simgear/scene/sky/oursun.cxx

   1 // oursun.hxx -- model earth's sun
   2 //
   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).
   7 //
   8 // Separated out rendering pieces and converted to ssg by Curt Olson,
   9 // March 2000
  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.
  14 //
  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.
  19 //
  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.
  23 //
  24 // $Id$
  25
  26
  27 #ifdef HAVE_CONFIG_H
  28 #  include <simgear_config.h>
  29 #endif
  30
  31 #include <simgear/compiler.h>
  32
  33 #include <osg/AlphaFunc>
  34 #include <osg/BlendFunc>
  35 #include <osg/Fog>
  36 #include <osg/Geode>
  37 #include <osg/Geometry>
  38 #include <osg/Material>
  39 #include <osg/ShadeModel>
  40 #include <osg/TexEnv>
  41 #include <osg/Texture2D>
  42 #include <osgDB/ReadFile>
  43
  44 #include <simgear/misc/PathOptions.hxx>
  45 #include <simgear/screen/colors.hxx>
  46 #include <simgear/scene/model/model.hxx>
  47 #include "oursun.hxx"
  48
  49 using namespace simgear;
  50
  51 // Constructor
  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)
  55 {
  56
  57 }
  58
  59
  60 // Destructor
  61 SGSun::~SGSun( void ) {
  62 }
  63
  64
  65 // initialize the sun object and connect it into our scene graph root
  66 osg::Node*
  67 SGSun::build( SGPath path, double sun_size, SGPropertyNode *property_tree_Node ) {
  68
  69     env_node = property_tree_Node;
  70
  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();
  77
  78     osg::TexEnv* texEnv = new osg::TexEnv;
  79     texEnv->setMode(osg::TexEnv::MODULATE);
  80     stateSet->setTextureAttribute(0, texEnv, osg::StateAttribute::ON);
  81
  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);
  87
  88     osg::ShadeModel* shadeModel = new osg::ShadeModel;
  89     shadeModel->setMode(osg::ShadeModel::SMOOTH);
  90     stateSet->setAttributeAndModes(shadeModel);
  91
  92     osg::AlphaFunc* alphaFunc = new osg::AlphaFunc;
  93     alphaFunc->setFunction(osg::AlphaFunc::ALWAYS);
  94     stateSet->setAttributeAndModes(alphaFunc);
  95
  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);
 100
 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);
 105
 106     osg::Geode* geode = new osg::Geode;
 107     stateSet = geode->getOrCreateStateSet();
 108
 109     stateSet->setRenderBinDetails(-6, "RenderBin");
 110
 111     // set up the sun-state
 112     osg::Texture2D* texture = SGLoadTexture2D("sun.png", options.get());
 113     stateSet->setTextureAttributeAndModes(0, texture);
 114
 115     // Build scenegraph
 116     sun_cl = new osg::Vec4Array;
 117     sun_cl->push_back(osg::Vec4(1, 1, 1, 1));
 118
 119     scene_cl = new osg::Vec4Array;
 120     scene_cl->push_back(osg::Vec4(1, 1, 1, 1));
 121
 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));
 127
 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));
 133
 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);
 143
 144     sun_transform->addChild( geode );
 145
 146     // set up the inner-halo state
 147     geode = new osg::Geode;
 148     stateSet = geode->getOrCreateStateSet();
 149     stateSet->setRenderBinDetails(-7, "RenderBin");
 150
 151     texture = SGLoadTexture2D("inner_halo.png", options.get());
 152     stateSet->setTextureAttributeAndModes(0, texture);
 153
 154     // Build ssg structure
 155     ihalo_cl = new osg::Vec4Array;
 156     ihalo_cl->push_back(osg::Vec4(1, 1, 1, 1));
 157
 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));
 164
 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));
 170
 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);
 180
 181     sun_transform->addChild( geode );
 182
 183     // set up the outer halo state
 184
 185     geode = new osg::Geode;
 186     stateSet = geode->getOrCreateStateSet();
 187     stateSet->setRenderBinDetails(-8, "RenderBin");
 188
 189     texture = SGLoadTexture2D("outer_halo.png", options.get());
 190     stateSet->setTextureAttributeAndModes(0, texture);
 191
 192     // Build ssg structure
 193     ohalo_cl = new osg::Vec4Array;
 194     ohalo_cl->push_back(osg::Vec4(1, 1, 1, 1));
 195
 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));
 202
 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));
 208
 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);
 218
 219     sun_transform->addChild( geode );
 220
 221     // force a repaint of the sun colors with arbitrary defaults
 222     repaint( 0.0, 1.0 );
 223
 224     return sun_transform.get();
 225 }
 226
 227
 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 ) {
 234
 235     if ( visibility != new_visibility ) {
 236         if (new_visibility < 100.0) new_visibility = 100.0;
 237         else if (new_visibility > 45000.0) new_visibility = 45000.0;
 238         visibility = new_visibility;
 239         sun_exp2_punch_through = 2.0/log(visibility);
 240     }
 241
 242     if ( prev_sun_angle != sun_angle ) {
 243         prev_sun_angle = sun_angle;
 244
 245         // determine how much aerosols are in the air (rough guess)
 246         double aerosol_factor;
 247         if ( visibility < 100 ) {
 248             aerosol_factor = 8000;
 249         }
 250         else {
 251             aerosol_factor = 80.5 / log( visibility / 99.9 );
 252         }
 253
 254         // get environmental data from property tree or use defaults
 255         double rel_humidity, density_avg;
 256
 257         if ( !env_node ) {
 258             rel_humidity = 0.5;
 259             density_avg = 0.7;
 260         }
 261         else {
 262             rel_humidity = env_node->getFloatValue( "relative-humidity" );
 263             density_avg =  env_node->getFloatValue( "atmosphere/density-tropo-avg" );
 264         }
 265
 266         // ok, now let's go and generate the sun and scene color
 267         osg::Vec4 i_halo_color, o_halo_color, scene_color, sun_color;
 268
 269         // Some comments:
 270         // * When the sunangle changes, light has to travel a longer
 271         //   distance through the atmosphere. So it's scattered more due
 272         //   to raleigh scattering, which affects blue more than green
 273         //   light.
