1 // oursun.hxx -- model earth's sun
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.
28 # include <simgear_config.h>
31 #include <simgear/compiler.h>
33 #include <osg/AlphaFunc>
34 #include <osg/BlendFunc>
37 #include <osg/Geometry>
38 #include <osg/Material>
39 #include <osg/ShadeModel>
41 #include <osg/Texture2D>
42 #include <osgDB/ReadFile>
44 #include <simgear/misc/PathOptions.hxx>
45 #include <simgear/screen/colors.hxx>
46 #include <simgear/scene/model/model.hxx>
49 using namespace simgear;
52 SGSun::SGSun( void ) :
53 visibility(-9999.0), prev_sun_angle(-9999.0), path_distance(60000.0),
54 sun_exp2_punch_through(7.0e-06)
61 SGSun::~SGSun( void ) {
65 // initialize the sun object and connect it into our scene graph root
67 SGSun::build( SGPath path, double sun_size, SGPropertyNode *property_tree_Node ) {
69 env_node = property_tree_Node;
71 osg::ref_ptr<osgDB::ReaderWriter::Options> options
72 = makeOptionsFromPath(path);
73 // build the ssg scene graph sub tree for the sky and connected
74 // into the provide scene graph branch
75 sun_transform = new osg::MatrixTransform;
76 osg::StateSet* stateSet = sun_transform->getOrCreateStateSet();
78 osg::TexEnv* texEnv = new osg::TexEnv;
79 texEnv->setMode(osg::TexEnv::MODULATE);
80 stateSet->setTextureAttribute(0, texEnv, osg::StateAttribute::ON);
82 osg::Material* material = new osg::Material;
83 material->setColorMode(osg::Material::AMBIENT_AND_DIFFUSE);
84 material->setEmission(osg::Material::FRONT_AND_BACK, osg::Vec4(0,0,0,1));
85 material->setSpecular(osg::Material::FRONT_AND_BACK, osg::Vec4(0,0,0,1));
86 stateSet->setAttribute(material);
88 osg::ShadeModel* shadeModel = new osg::ShadeModel;
89 shadeModel->setMode(osg::ShadeModel::SMOOTH);
90 stateSet->setAttributeAndModes(shadeModel);
92 osg::AlphaFunc* alphaFunc = new osg::AlphaFunc;
93 alphaFunc->setFunction(osg::AlphaFunc::ALWAYS);
94 stateSet->setAttributeAndModes(alphaFunc);
96 osg::BlendFunc* blendFunc = new osg::BlendFunc;
97 blendFunc->setSource(osg::BlendFunc::SRC_ALPHA);
98 blendFunc->setDestination(osg::BlendFunc::ONE_MINUS_SRC_ALPHA);
99 stateSet->setAttributeAndModes(blendFunc);
101 stateSet->setMode(GL_FOG, osg::StateAttribute::OFF);
102 stateSet->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
103 stateSet->setMode(GL_CULL_FACE, osg::StateAttribute::OFF);
104 stateSet->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);
106 osg::Geode* geode = new osg::Geode;
107 stateSet = geode->getOrCreateStateSet();
109 stateSet->setRenderBinDetails(-6, "RenderBin");
111 // set up the sun-state
112 osg::Texture2D* texture = SGLoadTexture2D("sun.png", options.get());
113 stateSet->setTextureAttributeAndModes(0, texture);
116 sun_cl = new osg::Vec4Array;
117 sun_cl->push_back(osg::Vec4(1, 1, 1, 1));
119 scene_cl = new osg::Vec4Array;
120 scene_cl->push_back(osg::Vec4(1, 1, 1, 1));
122 osg::Vec3Array* sun_vl = new osg::Vec3Array;
123 sun_vl->push_back(osg::Vec3(-sun_size, 0, -sun_size));
124 sun_vl->push_back(osg::Vec3(sun_size, 0, -sun_size));
125 sun_vl->push_back(osg::Vec3(-sun_size, 0, sun_size));
126 sun_vl->push_back(osg::Vec3(sun_size, 0, sun_size));
128 osg::Vec2Array* sun_tl = new osg::Vec2Array;
129 sun_tl->push_back(osg::Vec2(0, 0));
130 sun_tl->push_back(osg::Vec2(1, 0));
131 sun_tl->push_back(osg::Vec2(0, 1));
132 sun_tl->push_back(osg::Vec2(1, 1));
