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.
28 #include <simgear/compiler.h>
29 #include <simgear/debug/logstream.hxx>
40 // Set up star rendering call backs
41 static int sgStarPreDraw( ssgEntity *e ) {
42 /* cout << endl << "Star pre draw" << endl << "----------------"
45 ssgLeaf *f = (ssgLeaf *)e;
46 if ( f -> hasState () ) f->getState()->apply() ;
48 glPushAttrib( GL_DEPTH_BUFFER_BIT | GL_FOG_BIT );
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 << "----------------"
63 // glEnable( GL_DEPTH_TEST );
64 // glEnable( GL_FOG );
71 SGStars::SGStars( void ) :
78 SGStars::~SGStars( void ) {
82 // initialize the stars object and connect it into our scene graph root
83 ssgBranch * SGStars::build( int num, sgdVec3 *star_data, double star_dist ) {
86 if ( star_data == NULL )
87 SG_LOG( SG_EVENT, SG_WARN, "null star data passed to SGStars::build()");
90 // set up the orb state
91 state = new ssgSimpleState();
92 state->disable( GL_LIGHTING );
93 state->disable( GL_CULL_FACE );
94 state->disable( GL_TEXTURE_2D );
95 state->enable( GL_COLOR_MATERIAL );
96 state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
97 state->setMaterial( GL_EMISSION, 0, 0, 0, 1 );
98 state->setMaterial( GL_SPECULAR, 0, 0, 0, 1 );
99 state->enable( GL_BLEND );
100 state->disable( GL_ALPHA_TEST );
102 vl = new ssgVertexArray( num );
103 cl = new ssgColourArray( num );
104 // cl = new ssgColourArray( 1 );
105 // sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
108 // Build ssg structure
110 for ( int i = 0; i < num; ++i ) {
111 // position seeded to arbitrary values
113 star_dist * cos( star_data[i][0] )
114 * cos( star_data[i][1] ),
115 star_dist * sin( star_data[i][0] )
116 * cos( star_data[i][1] ),
117 star_dist * sin( star_data[i][1] )
122 sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
127 new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
128 stars_obj->setState( state );
129 stars_obj->setCallback( SSG_CALLBACK_PREDRAW, sgStarPreDraw );
130 stars_obj->setCallback( SSG_CALLBACK_POSTDRAW, sgStarPostDraw );
132 // build the ssg scene graph sub tree for the sky and connected
133 // into the provide scene graph branch
134 stars_transform = new ssgTransform;
136 stars_transform->addKid( stars_obj );
138 SG_LOG( SG_EVENT, SG_INFO, "stars = " << stars_transform);
140 return stars_transform;
144 // repaint the sun colors based on current value of sun_angle in
145 // degrees relative to verticle
146 // 0 degrees = high noon
147 // 90 degrees = sun rise/set
148 // 180 degrees = darkest midnight
149 bool SGStars::repaint( double sun_angle, int num, sgdVec3 *star_data ) {
150 // cout << "repainting stars" << endl;
152 // double max = -100;
153 double mag, nmag, alpha, factor, cutoff;
158 // determine which star structure to draw
159 if ( sun_angle > (0.5 * SGD_PI + 10.0 * SGD_DEGREES_TO_RADIANS ) ) {
164 } else if ( sun_angle > (0.5 * SGD_PI + 8.8 * SGD_DEGREES_TO_RADIANS ) ) {
168 } else if ( sun_angle > (0.5 * SGD_PI + 7.5 * SGD_DEGREES_TO_RADIANS ) ) {
172 } else if ( sun_angle > (0.5 * SGD_PI + 7.0 * SGD_DEGREES_TO_RADIANS ) ) {
176 } else if ( sun_angle > (0.5 * SGD_PI + 6.5 * SGD_DEGREES_TO_RADIANS ) ) {
180 } else if ( sun_angle > (0.5 * SGD_PI + 6.0 * SGD_DEGREES_TO_RADIANS ) ) {
184 } else if ( sun_angle > (0.5 * SGD_PI + 5.5 * SGD_DEGREES_TO_RADIANS ) ) {
189 // early dusk or late dawn
195 if( phase != old_phase ) {
196 // cout << " phase change, repainting stars, num = " << num << endl;
198 for ( int i = 0; i < num; ++i ) {
199 // if ( star_data[i][2] < min ) { min = star_data[i][2]; }
200 // if ( star_data[i][2] > max ) { max = star_data[i][2]; }
202 // magnitude ranges from -1 (bright) to 4 (dim). The
203 // range of star and planet magnitudes can actually go
204 // outside of this, but for our purpose, if it is brighter
205 // that -1, we'll color it full white/alpha anyway and 4
206 // is a convenient cutoff point which keeps the number of
207 // stars drawn at about 500.
210 mag = star_data[i][2];
211 if ( mag < cutoff ) {
212 nmag = ( 4.5 - mag ) / 5.5; // translate to 0 ... 1.0 scale
213 // alpha = nmag * 0.7 + 0.3; // translate to a 0.3 ... 1.0 scale
214 alpha = nmag * 0.85 + 0.15; // translate to a 0.15 ... 1.0 scale
215 alpha *= factor; // dim when the sun is brighter
220 if (alpha > 1.0) { alpha = 1.0; }
221 if (alpha < 0.0) { alpha = 0.0; }
223 color = cl->get( i );
224 sgSetVec4( color, 1.0, 1.0, 1.0, alpha );
225 // cout << "alpha[" << i << "] = " << alpha << endl;
228 // cout << " no phase change, skipping" << endl;
231 // cout << "min = " << min << " max = " << max << " count = " << num
238 // reposition the stars for the specified time (GST rotation),
239 // offset by our current position (p) so that it appears fixed at a
240 // great distance from the viewer.
241 bool SGStars::reposition( sgVec3 p, double angle )
246 sgMakeTransMat4( T1, p );
248 sgSetVec3( axis, 0.0, 0.0, -1.0 );
249 sgMakeRotMat4( GST, angle, axis );
252 sgCopyMat4( TRANSFORM, T1 );
253 sgPreMultMat4( TRANSFORM, GST );
256 sgSetCoord( &skypos, TRANSFORM );
258 stars_transform->setTransform( &skypos );