 274         // * Red is almost not scattered and effectively only get's
 275         //   touched when the sun is near the horizon.
 276         // * Visability also affects suncolor inasmuch as more particles
 277         //   are in the air that cause more scattering.
 278         // * We base our calculation on the halo's color, which is most
 279         //   scattered.
 280         double red_scat_f, red_scat_corr_f, green_scat_f, blue_scat_f;
 281
 282         // Red - is almost not scattered
 283         // Lambda is 700 nm
 284
 285         red_scat_f = (aerosol_factor * path_distance * density_avg)/5E+07;
 286         red_scat_corr_f = sun_exp2_punch_through / (1 - red_scat_f);
 287         sun_color[0] = 1;
 288         scene_color[0] = 1 - red_scat_f;
 289
 290         // Green - 546.1 nm
 291         green_scat_f = (aerosol_factor * path_distance * density_avg)/8.8938E+06;
 292         sun_color[1] = 1 - green_scat_f * red_scat_corr_f;
 293         scene_color[1] = 1 - green_scat_f;
 294
 295         // Blue - 435.8 nm
 296         blue_scat_f = (aerosol_factor * path_distance * density_avg)/3.607E+06;
 297         sun_color[2] = 1 - blue_scat_f * red_scat_corr_f;
 298         scene_color[2] = 1 - blue_scat_f;
 299
 300         // Alpha
 301         sun_color[3] = 1;
 302         scene_color[3] = 1;
 303
 304         // Now that we have the color calculated
 305         // let's consider the saturation which is produced by mie scattering
 306         double saturation = 1 - ( rel_humidity / 200 );
 307         scene_color[1] += (( 1 - saturation ) * ( 1 - scene_color[1] ));
 308         scene_color[2] += (( 1 - saturation ) * ( 1 - scene_color[2] ));
 309
 310         if (sun_color[0] > 1.0) sun_color[0] = 1.0;
 311         if (sun_color[0] < 0.0) sun_color[0] = 0.0;
 312         if (sun_color[1] > 1.0) sun_color[1] = 1.0;
 313         if (sun_color[1] < 0.0) sun_color[1] = 0.0;
 314         if (sun_color[2] > 1.0) sun_color[2] = 1.0;
 315         if (sun_color[2] < 0.0) sun_color[2] = 0.0;
 316
 317         if (scene_color[0] > 1.0) scene_color[0] = 1.0;
 318         if (scene_color[0] < 0.0) scene_color[0] = 0.0;
 319         if (scene_color[1] > 1.0) scene_color[1] = 1.0;
 320         if (scene_color[1] < 0.0) scene_color[1] = 0.0;
 321         if (scene_color[2] > 1.0) scene_color[2] = 1.0;
 322         if (scene_color[2] < 0.0) scene_color[2] = 0.0;
 323
 324         double scene_f = 0.5 * (1 / (1 - red_scat_f));
 325         double sun_f = 1.0 - scene_f;
 326         i_halo_color[0] = sun_f * sun_color[0] + scene_f * scene_color[0];
 327         i_halo_color[1] = sun_f * sun_color[1] + scene_f * scene_color[1];
 328         i_halo_color[2] = sun_f * sun_color[2] + scene_f * scene_color[2];
 329         i_halo_color[3] = 1;
 330
 331         o_halo_color[0] = 0.2 * sun_color[0] + 0.8 * scene_color[0];
 332         o_halo_color[1] = 0.2 * sun_color[1] + 0.8 * scene_color[1];
 333         o_halo_color[2] = 0.2 * sun_color[2] + 0.8 * scene_color[2];
 334         o_halo_color[3] = blue_scat_f;
 335         if ((visibility < 10000) && (blue_scat_f > 1)) {
 336             o_halo_color[3] = 2 - blue_scat_f;
 337         }
 338         if (o_halo_color[3] > 1) o_halo_color[3] = 1;
 339         if (o_halo_color[3] < 0) o_halo_color[3] = 0;
 340
 341         gamma_correct_rgb( i_halo_color._v );
 342         gamma_correct_rgb( o_halo_color._v );
 343         gamma_correct_rgb( scene_color._v );
 344         gamma_correct_rgb( sun_color._v );
 345
 346         (*sun_cl)[0] = sun_color;
 347         sun_cl->dirty();
 348         (*scene_cl)[0] = scene_color;
 349         scene_cl->dirty();
 350         (*ihalo_cl)[0] = i_halo_color;
 351         ihalo_cl->dirty();
 352         (*ohalo_cl)[0] = o_halo_color;
 353         ohalo_cl->dirty();
 354     }
 355
 356     return true;
 357 }
 358
 359
 360 // reposition the sun at the specified right ascension and
 361 // declination, offset by our current position (p) so that it appears
 362 // fixed at a great distance from the viewer.  Also add in an optional
 363 // rotation (i.e. for the current time of day.)
