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 General Public License
21 // along with this program; if not, write to the Free Software
22 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
27 # include <simgear_config.h>
30 #include <simgear/compiler.h>
31 #include <simgear/constants.h>
32 #include <simgear/debug/logstream.hxx>
37 #include <osg/AlphaFunc>
38 #include <osg/BlendFunc>
40 #include <osg/Geometry>
42 #include <osg/Material>
44 #include <osg/ShadeModel>
50 SGStars::SGStars( void ) :
57 SGStars::~SGStars( void ) {
61 // initialize the stars object and connect it into our scene graph root
63 SGStars::build( int num, const SGVec3d star_data[], double star_dist ) {
64 osg::Geode* geode = new osg::Geode;
65 osg::StateSet* stateSet = geode->getOrCreateStateSet();
66 stateSet->setRenderBinDetails(-9, "RenderBin");
68 // set up the star state
69 osg::BlendFunc* blendFunc = new osg::BlendFunc;
70 blendFunc->setFunction(osg::BlendFunc::SRC_ALPHA,
71 osg::BlendFunc::ONE_MINUS_SRC_ALPHA);
72 stateSet->setAttributeAndModes(blendFunc);
74 // osg::Point* point = new osg::Point;
76 // stateSet->setAttributeAndModes(point);
78 stateSet->setMode(GL_FOG, osg::StateAttribute::OFF);
79 stateSet->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
80 stateSet->setMode(GL_CULL_FACE, osg::StateAttribute::OFF);
81 stateSet->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);
82 stateSet->setMode(GL_ALPHA_TEST, osg::StateAttribute::OFF);
84 // Build scenegraph structure
86 cl = new osg::Vec4Array;
87 osg::Vec3Array* vl = new osg::Vec3Array;
89 // Build scenegraph structure
90 for ( int i = 0; i < num; ++i ) {
91 // position seeded to arbitrary values
92 vl->push_back(osg::Vec3(star_dist * cos( star_data[i][0])
93 * cos( star_data[i][1] ),
94 star_dist * sin( star_data[i][0])
95 * cos( star_data[i][1] ),
96 star_dist * sin( star_data[i][1])));
99 cl->push_back(osg::Vec4(1, 1, 1, 1));
102 osg::Geometry* geometry = new osg::Geometry;
103 geometry->setUseDisplayList(false);
104 geometry->setVertexArray(vl);
105 geometry->setColorArray(cl.get());
106 geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
107 geometry->setNormalBinding(osg::Geometry::BIND_OFF);
108 geometry->addPrimitiveSet(new osg::DrawArrays(GL_POINTS, 0, vl->size()));
109 geode->addDrawable(geometry);
115 // repaint the sun colors based on current value of sun_angle in
116 // degrees relative to verticle
117 // 0 degrees = high noon
118 // 90 degrees = sun rise/set
119 // 180 degrees = darkest midnight
120 bool SGStars::repaint( double sun_angle, int num, const SGVec3d star_data[] ) {
121 // cout << "repainting stars" << endl;
123 // double max = -100;
124 double mag, nmag, alpha, factor, cutoff;
128 // determine which star structure to draw
129 if ( sun_angle > (SGD_PI_2 + 10.0 * SGD_DEGREES_TO_RADIANS ) ) {
134 } else if ( sun_angle > (SGD_PI_2 + 8.8 * SGD_DEGREES_TO_RADIANS ) ) {
138 } else if ( sun_angle > (SGD_PI_2 + 7.5 * SGD_DEGREES_TO_RADIANS ) ) {
142 } else if ( sun_angle > (SGD_PI_2 + 7.0 * SGD_DEGREES_TO_RADIANS ) ) {
146 } else if ( sun_angle > (SGD_PI_2 + 6.5 * SGD_DEGREES_TO_RADIANS ) ) {
150 } else if ( sun_angle > (SGD_PI_2 + 6.0 * SGD_DEGREES_TO_RADIANS ) ) {
154 } else if ( sun_angle > (SGD_PI_2 + 5.5 * SGD_DEGREES_TO_RADIANS ) ) {
159 // early dusk or late dawn
165 if( phase != old_phase ) {
166 // cout << " phase change, repainting stars, num = " << num << endl;
168 for ( int i = 0; i < num; ++i ) {
169 // if ( star_data[i][2] < min ) { min = star_data[i][2]; }
170 // if ( star_data[i][2] > max ) { max = star_data[i][2]; }
172 // magnitude ranges from -1 (bright) to 4 (dim). The
173 // range of star and planet magnitudes can actually go
174 // outside of this, but for our purpose, if it is brighter
175 // that -1, we'll color it full white/alpha anyway and 4
176 // is a convenient cutoff point which keeps the number of
177 // stars drawn at about 500.
180 mag = star_data[i][2];
181 if ( mag < cutoff ) {
182 nmag = ( 4.5 - mag ) / 5.5; // translate to 0 ... 1.0 scale
183 alpha = nmag * 0.85 + 0.15; // translate to a 0.15 ... 1.0 scale
184 alpha *= factor; // dim when the sun is brighter
189 if (alpha > 1.0) { alpha = 1.0; }
190 if (alpha < 0.0) { alpha = 0.0; }
192 (*cl)[i] = osg::Vec4(1, 1, 1, alpha);
193 // cout << "alpha[" << i << "] = " << alpha << endl;
197 // cout << " no phase change, skipping" << endl;
200 // cout << "min = " << min << " max = " << max << " count = " << num