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>
38 #if !defined (SG_HAVE_NATIVE_SGI_COMPILERS)
44 // Set up star rendering call backs
45 static int sgStarPreDraw( ssgEntity *e ) {
46 /* cout << endl << "Star pre draw" << endl << "----------------"
49 ssgLeaf *f = (ssgLeaf *)e;
50 if ( f -> hasState () ) f->getState()->apply() ;
52 glPushAttrib( GL_DEPTH_BUFFER_BIT | GL_FOG_BIT );
54 glDisable( GL_DEPTH_TEST );
56 // glBlendFunc ( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA ) ;
61 static int sgStarPostDraw( ssgEntity *e ) {
62 /* cout << endl << "Star post draw" << endl << "----------------"
67 // glEnable( GL_DEPTH_TEST );
68 // glEnable( GL_FOG );
75 SGStars::SGStars( void ) {
80 SGStars::~SGStars( void ) {
84 // initialize the stars object and connect it into our scene graph root
85 ssgBranch * SGStars::build( int num, sgdVec3 *star_data, double star_dist ) {
88 if ( star_data == NULL ) {
89 cout << "WARNING: null star data passed to SGStars::build()" << endl;
92 // set up the orb state
93 state = new ssgSimpleState();
94 state->disable( GL_LIGHTING );
95 state->disable( GL_CULL_FACE );
96 state->disable( GL_TEXTURE_2D );
97 state->enable( GL_COLOR_MATERIAL );
98 state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE );
99 state->setMaterial( GL_EMISSION, 0, 0, 0, 1 );
100 state->setMaterial( GL_SPECULAR, 0, 0, 0, 1 );
101 state->enable( GL_BLEND );
102 state->disable( GL_ALPHA_TEST );
104 vl = new ssgVertexArray( num );
105 cl = new ssgColourArray( num );
106 // cl = new ssgColourArray( 1 );
107 // sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
110 // Build ssg structure
112 for ( int i = 0; i < num; ++i ) {
113 // position seeded to arbitrary values
115 star_dist * cos( star_data[i][0] )
116 * cos( star_data[i][1] ),
117 star_dist * sin( star_data[i][0] )
118 * cos( star_data[i][1] ),
119 star_dist * sin( star_data[i][1] )
124 sgSetVec4( color, 1.0, 1.0, 1.0, 1.0 );
129 new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
130 stars_obj->setState( state );
131 stars_obj->setCallback( SSG_CALLBACK_PREDRAW, sgStarPreDraw );
132 stars_obj->setCallback( SSG_CALLBACK_POSTDRAW, sgStarPostDraw );
134 // build the ssg scene graph sub tree for the sky and connected
135 // into the provide scene graph branch
136 stars_transform = new ssgTransform;
138 stars_transform->addKid( stars_obj );
140 cout << "stars = " << stars_transform << endl;
142 return stars_transform;
146 // repaint the sun colors based on current value of sun_angle in
147 // degrees relative to verticle
148 // 0 degrees = high noon
149 // 90 degrees = sun rise/set
150 // 180 degrees = darkest midnight
151 bool SGStars::repaint( double sun_angle, int num, sgdVec3 *star_data ) {
153 // double max = -100;
154 double mag, nmag, alpha, factor, cutoff;
157 // determine which star structure to draw
158 if ( sun_angle > (0.5 * SGD_PI + 10.0 * SGD_DEGREES_TO_RADIANS ) ) {
162 } else if ( sun_angle > (0.5 * SGD_PI + 8.8 * SGD_DEGREES_TO_RADIANS ) ) {
165 } else if ( sun_angle > (0.5 * SGD_PI + 7.5 * SGD_DEGREES_TO_RADIANS ) ) {
168 } else if ( sun_angle > (0.5 * SGD_PI + 7.0 * SGD_DEGREES_TO_RADIANS ) ) {
171 } else if ( sun_angle > (0.5 * SGD_PI + 6.5 * SGD_DEGREES_TO_RADIANS ) ) {
174 } else if ( sun_angle > (0.5 * SGD_PI + 6.0 * SGD_DEGREES_TO_RADIANS ) ) {
177 } else if ( sun_angle > (0.5 * SGD_PI + 5.5 * SGD_DEGREES_TO_RADIANS ) ) {
181 // early dusk or late dawn
186 for ( int i = 0; i < num; ++i ) {
187 // if ( star_data[i][2] < min ) { min = star_data[i][2]; }
188 // if ( star_data[i][2] > max ) { max = star_data[i][2]; }
190 // magnitude ranges from -1 (bright) to 4 (dim). The range of
191 // star and planet magnitudes can actually go outside of this,
192 // but for our purpose, if it is brighter that -1, we'll color
193 // it full white/alpha anyway and 4 is a convenient cutoff
194 // point which keeps the number of stars drawn at about 500.
197 mag = star_data[i][2];
198 if ( mag < cutoff ) {
199 nmag = ( 4.5 - mag ) / 5.5; // translate to 0 ... 1.0 scale
200 // alpha = nmag * 0.7 + 0.3; // translate to a 0.3 ... 1.0 scale
201 alpha = nmag * 0.85 + 0.15; // translate to a 0.15 ... 1.0 scale
202 alpha *= factor; // dim when the sun is brighter
207 if (alpha > 1.0) { alpha = 1.0; }
208 if (alpha < 0.0) { alpha = 0.0; }
210 color = cl->get( i );
211 sgSetVec4( color, 1.0, 1.0, 1.0, alpha );
212 // cout << "alpha[" << i << "] = " << alpha << endl;
215 // cout << "min = " << min << " max = " << max << " count = " << num
222 // reposition the stars for the specified time (GST rotation),
223 // offset by our current position (p) so that it appears fixed at a
224 // great distance from the viewer.
225 bool SGStars::reposition( sgVec3 p, double angle )
230 sgMakeTransMat4( T1, p );
232 sgSetVec3( axis, 0.0, 0.0, -1.0 );
233 sgMakeRotMat4( GST, angle, axis );
236 sgCopyMat4( TRANSFORM, T1 );
237 sgPreMultMat4( TRANSFORM, GST );
240 sgSetCoord( &skypos, TRANSFORM );
242 stars_transform->setTransform( &skypos );