From 427f309aeab8afc80c3ced99ea03233033a1ea9e Mon Sep 17 00:00:00 2001
From: curt <curt>
Date: Thu, 16 Mar 2000 03:17:04 +0000
Subject: [PATCH] Complete overhaul of the sky/sun/moon/stars/planets.  It is
 now an ssg model that get's inserted into the scene graph.

---
 simgear/sky/Makefile.am                |  10 +-
 simgear/sky/{skydome.cxx => dome.cxx}  | 378 +++----------------------
 simgear/sky/{skydome.hxx => dome.hxx}  |  40 +--
 simgear/sky/{skymoon.cxx => moon.cxx}  | 113 +++++---
 simgear/sky/{skymoon.hxx => moon.hxx}  |  56 +---
 simgear/sky/{skysun.cxx => oursun.cxx} | 106 ++++---
 simgear/sky/{skysun.hxx => oursun.hxx} | 108 +------
 simgear/sky/sky.cxx                    | 117 ++++++++
 simgear/sky/sky.hxx                    | 113 ++++++++
 simgear/sky/sphere.cxx                 |   5 +-
 simgear/sky/sphere.hxx                 |   3 +-
 simgear/sky/stars.cxx                  | 177 ++++++++++++
 simgear/sky/stars.hxx                  |  69 +++++
 13 files changed, 690 insertions(+), 605 deletions(-)
 rename simgear/sky/{skydome.cxx => dome.cxx} (56%)
 rename simgear/sky/{skydome.hxx => dome.hxx} (75%)
 rename simgear/sky/{skymoon.cxx => moon.cxx} (73%)
 rename simgear/sky/{skymoon.hxx => moon.hxx} (69%)
 rename simgear/sky/{skysun.cxx => oursun.cxx} (81%)
 rename simgear/sky/{skysun.hxx => oursun.hxx} (53%)
 create mode 100644 simgear/sky/sky.cxx
 create mode 100644 simgear/sky/sky.hxx
 create mode 100644 simgear/sky/stars.cxx
 create mode 100644 simgear/sky/stars.hxx

diff --git a/simgear/sky/Makefile.am b/simgear/sky/Makefile.am
index fe5d1b12..d71c6201 100644
--- a/simgear/sky/Makefile.am
+++ b/simgear/sky/Makefile.am
@@ -1,9 +1,11 @@
 noinst_LIBRARIES = libSky.a
 
 libSky_a_SOURCES = \
-	skydome.cxx skydome.hxx \
-	skymoon.cxx skymoon.hxx \
-	skysun.cxx skysun.hxx \
-	sphere.cxx sphere.hxx
+	dome.cxx dome.hxx \
+	moon.cxx moon.hxx \
+	oursun.cxx oursun.hxx \
+	sky.cxx sky.hxx \
+	sphere.cxx sphere.hxx \
+	stars.cxx stars.hxx
 
 INCLUDES += -I$(top_builddir) -I$(top_builddir)/src
diff --git a/simgear/sky/skydome.cxx b/simgear/sky/dome.cxx
similarity index 56%
rename from simgear/sky/skydome.cxx
rename to simgear/sky/dome.cxx
index a834ada9..6f2a2c59 100644
--- a/simgear/sky/skydome.cxx
+++ b/simgear/sky/dome.cxx
@@ -1,4 +1,4 @@
-// skydome.cxx -- model sky with an upside down "bowl"
+// dome.cxx -- model sky with an upside down "bowl"
 //
 // Written by Curtis Olson, started December 1997.
 // SSG-ified by Curtis Olson, February 2000.
@@ -39,13 +39,7 @@
 #include <simgear/debug/logstream.hxx>
 #include <simgear/math/fg_random.h>
 
-// #include <Aircraft/aircraft.hxx>
-// #include <FDM/flight.hxx>
-// #include <Main/views.hxx>
-// #include <Time/event.hxx>
-// #include <Time/fg_time.hxx>
-
-#include "skydome.hxx"
+#include "dome.hxx"
 
 
 #ifdef __MWERKS__
@@ -69,27 +63,43 @@
 #define BOTTOM_ELEV   -2000.0
 
 
+// Set up dome rendering callbacks
+static int sgSkyDomePreDraw( ssgEntity *e ) {
+    /* cout << endl << "Dome Pre Draw" << endl << "----------------" 
+	 << endl << endl; */
+    glDisable( GL_DEPTH_TEST );
+    glDisable( GL_FOG );
+
+    return true;
+}
+
+static int sgSkyDomePostDraw( ssgEntity *e ) {
+    /* cout << endl << "Dome Post Draw" << endl << "----------------" 
+	 << endl << endl; */
+    glEnable( GL_DEPTH_TEST );
+    glEnable( GL_FOG );
+
+    return true;
+}
+
+
 // Constructor
-FGSkyDome::FGSkyDome( void ) {
+SGSkyDome::SGSkyDome( void ) {
 }
 
 
 // Destructor
-FGSkyDome::~FGSkyDome( void ) {
+SGSkyDome::~SGSkyDome( void ) {
 }
 
 
 // initialize the sky object and connect it into our scene graph
-bool FGSkyDome::initialize( ) {
+ssgBranch * SGSkyDome::build( ) {
     sgVec4 color;
 
     float theta;
     int i;
 
-    // create the scene graph for the dome
-    dome = new ssgRoot;
-    dome->setName( "Sky Dome" );
-
     // set up the state
     dome_state = new ssgSimpleState();
     dome_state->setShadeModel( GL_SMOOTH );
@@ -209,9 +219,6 @@ bool FGSkyDome::initialize( ) {
 
     // build the ssg scene graph sub tree for the sky and connected
     // into the provide scene graph branch
-    dome_selector = new ssgSelector;
-    dome_transform = new ssgTransform;
-
     ssgVtxTable *center_disk, *upper_ring, *middle_ring, *lower_ring;
 
     center_disk = new ssgVtxTable( GL_TRIANGLE_FAN, 
@@ -231,17 +238,27 @@ bool FGSkyDome::initialize( ) {
     middle_ring->setState( dome_state );
     lower_ring->setState( dome_state );
 
+    dome_transform = new ssgTransform;
     dome_transform->addKid( center_disk );
     dome_transform->addKid( upper_ring );
     dome_transform->addKid( middle_ring );
     dome_transform->addKid( lower_ring );
 
-    dome_selector->addKid( dome_transform );
-    dome_selector->clrTraversalMaskBits( SSGTRAV_HOT );
+    // not entirely satisfying.  We are depending here that the first
+    // thing we add to a parent is the first drawn
+    center_disk->setCallback( SSG_CALLBACK_PREDRAW, sgSkyDomePreDraw );
+    center_disk->setCallback( SSG_CALLBACK_POSTDRAW, sgSkyDomePostDraw );
 
-    dome->addKid( dome_selector );
+    upper_ring->setCallback( SSG_CALLBACK_PREDRAW, sgSkyDomePreDraw );
+    upper_ring->setCallback( SSG_CALLBACK_POSTDRAW, sgSkyDomePostDraw );
 
-    return true;
+    middle_ring->setCallback( SSG_CALLBACK_PREDRAW, sgSkyDomePreDraw );
+    middle_ring->setCallback( SSG_CALLBACK_POSTDRAW, sgSkyDomePostDraw );
+
+    lower_ring->setCallback( SSG_CALLBACK_PREDRAW, sgSkyDomePreDraw );
+    lower_ring->setCallback( SSG_CALLBACK_POSTDRAW, sgSkyDomePostDraw );
+
+    return dome_transform;
 }
 
 
@@ -251,7 +268,7 @@ bool FGSkyDome::initialize( ) {
 // 0 degrees = high noon
 // 90 degrees = sun rise/set
 // 180 degrees = darkest midnight
-bool FGSkyDome::repaint( sgVec4 sky_color, sgVec4 fog_color, double sun_angle )
+bool SGSkyDome::repaint( sgVec4 sky_color, sgVec4 fog_color, double sun_angle )
 {
     double diff;
     sgVec3 outer_param, outer_amt, outer_diff;
@@ -452,7 +469,7 @@ bool FGSkyDome::repaint( sgVec4 sky_color, sgVec4 fog_color, double sun_angle )
 // lat specifies a rotation about the new Y axis
 // spin specifies a rotation about the new Z axis (and orients the
 // sunrise/set effects
-bool FGSkyDome::reposition( sgVec3 p, double lon, double lat, double spin ) {
+bool SGSkyDome::reposition( sgVec3 p, double lon, double lat, double spin ) {
     sgMat4 T, LON, LAT, SPIN;
     sgVec3 axis;
 