134 osg::Geometry* geometry = new osg::Geometry;
135 geometry->setUseDisplayList(false);
136 geometry->setVertexArray(sun_vl);
137 geometry->setColorArray(sun_cl.get());
138 geometry->setColorBinding(osg::Geometry::BIND_OVERALL);
139 geometry->setNormalBinding(osg::Geometry::BIND_OFF);
140 geometry->setTexCoordArray(0, sun_tl);
141 geometry->addPrimitiveSet(new osg::DrawArrays(GL_TRIANGLE_STRIP, 0, 4));
142 geode->addDrawable(geometry);
144 sun_transform->addChild( geode );
146 // set up the inner-halo state
147 geode = new osg::Geode;
148 stateSet = geode->getOrCreateStateSet();
149 stateSet->setRenderBinDetails(-7, "RenderBin");
151 texture = SGLoadTexture2D("inner_halo.png", options.get());
152 stateSet->setTextureAttributeAndModes(0, texture);
154 // Build ssg structure
155 ihalo_cl = new osg::Vec4Array;
156 ihalo_cl->push_back(osg::Vec4(1, 1, 1, 1));
158 float ihalo_size = sun_size * 2.0;
159 osg::Vec3Array* ihalo_vl = new osg::Vec3Array;
160 ihalo_vl->push_back(osg::Vec3(-ihalo_size, 0, -ihalo_size));
161 ihalo_vl->push_back(osg::Vec3(ihalo_size, 0, -ihalo_size));
162 ihalo_vl->push_back(osg::Vec3(-ihalo_size, 0, ihalo_size));
163 ihalo_vl->push_back(osg::Vec3(ihalo_size, 0, ihalo_size));
165 osg::Vec2Array* ihalo_tl = new osg::Vec2Array;
166 ihalo_tl->push_back(osg::Vec2(0, 0));
167 ihalo_tl->push_back(osg::Vec2(1, 0));
168 ihalo_tl->push_back(osg::Vec2(0, 1));
169 ihalo_tl->push_back(osg::Vec2(1, 1));
171 geometry = new osg::Geometry;
172 geometry->setUseDisplayList(false);
173 geometry->setVertexArray(ihalo_vl);
174 geometry->setColorArray(ihalo_cl.get());
175 geometry->setColorBinding(osg::Geometry::BIND_OVERALL);
176 geometry->setNormalBinding(osg::Geometry::BIND_OFF);
177 geometry->setTexCoordArray(0, ihalo_tl);
178 geometry->addPrimitiveSet(new osg::DrawArrays(GL_TRIANGLE_STRIP, 0, 4));
179 geode->addDrawable(geometry);
181 sun_transform->addChild( geode );
183 // set up the outer halo state
185 geode = new osg::Geode;
186 stateSet = geode->getOrCreateStateSet();
187 stateSet->setRenderBinDetails(-8, "RenderBin");
189 texture = SGLoadTexture2D("outer_halo.png", options.get());
190 stateSet->setTextureAttributeAndModes(0, texture);
192 // Build ssg structure
193 ohalo_cl = new osg::Vec4Array;
194 ohalo_cl->push_back(osg::Vec4(1, 1, 1, 1));
196 double ohalo_size = sun_size * 8.0;
197 osg::Vec3Array* ohalo_vl = new osg::Vec3Array;
198 ohalo_vl->push_back(osg::Vec3(-ohalo_size, 0, -ohalo_size));
199 ohalo_vl->push_back(osg::Vec3(ohalo_size, 0, -ohalo_size));
200 ohalo_vl->push_back(osg::Vec3(-ohalo_size, 0, ohalo_size));
201 ohalo_vl->push_back(osg::Vec3(ohalo_size, 0, ohalo_size));
203 osg::Vec2Array* ohalo_tl = new osg::Vec2Array;
204 ohalo_tl->push_back(osg::Vec2(0, 0));
205 ohalo_tl->push_back(osg::Vec2(1, 0));
206 ohalo_tl->push_back(osg::Vec2(0, 1));
207 ohalo_tl->push_back(osg::Vec2(1, 1));
209 geometry = new osg::Geometry;
210 geometry->setUseDisplayList(false);
211 geometry->setVertexArray(ohalo_vl);
212 geometry->setColorArray(ohalo_cl.get());
213 geometry->setColorBinding(osg::Geometry::BIND_OVERALL);
214 geometry->setNormalBinding(osg::Geometry::BIND_OFF);
215 geometry->setTexCoordArray(0, ohalo_tl);
216 geometry->addPrimitiveSet(new osg::DrawArrays(GL_TRIANGLE_STRIP, 0, 4));
217 geode->addDrawable(geometry);
219 sun_transform->addChild( geode );
