用OpenSceneGraph实现的NeHe OpenGL教程 - 第十九课_附录1

• 简介

在第十九课中我们使用NeHe教程中的方式实现了一个简单的粒子效果，在osg中也提供了一个专门处理粒子系统的库---osgParticle，下面我们就用osgParticle库来实现同样的效果。

• 实现

在具体实现之前，我们先了解一下osgParticle，osgParticle的粒子系统主要的模块包括如下部分：

• ParticleSystem粒子系统类，继承自osg::Drawable可绘制对象，用来管理粒子的绘制，它包含一个Particle的数组，Particle可以理解为很多粒子中其中的一个。

ParticleSystem利用粒子的模板来产生大量的粒子

• Particle类，刚才已经解释了，Particle可以看做ParticleSystem的一个模板，ParticleSystem依据它产生大量的粒子
• Emitter类：它包含三个部分（一个组合类）：即Shooter(发射器：发射出粒子的速度和方向)，Counter(计数器：每帧发射多少粒子)以及Placer(放置器：决定粒子初始位置在哪儿)
• Program类：Program类里面包含一个Operator类的数组，用来存放一系列的操作，在对粒子进行渲染之前、渲染中以及渲染后都可以进行一些设置，包括粒子的方方面面(颜色、位置、生命、加速度等等)，非常的灵活。我们需要自定义粒子的一些操作实际上是继承Operator类并重写里面的operator函数来完成粒子的一些自定义操作

粒子系统的基本操作过程可以参考osg示例解析之osgParticle，里面对粒子系统的设置过程进行了说明。

同样我们还是需要定义粒子结构体用来更新数据：

struct Particle{bool active;  float life;float fade;float r;        float g;float b;float x;float y;float z;float xi;    float yi;    float zi;float xg;float yg;float zg;};

设置particles的初始值与之前的代码一样

for (int i=0;  i<MaxParticles; i++){particles[i].active=true;particles[i].life=1.0f;particles[i].fade=float(rand()%100)/1000.0f+0.003f;particles[i].r=colors[int(i*(12.0/MaxParticles))][0];particles[i].g=colors[int(i*(12.0/MaxParticles))][1];particles[i].b=colors[int(i*(12.0/MaxParticles))][2];particles[i].xi=float((rand()%50)-26.0f)*10.0f;particles[i].yi=float((rand()%50)-25.0f)*10.0f;particles[i].zi=float((rand()%50)-25.0f)*10.0f;particles[i].xg=0.0f;particles[i].yg=-0.8f;particles[i].zg=0.0f;}

因为我们需要控制粒子的整个运行过程(产生的1000个粒子需要一直让我们来操作，这些粒子不会增加也不会减少，因此我把粒子的生命设置为永远"存活"，并且当粒子数量达到1000个之后，就不在发射粒子(Counter设置为0))，这与osgParticle示例中的方式不一样，osgParticle会一直产生粒子。

//设置粒子模板osgParticle::Particle particleTemplate;particleTemplate.setShape(osgParticle::Particle::QUAD_TRIANGLESTRIP);//负值表示粒子永远不会"死亡"particleTemplate.setLifeTime(-1);particleTemplate.setPosition(osg::Vec3(0.0, 0.0, 0.0));particleTemplate.setRadius(1.0f);

//设置粒子系统的光照，纹理等(与普通的Drawable设置一样)osgParticle::ParticleSystem *particleSystem = new osgParticle::ParticleSystem();particleSystem->setDefaultAttributes("Data/Particle.bmp", false, false);osg::BlendFunc *blendFunc = new osg::BlendFunc(GL_SRC_ALPHA, GL_ONE);particleSystem->getOrCreateStateSet()->setAttributeAndModes(blendFunc,osg::StateAttribute::ON);particleSystem->getOrCreateStateSet()->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);particleSystem->setDefaultParticleTemplate(particleTemplate);