@@ -493,316 +510,3 @@ bool FGSkyDome::reposition( sgVec3 p, double lon, double lat, double spin ) {
 
     return true;
 }
-
-
-// Draw the skydome
-bool FGSkyDome::draw() {
-    ssgCullAndDraw( dome );
-
-    return true;
-}
-
-
-#if 0
-
-// depricated code from here to the end 
-
-
-// Calculate the sky structure vertices
-void fgSkyVerticesInit() {
-    float theta;
-    int i;
-
-    FG_LOG(FG_ASTRO, FG_INFO, "  Generating the sky dome vertices.");
-
-    for ( i = 0; i < 12; i++ ) {
-	theta = (i * 30.0) * DEG_TO_RAD;
-	
-	inner_vertex[i][0] = cos(theta) * UPPER_RADIUS;
-	inner_vertex[i][1] = sin(theta) * UPPER_RADIUS;
-	inner_vertex[i][2] = UPPER_ELEV;
-	
-	// printf("    %.2f %.2f\n", cos(theta) * UPPER_RADIUS, 
-	//        sin(theta) * UPPER_RADIUS);
-
-	middle_vertex[i][0] = cos((double)theta) * MIDDLE_RADIUS;
-	middle_vertex[i][1] = sin((double)theta) * MIDDLE_RADIUS;
-	middle_vertex[i][2] = MIDDLE_ELEV;
-	    
-	outer_vertex[i][0] = cos((double)theta) * LOWER_RADIUS;
-	outer_vertex[i][1] = sin((double)theta) * LOWER_RADIUS;
-	outer_vertex[i][2] = LOWER_ELEV;
-	    
-	bottom_vertex[i][0] = cos((double)theta) * BOTTOM_RADIUS;
-	bottom_vertex[i][1] = sin((double)theta) * BOTTOM_RADIUS;
-	bottom_vertex[i][2] = BOTTOM_ELEV;
-    }
-}
-
-
-// (Re)calculate the sky colors at each vertex
-void fgSkyColorsInit() {
-    fgLIGHT *l;
-    double sun_angle, diff;
-    double outer_param[3], outer_amt[3], outer_diff[3];
-    double middle_param[3], middle_amt[3], middle_diff[3];
-    int i, j;
-
-    l = &cur_light_params;
-
-    FG_LOG( FG_ASTRO, FG_INFO, 
-	    "  Generating the sky colors for each vertex." );
-
-    // setup for the possibility of sunset effects
-    sun_angle = l->sun_angle * RAD_TO_DEG;
-    // fgPrintf( FG_ASTRO, FG_INFO, 
-    //           "  Sun angle in degrees = %.2f\n", sun_angle);
-
-    if ( (sun_angle > 80.0) && (sun_angle < 100.0) ) {
-	// 0.0 - 0.4
-	outer_param[0] = (10.0 - fabs(90.0 - sun_angle)) / 20.0;
-	outer_param[1] = (10.0 - fabs(90.0 - sun_angle)) / 40.0;
-	outer_param[2] = -(10.0 - fabs(90.0 - sun_angle)) / 30.0;
-	// outer_param[2] = 0.0;
-
-	middle_param[0] = (10.0 - fabs(90.0 - sun_angle)) / 40.0;
-	middle_param[1] = (10.0 - fabs(90.0 - sun_angle)) / 80.0;
-	middle_param[2] = 0.0;
-
-	outer_diff[0] = outer_param[0] / 6.0;
-	outer_diff[1] = outer_param[1] / 6.0;
-	outer_diff[2] = outer_param[2] / 6.0;
-
-	middle_diff[0] = middle_param[0] / 6.0;
-	middle_diff[1] = middle_param[1] / 6.0;
-	middle_diff[2] = middle_param[2] / 6.0;
-    } else {
-	outer_param[0] = outer_param[1] = outer_param[2] = 0.0;
-	middle_param[0] = middle_param[1] = middle_param[2] = 0.0;
-
-	outer_diff[0] = outer_diff[1] = outer_diff[2] = 0.0;
-	middle_diff[0] = middle_diff[1] = middle_diff[2] = 0.0;
-    }
-    // printf("  outer_red_param = %.2f  outer_red_diff = %.2f\n", 
-    //        outer_red_param, outer_red_diff);
-
-    // calculate transition colors between sky and fog
-    for ( j = 0; j < 3; j++ ) {
-	outer_amt[j] = outer_param[j];
-	middle_amt[j] = middle_param[j];
-    }
-
-    for ( i = 0; i < 6; i++ ) {
-	for ( j = 0; j < 3; j++ ) {
-	    diff = l->sky_color[j] - l->fog_color[j];
-
-	    // printf("sky = %.2f  fog = %.2f  diff = %.2f\n", 
-	    //        l->sky_color[j], l->fog_color[j], diff);
-
-	    upper_color[i][j] = (GLubyte)((l->sky_color[j] - diff * 0.3) * 255);
-	    middle_color[i][j] = (GLubyte)((l->sky_color[j] - diff * 0.9 
-					   + middle_amt[j]) * 255);
-	    lower_color[i][j] = (GLubyte)((l->fog_color[j] + outer_amt[j]) 
-					  * 255);
-
-	    if ( upper_color[i][j] > 255 ) { upper_color[i][j] = 255; }
-	    if ( upper_color[i][j] < 25 ) { upper_color[i][j] = 25; }
-	    if ( middle_color[i][j] > 255 ) { middle_color[i][j] = 255; }
-	    if ( middle_color[i][j] < 25 ) { middle_color[i][j] = 25; }
-	    if ( lower_color[i][j] > 255 ) { lower_color[i][j] = 255; }
-	    if ( lower_color[i][j] < 25 ) { lower_color[i][j] = 25; }
-	}
-	upper_color[i][3] = middle_color[i][3] = lower_color[i][3] = 
-	    (GLubyte)(l->sky_color[3] * 255);
-
-	for ( j = 0; j < 3; j++ ) {
-	    outer_amt[j] -= outer_diff[j];
-	    middle_amt[j] -= middle_diff[j];
-	}
-
-	/*
-	printf("upper_color[%d] = %.2f %.2f %.2f %.2f\n", i, upper_color[i][0],
-	       upper_color[i][1], upper_color[i][2], upper_color[i][3]);
-	printf("middle_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
-	       middle_color[i][0], middle_color[i][1], middle_color[i][2], 
-	       middle_color[i][3]);
-	printf("lower_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
-	       lower_color[i][0], lower_color[i][1], lower_color[i][2], 
-	       lower_color[i][3]);
-	*/
-    }
-
-    for ( j = 0; j < 3; j++ ) {
-	outer_amt[j] = 0.0;
-	middle_amt[j] = 0.0;
-    }
-
-    for ( i = 6; i < 12; i++ ) {
-
-	for ( j = 0; j < 3; j++ ) {
-	    diff = l->sky_color[j] - l->fog_color[j];
-
-	    // printf("sky = %.2f  fog = %.2f  diff = %.2f\n", 
-	    //        l->sky_color[j], l->fog_color[j], diff);
-
-	    upper_color[i][j] = (GLubyte)((l->sky_color[j] - diff * 0.3) * 255);
-	    middle_color[i][j] = (GLubyte)((l->sky_color[j] - diff * 0.9 
-					    + middle_amt[j]) * 255);
-	    lower_color[i][j] = (GLubyte)((l->fog_color[j] + outer_amt[j]) 
-					  * 255);
-
-	    if ( upper_color[i][j] > 255 ) { upper_color[i][j] = 255; }
-	    if ( upper_color[i][j] < 25 ) { upper_color[i][j] = 25; }
-	    if ( middle_color[i][j] > 255 ) { middle_color[i][j] = 255; }
