1 // stars.cxx -- model the stars
3 // Written by Durk Talsma. Originally started October 1997, for distribution
4 // with the FlightGear project. Version 2 was written in August and
5 // September 1998. This code is based upon algorithms and data kindly
6 // provided by Mr. Paul Schlyter. (pausch@saaf.se).
8 // Separated out rendering pieces and converted to ssg by Curt Olson,
10 // This program is free software; you can redistribute it and/or
11 // modify it under the terms of the GNU General Public License as
12 // published by the Free Software Foundation; either version 2 of the
13 // License, or (at your option) any later version.
15 // This program is distributed in the hope that it will be useful, but
16 // WITHOUT ANY WARRANTY; without even the implied warranty of
17 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 // General Public License for more details.
20 // You should have received a copy of the GNU General Public License
21 // along with this program; if not, write to the Free Software
22 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
32 #include <simgear/constants.h>
37 // Set up star rendering call backs
38 static int sgStarPreDraw( ssgEntity *e ) {
39 /* cout << endl << "Star pre draw" << endl << "----------------"
41 glDisable( GL_DEPTH_TEST );
43 glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
48 static int sgStarPostDraw( ssgEntity *e ) {
49 /* cout << endl << "Star post draw" << endl << "----------------"
51 glEnable( GL_DEPTH_TEST );
59 SGStars::SGStars( void ) {
64 SGStars::~SGStars( void ) {
68 // initialize the stars object and connect it into our scene graph root
69 ssgBranch * SGStars::build( int num, sgdVec3 *star_data, double star_dist ) {
72 if ( star_data == NULL ) {
73 cout << "WARNING: null star data passed to SGStars::build()" << endl;
76 // set up the orb state
77 state = new ssgSimpleState();
78 state->disable( GL_LIGHTING );
79 state->disable( GL_CULL_FACE );
80 state->disable( GL_TEXTURE_2D );
81 state->enable( GL_COLOR_MATERIAL );
82 state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
83 state->enable( GL_BLEND );
84 state->disable( GL_ALPHA_TEST );
86 vl = new ssgVertexArray( num );
87 cl = new ssgColourArray( num );
88 // cl = new ssgColourArray( 1 );
89 // sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
92 // Build ssg structure
94 for ( int i = 0; i < num; ++i ) {
95 // position seeded to arbitrary values
97 star_dist * cos( star_data[i][0] )
98 * cos( star_data[i][1] ),
99 star_dist * sin( star_data[i][0] )
100 * cos( star_data[i][1] ),
101 star_dist * sin( star_data[i][1] )
106 sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
111 new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
112 stars_obj->setState( state );
113 stars_obj->setCallback( SSG_CALLBACK_PREDRAW, sgStarPreDraw );
114 stars_obj->setCallback( SSG_CALLBACK_POSTDRAW, sgStarPostDraw );
116 // build the ssg scene graph sub tree for the sky and connected
117 // into the provide scene graph branch
118 stars_transform = new ssgTransform;
120 stars_transform->addKid( stars_obj );
122 cout << "stars = " << stars_transform << endl;
124 return stars_transform;
128 // repaint the sun colors based on current value of sun_angle in
129 // degrees relative to verticle
130 // 0 degrees = high noon
131 // 90 degrees = sun rise/set
132 // 180 degrees = darkest midnight
133 bool SGStars::repaint( double sun_angle, int num, sgdVec3 *star_data ) {
135 // double max = -100;
136 double mag, nmag, alpha, factor, cutoff;
139 // determine which star structure to draw
140 if ( sun_angle > (FG_PI_2 + 10.0 * DEG_TO_RAD ) ) {
144 } else if ( sun_angle > (FG_PI_2 + 8.8 * DEG_TO_RAD ) ) {
147 } else if ( sun_angle > (FG_PI_2 + 7.5 * DEG_TO_RAD ) ) {
150 } else if ( sun_angle > (FG_PI_2 + 7.0 * DEG_TO_RAD ) ) {
153 } else if ( sun_angle > (FG_PI_2 + 6.5 * DEG_TO_RAD ) ) {
156 } else if ( sun_angle > (FG_PI_2 + 6.0 * DEG_TO_RAD ) ) {
159 } else if ( sun_angle > (FG_PI_2 + 5.5 * DEG_TO_RAD ) ) {
163 // early dusk or late dawn
168 for ( int i = 0; i < num; ++i ) {
169 // if ( star_data[i][2] < min ) { min = star_data[i][2]; }
170 // if ( star_data[i][2] > max ) { max = star_data[i][2]; }
172 // magnitude ranges from -1 (bright) to 4 (dim). The range of
173 // star and planet magnitudes can actually go outside of this,
174 // but for our purpose, if it is brighter that -1, we'll color
175 // it full white/alpha anyway and 4 is a convenient cutoff
176 // point which keeps the number of stars drawn at about 500.
179 mag = star_data[i][2];
180 if ( mag < cutoff ) {
181 nmag = ( 4 - mag ) / 5.0; // translate to 0 ... 1.0 scale
182 alpha = nmag * 0.7 + 0.3; // translate to a 0.3 ... 1.0 scale
183 alpha *= factor; // dim when the sun is brighter
188 if (alpha > 1.0) { alpha = 1.0; }
189 if (alpha < 0.0) { alpha = 0.0; }
191 color = cl->get( i );
192 sgSetVec4( color, 1.0, 1.0, 1.0, alpha );
193 // cout << "alpha[" << i << "] = " << alpha << endl;
196 // cout << "min = " << min << " max = " << max << " count = " << num
203 // reposition the stars for the specified time (GST rotation),
204 // offset by our current position (p) so that it appears fixed at a
205 // great distance from the viewer.
206 bool SGStars::reposition( sgVec3 p, double angle )
211 sgMakeTransMat4( T1, p );
213 sgSetVec3( axis, 0.0, 0.0, -1.0 );
214 sgMakeRotMat4( GST, angle, axis );
217 sgCopyMat4( TRANSFORM, T1 );
218 sgPreMultMat4( TRANSFORM, GST );
221 sgSetCoord( &skypos, TRANSFORM );
223 stars_transform->setTransform( &skypos );