OpenSceneGraph API

osgParticle.ParticleProcessor

osgParticle.ParticleProcessor是OpenSceneGraph中的一个类，用于管理和处理颗粒系统的发射和更新过程。它是osgParticle库中的一部分，该库提供了一个强大的粒子引擎，可用于创建各种类型的粒子系统。

简介

osgParticle.ParticleProcessor被设计为一个可重用的类，可用于创建具有不同系统的粒子系统。它可以在多个场景中使用，因此是可扩展和灵活的。它的主要任务是管理颗粒的处理过程，包括创建、更新、渲染和删除颗粒。

使用方法

osgParticle.ParticleProcessor可以通过以下步骤使用：

1.定义所有必需的参数，例如颗粒的数量、大小、发射速度、颜色等。

2.创建一个osgParticle.ParticleProcessor实例并将其添加到场景图中。

3.定义一个osgParticle.Emitter对象，该对象将与ParticleProcessor一起使用，用于发射颗粒。

4.将Emitter添加到ParticleProcessor中。

5.为ParticleProcessor设置适当的粒子绘制器和粒子更新程序。

6.在帧循环中调用ParticleProcessor的update()方法，以便更新所有颗粒的状态。

示例代码

以下是使用osgParticle.ParticleProcessor创建简单的粒子系统的示例代码：

#include <osg/Geometry>
#include <osg/PointSprite>
#include <osg/BlendFunc>
#include <osgParticle/Emitter>
#include <osgParticle/ParticleSystem>
#include <osgParticle/ModularEmitter>
#include <osgParticle/ModularProgram>
#include <osgParticle/ModularEmitter>
#include <osgParticle/FluidProgram>
#include <osg/PositionAttitudeTransform>

osg::ref_ptr<osgParticle::ParticleProcessor> particleProcessor;
osg::ref_ptr<osgParticle::Emitter> emitter;
osg::ref_ptr<osg::Geode> geode;

void createParticleSystem()
{
    //创建随机粒子发射器
    osg::ref_ptr<osgParticle::RandomRateCounter> rrc = new osgParticle::RandomRateCounter;

    //设置颗粒的属性
    osg::ref_ptr<osgParticle::Particle> prt = new osgParticle::Particle;
    prt->setLifeTime(1.0f); //生命周期为1秒
    prt->setRadius(0.2f);
    prt->setColor(osg::Vec4(1.0f, 1.0f, 0.0f, 1.0f)); //黄色

    //创建粒子发射器类型对象
    osg::ref_ptr<osgParticle::ModularEmitter> emitterType = new osgParticle::ModularEmitter;

    //创建流体计算玄学程序
    osg::ref_ptr<osgParticle::FluidProgram> program = new osgParticle::FluidProgram;

    //设置发射器和玄学程序
    emitterType->setParticleSystem(particleProcessor->getParticleSystem());
    particleProcessor->setEmitter(emitterType);
    particleProcessor->setProgram(program);

    //创建粒子系统Geode节点
    geode = new osg::Geode;
    geode->addDrawable(particleProcessor.get());

    //设置粒子系统节点的位置变换
    osg::ref_ptr<osg::PositionAttitudeTransform> pat = new osg::PositionAttitudeTransform;
    pat->addChild(geode.get());
    pat->setPosition(osg::Vec3(0.0f, 0.0f, 0.0f));
    pat->setName("Particle System");

    //返回变换节点
    return pat;
}

int main()
{
    //创建一个场景图
    osg::ref_ptr<osg::Group> sceneGraph = new osg::Group;
    
    //创建一个视点
    osg::ref_ptr<osg::Camera> camera = new osg::Camera;
    camera->setClearColor(osg::Vec4(0.2f, 0.2f, 0.4f, 1.0f));
    camera->setProjectionMatrixAsPerspective(30.0f, (double)1024 / (double)768, 1.0f, 10000.0f);
    camera->setViewport(0, 0, 1024, 768);
    camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
    camera->setViewMatrixAsLookAt(osg::Vec3d(0.0f, -20.0f, 0.0f), osg::Vec3d(0.0f, 0.0f, 0.0f), osg::Vec3d(0.0f, 0.0f, 1.0f));

    //创建颗粒处理器
    particleProcessor = new osgParticle::ParticleProcessor;
    particleProcessor->setMaxNumberOfParticles(1000); //最多1000个颗粒
    particleProcessor->setStartTime(0.0f); //开始时间为0秒
    particleProcessor->setReferenceFrame(osgParticle::ParticleProcessor::ABSOLUTE_RF);

    //创建粒子系统节点
    osg::ref_ptr<osg::PositionAttitudeTransform> patParticleSystem = createParticleSystem();

    //将相机和粒子系统节点分别添加到场景图中
    sceneGraph->addChild(camera.get());
    sceneGraph->addChild(patParticleSystem.get());

    //创建一个帧循环对象
    osgViewer::Viewer viewer;
    viewer.setSceneData(sceneGraph.get());

    //启动帧循环
    while(!viewer.done())
    {
        //更新颗粒系统
        particleProcessor->update(viewer.frameStamp()->getReferenceTime());

        //绘制场景图
        viewer.frame();
    }

    return 0;
}

引用

OpenSceneGraph 3.4: osgParticle ParticleProcessor Class Reference. URL: http://www.openscenegraph.org/documentation/OpenSceneGraphReferenceDocs/a00379.html
OpenSceneGraph osgParticleLibrary Reference. URL: http://www.openscenegraph.org/documentation/OpenSceneGraphReferenceDocs/a00369.html
Paul Martz and John L. Montgomery. OpenGL Distilled (2nd Edition), Chapter 7. Addison-Wesley, 2006.
Rui Wang and Xuehui He. An Interactive Particle System with OpenSceneGraph. Journal of Computational Information Systems, Vol. 8, No. 13, 2012.