-	    if ( middle_color[i][j] < 25 ) { middle_color[i][j] = 25; }
-	    if ( lower_color[i][j] > 255 ) { lower_color[i][j] = 255; }
-	    if ( lower_color[i][j] < 35 ) { lower_color[i][j] = 35; }
-	}
-	upper_color[i][3] = middle_color[i][3] = lower_color[i][3] = 
-	    (GLubyte)(l->sky_color[3] * 255);
-
-	for ( j = 0; j < 3; j++ ) {
-	    outer_amt[j] += outer_diff[j];
-	    middle_amt[j] += middle_diff[j];
-	}
-
-	/*
-	printf("upper_color[%d] = %.2f %.2f %.2f %.2f\n", i, upper_color[i][0],
-	       upper_color[i][1], upper_color[i][2], upper_color[i][3]);
-	printf("middle_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
-	       middle_color[i][0], middle_color[i][1], middle_color[i][2], 
-	       middle_color[i][3]);
-	printf("lower_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
-	       lower_color[i][0], lower_color[i][1], lower_color[i][2], 
-	       lower_color[i][3]);
-	*/
-    }
-}
-
-
-// Initialize the sky structure and colors
-void fgSkyInit() {
-    FG_LOG( FG_ASTRO, FG_INFO, "Initializing the sky" );
-
-    fgSkyVerticesInit();
-
-    // regester fgSkyColorsInit() as an event to be run periodically
-    global_events.Register( "fgSkyColorsInit()", fgSkyColorsInit, 
-		            fgEVENT::FG_EVENT_READY, 30000);
-}
-
-
-// Draw the Sky
-void fgSkyRender() {
-    FGInterface *f;
-    fgLIGHT *l;
-    GLubyte sky_color[4];
-    GLubyte upper_color[4];
-    GLubyte middle_color[4];
-    GLubyte lower_color[4];
-    double diff;
-    int i;
-
-    f = current_aircraft.fdm_state;
-    l = &cur_light_params;
-
-    // printf("Rendering the sky.\n");
-
-    // calculate the proper colors
-    for ( i = 0; i < 3; i++ ) {
-	diff = l->sky_color[i] - l->adj_fog_color[i];
-
-	// printf("sky = %.2f  fog = %.2f  diff = %.2f\n", 
-	//        l->sky_color[j], l->adj_fog_color[j], diff);
-
-	upper_color[i] = (GLubyte)((l->sky_color[i] - diff * 0.3) * 255);
-	middle_color[i] = (GLubyte)((l->sky_color[i] - diff * 0.9) * 255);
-	lower_color[i] = (GLubyte)(l->adj_fog_color[i] * 255);
-    }
-    upper_color[3] = middle_color[3] = lower_color[3] = 
-	(GLubyte)(l->adj_fog_color[3] * 255);
-
-    xglPushMatrix();
-
-    // Translate to view position
-    Point3D zero_elev = current_view.get_cur_zero_elev();
-    xglTranslatef( zero_elev.x(), zero_elev.y(), zero_elev.z() );
-    // printf("  Translated to %.2f %.2f %.2f\n", 
-    //        zero_elev.x, zero_elev.y, zero_elev.z );
-
-    // Rotate to proper orientation
-    // printf("  lon = %.2f  lat = %.2f\n", FG_Longitude * RAD_TO_DEG,
-    //        FG_Latitude * RAD_TO_DEG);
-    xglRotatef( f->get_Longitude() * RAD_TO_DEG, 0.0, 0.0, 1.0 );
-    xglRotatef( 90.0 - f->get_Latitude() * RAD_TO_DEG, 0.0, 1.0, 0.0 );
-    xglRotatef( l->sun_rotation * RAD_TO_DEG, 0.0, 0.0, 1.0 );
-
-    // Draw inner/center section of sky*/
-    xglBegin( GL_TRIANGLE_FAN );
-    for ( i = 0; i < 4; i++ ) {
-	sky_color[i] = (GLubyte)(l->sky_color[i] * 255);
-    }
-    xglColor4fv(l->sky_color);
-    xglVertex3f(0.0, 0.0, CENTER_ELEV);
-    for ( i = 11; i >= 0; i-- ) {
-	xglColor4ubv( upper_color );
-	xglVertex3fv( inner_vertex[i] );
-    }
-    xglColor4ubv( upper_color );
-    xglVertex3fv( inner_vertex[11] );
-    xglEnd();
-
-    // Draw the middle ring
-    xglBegin( GL_TRIANGLE_STRIP );
-    for ( i = 0; i < 12; i++ ) {
-	xglColor4ubv( middle_color );
-	// printf("middle_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
-	//        middle_color[i][0], middle_color[i][1], middle_color[i][2], 
-	//        middle_color[i][3]);
-	// xglColor4f(1.0, 0.0, 0.0, 1.0);
-	xglVertex3fv( middle_vertex[i] );
-	xglColor4ubv( upper_color );
-	// printf("upper_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
-	//        upper_color[i][0], upper_color[i][1], upper_color[i][2], 
-	//        upper_color[i][3]);
-	// xglColor4f(0.0, 0.0, 1.0, 1.0);
-	xglVertex3fv( inner_vertex[i] );
-    }
-    xglColor4ubv( middle_color );
-    // xglColor4f(1.0, 0.0, 0.0, 1.0);
-    xglVertex3fv( middle_vertex[0] );
-    xglColor4ubv( upper_color );
-    // xglColor4f(0.0, 0.0, 1.0, 1.0);
-    xglVertex3fv( inner_vertex[0] );
-    xglEnd();
-
-    // Draw the outer ring
-    xglBegin( GL_TRIANGLE_STRIP );
-    for ( i = 0; i < 12; i++ ) {
-	xglColor4ubv( lower_color );
-	xglVertex3fv( outer_vertex[i] );
-	xglColor4ubv( middle_color );
-	xglVertex3fv( middle_vertex[i] );
-    }
-    xglColor4ubv( lower_color );
-    xglVertex3fv( outer_vertex[0] );
-    xglColor4ubv( middle_color );
-    xglVertex3fv( middle_vertex[0] );
-    xglEnd();
-
-    // Draw the bottom skirt
-    xglBegin( GL_TRIANGLE_STRIP );
-    xglColor4ubv( lower_color );
-    for ( i = 0; i < 12; i++ ) {
-	xglVertex3fv( bottom_vertex[i] );
-	xglVertex3fv( outer_vertex[i] );
-    }
-    xglVertex3fv( bottom_vertex[0] );
-    xglVertex3fv( outer_vertex[0] );
-    xglEnd();
-
-    xglPopMatrix();
-}
-
-
-#endif
diff --git a/simgear/sky/skydome.hxx b/simgear/sky/dome.hxx
similarity index 75%
rename from simgear/sky/skydome.hxx
rename to simgear/sky/dome.hxx
index 7cb7249d..e90f8976 100644
--- a/simgear/sky/skydome.hxx
+++ b/simgear/sky/dome.hxx
@@ -1,4 +1,4 @@
-// skydome.hxx -- model sky with an upside down "bowl"
+// dome.hxx -- model sky with an upside down "bowl"
 //
 // Written by Curtis Olson, started December 1997.
 // SSG-ified by Curtis Olson, February 2000.
@@ -34,11 +34,7 @@
 #include <plib/ssg.h>		// plib include
 
