simgear/scene/tgdb/pt_lights.cxx

   1 // pt_lights.cxx -- build a 'directional' light on the fly
   2 //
   3 // Written by Curtis Olson, started March 2002.
   4 //
   5 // Copyright (C) 2002  Curtis L. Olson  - http://www.flightgear.org/~curt
   6 //
   7 // This program is free software; you can redistribute it and/or
   8 // modify it under the terms of the GNU General Public License as
   9 // published by the Free Software Foundation; either version 2 of the
  10 // License, or (at your option) any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful, but
  13 // WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 // General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License
  18 // along with this program; if not, write to the Free Software
  19 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  20 //
  21 // $Id$
  22
  23 #ifdef HAVE_CONFIG_H
  24 #  include <simgear_config.h>
  25 #endif
  26
  27 #include "pt_lights.hxx"
  28
  29 #include <map>
  30 #include <boost/tuple/tuple_comparison.hpp>
  31
  32 #include <osg/Array>
  33 #include <osg/Geometry>
  34 #include <osg/CullFace>
  35 #include <osg/Geode>
  36 #include <osg/MatrixTransform>
  37 #include <osg/NodeCallback>
  38 #include <osg/NodeVisitor>
  39 #include <osg/Texture2D>
  40 #include <osg/AlphaFunc>
  41 #include <osg/BlendFunc>
  42 #include <osg/TexEnv>
  43 #include <osg/Sequence>
  44 #include <osg/PolygonMode>
  45 #include <osg/Fog>
  46 #include <osg/FragmentProgram>
  47 #include <osg/VertexProgram>
  48 #include <osg/Point>
  49 #include <osg/PointSprite>
  50 #include <osg/Material>
  51 #include <osg/Group>
  52 #include <osg/StateSet>
  53
  54 #include <osgUtil/CullVisitor>
  55
  56 #include <OpenThreads/Mutex>
  57 #include <OpenThreads/ScopedLock>
  58
  59 #include <simgear/math/sg_random.h>
  60 #include <simgear/debug/logstream.hxx>
  61 #include <simgear/scene/util/RenderConstants.hxx>
  62 #include <simgear/scene/util/SGEnlargeBoundingBox.hxx>
  63 #include <simgear/scene/util/OsgMath.hxx>
  64 #include <simgear/scene/util/StateAttributeFactory.hxx>
  65
  66 #include <simgear/scene/material/Effect.hxx>
  67 #include <simgear/scene/material/EffectGeode.hxx>
  68 #include <simgear/scene/material/Technique.hxx>
  69 #include <simgear/scene/material/Pass.hxx>
  70
  71 #include "SGVasiDrawable.hxx"
  72
  73 using OpenThreads::Mutex;
  74 using OpenThreads::ScopedLock;
  75
  76 using namespace osg;
  77 using namespace simgear;
  78
  79 static void
  80 setPointSpriteImage(unsigned char* data, unsigned log2resolution,
  81                     unsigned charsPerPixel)
  82 {
  83   int env_tex_res = (1 << log2resolution);
  84   for (int i = 0; i < env_tex_res; ++i) {
  85     for (int j = 0; j < env_tex_res; ++j) {
  86       int xi = 2*i + 1 - env_tex_res;
  87       int yi = 2*j + 1 - env_tex_res;
  88       if (xi < 0)
  89         xi = -xi;
  90       if (yi < 0)
  91         yi = -yi;
  92
  93       xi -= 1;
  94       yi -= 1;
  95
  96       if (xi < 0)
  97         xi = 0;
  98       if (yi < 0)
  99         yi = 0;
 100
 101       float x = 1.5*xi/(float)(env_tex_res);
 102       float y = 1.5*yi/(float)(env_tex_res);
 103       //       float x = 2*xi/(float)(env_tex_res);
 104       //       float y = 2*yi/(float)(env_tex_res);
 105       float dist = sqrt(x*x + y*y);
 106       float bright = SGMiscf::clip(255*(1-dist), 0, 255);
 107       for (unsigned l = 0; l < charsPerPixel; ++l)
 108         data[charsPerPixel*(i*env_tex_res + j) + l] = (unsigned char)bright;
 109     }
 110   }
 111 }
 112
 113 static osg::Image*
 114 getPointSpriteImage(int logResolution)
 115 {
 116   osg::Image* image = new osg::Image;
 117
 118   osg::Image::MipmapDataType mipmapOffsets;
 119   unsigned off = 0;
 120   for (int i = logResolution; 0 <= i; --i) {
