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>
34 #include <simgear/compiler.h>
35 #include <simgear/constants.h>
36 #include <simgear/debug/logstream.hxx>
41 #include <osg/AlphaFunc>
42 #include <osg/BlendFunc>
44 #include <osg/Geometry>
46 #include <osg/Material>
48 #include <osg/ShadeModel>
53 SGStars::SGStars( void ) :
60 SGStars::~SGStars( void ) {
64 // initialize the stars object and connect it into our scene graph root
66 SGStars::build( int num, const SGVec3d star_data[], double star_dist ) {
67 // build the ssg scene graph sub tree for the sky and connected
68 // into the provide scene graph branch
69 stars_transform = new osg::MatrixTransform;
71 osg::Geode* geode = new osg::Geode;
72 osg::StateSet* stateSet = geode->getOrCreateStateSet();
73 stateSet->setRenderBinDetails(-9, "RenderBin");
75 // set up the star state
77 // Ok, the old implementation did have a color material set.
78 // But with lighting off, I don't see how this should change the result
79 osg::Material* material = new osg::Material;
80 // material->setColorMode(osg::Material::AMBIENT_AND_DIFFUSE);
81 // material->setEmission(osg::Material::FRONT_AND_BACK,
82 // osg::Vec4(0, 0, 0, 1));
83 // material->setSpecular(osg::Material::FRONT_AND_BACK,
84 // osg::Vec4(0, 0, 0, 1));
85 stateSet->setAttribute(material);
87 osg::BlendFunc* blendFunc = new osg::BlendFunc;
88 blendFunc->setFunction(osg::BlendFunc::SRC_ALPHA,
89 osg::BlendFunc::ONE_MINUS_SRC_ALPHA);
90 stateSet->setAttributeAndModes(blendFunc);
92 // osg::Point* point = new osg::Point;
94 // stateSet->setAttributeAndModes(point);
96 stateSet->setMode(GL_FOG, osg::StateAttribute::OFF);
97 stateSet->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
98 stateSet->setMode(GL_CULL_FACE, osg::StateAttribute::OFF);
99 stateSet->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);
100 stateSet->setMode(GL_ALPHA_TEST, osg::StateAttribute::OFF);
102 // Build scenegraph structure
104 cl = new osg::Vec4Array;
105 osg::Vec3Array* vl = new osg::Vec3Array;
107 // Build scenegraph structure
108 for ( int i = 0; i < num; ++i ) {
109 // position seeded to arbitrary values
110 vl->push_back(osg::Vec3(star_dist * cos( star_data[i][0])
111 * cos( star_data[i][1] ),
112 star_dist * sin( star_data[i][0])
113 * cos( star_data[i][1] ),
114 star_dist * sin( star_data[i][1])));
117 cl->push_back(osg::Vec4(1, 1, 1, 1));
120 osg::Geometry* geometry = new osg::Geometry;
121 geometry->setUseDisplayList(false);
122 geometry->setVertexArray(vl);
123 geometry->setColorArray(cl.get());
124 geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
125 geometry->setNormalBinding(osg::Geometry::BIND_OFF);
126 geometry->addPrimitiveSet(new osg::DrawArrays(GL_POINTS, 0, vl->size()));
127 geode->addDrawable(geometry);
129 stars_transform->addChild(geode);
131 SG_LOG( SG_EVENT, SG_INFO, "stars = " << stars_transform.get());
133 return stars_transform.get();
137 // repaint the sun colors based on current value of sun_angle in
138 // degrees relative to verticle
139 // 0 degrees = high noon
140 // 90 degrees = sun rise/set
141 // 180 degrees = darkest midnight
142 bool SGStars::repaint( double sun_angle, int num, const SGVec3d star_data[] ) {
143 // cout << "repainting stars" << endl;
145 // double max = -100;
146 double mag, nmag, alpha, factor, cutoff;
150 // determine which star structure to draw
151 if ( sun_angle > (SGD_PI_2 + 10.0 * SGD_DEGREES_TO_RADIANS ) ) {
156 } else if ( sun_angle > (SGD_PI_2 + 8.8 * SGD_DEGREES_TO_RADIANS ) ) {
160 } else if ( sun_angle > (SGD_PI_2 + 7.5 * SGD_DEGREES_TO_RADIANS ) ) {
164 } else if ( sun_angle > (SGD_PI_2 + 7.0 * SGD_DEGREES_TO_RADIANS ) ) {
168 } else if ( sun_angle > (SGD_PI_2 + 6.5 * SGD_DEGREES_TO_RADIANS ) ) {
172 } else if ( sun_angle > (SGD_PI_2 + 6.0 * SGD_DEGREES_TO_RADIANS ) ) {
176 } else if ( sun_angle > (SGD_PI_2 + 5.5 * SGD_DEGREES_TO_RADIANS ) ) {
181 // early dusk or late dawn
187 if( phase != old_phase ) {
188 // cout << " phase change, repainting stars, num = " << num << endl;
190 for ( int i = 0; i < num; ++i ) {
191 // if ( star_data[i][2] < min ) { min = star_data[i][2]; }
192 // if ( star_data[i][2] > max ) { max = star_data[i][2]; }
194 // magnitude ranges from -1 (bright) to 4 (dim). The
195 // range of star and planet magnitudes can actually go
196 // outside of this, but for our purpose, if it is brighter
197 // that -1, we'll color it full white/alpha anyway and 4
198 // is a convenient cutoff point which keeps the number of
199 // stars drawn at about 500.
202 mag = star_data[i][2];
203 if ( mag < cutoff ) {
204 nmag = ( 4.5 - mag ) / 5.5; // translate to 0 ... 1.0 scale
205 // alpha = nmag * 0.7 + 0.3; // translate to a 0.3 ... 1.0 scale
206 alpha = nmag * 0.85 + 0.15; // translate to a 0.15 ... 1.0 scale
207 alpha *= factor; // dim when the sun is brighter
212 if (alpha > 1.0) { alpha = 1.0; }
213 if (alpha < 0.0) { alpha = 0.0; }
215 (*cl)[i] = osg::Vec4(1, 1, 1, alpha);
216 // cout << "alpha[" << i << "] = " << alpha << endl;
220 // cout << " no phase change, skipping" << endl;
223 // cout << "min = " << min << " max = " << max << " count = " << num
230 // reposition the stars for the specified time (GST rotation),
231 // offset by our current position (p) so that it appears fixed at a
232 // great distance from the viewer.
234 SGStars::reposition( const SGVec3f& p, double angle )
237 T1.makeTranslate(p.osg());
239 GST.makeRotate(angle*SGD_DEGREES_TO_RADIANS, osg::Vec3(0, 0, -1));
241 stars_transform->setMatrix(GST*T1);