 
-class FGSkyDome {
-    // scene graph root for the skydome
-    ssgRoot *dome;
-
-    ssgSelector *dome_selector;
+class SGSkyDome {
     ssgTransform *dome_transform;
     ssgSimpleState *dome_state;
 
@@ -57,14 +53,14 @@ class FGSkyDome {
 public:
 
     // Constructor
-    FGSkyDome( void );
+    SGSkyDome( void );
 
     // Destructor
-    ~FGSkyDome( void );
+    ~SGSkyDome( void );
 
     // initialize the sky object and connect it into our scene graph
     // root
-    bool initialize();
+    ssgBranch *build();
 
     // repaint the sky colors based on current value of sun_angle,
     // sky, and fog colors.  This updates the color arrays for
@@ -81,31 +77,7 @@ public:
     // spin specifies a rotation about the new Z axis (and orients the
     // sunrise/set effects
     bool reposition( sgVec3 p, double lon, double lat, double spin );
-
-    // Draw the skydome
-    bool draw();
-
-    // enable the sky in the scene graph (default)
-    void enable() { dome_selector->select( 1 ); }
-
-    // disable the sky in the scene graph.  The leaf node is still
-    // there, how ever it won't be traversed on the cullandrender
-    // phase.
-    void disable() { dome_selector->select( 0 ); }
-
 };
 
 
-// (Re)generate the display list
-// void fgSkyInit();
-
-// (Re)calculate the sky colors at each vertex
-// void fgSkyColorsInit();
-
-// Draw the Sky
-// void fgSkyRender();
-
-
-#endif // _SKYDOM_HXX
-
-
+#endif // _SKYDOME_HXX
diff --git a/simgear/sky/skymoon.cxx b/simgear/sky/moon.cxx
similarity index 73%
rename from simgear/sky/skymoon.cxx
rename to simgear/sky/moon.cxx
index 863e9d0a..d4e8883c 100644
--- a/simgear/sky/skymoon.cxx
+++ b/simgear/sky/moon.cxx
@@ -1,4 +1,4 @@
-// skymoon.hxx -- draw a moon object
+// moon.hxx -- model earth's moon
 //
 // Written by Durk Talsma. Originally started October 1997, for distribution  
 // with the FlightGear project. Version 2 was written in August and 
@@ -30,43 +30,81 @@
 #include <plib/ssg.h>
 
 #include <simgear/constants.h>
-#include <simgear/misc/fgpath.hxx>
 
 #include "sphere.hxx"
-#include "skymoon.hxx"
+#include "moon.hxx"
 
 
-// Constructor
-FGSkyMoon::FGSkyMoon( void ) {
+// Set up moon rendering call backs
+static int sgMoonOrbPreDraw( ssgEntity *e ) {
+    /* cout << endl << "Moon orb pre draw" << endl << "----------------" 
+	 << endl << endl; */
+    glDisable( GL_DEPTH_TEST );
+    glDisable( GL_FOG );
+    glBlendFunc ( GL_SRC_ALPHA, GL_ONE ) ;
+    // sgVec4 color;
+    // sgSetVec4( color, 0.0, 0.0, 0.0, 1.0 );
+    // glMaterialfv ( GL_FRONT_AND_BACK, GL_AMBIENT, color ) ;
+
+    return true;
 }
 
+static int sgMoonOrbPostDraw( ssgEntity *e ) {
+    /* cout << endl << "Moon orb post draw" << endl << "----------------" 
+	 << endl << endl; */
+    glEnable( GL_DEPTH_TEST );
+    glEnable( GL_FOG );
+    glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
 
-// Destructor
-FGSkyMoon::~FGSkyMoon( void ) {
+    return true;
+}
+
+static int sgMoonHaloPreDraw( ssgEntity *e ) {
+    /* cout << endl << "Moon halo pre draw" << endl << "----------------" 
+	 << endl << endl; */
+    glDisable( GL_DEPTH_TEST );
+    glDisable( GL_FOG );
+    glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
+
+    return true;
+}
+
+static int sgMoonHaloPostDraw( ssgEntity *e ) {
+    /* cout << endl << "Moon halo post draw" << endl << "----------------" 
+	 << endl << endl; */
+    glEnable( GL_DEPTH_TEST );
+    glEnable( GL_FOG );
+    glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
+
+    return true;
+}
+
+
+// Constructor
+SGMoon::SGMoon( void ) {
 }
 
 
-// initialize the moon object and connect it into our scene graph root
-bool FGSkyMoon::initialize( const FGPath& path ) {
+// Destructor
+SGMoon::~SGMoon( void ) {
+}
 
-    // create the scene graph for the moon/halo
-    FGPath moontex = path;
-    moontex.append( "moon.rgba" );
 
-    skymoon = new ssgRoot;
-    skymoon->setName( "Sky Moon" );
+// build the moon object
+ssgBranch * SGMoon::build( FGPath path, double moon_size ) {
 
     // set up the orb state
+    path.append( "moon.rgba" );
     orb_state = new ssgSimpleState();
-    orb_state->setTexture( (char *)moontex.c_str() );
+    orb_state->setTexture( (char *)path.c_str() );
     orb_state->setShadeModel( GL_SMOOTH );
     orb_state->enable( GL_LIGHTING );
     orb_state->enable( GL_CULL_FACE );
     orb_state->enable( GL_TEXTURE_2D );
     orb_state->enable( GL_COLOR_MATERIAL );
     orb_state->setColourMaterial( GL_DIFFUSE );
-    orb_state->setMaterial( GL_AMBIENT, 0.0, 0.0, 0.0, 0.0 );
-    orb_state->setMaterial( GL_SPECULAR, 0.0, 0.0, 0.0, 0.0 );
+    orb_state->setMaterial( GL_AMBIENT, 0.0, 0.0, 0.0, 1.0 );
+    orb_state->setMaterial( GL_SPECULAR, 0.0, 0.0, 0.0, 1.0 );
     orb_state->enable( GL_BLEND );
     orb_state->enable( GL_ALPHA_TEST );
     orb_state->setAlphaClamp( 0.01 );
@@ -76,7 +114,8 @@ bool FGSkyMoon::initialize( const FGPath& path ) {
     sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
     cl->add( color );
 
-    ssgBranch *orb = ssgMakeSphere( orb_state, cl, 550.0, 15, 15 );
+    ssgBranch *orb = ssgMakeSphere( orb_state, cl, moon_size, 15, 15,
+				    sgMoonOrbPreDraw, sgMoonOrbPostDraw );
 
     // force a repaint of the moon colors with arbitrary defaults
     repaint( 0.0 );
@@ -86,9 +125,10 @@ bool FGSkyMoon::initialize( const FGPath& path ) {
     // moon_texid = makeHalo( moon_texbuf, 64 );
     // my_glWritePPMFile("moonhalo.ppm", moon_texbuf, 64, 64, RGB);
 
+#if 0
     // set up the halo state
     halo_state = new ssgSimpleState();
-    halo_state->setTexture( "halo.rgba" );
+    halo_state->setTexture( "halo.rgb" );
     // halo_state->setTexture( moon_texid );
     halo_state->enable( GL_TEXTURE_2D );
     halo_state->disable( GL_LIGHTING );
@@ -101,23 +141,22 @@ bool FGSkyMoon::initialize( const FGPath& path ) {
     halo_state -> setMaterial ( GL_EMISSION, 0, 0, 0, 1 ) ;
     halo_state -> setMaterial ( GL_SPECULAR, 0, 0, 0, 1 ) ;
     // halo_state -> setShininess ( 0 ) ;
-
-    halo_state->setTranslucent();
     halo_state->enable( GL_ALPHA_TEST );
     halo_state->setAlphaClamp(0.01);
     halo_state->enable ( GL_BLEND ) ;
 
 
     // Build ssg structure
+    double size = moon_size * 10.0;
     sgVec3 v3;
     halo_vl = new ssgVertexArray;
-    sgSetVec3( v3, -5000.0, 0.0, -5000.0 );
+    sgSetVec3( v3, -size, 0.0, -size );
     halo_vl->add( v3 );
-    sgSetVec3( v3, 5000.0, 0.0, -5000.0 );
+    sgSetVec3( v3, size, 0.0, -size );
     halo_vl->add( v3 );
-    sgSetVec3( v3, -5000.0, 0.0,  5000.0 );
+    sgSetVec3( v3, -size, 0.0,  size );
     halo_vl->add( v3 );
-    sgSetVec3( v3, 5000.0, 0.0,  5000.0 );
+    sgSetVec3( v3, size, 0.0,  size );
     halo_vl->add( v3 );
 
     sgVec2 v2;
@@ -134,21 +173,16 @@ bool FGSkyMoon::initialize( const FGPath& path ) {
     ssgLeaf *halo = 
 	new ssgVtxTable ( GL_TRIANGLE_STRIP, halo_vl, NULL, halo_tl, cl );
     halo->setState( halo_state );
+#endif
 
