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 library is free software; you can redistribute it and/or
11 // modify it under the terms of the GNU Library General Public
12 // License as published by the Free Software Foundation; either
13 // version 2 of the License, or (at your option) any later version.
15 // This library is distributed in the hope that it will be useful,
16 // but WITHOUT ANY WARRANTY; without even the implied warranty of
17 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 // Library General Public License for more details.
20 // You should have received a copy of the GNU Library General Public
21 // License along with this library; if not, write to the
22 // Free Software Foundation, Inc., 59 Temple Place - Suite 330,
23 // Boston, MA 02111-1307, USA.
46 // Set up star rendering call backs
47 static int sgStarPreDraw( ssgEntity *e ) {
48 /* cout << endl << "Star pre draw" << endl << "----------------"
50 glDisable( GL_DEPTH_TEST );
52 glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
57 static int sgStarPostDraw( ssgEntity *e ) {
58 /* cout << endl << "Star post draw" << endl << "----------------"
60 glEnable( GL_DEPTH_TEST );
68 SGStars::SGStars( void ) {
73 SGStars::~SGStars( void ) {
77 // initialize the stars object and connect it into our scene graph root
78 ssgBranch * SGStars::build( int num, sgdVec3 *star_data, double star_dist ) {
81 if ( star_data == NULL ) {
82 cout << "WARNING: null star data passed to SGStars::build()" << endl;
85 // set up the orb state
86 state = new ssgSimpleState();
87 state->disable( GL_LIGHTING );
88 state->disable( GL_CULL_FACE );
89 state->disable( GL_TEXTURE_2D );
90 state->enable( GL_COLOR_MATERIAL );
91 state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
92 state->setMaterial( GL_EMISSION, 0, 0, 0, 1 );
93 state->setMaterial( GL_SPECULAR, 0, 0, 0, 1 );
94 state->enable( GL_BLEND );
95 state->disable( GL_ALPHA_TEST );
97 vl = new ssgVertexArray( num );
98 cl = new ssgColourArray( num );
99 // cl = new ssgColourArray( 1 );
100 // sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
103 // Build ssg structure
105 for ( int i = 0; i < num; ++i ) {
106 // position seeded to arbitrary values
108 star_dist * cos( star_data[i][0] )
109 * cos( star_data[i][1] ),
110 star_dist * sin( star_data[i][0] )
111 * cos( star_data[i][1] ),
112 star_dist * sin( star_data[i][1] )
117 sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
122 new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
123 stars_obj->setState( state );
124 stars_obj->setCallback( SSG_CALLBACK_PREDRAW, sgStarPreDraw );
125 stars_obj->setCallback( SSG_CALLBACK_POSTDRAW, sgStarPostDraw );
127 // build the ssg scene graph sub tree for the sky and connected
128 // into the provide scene graph branch
129 stars_transform = new ssgTransform;
131 stars_transform->addKid( stars_obj );
133 cout << "stars = " << stars_transform << endl;
135 return stars_transform;
139 // repaint the sun colors based on current value of sun_angle in
140 // degrees relative to verticle
141 // 0 degrees = high noon
142 // 90 degrees = sun rise/set
143 // 180 degrees = darkest midnight
144 bool SGStars::repaint( double sun_angle, int num, sgdVec3 *star_data ) {
146 // double max = -100;
147 double mag, nmag, alpha, factor, cutoff;
150 // determine which star structure to draw
151 if ( sun_angle > (0.5 * SGD_PI + 10.0 * SGD_DEGREES_TO_RADIANS ) ) {
155 } else if ( sun_angle > (0.5 * SGD_PI + 8.8 * SGD_DEGREES_TO_RADIANS ) ) {
158 } else if ( sun_angle > (0.5 * SGD_PI + 7.5 * SGD_DEGREES_TO_RADIANS ) ) {
161 } else if ( sun_angle > (0.5 * SGD_PI + 7.0 * SGD_DEGREES_TO_RADIANS ) ) {
164 } else if ( sun_angle > (0.5 * SGD_PI + 6.5 * SGD_DEGREES_TO_RADIANS ) ) {
167 } else if ( sun_angle > (0.5 * SGD_PI + 6.0 * SGD_DEGREES_TO_RADIANS ) ) {
170 } else if ( sun_angle > (0.5 * SGD_PI + 5.5 * SGD_DEGREES_TO_RADIANS ) ) {
174 // early dusk or late dawn
179 for ( int i = 0; i < num; ++i ) {
180 // if ( star_data[i][2] < min ) { min = star_data[i][2]; }
181 // if ( star_data[i][2] > max ) { max = star_data[i][2]; }
183 // magnitude ranges from -1 (bright) to 4 (dim). The range of
184 // star and planet magnitudes can actually go outside of this,
185 // but for our purpose, if it is brighter that -1, we'll color
186 // it full white/alpha anyway and 4 is a convenient cutoff
187 // point which keeps the number of stars drawn at about 500.
190 mag = star_data[i][2];
191 if ( mag < cutoff ) {
192 nmag = ( 4.5 - mag ) / 5.5; // translate to 0 ... 1.0 scale
193 // alpha = nmag * 0.7 + 0.3; // translate to a 0.3 ... 1.0 scale
194 alpha = nmag * 0.85 + 0.15; // translate to a 0.15 ... 1.0 scale
195 alpha *= factor; // dim when the sun is brighter
200 if (alpha > 1.0) { alpha = 1.0; }
201 if (alpha < 0.0) { alpha = 0.0; }
203 color = cl->get( i );
204 sgSetVec4( color, 1.0, 1.0, 1.0, alpha );
205 // cout << "alpha[" << i << "] = " << alpha << endl;
208 // cout << "min = " << min << " max = " << max << " count = " << num
215 // reposition the stars for the specified time (GST rotation),
216 // offset by our current position (p) so that it appears fixed at a
217 // great distance from the viewer.
218 bool SGStars::reposition( sgVec3 p, double angle )
223 sgMakeTransMat4( T1, p );
225 sgSetVec3( axis, 0.0, 0.0, -1.0 );
226 sgMakeRotMat4( GST, angle, axis );
229 sgCopyMat4( TRANSFORM, T1 );
230 sgPreMultMat4( TRANSFORM, GST );
233 sgSetCoord( &skypos, TRANSFORM );
235 stars_transform->setTransform( &skypos );