221 // force a repaint of the sun colors with arbitrary defaults
224 return sun_transform.get();
228 // repaint the sun colors based on current value of sun_angle in
229 // degrees relative to verticle
230 // 0 degrees = high noon
231 // 90 degrees = sun rise/set
232 // 180 degrees = darkest midnight
233 bool SGSun::repaint( double sun_angle, double new_visibility ) {
235 if ( visibility != new_visibility ) {
236 visibility = new_visibility;
238 if (new_visibility < 100.0) new_visibility = 100.0;
239 else if (new_visibility > 45000.0) new_visibility = 45000.0;
240 sun_exp2_punch_through = 2.0/log(visibility);
243 if ( prev_sun_angle != sun_angle ) {
244 prev_sun_angle = sun_angle;
246 // determine how much aerosols are in the air (rough guess)
247 double aerosol_factor;
248 if ( visibility < 100 ) {
249 aerosol_factor = 8000;
252 aerosol_factor = 80.5 / log( visibility / 100 );
255 // get environmental data from property tree or use defaults
256 double rel_humidity, density_avg;
263 rel_humidity = env_node->getFloatValue( "relative-humidity" );
264 density_avg = env_node->getFloatValue( "atmosphere/density-tropo-avg" );
267 // ok, now let's go and generate the sun and scene color
268 osg::Vec4 i_halo_color, o_halo_color, scene_color, sun_color;
271 // * When the sunangle changes, light has to travel a longer
272 // distance through the atmosphere. So it's scattered more due
273 // to raleigh scattering, which affects blue more than green
275 // * Red is almost not scattered and effectively only get's
276 // touched when the sun is near the horizon.
277 // * Visability also affects suncolor inasmuch as more particles
278 // are in the air that cause more scattering.
279 // * We base our calculation on the halo's color, which is most
281 double red_scat_f, red_scat_corr_f, green_scat_f, blue_scat_f;
283 // Red - is almost not scattered
286 red_scat_f = (aerosol_factor * path_distance * density_avg)/5E+07;
287 red_scat_corr_f = sun_exp2_punch_through / (1 - red_scat_f);
289 scene_color[0] = 1 - red_scat_f;
292 green_scat_f = (aerosol_factor * path_distance * density_avg)/8.8938E+06;
293 sun_color[1] = 1 - green_scat_f * red_scat_corr_f;
294 scene_color[1] = 1 - green_scat_f;
297 blue_scat_f = (aerosol_factor * path_distance * density_avg)/3.607E+06;
298 sun_color[2] = 1 - blue_scat_f * red_scat_corr_f;
299 scene_color[2] = 1 - blue_scat_f;
305 // Now that we have the color calculated
306 // let's consider the saturation which is produced by mie scattering
307 double saturation = 1 - ( rel_humidity / 200 );
308 scene_color[1] += (( 1 - saturation ) * ( 1 - scene_color[1] ));
309 scene_color[2] += (( 1 - saturation ) * ( 1 - scene_color[2] ));
311 if (sun_color[0] > 1.0) sun_color[0] = 1.0;
312 if (sun_color[0] < 0.0) sun_color[0] = 0.0;
313 if (sun_color[1] > 1.0) sun_color[1] = 1.0;
314 if (sun_color[1] < 0.0) sun_color[1] = 0.0;
315 if (sun_color[2] > 1.0) sun_color[2] = 1.0;
316 if (sun_color[2] < 0.0) sun_color[2] = 0.0;
318 if (scene_color[0] > 1.0) scene_color[0] = 1.0;
319 if (scene_color[0] < 0.0) scene_color[0] = 0.0;
320 if (scene_color[1] > 1.0) scene_color[1] = 1.0;
321 if (scene_color[1] < 0.0) scene_color[1] = 0.0;
322 if (scene_color[2] > 1.0) scene_color[2] = 1.0;
323 if (scene_color[2] < 0.0) scene_color[2] = 0.0;
325 double scene_f = 0.5 * (1 / (1 - red_scat_f));