     // build the ssg scene graph sub tree for the sky and connected
     // into the provide scene graph branch
-    moon_selector = new ssgSelector;
     moon_transform = new ssgTransform;
 
-    moon_selector->addKid( moon_transform );
-    moon_selector->clrTraversalMaskBits( SSGTRAV_HOT );
-
-    skymoon->addKid( moon_selector );
-
     // moon_transform->addKid( halo );
     moon_transform->addKid( orb );
 
-    return true;
+    return moon_transform;
 }
 
 
@@ -157,7 +191,7 @@ bool FGSkyMoon::initialize( const FGPath& path ) {
 // 0 degrees = high noon
 // 90 degrees = moon rise/set
 // 180 degrees = darkest midnight
-bool FGSkyMoon::repaint( double moon_angle ) {
+bool SGMoon::repaint( double moon_angle ) {
     if ( moon_angle * RAD_TO_DEG < 100 ) {
 	// else moon is well below horizon (so no point in repainting it)
     
@@ -197,8 +231,9 @@ bool FGSkyMoon::repaint( double moon_angle ) {
 // declination, offset by our current position (p) so that it appears
 // fixed at a great distance from the viewer.  Also add in an optional
 // rotation (i.e. for the current time of day.)
-bool FGSkyMoon::reposition( sgVec3 p, double angle,
-			   double rightAscension, double declination )
+bool SGMoon::reposition( sgVec3 p, double angle,
+			 double rightAscension, double declination,
+			 double moon_dist )
 {
     sgMat4 T1, T2, GST, RA, DEC;
     sgVec3 axis;
@@ -235,11 +270,3 @@ bool FGSkyMoon::reposition( sgVec3 p, double angle,
 
     return true;
 }
-
-
-// Draw the moon
-bool FGSkyMoon::draw() {
-    ssgCullAndDraw( skymoon );
-
-    return true;
-}
diff --git a/simgear/sky/skymoon.hxx b/simgear/sky/moon.hxx
similarity index 69%
rename from simgear/sky/skymoon.hxx
rename to simgear/sky/moon.hxx
index abac5d21..4c705bd0 100644
--- a/simgear/sky/skymoon.hxx
+++ b/simgear/sky/moon.hxx
@@ -1,4 +1,4 @@
-// skymoon.hxx -- draw a moon object
+// moon.hxx -- model earth's moon
 //
 // Written by Durk Talsma. Originally started October 1997, for distribution  
 // with the FlightGear project. Version 2 was written in August and 
@@ -25,20 +25,17 @@
 // $Id$
 
 
-#ifndef _SKYMOON_HXX_
-#define _SKYMOON_HXX_
+#ifndef _SG_MOON_HXX_
+#define _SG_MOON_HXX_
 
 
 #include <plib/ssg.h>
-#include <simgear/misc/fgpath.hxx>
 
+#include <simgear/misc/fgpath.hxx>
 
-class FGSkyMoon {
 
-    // scene graph root for the skymoon
-    ssgRoot *skymoon;
+class SGMoon {
 
-    ssgSelector *moon_selector;
     ssgTransform *moon_transform;
     ssgSimpleState *orb_state;
     ssgSimpleState *halo_state;
@@ -48,20 +45,16 @@ class FGSkyMoon {
     ssgVertexArray *halo_vl;
     ssgTexCoordArray *halo_tl;
 
-    GLuint moon_texid;
-    GLubyte *moon_texbuf;
-
 public:
 
     // Constructor
-    FGSkyMoon( void );
+    SGMoon( void );
 
     // Destructor
-    ~FGSkyMoon( void );
+    ~SGMoon( void );
 
-    // initialize the moon object and connect it into our scene graph
-    // root
-    bool initialize( const FGPath& path );
+    // build the moon object
+    ssgBranch *build( FGPath path, double moon_size );
 
     // repaint the moon colors based on current value of moon_anglein
     // degrees relative to verticle
@@ -75,34 +68,9 @@ public:
     // appears fixed at a great distance from the viewer.  Also add in
     // an optional rotation (i.e. for the current time of day.)
     bool reposition( sgVec3 p, double angle,
-		     double rightAscension, double declination );
-
-    // Draw the moon
-    bool draw();
-
-    // enable the moon in the scene graph (default)
-    void enable() { moon_selector->select( 1 ); }
-
-    // disable the moon in the scene graph.  The leaf node is still
-    // there, how ever it won't be traversed on the cullandrender
-    // phase.
-    void disable() { moon_selector->select( 0 ); }
-
+		     double rightAscension, double declination,
+		     double moon_dist  );
 };
 
 
-#endif // _SKYMOON_HXX_
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+#endif // _SG_MOON_HXX_
diff --git a/simgear/sky/skysun.cxx b/simgear/sky/oursun.cxx
similarity index 81%
rename from simgear/sky/skysun.cxx
rename to simgear/sky/oursun.cxx
index 1e40e2a5..80d12c07 100644
--- a/simgear/sky/skysun.cxx
+++ b/simgear/sky/oursun.cxx
@@ -1,4 +1,4 @@
-// skysun.hxx -- draw a sun object
+// oursun.hxx -- model earth's sun
 //
 // Written by Durk Talsma. Originally started October 1997, for distribution  
 // with the FlightGear project. Version 2 was written in August and 
@@ -30,19 +30,57 @@
 #include <plib/ssg.h>
 
 #include <simgear/constants.h>
-#include <simgear/misc/fgpath.hxx>
 
 #include "sphere.hxx"
-#include "skysun.hxx"
+#include "oursun.hxx"
+
+
+// Set up sun rendering call backs
+static int sgSunOrbPreDraw( ssgEntity *e ) {
+    /* cout << endl << "Sun orb pre draw" << endl << "----------------" 
+	 << endl << endl; */
+    glDisable( GL_DEPTH_TEST );
+    glDisable( GL_FOG );
+
+    return true;
+}
+
+static int sgSunOrbPostDraw( ssgEntity *e ) {
+    /* cout << endl << "Sun orb post draw" << endl << "----------------" 
+	 << endl << endl; */
+    glEnable( GL_DEPTH_TEST );
+    glEnable( GL_FOG );
+
+    return true;
+}
+
+static int sgSunHaloPreDraw( ssgEntity *e ) {
+    /* cout << endl << "Sun halo pre draw" << endl << "----------------" 
+	 << endl << endl; */
+    glDisable( GL_DEPTH_TEST );
+    glDisable( GL_FOG );
+    glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
+
+    return true;
+}
+
+static int sgSunHaloPostDraw( ssgEntity *e ) {
+    /* cout << endl << "Sun halo post draw" << endl << "----------------" 
+	 << endl << endl; */
+    glEnable( GL_DEPTH_TEST );
+    glEnable( GL_FOG );
+
+    return true;
+}
 
 
 // Constructor
-FGSkySun::FGSkySun( void ) {
+SGSun::SGSun( void ) {
 }
 
 
 // Destructor
-FGSkySun::~FGSkySun( void ) {
+SGSun::~SGSun( void ) {
 }
 
 
@@ -156,10 +194,7 @@ void my_glWritePPMFile(const char *filename, GLubyte *buffer, int win_width, int
 
 
 // initialize the sun object and connect it into our scene graph root
-bool FGSkySun::initialize( const FGPath& path ) {
-    // create the scene graph for the sun/halo
-    skysun = new ssgRoot;
-    skysun->setName( "Sky Sun" );
+ssgBranch * SGSun::build( FGPath path, double sun_size ) {
 
     // set up the orb state
     orb_state = new ssgSimpleState();
@@ -177,7 +212,8 @@ bool FGSkySun::initialize( const FGPath& path ) {
     sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
     cl->add( color );
 
-    ssgBranch *orb = ssgMakeSphere( orb_state, cl, 550.0, 10, 10 );
+    ssgBranch *orb = ssgMakeSphere( orb_state, cl, sun_size, 10, 10, 
+				    sgSunOrbPreDraw, sgSunOrbPostDraw );
 
