Minor tweaks to aid Win32 port.
//
// Revision 1.33  1997/07/12 03:50:20  curt
// Added an #include <Windows32/Base.h> to help compiling for Win32
//
// Revision 1.32  1997/07/11 03:23:18  curt
// Solved some scenery display/orientation problems.  Still have a positioning
// (or transformation?) problem.
//
// Revision 1.31  1997/07/11 01:29:58  curt
// More tweaking of terrian floor.
//
// Revision 1.30  1997/07/10 04:26:37  curt
// We now can interpolated ground elevation for any position in the grid.  We
// can use this to enforce a "hard" ground.  We still need to enforce some
// bounds checking so that we don't try to lookup data points outside the
// grid data set.
//
// Revision 1.29  1997/07/09 21:31:12  curt
// Working on making the ground "hard."
//
// Revision 1.28  1997/07/08 18:20:12  curt
// Working on establishing a hard ground.
//
// Revision 1.27  1997/07/07 20:59:49  curt
// Working on scenery transformations to enable us to fly fluidly over the
// poles with no discontinuity/distortion in scenery.
//
// Revision 1.26  1997/07/05 20:43:34  curt
// renamed mat3 directory to Math so we could add other math related routines.
//
// Revision 1.25  1997/06/29 21:19:17  curt
// Working on scenery management system.
//
// Revision 1.24  1997/06/26 22:14:53  curt
// Beginning work on a scenery management system.
//
// Revision 1.23  1997/06/26 19:08:33  curt
// Restructuring make, adding automatic "make dep" support.
//
// Revision 1.22  1997/06/25 15:39:47  curt
// Minor changes to compile with rsxnt/win32.
//
// Revision 1.21  1997/06/22 21:44:41  curt
// Working on intergrating the VRML (subset) parser.
//
// Revision 1.20  1997/06/21 17:12:53  curt
// Capitalized subdirectory names.
//
// Revision 1.19  1997/06/18 04:10:31  curt
// A couple more runway tweaks ...
//
// Revision 1.18  1997/06/18 02:21:24  curt
// Hacked in a runway
//
// Revision 1.17  1997/06/17 16:51:58  curt
// Timer interval stuff now uses gettimeofday() instead of ftime()
//
// Revision 1.16  1997/06/17 04:19:16  curt
// More timer related tweaks with respect to view direction changes.
//
// Revision 1.15  1997/06/17 03:41:10  curt
// Nonsignal based interval timing is now working.
// This would be a good time to look at cleaning up the code structure a bit.
//
// Revision 1.14  1997/06/16 19:32:51  curt
// Starting to add general timer support.
//
// Revision 1.13  1997/06/02 03:40:06  curt
// A tiny bit more view tweaking.
//
// Revision 1.12  1997/06/02 03:01:38  curt
// Working on views (side, front, back, transitions, etc.)
//
// Revision 1.11  1997/05/31 19:16:25  curt
// Elevator trim added.
//
// Revision 1.10  1997/05/31 04:13:52  curt
// WE CAN NOW FLY!!!
//
// Continuing work on the LaRCsim flight model integration.
// Added some MSFS-like keyboard input handling.
//
// Revision 1.9  1997/05/30 19:27:01  curt
// The LaRCsim flight model is starting to look like it is working.
//
// Revision 1.8  1997/05/30 03:54:10  curt
// Made a bit more progress towards integrating the LaRCsim flight model.
//
// Revision 1.7  1997/05/29 22:39:49  curt
// Working on incorporating the LaRCsim flight model.
//
// Revision 1.6  1997/05/29 12:31:39  curt
// Minor tweaks, moving towards general flight model integration.
//
// Revision 1.5  1997/05/29 02:33:23  curt
// Updated to reflect changing interfaces in other "modules."
//
// Revision 1.4  1997/05/27 17:44:31  curt
// Renamed & rearranged variables and routines.   Added some initial simple
// timer/alarm routines so the flight model can be updated on a regular 
// interval.
//
// Revision 1.3  1997/05/23 15:40:25  curt
// Added GNU copyright headers.
// Fog now works!
//
// Revision 1.2  1997/05/23 00:35:12  curt
// Trying to get fog to work ...
//
// Revision 1.1  1997/05/21 15:57:51  curt
// Renamed due to added GLUT support.
//
// Revision 1.3  1997/05/19 18:22:42  curt
// Parameter tweaking ... starting to stub in fog support.
//
// Revision 1.2  1997/05/17 00:17:34  curt
// Trying to stub in support for standard OpenGL.
//
// Revision 1.1  1997/05/16 16:05:52  curt
// Initial revision.
//