 121     unsigned res = 1 << i;
 122     off += res*res;
 123     mipmapOffsets.push_back(off);
 124   }
 125
 126   int env_tex_res = (1 << logResolution);
 127
 128   unsigned char* imageData = new unsigned char[off];
 129   image->setImage(env_tex_res, env_tex_res, 1,
 130                   GL_ALPHA, GL_ALPHA, GL_UNSIGNED_BYTE, imageData,
 131                   osg::Image::USE_NEW_DELETE);
 132   image->setMipmapLevels(mipmapOffsets);
 133
 134   for (int k = logResolution; 0 <= k; --k) {
 135     setPointSpriteImage(image->getMipmapData(logResolution - k), k, 1);
 136   }
 137
 138   return image;
 139 }
 140
 141 static Mutex lightMutex;
 142
 143 static osg::Texture2D*
 144 gen_standard_light_sprite(void)
 145 {
 146   // Always called from when the lightMutex is already taken
 147   static osg::ref_ptr<osg::Texture2D> texture;
 148   if (texture.valid())
 149     return texture.get();
 150
 151   texture = new osg::Texture2D;
 152   texture->setImage(getPointSpriteImage(6));
 153   texture->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP);
 154   texture->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP);
 155
 156   return texture.get();
 157 }
 158
 159 namespace
 160 {
 161 typedef boost::tuple<float, osg::Vec3, float, float, bool> PointParams;
 162 typedef std::map<PointParams, observer_ptr<Effect> > EffectMap;
 163
 164 EffectMap effectMap;
 165
 166 ref_ptr<PolygonMode> polyMode = new PolygonMode(PolygonMode::FRONT,
 167                                                 PolygonMode::POINT);
 168 ref_ptr<PointSprite> pointSprite = new PointSprite;
 169 }
 170
 171 Effect* getLightEffect(float size, const Vec3& attenuation,
 172                        float minSize, float maxSize, bool directional)
 173 {
 174     PointParams pointParams(size, attenuation, minSize, maxSize, directional);
 175     ScopedLock<Mutex> lock(lightMutex);
 176     EffectMap::iterator eitr = effectMap.find(pointParams);
 177     if (eitr != effectMap.end())
 178     {
 179         ref_ptr<Effect> effect;
 180         if (eitr->second.lock(effect))
 181             return effect.release();
 182     }
 183     // Basic stuff; no sprite or attenuation support
 184     Pass *basicPass = new Pass;
 185     basicPass->setRenderBinDetails(POINT_LIGHTS_BIN, "DepthSortedBin");
 186     basicPass->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
 187     StateAttributeFactory *attrFact = StateAttributeFactory::instance();
 188     basicPass->setAttributeAndModes(attrFact->getStandardBlendFunc());
 189     basicPass->setAttributeAndModes(attrFact->getStandardAlphaFunc());
 190     if (directional) {
 191         basicPass->setAttributeAndModes(attrFact->getCullFaceBack());
 192         basicPass->setAttribute(polyMode.get());
 193     }
 194     Pass *attenuationPass = clone(basicPass, CopyOp::SHALLOW_COPY);
 195     osg::Point* point = new osg::Point;
 196     point->setMinSize(minSize);
 197     point->setMaxSize(maxSize);
 198     point->setSize(size);
 199     point->setDistanceAttenuation(attenuation);
 200     attenuationPass->setAttributeAndModes(point);
 201     Pass *spritePass = clone(basicPass, CopyOp::SHALLOW_COPY);
 202     spritePass->setTextureAttributeAndModes(0, pointSprite.get(),
 203                                             osg::StateAttribute::ON);
 204     Texture2D* texture = gen_standard_light_sprite();
 205     spritePass->setTextureAttribute(0, texture);
 206     spritePass->setTextureMode(0, GL_TEXTURE_2D,
 207                                osg::StateAttribute::ON);
 208     spritePass->setTextureAttribute(0, attrFact->getStandardTexEnv());
 209     Pass *combinedPass = clone(spritePass, CopyOp::SHALLOW_COPY);
 210     combinedPass->setAttributeAndModes(point);
 211     ref_ptr<Effect> effect = new Effect;
 212     std::vector<std::string> parameterExtensions;