     // force a repaint of the sun colors with arbitrary defaults
     repaint( 0.0 );
@@ -188,40 +224,31 @@ bool FGSkySun::initialize( const FGPath& path ) {
     // my_glWritePPMFile("sunhalo.ppm", sun_texbuf, 64, 64, RGB);
 
     // set up the halo state
-    FGPath halo_path = path;
-    halo_path.append( "halo.rgba" );
-
+    path.append( "halo.rgba" );
     halo_state = new ssgSimpleState();
-    halo_state->setTexture( (char *)halo_path.c_str() );
+    halo_state->setTexture( (char *)path.c_str() );
     // halo_state->setTexture( sun_texid );
     halo_state->enable( GL_TEXTURE_2D );
     halo_state->disable( GL_LIGHTING );
     halo_state->setShadeModel( GL_SMOOTH );
     halo_state->disable( GL_CULL_FACE );
-
-    halo_state->disable( GL_COLOR_MATERIAL );
+    halo_state->enable( GL_COLOR_MATERIAL );
     halo_state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
-    halo_state->setMaterial ( GL_AMBIENT_AND_DIFFUSE, 1, 1, 1, 1 ) ;
-    halo_state -> setMaterial ( GL_EMISSION, 0, 0, 0, 1 ) ;
-    halo_state -> setMaterial ( GL_SPECULAR, 0, 0, 0, 1 ) ;
-    // halo_state -> setShininess ( 0 ) ;
-
-    halo_state->setTranslucent();
     halo_state->enable( GL_ALPHA_TEST );
     halo_state->setAlphaClamp(0.01);
     halo_state->enable ( GL_BLEND ) ;
 
-
     // Build ssg structure
+    double size = sun_size * 10.0;
     sgVec3 v3;
     halo_vl = new ssgVertexArray;
-    sgSetVec3( v3, -5000.0, 0.0, -5000.0 );
+    sgSetVec3( v3, -size, 0.0, -size );
     halo_vl->add( v3 );
-    sgSetVec3( v3, 5000.0, 0.0, -5000.0 );
+    sgSetVec3( v3, size, 0.0, -size );
     halo_vl->add( v3 );
-    sgSetVec3( v3, -5000.0, 0.0,  5000.0 );
+    sgSetVec3( v3, -size, 0.0,  size );
     halo_vl->add( v3 );
-    sgSetVec3( v3, 5000.0, 0.0,  5000.0 );
+    sgSetVec3( v3, size, 0.0,  size );
     halo_vl->add( v3 );
 
     sgVec2 v2;
@@ -241,18 +268,14 @@ bool FGSkySun::initialize( const FGPath& path ) {
 
     // build the ssg scene graph sub tree for the sky and connected
     // into the provide scene graph branch
-    sun_selector = new ssgSelector;
     sun_transform = new ssgTransform;
 
-    sun_selector->addKid( sun_transform );
-    sun_selector->clrTraversalMaskBits( SSGTRAV_HOT );
-
-    skysun->addKid( sun_selector );
-
     sun_transform->addKid( halo );
+    halo->setCallback( SSG_CALLBACK_PREDRAW, sgSunHaloPreDraw );
+    halo->setCallback( SSG_CALLBACK_POSTDRAW, sgSunHaloPostDraw );
     sun_transform->addKid( orb );
 
-    return true;
+    return sun_transform;
 }
 
 
@@ -261,7 +284,7 @@ bool FGSkySun::initialize( const FGPath& path ) {
 // 0 degrees = high noon
 // 90 degrees = sun rise/set
 // 180 degrees = darkest midnight
-bool FGSkySun::repaint( double sun_angle ) {
+bool SGSun::repaint( double sun_angle ) {
     if ( sun_angle * RAD_TO_DEG < 100 ) {
 	// else sun is well below horizon (so no point in repainting it)
     
@@ -300,8 +323,9 @@ bool FGSkySun::repaint( double sun_angle ) {
 // declination, offset by our current position (p) so that it appears
 // fixed at a great distance from the viewer.  Also add in an optional
 // rotation (i.e. for the current time of day.)
-bool FGSkySun::reposition( sgVec3 p, double angle,
-			   double rightAscension, double declination )
+bool SGSun::reposition( sgVec3 p, double angle,
+			double rightAscension, double declination, 
+			double sun_dist )
 {
     sgMat4 T1, T2, GST, RA, DEC;
     sgVec3 axis;
@@ -338,11 +362,3 @@ bool FGSkySun::reposition( sgVec3 p, double angle,
 
     return true;
 }
-
-
-// Draw the sun
-bool FGSkySun::draw() {
-    ssgCullAndDraw( skysun );
-
-    return true;
-}
diff --git a/simgear/sky/skysun.hxx b/simgear/sky/oursun.hxx
similarity index 53%
rename from simgear/sky/skysun.hxx
rename to simgear/sky/oursun.hxx
index d1ed47d3..c9a6f8d9 100644
--- a/simgear/sky/skysun.hxx
+++ b/simgear/sky/oursun.hxx
@@ -1,4 +1,4 @@
-// skysun.hxx -- draw a sun object
+// oursun.hxx -- model earth's sun
 //
 // Written by Durk Talsma. Originally started October 1997, for distribution  
 // with the FlightGear project. Version 2 was written in August and 
@@ -25,19 +25,17 @@
 // $Id$
 
 
-#ifndef _SKYSUN_HXX_
-#define _SKYSUN_HXX_
+#ifndef _SG_SUN_HXX_
+#define _SG_SUN_HXX_
 
 
 #include <plib/ssg.h>
+
 #include <simgear/misc/fgpath.hxx>
 
-class FGSkySun {
 
-    // scene graph root for the skysun
-    ssgRoot *skysun;
+class SGSun {
 
-    ssgSelector *sun_selector;
     ssgTransform *sun_transform;
     ssgSimpleState *orb_state;
     ssgSimpleState *halo_state;
@@ -53,15 +51,13 @@ class FGSkySun {
 public:
 
     // Constructor
-    FGSkySun( void );
+    SGSun( void );
 
     // Destructor
-    ~FGSkySun( void );
+    ~SGSun( void );
 
-    // initialize the sun object and connect it into our scene graph
-    // root.  Pass in the path to your texture directory so
-    // initialize() can find the halo.rgba texture
-    bool initialize( const FGPath& path );
+    // return the sun object
+    ssgBranch *build( FGPath path, double sun_size );
 
     // repaint the sun colors based on current value of sun_anglein
     // degrees relative to verticle
@@ -75,89 +71,9 @@ public:
     // appears fixed at a great distance from the viewer.  Also add in
     // an optional rotation (i.e. for the current time of day.)
     bool reposition( sgVec3 p, double angle,
-		     double rightAscension, double declination );
-
-    // Draw the sun
-    bool draw();
-
-    // enable the sun in the scene graph (default)
-    void enable() { sun_selector->select( 1 ); }
-
-    // disable the sun in the scene graph.  The leaf node is still
-    // there, how ever it won't be traversed on the cullandrender
-    // phase.
-    void disable() { sun_selector->select( 0 ); }
-
-};
-
-
-#if 0
-class Star : public CelestialBody
-{
-private:
-  //double longitude;  // the sun's true longitude - this is depreciated by
-                       // CelestialBody::lonEcl 
-  double xs, ys;     // the sun's rectangular geocentric coordinates
-  double distance;   // the sun's distance to the earth
-   GLUquadricObj *SunObject;
-  GLuint sun_texid;
-  GLubyte *sun_texbuf;
-
-  void setTexture();
-public:
-  Star (FGTime *t);
-  ~Star();
-  void updatePosition(FGTime *t);
-  double getM();
-  double getw();
-  //double getLon();
-  double getxs();
-  double getys();
-  double getDistance();
-  void newImage();
+		     double rightAscension, double declination,
+		     double sun_dist );
 };
 