设置Emitter的各个参数：

osgParticle::ModularEmitter *emitter = new osgParticle::ModularEmitter;emitter->setParticleSystem(particleSystem);osgParticle::PointPlacer *placer = new osgParticle::PointPlacer;placer->setCenter(0, 0, 0);emitter->setPlacer(placer);osgParticle::RandomRateCounter *counter = new osgParticle::RandomRateCounter;counter->setRateRange(1000, 1000);emitter->setCounter(counter);g_counter = counter; //为了设置1000个粒子之后停止发射osgParticle::RadialShooter *shooter = new osgParticle::RadialShooter;emitter->setShooter(shooter);

设置Program来定义自定义的操作

osgParticle::ModularProgram *program = new osgParticle::ModularProgram;program->setParticleSystem(particleSystem);ColorOption *co = new ColorOption;program->addOperator(co);

在ColorOption中完成了对所有粒子的位置和颜色的更新：（更新方式使用NeHe教程中的方式）

void beginOperate(osgParticle::Program *pro)

最后把粒子系统添加到一个Group节点中并设置到场景里面：

osg::Geode *particleGeode = new osg::Geode;particleGeode->addDrawable(particleSystem);osg::Group *particleEffect = new osg::Group;particleEffect->addChild(emitter);particleEffect->addChild(particleGeode);particleEffect->addChild(program);particleEffect->addChild(psu);

当场景中的粒子数量到达1000之后，停止产生新的粒子：

osgParticle::ParticleSystem *ps = pro->getParticleSystem();if (ps->numParticles() >= MaxParticles){g_counter->setRateRange(0,0);}

键盘的交互部分和第十九课中的代码类似，详细部分参看本课的完整代码。

编译运行程序：

附：本课源码(源码中可能存在错误和不足，仅供参考)