 213
 214     if (SGSceneFeatures::instance()->getEnablePointSpriteLights())
 215     {
 216         std::vector<std::string> combinedExtensions;
 217         combinedExtensions.push_back("GL_ARB_point_sprite");
 218         combinedExtensions.push_back("GL_ARB_point_parameters");
 219         Technique* combinedTniq = new Technique;
 220         combinedTniq->passes.push_back(combinedPass);
 221         combinedTniq->setGLExtensionsPred(2.0, combinedExtensions);
 222         effect->techniques.push_back(combinedTniq);
 223         std::vector<std::string> spriteExtensions;
 224         spriteExtensions.push_back(combinedExtensions.front());
 225         Technique* spriteTniq = new Technique;
 226         spriteTniq->passes.push_back(spritePass);
 227         spriteTniq->setGLExtensionsPred(2.0, spriteExtensions);
 228         effect->techniques.push_back(spriteTniq);
 229         parameterExtensions.push_back(combinedExtensions.back());
 230     }
 231
 232     Technique* parameterTniq = new Technique;
 233     parameterTniq->passes.push_back(attenuationPass);
 234     parameterTniq->setGLExtensionsPred(1.4, parameterExtensions);
 235     effect->techniques.push_back(parameterTniq);
 236     Technique* basicTniq = new Technique(true);
 237     basicTniq->passes.push_back(basicPass);
 238     effect->techniques.push_back(basicTniq);
 239     if (eitr == effectMap.end())
 240         effectMap.insert(std::make_pair(pointParams, effect));
 241     else
 242         eitr->second = effect; // update existing, but empty observer
 243     return effect.release();
 244 }
 245
 246
 247 osg::Drawable*
 248 SGLightFactory::getLightDrawable(const SGLightBin::Light& light)
 249 {
 250   osg::Vec3Array* vertices = new osg::Vec3Array;
 251   osg::Vec4Array* colors = new osg::Vec4Array;
 252
 253   vertices->push_back(toOsg(light.position));
 254   colors->push_back(toOsg(light.color));
 255
 256   osg::Geometry* geometry = new osg::Geometry;
 257   geometry->setVertexArray(vertices);
 258   geometry->setNormalBinding(osg::Geometry::BIND_OFF);
 259   geometry->setColorArray(colors);
 260   geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
 261
 262   // Enlarge the bounding box to avoid such light nodes being victim to
 263   // small feature culling.
 264   geometry->setComputeBoundingBoxCallback(new SGEnlargeBoundingBox(1));
 265
 266   osg::DrawArrays* drawArrays;
 267   drawArrays = new osg::DrawArrays(osg::PrimitiveSet::POINTS,
 268                                    0, vertices->size());
 269   geometry->addPrimitiveSet(drawArrays);
 270   return geometry;
 271 }
 272
 273 osg::Drawable*
 274 SGLightFactory::getLightDrawable(const SGDirectionalLightBin::Light& light)
 275 {
 276   osg::Vec3Array* vertices = new osg::Vec3Array;
 277   osg::Vec4Array* colors = new osg::Vec4Array;
 278
 279   SGVec4f visibleColor(light.color);
 280   SGVec4f invisibleColor(visibleColor[0], visibleColor[1],
 281                          visibleColor[2], 0);
 282   SGVec3f normal = normalize(light.normal);
 283   SGVec3f perp1 = perpendicular(normal);
 284   SGVec3f perp2 = cross(normal, perp1);
 285   SGVec3f position = light.position;
 286   vertices->push_back(toOsg(position));
 287   vertices->push_back(toOsg(position + perp1));
 288   vertices->push_back(toOsg(position + perp2));
 289   colors->push_back(toOsg(visibleColor));
 290   colors->push_back(toOsg(invisibleColor));
 291   colors->push_back(toOsg(invisibleColor));
 292
 293   osg::Geometry* geometry = new osg::Geometry;
 294   geometry->setVertexArray(vertices);
 295   geometry->setNormalBinding(osg::Geometry::BIND_OFF);
 296   geometry->setColorArray(colors);
 297   geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
 298   // Enlarge the bounding box to avoid such light nodes being victim to
 299   // small feature culling.