 364 // Then calculate stuff needed for the sun-coloring
 365 bool SGSun::reposition( double rightAscension, double declination,
 366                         double sun_dist, double lat, double alt_asl, double sun_angle)
 367 {
 368     // GST - GMT sidereal time
 369     osg::Matrix T2, RA, DEC;
 370
 371     // xglRotatef( ((SGD_RADIANS_TO_DEGREES * rightAscension)- 90.0),
 372     //             0.0, 0.0, 1.0);
 373     RA.makeRotate(rightAscension - 90*SGD_DEGREES_TO_RADIANS, osg::Vec3(0, 0, 1));
 374
 375     // xglRotatef((SGD_RADIANS_TO_DEGREES * declination), 1.0, 0.0, 0.0);
 376     DEC.makeRotate(declination, osg::Vec3(1, 0, 0));
 377
 378     // xglTranslatef(0,sun_dist);
 379     T2.makeTranslate(osg::Vec3(0, sun_dist, 0));
 380
 381     sun_transform->setMatrix(T2*DEC*RA);
 382
 383     // Suncolor related things:
 384     if ( prev_sun_angle != sun_angle ) {
 385       if ( sun_angle == 0 ) sun_angle = 0.1;
 386          const double r_earth_pole = 6356752.314;
 387          const double r_tropo_pole = 6356752.314 + 8000;
 388          const double epsilon_earth2 = 6.694380066E-3;
 389          const double epsilon_tropo2 = 9.170014946E-3;
 390
 391          double r_tropo = r_tropo_pole / sqrt ( 1 - ( epsilon_tropo2 * pow ( cos( lat ), 2 )));
 392          double r_earth = r_earth_pole / sqrt ( 1 - ( epsilon_earth2 * pow ( cos( lat ), 2 )));
 393
 394          double position_radius = r_earth + alt_asl;
 395
 396          double gamma =  SG_PI - sun_angle;
 397          double sin_beta =  ( position_radius * sin ( gamma )  ) / r_tropo;
 398          if (sin_beta > 1.0) sin_beta = 1.0;
 399          double alpha =  SG_PI - gamma - asin( sin_beta );
 400
 401          // OK, now let's calculate the distance the light travels
 402          path_distance = sqrt( pow( position_radius, 2 ) + pow( r_tropo, 2 )
 403                         - ( 2 * position_radius * r_tropo * cos( alpha ) ));
 404
 405          double alt_half = sqrt( pow ( r_tropo, 2 ) + pow( path_distance / 2, 2 ) - r_tropo * path_distance * cos( asin( sin_beta )) ) - r_earth;
 406
 407          if ( alt_half < 0.0 ) alt_half = 0.0;
 408
 409          // Push the data to the property tree, so it can be used in the enviromental code
 410          if ( env_node ){
 411             env_node->setDoubleValue( "atmosphere/altitude-troposphere-top", r_tropo - r_earth );
 412             env_node->setDoubleValue( "atmosphere/altitude-half-to-sun", alt_half );
 413       }
 414     }
 415
 416     return true;
 417 }
 418
 419 SGVec4f
 420 SGSun::get_color()
 421 {
 422     return SGVec4f((*sun_cl)[0][0], (*sun_cl)[0][1], (*sun_cl)[0][2], (*sun_cl)[0][3]);
 423 }
 424
 425 SGVec4f
 426 SGSun::get_scene_color()
 427 {
 428     return SGVec4f((*scene_cl)[0][0], (*scene_cl)[0][1], (*scene_cl)[0][2], (*scene_cl)[0][3]);
 429 }