#include "../osgNeHe.h"#include <QtCore/QTimer>#include <QtGui/QApplication>#include <QtGui/QVBoxLayout>#include <osgViewer/Viewer>#include <osgDB/ReadFile>#include <osgQt/GraphicsWindowQt>#include <osg/MatrixTransform>#include <osg/BlendFunc>// osgParticle Related Header Files#include <osgParticle/Particle>#include <osgParticle/ParticleSystem>#include <osgParticle/ParticleSystemUpdater>#include <osgParticle/ModularEmitter>#include <osgParticle/ModularProgram>#include <osgParticle/RandomRateCounter>#include <osgParticle/PointPlacer>#include <osgParticle/SectorPlacer>#include <osgParticle/RadialShooter>#include <osgParticle/AccelOperator>#include <osgParticle/FluidFrictionOperator>//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////const int MaxParticles = 1000;float slowdown = 2.0f;float xspeed;float yspeed;float zoom = -40.0f;GLuint delay;int col;bool g_restart = false;struct Particle{bool active;  float life;float fade;float r;        float g;float b;float x;float y;float z;float xi;    float yi;    float zi;float xg;float yg;float zg;};Particle particles[MaxParticles];static GLfloat colors[12][4] ={{1.0f,0.5f,0.5f, 1.0f},{1.0f,0.75f,0.5f, 1.0f},{1.0f,1.0f,0.5f, 1.0f},{0.75f,1.0f,0.5f, 1.0f},{0.5f,1.0f,0.5f, 1.0f},{0.5f,1.0f,0.75f, 1.0f},{0.5f,1.0f,1.0f, 1.0f},{0.5f,0.75f,1.0f, 1.0f},{0.5f,0.5f,1.0f, 1.0f},{0.75f,0.5f,1.0f,1.0f},{1.0f,0.5f,1.0f, 1.0f},{1.0f,0.5f,0.75f, 1.0f}};//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////Particle Manipulatorclass ParticleEventHandler : public osgGA::GUIEventHandler{public:ParticleEventHandler(){}virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa){osgViewer::Viewer *viewer = dynamic_cast<osgViewer::Viewer*>(&aa);if (!viewer)return false;if (!viewer->getSceneData())return false;if (ea.getHandled()) return false;switch(ea.getEventType()){case(osgGA::GUIEventAdapter::KEYDOWN):{if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Tab){g_restart = true;}if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Up){if ((yspeed<200)) yspeed+=1.0f;}if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Down){if ((yspeed>-200)) yspeed-=1.0f;}if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Left){if ((xspeed>-200)) xspeed-=1.0f;}if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Right){if ((xspeed<200)) xspeed+=1.0f;}}default: break;}return false;}};class ViewerWidget : public QWidget, public osgViewer::Viewer{public:ViewerWidget(osg::Node *scene = NULL){QWidget* renderWidget = getRenderWidget( createGraphicsWindow(0,0,100,100), scene);QVBoxLayout* layout = new QVBoxLayout;layout->addWidget(renderWidget);layout->setContentsMargins(0, 0, 0, 1);setLayout( layout );connect( &_timer, SIGNAL(timeout()), this, SLOT(update()) );_timer.start( 10 );}QWidget* getRenderWidget( osgQt::GraphicsWindowQt* gw, osg::Node* scene ){osg::Camera* camera = this->getCamera();camera->setGraphicsContext( gw );const osg::GraphicsContext::Traits* traits = gw->getTraits();camera->setClearColor( osg::Vec4(0.0, 0.0, 0.0, 0.0) );camera->setViewport( new osg::Viewport(0, 0, traits->width, traits->height) );camera->setProjectionMatrixAsPerspective(45.0f, static_cast<double>(traits->width)/static_cast<double>(traits->height), 0.1f, 100.0f );camera->setViewMatrixAsLookAt(osg::Vec3d(0, 0, 1), osg::Vec3d(0, 0, 0), osg::Vec3d(0, 1, 0));this->setSceneData( scene );addEventHandler(new ParticleEventHandler);return gw->getGLWidget();}osgQt::GraphicsWindowQt* createGraphicsWindow( int x, int y, int w, int h, const std::string& name="", bool windowDecoration=false ){osg::DisplaySettings* ds = osg::DisplaySettings::instance().get();osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;traits->windowName = name;traits->windowDecoration = windowDecoration;traits->x = x;traits->y = y;traits->width = w;traits->height = h;traits->doubleBuffer = true;traits->alpha = ds->getMinimumNumAlphaBits();traits->stencil = ds->getMinimumNumStencilBits();traits->sampleBuffers = ds->getMultiSamples();traits->samples = ds->getNumMultiSamples();return new osgQt::GraphicsWindowQt(traits.get());}virtual void paintEvent( QPaintEvent* event ){ frame(); }protected:QTimer _timer;};osgParticle::RandomRateCounter *g_counter = NULL;//////////////////////////////////////////////////////////////////////////class ColorOption : public osgParticle::Operator{public:ColorOption() : osgParticle::Operator(){}ColorOption(const ColorOption &copy, const osg::CopyOp &copyop = osg::CopyOp::SHALLOW_COPY): osgParticle::Operator(copy, copyop){}META_Object(osgParticle, ColorOption);void beginOperate(osgParticle::Program *pro){osgParticle::ParticleSystem *ps = pro->getParticleSystem();if(!ps)return;if (ps->numParticles() >= MaxParticles){g_counter->setRateRange(0,0);}//如果按下Tab键if (g_restart) {osgParticle::ParticleSystem *ps = pro->getParticleSystem();if (!ps)return;for (unsigned i = 0; i < ps->numParticles(); ++i){particles[i].x=0.0f;particles[i].y=0.0f;particles[i].z=0.0f;particles[i].xi=float((rand()%50)-26.0f)*10.0f;particles[i].yi=float((rand()%50)-25.0f)*10.0f;particles[i].zi=float((rand()%50)-25.0f)*10.0f;}g_restart = false;} else {for (int i = 0; i < ps->numParticles(); ++i){float x=particles[i].x;float y=particles[i].y;float z=particles[i].z+zoom;ps->getParticle(i)->setPosition(osg::Vec3(x,y,z));osg::Vec4 color(particles[i].r,particles[i].g,particles[i].b,particles[i].life);ps->getParticle(i)->setColorRange(osgParticle::rangev4(color, color));particles[i].x+=particles[i].xi/(slowdown*1000);particles[i].y+=particles[i].yi/(slowdown*1000);particles[i].z+=particles[i].zi/(slowdown*1000);particles[i].xi+=particles[i].xg;particles[i].yi+=particles[i].yg;particles[i].zi+=particles[i].zg;particles[i].life-=particles[i].fade;if (particles[i].life<0.0f){particles[i].life=1.0f;particles[i].fade=float(rand()%100)/1000.0f+0.003f;particles[i].x=0.0f;particles[i].y=0.0f;particles[i].z=0.0f;particles[i].xi=xspeed+float((rand()%60)-32.0f);particles[i].yi=yspeed+float((rand()%60)-30.0f);particles[i].zi=float((rand()%60)-30.0f);particles[i].r=colors[col][0];particles[i].g=colors[col][1];particles[i].b=colors[col][2];}}}}void operate (osgParticle::Particle *P, double dt){}};osg::Node*buildScene(){//////////////////////////////////////////////////////////////////////////for (int i=0;  i<MaxParticles; i++){particles[i].active=true;particles[i].life=1.0f;particles[i].fade=float(rand()%100)/1000.0f+0.003f;particles[i].r=colors[int(i*(12.0/MaxParticles))][0];particles[i].g=colors[int(i*(12.0/MaxParticles))][1];particles[i].b=colors[int(i*(12.0/MaxParticles))][2];particles[i].xi=float((rand()%50)-26.0f)*10.0f;particles[i].yi=float((rand()%50)-25.0f)*10.0f;particles[i].zi=float((rand()%50)-25.0f)*10.0f;particles[i].xg=0.0f;particles[i].yg=-0.8f;particles[i].zg=0.0f;}////////////////////////////////////////////////////////////////////////////设置粒子模板osgParticle::Particle particleTemplate;particleTemplate.setShape(osgParticle::Particle::QUAD_TRIANGLESTRIP);//负值表示粒子永远不会"死亡"particleTemplate.setLifeTime(-1);particleTemplate.setPosition(osg::Vec3(0.0, 0.0, 0.0));particleTemplate.setRadius(1.0f);//设置粒子系统osgParticle::ParticleSystem *particleSystem = new osgParticle::ParticleSystem();particleSystem->setDefaultAttributes("Data/Particle.bmp", false, false);osg::BlendFunc *blendFunc = new osg::BlendFunc(GL_SRC_ALPHA, GL_ONE);particleSystem->getOrCreateStateSet()->setAttributeAndModes(blendFunc,osg::StateAttribute::ON);particleSystem->getOrCreateStateSet()->setMode(GL_DEPTH_TEST, osg::StateAttribute::OFF);particleSystem->setDefaultParticleTemplate(particleTemplate);osgParticle::ModularEmitter *emitter = new osgParticle::ModularEmitter;emitter->setParticleSystem(particleSystem);osgParticle::PointPlacer *placer = new osgParticle::PointPlacer;placer->setCenter(0, 0, 0);emitter->setPlacer(placer);osgParticle::RandomRateCounter *counter = new osgParticle::RandomRateCounter;counter->setRateRange(1000, 1000);emitter->setCounter(counter);g_counter = counter;osgParticle::RadialShooter *shooter = new osgParticle::RadialShooter;emitter->setShooter(shooter);osgParticle::ModularProgram *program = new osgParticle::ModularProgram;program->setParticleSystem(particleSystem);ColorOption *co = new ColorOption;program->addOperator(co);osgParticle::ParticleSystemUpdater *psu = new osgParticle::ParticleSystemUpdater;psu->addParticleSystem(particleSystem);osg::Geode *particleGeode = new osg::Geode;particleGeode->addDrawable(particleSystem);osg::Group *particleEffect = new osg::Group;particleEffect->addChild(emitter);particleEffect->addChild(particleGeode);particleEffect->addChild(program);particleEffect->addChild(psu);osg::Group *root = new osg::Group;root->addChild(particleEffect);return root;}int main( int argc, char** argv ){QApplication app(argc, argv);ViewerWidget* viewWidget = new ViewerWidget(buildScene());viewWidget->setGeometry( 100, 100, 640, 480 );viewWidget->show();return app.exec();}