 300   geometry->setComputeBoundingBoxCallback(new SGEnlargeBoundingBox(1));
 301
 302   osg::DrawArrays* drawArrays;
 303   drawArrays = new osg::DrawArrays(osg::PrimitiveSet::TRIANGLES,
 304                                    0, vertices->size());
 305   geometry->addPrimitiveSet(drawArrays);
 306   return geometry;
 307 }
 308
 309 namespace
 310 {
 311   ref_ptr<StateSet> simpleLightSS;
 312 }
 313 osg::Drawable*
 314 SGLightFactory::getLights(const SGLightBin& lights, unsigned inc, float alphaOff)
 315 {
 316   if (lights.getNumLights() <= 0)
 317     return 0;
 318
 319   osg::Vec3Array* vertices = new osg::Vec3Array;
 320   osg::Vec4Array* colors = new osg::Vec4Array;
 321
 322   for (unsigned i = 0; i < lights.getNumLights(); i += inc) {
 323     vertices->push_back(toOsg(lights.getLight(i).position));
 324     SGVec4f color = lights.getLight(i).color;
 325     color[3] = SGMiscf::max(0, SGMiscf::min(1, color[3] + alphaOff));
 326     colors->push_back(toOsg(color));
 327   }
 328
 329   osg::Geometry* geometry = new osg::Geometry;
 330
 331   geometry->setVertexArray(vertices);
 332   geometry->setNormalBinding(osg::Geometry::BIND_OFF);
 333   geometry->setColorArray(colors);
 334   geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
 335
 336   osg::DrawArrays* drawArrays;
 337   drawArrays = new osg::DrawArrays(osg::PrimitiveSet::POINTS,
 338                                    0, vertices->size());
 339   geometry->addPrimitiveSet(drawArrays);
 340
 341   {
 342     ScopedLock<Mutex> lock(lightMutex);
 343     if (!simpleLightSS.valid()) {
 344       StateAttributeFactory *attrFact = StateAttributeFactory::instance();
 345       simpleLightSS = new StateSet;
 346       simpleLightSS->setRenderBinDetails(POINT_LIGHTS_BIN, "DepthSortedBin");
 347       simpleLightSS->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
 348       simpleLightSS->setAttributeAndModes(attrFact->getStandardBlendFunc());
 349       simpleLightSS->setAttributeAndModes(attrFact->getStandardAlphaFunc());
 350     }
 351   }
 352   geometry->setStateSet(simpleLightSS.get());
 353   return geometry;
 354 }
 355
 356
 357 osg::Drawable*
 358 SGLightFactory::getLights(const SGDirectionalLightBin& lights)
 359 {
 360   if (lights.getNumLights() <= 0)
 361     return 0;
 362
 363   osg::Vec3Array* vertices = new osg::Vec3Array;
 364   osg::Vec4Array* colors = new osg::Vec4Array;
 365
 366   for (unsigned i = 0; i < lights.getNumLights(); ++i) {
 367     SGVec4f visibleColor(lights.getLight(i).color);
 368     SGVec4f invisibleColor(visibleColor[0], visibleColor[1],
 369                            visibleColor[2], 0);
 370     SGVec3f normal = normalize(lights.getLight(i).normal);
 371     SGVec3f perp1 = perpendicular(normal);
 372     SGVec3f perp2 = cross(normal, perp1);
 373     SGVec3f position = lights.getLight(i).position;
 374     vertices->push_back(toOsg(position));
 375     vertices->push_back(toOsg(position + perp1));
 376     vertices->push_back(toOsg(position + perp2));
 377     colors->push_back(toOsg(visibleColor));
 378     colors->push_back(toOsg(invisibleColor));
 379     colors->push_back(toOsg(invisibleColor));
 380   }
 381
 382   osg::Geometry* geometry = new osg::Geometry;
 383
 384   geometry->setVertexArray(vertices);
 385   geometry->setNormalBinding(osg::Geometry::BIND_OFF);
 386   geometry->setColorArray(colors);
 387   geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
 388
 389   osg::DrawArrays* drawArrays;
 390   drawArrays = new osg::DrawArrays(osg::PrimitiveSet::TRIANGLES,
 391                                    0, vertices->size());
 392   geometry->addPrimitiveSet(drawArrays);
 393   return geometry;
 394 }
 395
 396 static SGVasiDrawable*
 397 buildVasi(const SGDirectionalLightBin& lights, const SGVec3f& up,
 398        const SGVec4f& red, const SGVec4f& white)
 399 {
 400   unsigned count = lights.getNumLights();
 401   if ( count == 4 ) {
