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.
32 #include <simgear/compiler.h>
44 #if !defined (SG_HAVE_NATIVE_SGI_COMPILERS)
50 // Set up star rendering call backs
51 static int sgStarPreDraw( ssgEntity *e ) {
52 /* cout << endl << "Star pre draw" << endl << "----------------"
55 ssgLeaf *f = (ssgLeaf *)e;
56 if ( f -> hasState () ) f->getState()->apply() ;
58 glPushAttrib( GL_DEPTH_BUFFER_BIT | GL_FOG_BIT );
60 glDisable( GL_DEPTH_TEST );
62 // glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
67 static int sgStarPostDraw( ssgEntity *e ) {
68 /* cout << endl << "Star post draw" << endl << "----------------"
73 // glEnable( GL_DEPTH_TEST );
74 // glEnable( GL_FOG );
81 SGStars::SGStars( void ) {
86 SGStars::~SGStars( void ) {
90 // initialize the stars object and connect it into our scene graph root
91 ssgBranch * SGStars::build( int num, sgdVec3 *star_data, double star_dist ) {
94 if ( star_data == NULL ) {
95 cout << "WARNING: null star data passed to SGStars::build()" << endl;
98 // set up the orb state
99 state = new ssgSimpleState();
100 state->disable( GL_LIGHTING );
101 state->disable( GL_CULL_FACE );
102 state->disable( GL_TEXTURE_2D );
103 state->enable( GL_COLOR_MATERIAL );
104 state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
105 state->setMaterial( GL_EMISSION, 0, 0, 0, 1 );
106 state->setMaterial( GL_SPECULAR, 0, 0, 0, 1 );
107 state->enable( GL_BLEND );
108 state->disable( GL_ALPHA_TEST );
110 vl = new ssgVertexArray( num );
111 cl = new ssgColourArray( num );
112 // cl = new ssgColourArray( 1 );
113 // sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
116 // Build ssg structure
118 for ( int i = 0; i < num; ++i ) {
119 // position seeded to arbitrary values
121 star_dist * cos( star_data[i][0] )
122 * cos( star_data[i][1] ),
123 star_dist * sin( star_data[i][0] )
124 * cos( star_data[i][1] ),
125 star_dist * sin( star_data[i][1] )
130 sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
135 new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
136 stars_obj->setState( state );
137 stars_obj->setCallback( SSG_CALLBACK_PREDRAW, sgStarPreDraw );
138 stars_obj->setCallback( SSG_CALLBACK_POSTDRAW, sgStarPostDraw );
140 // build the ssg scene graph sub tree for the sky and connected
141 // into the provide scene graph branch
142 stars_transform = new ssgTransform;
144 stars_transform->addKid( stars_obj );
146 cout << "stars = " << stars_transform << endl;
148 return stars_transform;
152 // repaint the sun colors based on current value of sun_angle in
153 // degrees relative to verticle
154 // 0 degrees = high noon
155 // 90 degrees = sun rise/set
156 // 180 degrees = darkest midnight
157 bool SGStars::repaint( double sun_angle, int num, sgdVec3 *star_data ) {
159 // double max = -100;
160 double mag, nmag, alpha, factor, cutoff;
163 // determine which star structure to draw
164 if ( sun_angle > (0.5 * SGD_PI + 10.0 * SGD_DEGREES_TO_RADIANS ) ) {
168 } else if ( sun_angle > (0.5 * SGD_PI + 8.8 * SGD_DEGREES_TO_RADIANS ) ) {
171 } else if ( sun_angle > (0.5 * SGD_PI + 7.5 * SGD_DEGREES_TO_RADIANS ) ) {
174 } else if ( sun_angle > (0.5 * SGD_PI + 7.0 * SGD_DEGREES_TO_RADIANS ) ) {
177 } 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 ) ) {
183 } else if ( sun_angle > (0.5 * SGD_PI + 5.5 * SGD_DEGREES_TO_RADIANS ) ) {
187 // early dusk or late dawn
192 for ( int i = 0; i < num; ++i ) {
193 // if ( star_data[i][2] < min ) { min = star_data[i][2]; }
194 // if ( star_data[i][2] > max ) { max = star_data[i][2]; }
196 // magnitude ranges from -1 (bright) to 4 (dim). The range of
197 // star and planet magnitudes can actually go outside of this,
198 // but for our purpose, if it is brighter that -1, we'll color
199 // it full white/alpha anyway and 4 is a convenient cutoff
200 // point which keeps the number of stars drawn at about 500.
203 mag = star_data[i][2];
204 if ( mag < cutoff ) {
205 nmag = ( 4.5 - mag ) / 5.5; // translate to 0 ... 1.0 scale
206 // alpha = nmag * 0.7 + 0.3; // translate to a 0.3 ... 1.0 scale
207 alpha = nmag * 0.85 + 0.15; // translate to a 0.15 ... 1.0 scale
208 alpha *= factor; // dim when the sun is brighter
213 if (alpha > 1.0) { alpha = 1.0; }
214 if (alpha < 0.0) { alpha = 0.0; }
216 color = cl->get( i );
217 sgSetVec4( color, 1.0, 1.0, 1.0, alpha );
218 // cout << "alpha[" << i << "] = " << alpha << endl;
221 // cout << "min = " << min << " max = " << max << " count = " << num
228 // reposition the stars for the specified time (GST rotation),
229 // offset by our current position (p) so that it appears fixed at a
230 // great distance from the viewer.
231 bool SGStars::reposition( sgVec3 p, double angle )
236 sgMakeTransMat4( T1, p );
238 sgSetVec3( axis, 0.0, 0.0, -1.0 );
239 sgMakeRotMat4( GST, angle, axis );
242 sgCopyMat4( TRANSFORM, T1 );
243 sgPreMultMat4( TRANSFORM, GST );
246 sgSetCoord( &skypos, TRANSFORM );
248 stars_transform->setTransform( &skypos );