 
-
-inline double Star::getM()
-{
-  return M;
-}
-
-inline double Star::getw()
-{
-  return w;
-}
-
-inline double Star::getxs()
-{
-  return xs;
-}
-
-inline double Star::getys()
-{
-  return ys;
-}
-
-inline double Star::getDistance()
-{
-  return distance;
-}
-#endif
-
-
-#endif // _SKYSUN_HXX_
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+#endif // _SG_SUN_HXX_
diff --git a/simgear/sky/sky.cxx b/simgear/sky/sky.cxx
new file mode 100644
index 00000000..3033e3b7
--- /dev/null
+++ b/simgear/sky/sky.cxx
@@ -0,0 +1,117 @@
+// sky.cxx -- ssg based sky model
+//
+// Written by Curtis Olson, started December 1997.
+// SSG-ified by Curtis Olson, February 2000.
+//
+// Copyright (C) 1997-2000  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.
+//
+// $Id$
+
+
+#include <plib/ssg.h>		// plib include
+
+#include "sky.hxx"
+
+
+// Constructor
+SGSky::SGSky( void ) {
+}
+
+
+// Destructor
+SGSky::~SGSky( void ) {
+}
+
+
+// initialize the sky and connect the components to the scene graph at
+// the provided branch
+ssgBranch * SGSky::build(  double sun_size, double moon_size,
+			   int nplanets, sgdVec3 *planet_data,
+			   double planet_dist,
+			   int nstars, sgdVec3 *star_data, double star_dist )
+{
+    sky_selector = new ssgSelector;
+    sky_transform = new ssgTransform;
+
+    dome = new SGSkyDome;
+    sky_transform -> addKid( dome->build() );
+
+    planets = new SGStars;
+    sky_transform -> addKid( planets->build(nplanets, planet_data,
+					    planet_dist)
+			     );
+
+    stars = new SGStars;
+    sky_transform -> addKid( stars->build(nstars, star_data, star_dist) );
+    
+    moon = new SGMoon;
+    sky_transform -> addKid( moon->build(tex_path, moon_size) );
+
+    oursun = new SGSun;
+    sky_transform -> addKid( oursun->build(tex_path, sun_size) );
+
+    sky_selector->addKid( sky_transform );
+    sky_selector->clrTraversalMaskBits( SSGTRAV_HOT );
+
+    return sky_selector;
+}
+
+
+// repaint the sky components based on current value of sun_angle,
+// sky, and fog colors.
+//
+// sun angle in degrees relative to verticle
+// 0 degrees = high noon
+// 90 degrees = sun rise/set
+// 180 degrees = darkest midnight
+bool SGSky::repaint( sgVec4 sky_color, sgVec4 fog_color,
+		     double sun_angle, double moon_angle,
+		     int nplanets, sgdVec3 *planet_data,
+		     int nstars, sgdVec3 *star_data )
+{
+    dome->repaint( sky_color, fog_color, sun_angle );
+    oursun->repaint( sun_angle );
+    moon->repaint( moon_angle );
+    planets->repaint( sun_angle, nplanets, planet_data );
+    stars->repaint( sun_angle, nstars, star_data );
+
+    return true;
+}
+
+
+// reposition the sky at the specified origin and orientation
+//
+// lon specifies a rotation about the Z axis
+// lat specifies a rotation about the new Y axis
+// spin specifies a rotation about the new Z axis (this allows
+// additional orientation for the sunrise/set effects and is used by
+// the skydome and perhaps clouds.
+bool SGSky::reposition( sgVec3 view_pos, sgVec3 zero_elev, 
+			double lon, double lat, double spin,
+			double gst, 
+			double sun_ra, double sun_dec, double sun_dist,
+			double moon_ra, double moon_dec, double moon_dist )
+{
+    double angle = gst * 15;	// degrees
+    dome->reposition( zero_elev, lon, lat, spin );
+    oursun->reposition( view_pos, angle, sun_ra, sun_dec, sun_dist );
+    moon->reposition( view_pos, angle, moon_ra, moon_dec, moon_dist );
+    planets->reposition( view_pos, angle );
+    stars->reposition( view_pos, angle );
+
+    return true;
+}
diff --git a/simgear/sky/sky.hxx b/simgear/sky/sky.hxx
new file mode 100644
index 00000000..355fe14b
--- /dev/null
+++ b/simgear/sky/sky.hxx
@@ -0,0 +1,113 @@
+// sky.hxx -- ssg based sky model
+//
+// Written by Curtis Olson, started December 1997.
+// SSG-ified by Curtis Olson, February 2000.
+//
+// Copyright (C) 1997-2000  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.
+//
+// $Id$
+
+
+#ifndef _SG_SKY_HXX
+#define _SG_SKY_HXX
+
+
+#ifndef __cplusplus                                                          
+# error This library requires C++
+#endif                                   
+
+
+#include <plib/ssg.h>		// plib include
+
+#include <simgear/misc/fgpath.hxx>
+
+#include "dome.hxx"
+#include "moon.hxx"
+#include "oursun.hxx"
+#include "stars.hxx"
+
+
+class SGSky {
+
+    // components of the sky
+    SGSkyDome *dome;
+    SGSun *oursun;
+    SGMoon *moon;
+    SGStars *planets;
+    SGStars *stars;
+
+    ssgSelector *sky_selector;
+    ssgTransform *sky_transform;
+
+    FGPath tex_path;
+
+public:
+
+    // Constructor
+    SGSky( void );
+
+    // Destructor
+    ~SGSky( void );
+
+    // initialize the sky and connect the components to the scene
+    // graph at the provided branch
+    ssgBranch *build( double sun_size, double moon_size,
+		      int nplanets, sgdVec3 *planet_data, double planet_dist,
+		      int nstars, sgdVec3 *star_data, double star_dist );
+
+    // repaint the sky components based on current value of sun_angle,
+    // sky, and fog colors.
+    //
+    // sun angle in degrees relative to verticle
+    // 0 degrees = high noon
+    // 90 degrees = sun rise/set
+    // 180 degrees = darkest midnight
+    bool repaint( sgVec4 sky_color, sgVec4 fog_color, 
+		  double sun_angle, double moon_angle,
+		  int nplanets, sgdVec3 *planet_data,
+		  int nstars, sgdVec3 *star_data );
+
+    // reposition the sky at the specified origin and orientation
+    //
+    // lon specifies a rotation about the Z axis
+    // lat specifies a rotation about the new Y axis
+    // spin specifies a rotation about the new Z axis (this allows
+    // additional orientation for the sunrise/set effects and is used
+    // by the skydome and perhaps clouds.
+    bool reposition( sgVec3 view_pos, sgVec3 zero_elev, 
+		     double lon, double lat, double spin,
+		     double gst, 
+		     double sun_ra, double sun_dec, double sun_dist,
+		     double moon_ra, double moon_dec, double moon_dist );
+
+    // specify the texture path (optional, defaults to current directory)
+    inline void texture_path( const string& path ) {
+	tex_path = FGPath( path );
+    }
+
+    // enable the sky in the scene graph (default)
+    inline void enable() { sky_selector->select( 1 ); }
+
+    // disable the sky in the scene graph.  The leaf node is still
+    // there, how ever it won't be traversed on by ssgCullandRender()
+    inline void disable() { sky_selector->select( 0 ); }
+};
+
+
+#endif // _SG_SKY_HXX
+
+
diff --git a/simgear/sky/sphere.cxx b/simgear/sky/sphere.cxx
index 17248992..d43cbc85 100644
--- a/simgear/sky/sphere.cxx
+++ b/simgear/sky/sphere.cxx
@@ -27,7 +27,8 @@
 