 402     SGVasiDrawable* drawable = new SGVasiDrawable(red, white);
 403
 404     // PAPI configuration
 405     // papi D
 406     drawable->addLight(lights.getLight(0).position,
 407                        lights.getLight(0).normal, up, 3.5);
 408     // papi C
 409     drawable->addLight(lights.getLight(1).position,
 410                        lights.getLight(1).normal, up, 3.167);
 411     // papi B
 412     drawable->addLight(lights.getLight(2).position,
 413                        lights.getLight(2).normal, up, 2.833);
 414     // papi A
 415     drawable->addLight(lights.getLight(3).position,
 416                        lights.getLight(3).normal, up, 2.5);
 417     return drawable;
 418
 419   } else if (count == 6) {
 420     SGVasiDrawable* drawable = new SGVasiDrawable(red, white);
 421
 422     // probably vasi, first 3 are downwind bar (2.5 deg)
 423     for (unsigned i = 0; i < 3; ++i)
 424       drawable->addLight(lights.getLight(i).position,
 425                          lights.getLight(i).normal, up, 2.5);
 426     // last 3 are upwind bar (3.0 deg)
 427     for (unsigned i = 3; i < 6; ++i)
 428       drawable->addLight(lights.getLight(i).position,
 429                          lights.getLight(i).normal, up, 3.0);
 430     return drawable;
 431
 432   } else if (count == 12) {
 433     SGVasiDrawable* drawable = new SGVasiDrawable(red, white);
 434
 435     // probably vasi, first 6 are downwind bar (2.5 deg)
 436     for (unsigned i = 0; i < 6; ++i)
 437       drawable->addLight(lights.getLight(i).position,
 438                          lights.getLight(i).normal, up, 2.5);
 439     // last 6 are upwind bar (3.0 deg)
 440     for (unsigned i = 6; i < 12; ++i)
 441       drawable->addLight(lights.getLight(i).position,
 442                          lights.getLight(i).normal, up, 3.0);
 443     return drawable;
 444
 445   } else {
 446     // fail safe
 447     SG_LOG(SG_TERRAIN, SG_ALERT,
 448            "unknown vasi/papi configuration, count = " << count);
 449     return 0;
 450   }
 451 }
 452
 453 osg::Drawable*
 454 SGLightFactory::getVasi(const SGVec3f& up, const SGDirectionalLightBin& lights,
 455                         const SGVec4f& red, const SGVec4f& white)
 456 {
 457   SGVasiDrawable* drawable = buildVasi(lights, up, red, white);
 458   if (!drawable)
 459     return 0;
 460
 461   osg::StateSet* stateSet = drawable->getOrCreateStateSet();
 462   stateSet->setRenderBinDetails(POINT_LIGHTS_BIN, "DepthSortedBin");
 463   stateSet->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
 464
 465   osg::BlendFunc* blendFunc = new osg::BlendFunc;
 466   stateSet->setAttribute(blendFunc);
 467   stateSet->setMode(GL_BLEND, osg::StateAttribute::ON);
 468
 469   osg::AlphaFunc* alphaFunc;
 470   alphaFunc = new osg::AlphaFunc(osg::AlphaFunc::GREATER, 0.01);
 471   stateSet->setAttribute(alphaFunc);
 472   stateSet->setMode(GL_ALPHA_TEST, osg::StateAttribute::ON);
 473
 474   return drawable;
 475 }
 476
 477 osg::Node*
 478 SGLightFactory::getSequenced(const SGDirectionalLightBin& lights)
 479 {
 480   if (lights.getNumLights() <= 0)
 481     return 0;
 482
 483   // generate a repeatable random seed
 484   sg_srandom(unsigned(lights.getLight(0).position[0]));
 485   float flashTime = 2e-2 + 5e-3*sg_random();
 486   osg::Sequence* sequence = new osg::Sequence;
 487   sequence->setDefaultTime(flashTime);
 488   Effect* effect = getLightEffect(10.0f, osg::Vec3(1.0, 0.0001, 0.00000001),
 489                                   6.0f, 10.0f, true);
 490   for (int i = lights.getNumLights() - 1; 0 <= i; --i) {
 491     EffectGeode* egeode = new EffectGeode;
 492     egeode->setEffect(effect);
 493     egeode->addDrawable(getLightDrawable(lights.getLight(i)));
 494     sequence->addChild(egeode, flashTime);
 495   }
 496   sequence->addChild(new osg::Group, 1 + 1e-1*sg_random());
 497   sequence->setInterval(osg::Sequence::LOOP, 0, -1);