326 double sun_f = 1.0 - scene_f;
327 i_halo_color[0] = sun_f * sun_color[0] + scene_f * scene_color[0];
328 i_halo_color[1] = sun_f * sun_color[1] + scene_f * scene_color[1];
329 i_halo_color[2] = sun_f * sun_color[2] + scene_f * scene_color[2];
332 o_halo_color[0] = 0.2 * sun_color[0] + 0.8 * scene_color[0];
333 o_halo_color[1] = 0.2 * sun_color[1] + 0.8 * scene_color[1];
334 o_halo_color[2] = 0.2 * sun_color[2] + 0.8 * scene_color[2];
335 o_halo_color[3] = blue_scat_f;
336 if ((new_visibility < 10000) && (blue_scat_f > 1)) {
337 o_halo_color[3] = 2 - blue_scat_f;
339 if (o_halo_color[3] > 1) o_halo_color[3] = 1;
340 if (o_halo_color[3] < 0) o_halo_color[3] = 0;
342 gamma_correct_rgb( i_halo_color._v );
343 gamma_correct_rgb( o_halo_color._v );
344 gamma_correct_rgb( scene_color._v );
345 gamma_correct_rgb( sun_color._v );
347 (*sun_cl)[0] = sun_color;
349 (*scene_cl)[0] = scene_color;
351 (*ihalo_cl)[0] = i_halo_color;
353 (*ohalo_cl)[0] = o_halo_color;
361 // reposition the sun at the specified right ascension and
362 // declination, offset by our current position (p) so that it appears
363 // fixed at a great distance from the viewer. Also add in an optional
364 // rotation (i.e. for the current time of day.)
365 // Then calculate stuff needed for the sun-coloring
366 bool SGSun::reposition( double rightAscension, double declination,
367 double sun_dist, double lat, double alt_asl, double sun_angle)
369 // GST - GMT sidereal time
370 osg::Matrix T2, RA, DEC;
372 // xglRotatef( ((SGD_RADIANS_TO_DEGREES * rightAscension)- 90.0),
374 RA.makeRotate(rightAscension - 90*SGD_DEGREES_TO_RADIANS, osg::Vec3(0, 0, 1));
376 // xglRotatef((SGD_RADIANS_TO_DEGREES * declination), 1.0, 0.0, 0.0);
377 DEC.makeRotate(declination, osg::Vec3(1, 0, 0));
379 // xglTranslatef(0,sun_dist);
380 T2.makeTranslate(osg::Vec3(0, sun_dist, 0));
382 sun_transform->setMatrix(T2*DEC*RA);
384 // Suncolor related things:
385 if ( prev_sun_angle != sun_angle ) {
386 if ( sun_angle == 0 ) sun_angle = 0.1;
387 const double r_earth_pole = 6356752.314;
388 const double r_tropo_pole = 6356752.314 + 8000;
389 const double epsilon_earth2 = 6.694380066E-3;
390 const double epsilon_tropo2 = 9.170014946E-3;
392 double r_tropo = r_tropo_pole / sqrt ( 1 - ( epsilon_tropo2 * pow ( cos( lat ), 2 )));
393 double r_earth = r_earth_pole / sqrt ( 1 - ( epsilon_earth2 * pow ( cos( lat ), 2 )));
395 double position_radius = r_earth + alt_asl;
397 double gamma = SG_PI - sun_angle;
398 double sin_beta = ( position_radius * sin ( gamma ) ) / r_tropo;
399 if (sin_beta > 1.0) sin_beta = 1.0;
400 double alpha = SG_PI - gamma - asin( sin_beta );
402 // OK, now let's calculate the distance the light travels
403 path_distance = sqrt( pow( position_radius, 2 ) + pow( r_tropo, 2 )
404 - ( 2 * position_radius * r_tropo * cos( alpha ) ));
406 double alt_half = sqrt( pow ( r_tropo, 2 ) + pow( path_distance / 2, 2 ) - r_tropo * path_distance * cos( asin( sin_beta )) ) - r_earth;
408 if ( alt_half < 0.0 ) alt_half = 0.0;
410 // Push the data to the property tree, so it can be used in the enviromental code
412 env_node->setDoubleValue( "atmosphere/altitude-troposphere-top", r_tropo - r_earth );
413 env_node->setDoubleValue( "atmosphere/altitude-half-to-sun", alt_half );
423 return SGVec4f((*scene_cl)[0][0], (*scene_cl)[0][1], (*scene_cl)[0][2], (*scene_cl)[0][3]);