 // return a sphere object as an ssgBranch
 ssgBranch *ssgMakeSphere( ssgSimpleState *state, ssgColourArray *cl,
-			  double radius, int slices, int stacks )
+			  double radius, int slices, int stacks,
+			  ssgCallback predraw, ssgCallback postdraw )
 {
     float rho, drho, theta, dtheta;
     float x, y, z;
@@ -119,6 +120,8 @@ ssgBranch *ssgMakeSphere( ssgSimpleState *state, ssgColourArray *cl,
 	ssgLeaf *slice = 
 	    new ssgVtxTable ( GL_TRIANGLE_STRIP, vl, nl, tl, cl );
 	slice->setState( state );
+	slice->setCallback( SSG_CALLBACK_PREDRAW, predraw );
+	slice->setCallback( SSG_CALLBACK_POSTDRAW, postdraw );
 
 	sphere->addKid( slice );
 
diff --git a/simgear/sky/sphere.hxx b/simgear/sky/sphere.hxx
index 566fe1c0..a429dfc2 100644
--- a/simgear/sky/sphere.hxx
+++ b/simgear/sky/sphere.hxx
@@ -28,6 +28,7 @@
 // return a sphere object as an ssgBranch (and connect in the
 // specified ssgSimpleState
 ssgBranch *ssgMakeSphere( ssgSimpleState *state, ssgColourArray *cl, 
-			  double radius, int slices, int stacks );
+			  double radius, int slices, int stacks,
+			  ssgCallback predraw, ssgCallback postdraw );
 
 
diff --git a/simgear/sky/stars.cxx b/simgear/sky/stars.cxx
new file mode 100644
index 00000000..c5d059c2
--- /dev/null
+++ b/simgear/sky/stars.cxx
@@ -0,0 +1,177 @@
+// stars.cxx -- model the stars
+//
+// Written by Durk Talsma. Originally started October 1997, for distribution  
+// with the FlightGear project. Version 2 was written in August and 
+// September 1998. This code is based upon algorithms and data kindly 
+// provided by Mr. Paul Schlyter. (pausch@saaf.se). 
+//
+// Separated out rendering pieces and converted to ssg by Curt Olson,
+// March 2000
+// 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.
+//
+// $Id$
+
+
+#include <stdio.h>
+#include <iostream>
+
+#include <plib/ssg.h>
+
+#include <simgear/constants.h>
+
+#include "stars.hxx"
+
+
+// Set up star rendering call backs
+static int sgStarPreDraw( ssgEntity *e ) {
+    /* cout << endl << "Star pre draw" << endl << "----------------" 
+	 << endl << endl; */
+    glDisable( GL_DEPTH_TEST );
+    glDisable( GL_FOG );
+    glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
+
+    return true;
+}
+
+static int sgStarPostDraw( ssgEntity *e ) {
+    /* cout << endl << "Star post draw" << endl << "----------------" 
+	 << endl << endl; */
+    glEnable( GL_DEPTH_TEST );
+    glEnable( GL_FOG );
+
+    return true;
+}
+
+
+// Constructor
+SGStars::SGStars( void ) {
+}
+
+
+// Destructor
+SGStars::~SGStars( void ) {
+}
+
+
+// initialize the stars object and connect it into our scene graph root
+ssgBranch * SGStars::build( int num, sgdVec3 *star_data, double star_dist ) {
+    sgVec4 color;
+
+    if ( star_data == NULL ) {
+	cout << "WARNING: null star data passed to SGStars::build()" << endl;
+    }
+
+    // set up the orb state
+    state = new ssgSimpleState();
+    state->disable( GL_LIGHTING );
+    state->disable( GL_CULL_FACE );
+    state->disable( GL_TEXTURE_2D );
+    state->enable( GL_COLOR_MATERIAL );
+    state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
+    state->enable( GL_BLEND );
+    state->disable( GL_ALPHA_TEST );
+
+    vl = new ssgVertexArray( num );
+    cl = new ssgColourArray( num );
+    // cl = new ssgColourArray( 1 );
+    // sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
+    // cl->add( color );
+   
+    // Build ssg structure
+    sgVec3 p;
+    for ( int i = 0; i < num; ++i ) {
+	// position seeded to arbitrary values
+	sgSetVec3( p, 
+		   star_dist * cos( star_data[i][0] )
+		       * cos( star_data[i][1] ),
+                   star_dist * sin( star_data[i][0] )
+		       * cos( star_data[i][1] ),
+                   star_dist * sin( star_data[i][1] )
+		   );
+	vl->add( p );
+
+	// color (magnitude)
+	sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
+	cl->add( color );
+    }
+
+    ssgLeaf *stars_obj = 
+	new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
+    stars_obj->setState( state );
+    stars_obj->setCallback( SSG_CALLBACK_PREDRAW, sgStarPreDraw );
+    stars_obj->setCallback( SSG_CALLBACK_POSTDRAW, sgStarPostDraw );
+
+    // build the ssg scene graph sub tree for the sky and connected
+    // into the provide scene graph branch
+    stars_transform = new ssgTransform;
+
+    stars_transform->addKid( stars_obj );
+
+    cout << "stars = " << stars_transform << endl;
+
+    return stars_transform;
+}
+
+
+// repaint the sun colors based on current value of sun_angle in
+// degrees relative to verticle
+// 0 degrees = high noon
+// 90 degrees = sun rise/set
+// 180 degrees = darkest midnight
+bool SGStars::repaint( double sun_angle, int num, sgdVec3 *star_data ) {
+    // TEST return true;
+
+    float *color;
+    for ( int i = 0; i < num; ++i ) {
+	// color (magnitude)
+	double magnitude = (0.0 - star_data[i][2]) / 5.0 + 1.0;
+	magnitude = magnitude * 0.7 + (3 * 0.1);
+	if (magnitude > 1.0) magnitude = 1.0;
+	if (magnitude < 0.0) magnitude = 0.0;
+
+	color = cl->get( i );
+	sgSetVec4( color, 1.0, 1.0, 1.0, magnitude );
+	// sgSetVec4( color, 1, 1, 1, 1.0 );
+	// cout << "color[" << i << "] = " << magnitude << endl;
+    }
+
+    return true;
+}
+
+
+// reposition the stars for the specified time (GST rotation),
+// offset by our current position (p) so that it appears fixed at a
+// great distance from the viewer.
+bool SGStars::reposition( sgVec3 p, double angle )
+{
+    sgMat4 T1, GST;
+    sgVec3 axis;
+
+    sgMakeTransMat4( T1, p );
+
+    sgSetVec3( axis, 0.0, 0.0, -1.0 );
+    sgMakeRotMat4( GST, angle, axis );
+
+    sgMat4 TRANSFORM;
+    sgCopyMat4( TRANSFORM, T1 );
+    sgPreMultMat4( TRANSFORM, GST );
+
+    sgCoord skypos;
+    sgSetCoord( &skypos, TRANSFORM );
+
+    stars_transform->setTransform( &skypos );
+
+    return true;
+}
diff --git a/simgear/sky/stars.hxx b/simgear/sky/stars.hxx
new file mode 100644
index 00000000..d7665a60
--- /dev/null
+++ b/simgear/sky/stars.hxx
@@ -0,0 +1,69 @@
+// stars.hxx -- model the stars
+//
+// Written by Durk Talsma. Originally started October 1997, for distribution  
+// with the FlightGear project. Version 2 was written in August and 
+// September 1998. This code is based upon algorithms and data kindly 
+// provided by Mr. Paul Schlyter. (pausch@saaf.se). 
+//
+// Separated out rendering pieces and converted to ssg by Curt Olson,
+// March 2000
+//
+// 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.
+//
+// $Id$
+
+
+#ifndef _SG_STARS_HXX_
+#define _SG_STARS_HXX_
+
+
+#include <plib/ssg.h>
+
+
+class SGStars {
+
+    ssgTransform *stars_transform;
+    ssgSimpleState *state;
+
+    ssgColourArray *cl;
+    ssgVertexArray *vl;
+
+public:
+
+    // Constructor
+    SGStars( void );
+
+    // Destructor
+    ~SGStars( void );
+
+    // initialize the stars structure
+    ssgBranch *build( int num, sgdVec3 *star_data, double star_dist );
+
+    // repaint the planet magnitudes based on current value of
+    // sun_angle in degrees relative to verticle (so we can make them
+    // relatively dimmer during dawn and dusk
+    // 0 degrees = high noon
+    // 90 degrees = sun rise/set
+    // 180 degrees = darkest midnight
+    bool repaint( double sun_angle, int num, sgdVec3 *star_data );
+
+    // reposition the stars for the specified time (GST rotation),
+    // offset by our current position (p) so that it appears fixed at
+    // a great distance from the viewer.
+    bool reposition( sgVec3 p, double angle );
+};
+
+
+#endif // _SG_STARS_HXX_
-- 
2.39.5