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 ) {
137 for ( int i = 0; i < num; ++i ) {
139 double magnitude = (0.0 - star_data[i][2]) / 5.0 + 1.0;
140 magnitude = magnitude * 0.7 + (3 * 0.1);
141 if (magnitude > 1.0) magnitude = 1.0;
142 if (magnitude < 0.0) magnitude = 0.0;
144 color = cl->get( i );
145 sgSetVec4( color, 1.0, 1.0, 1.0, magnitude );
146 // sgSetVec4( color, 1, 1, 1, 1.0 );
147 // cout << "color[" << i << "] = " << magnitude << endl;
154 // reposition the stars for the specified time (GST rotation),
155 // offset by our current position (p) so that it appears fixed at a
156 // great distance from the viewer.
157 bool SGStars::reposition( sgVec3 p, double angle )
162 sgMakeTransMat4( T1, p );
164 sgSetVec3( axis, 0.0, 0.0, -1.0 );
165 sgMakeRotMat4( GST, angle, axis );
168 sgCopyMat4( TRANSFORM, T1 );
169 sgPreMultMat4( TRANSFORM, GST );
172 sgSetCoord( &skypos, TRANSFORM );
174 stars_transform->setTransform( &skypos );