 498   sequence->setDuration(1.0f, -1);
 499   sequence->setMode(osg::Sequence::START);
 500   sequence->setSync(true);
 501   return sequence;
 502 }
 503
 504 osg::Node*
 505 SGLightFactory::getOdal(const SGLightBin& lights)
 506 {
 507   if (lights.getNumLights() < 2)
 508     return 0;
 509
 510   // generate a repeatable random seed
 511   sg_srandom(unsigned(lights.getLight(0).position[0]));
 512   float flashTime = 2e-2 + 5e-3*sg_random();
 513   osg::Sequence* sequence = new osg::Sequence;
 514   sequence->setDefaultTime(flashTime);
 515   Effect* effect = getLightEffect(10.0f, osg::Vec3(1.0, 0.0001, 0.00000001),
 516                                   6.0, 10.0, false);
 517   // centerline lights
 518   for (int i = lights.getNumLights(); i > 1; --i) {
 519     EffectGeode* egeode = new EffectGeode;
 520     egeode->setEffect(effect);
 521     egeode->addDrawable(getLightDrawable(lights.getLight(i)));
 522     sequence->addChild(egeode, flashTime);
 523   }
 524   // runway end lights
 525   osg::Group* group = new osg::Group;
 526   for (unsigned i = 0; i < 2; ++i) {
 527     EffectGeode* egeode = new EffectGeode;
 528     egeode->setEffect(effect);
 529     egeode->addDrawable(getLightDrawable(lights.getLight(i)));
 530     group->addChild(egeode);
 531   }
 532   sequence->addChild(group, flashTime);
 533
 534   // add an extra empty group for a break
 535   sequence->addChild(new osg::Group, 2 + 1e-1*sg_random());
 536   sequence->setInterval(osg::Sequence::LOOP, 0, -1);
 537   sequence->setDuration(1.0f, -1);
 538   sequence->setMode(osg::Sequence::START);
 539   sequence->setSync(true);
 540
 541   return sequence;
 542 }
 543
 544 // Blinking hold short line lights
 545 osg::Node*
 546 SGLightFactory::getHoldShort(const SGDirectionalLightBin& lights)
 547 {
 548   if (lights.getNumLights() < 2)
 549     return 0;
 550
 551   sg_srandom(unsigned(lights.getLight(0).position[0]));
 552   float flashTime = 1 + 0.1 * sg_random();
 553   osg::Sequence* sequence = new osg::Sequence;
 554
 555   // start with lights off
 556   sequence->addChild(new osg::Group, flashTime);
 557   // ...and increase the lights in steps
 558   for (int i = 2; i < 7; i+=2) {
 559       Effect* effect = getLightEffect(i, osg::Vec3(1, 0.001, 0.000002),
 560                                       0.0f, i, true);
 561       EffectGeode* egeode = new EffectGeode;
 562       for (unsigned int j = 0; j < lights.getNumLights(); ++j) {
 563           egeode->addDrawable(getLightDrawable(lights.getLight(j)));
 564           egeode->setEffect(effect);
 565       }
 566       sequence->addChild(egeode, (i==6) ? flashTime : 0.1);
 567   }
 568
 569   sequence->setInterval(osg::Sequence::SWING, 0, -1);
 570   sequence->setDuration(1.0f, -1);
 571   sequence->setMode(osg::Sequence::START);
 572
 573   return sequence;
 574 }
 575
 576 // Alternating runway guard lights ("wig-wag")
 577 osg::Node*
 578 SGLightFactory::getGuard(const SGDirectionalLightBin& lights)
 579 {
 580   if (lights.getNumLights() < 2)
 581     return 0;
 582
 583   // generate a repeatable random seed
 584   sg_srandom(unsigned(lights.getLight(0).position[0]));
 585   float flashTime = 1.0f + 1*sg_random();
 586   osg::Sequence* sequence = new osg::Sequence;
 587   sequence->setDefaultTime(flashTime);
 588   Effect* effect = getLightEffect(10.0f, osg::Vec3(1.0, 0.001, 0.000002),
 589                                   0.0f, 8.0f, true);
 590   for (unsigned int i = 0; i < lights.getNumLights(); ++i) {
 591     EffectGeode* egeode = new EffectGeode;
 592     egeode->setEffect(effect);
 593     egeode->addDrawable(getLightDrawable(lights.getLight(i)));
 594     sequence->addChild(egeode, flashTime);
 595   }
 596   sequence->setInterval(osg::Sequence::LOOP, 0, -1);
 597   sequence->setDuration(1.0f, -1);
 598   sequence->setMode(osg::Sequence::START);
 599   sequence->setSync(true);
 600   return sequence;
 601 }