OpenSceneGraph实现的NeHe OpenGL教程 - 第四十一课

简介

这节课也是在场景中添加雾效的效果，与之类似的是第十六课，所不同的是这节课使用了雾坐标来计算雾效。为了能运行这一课，你的显卡必须支持GL_EXT_fot_coord扩展。

实现

这节课的实现过程比较简单，在OSG中为几何体的顶点封装好了顶点的各项属性，包括顶点坐标、顶点纹理坐标、顶点颜色，当然也包括本课中的雾坐标。

首先我们还是添加顶点的各项数据：

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    osg::Geode *geode = new osg::Geode;  

    osg::Geometry *geometry = new osg::Geometry;  

    osg::Vec3Array *vertexArray = new osg::Vec3Array;  

    osg::FloatArray *fogArray = new osg::FloatArray;  

    osg::Vec2Array *textureArray = new osg::Vec2Array;  

        vertexArray->push_back(osg::Vec3(-2.5f,-2.5f,-15.0f));  

        vertexArray->push_back(osg::Vec3(2.5f,-2.5f,-15.0f));  

        vertexArray->push_back(osg::Vec3(2.5f,2.5f,-15.0f));  

        vertexArray->push_back(osg::Vec3(-2.5f,2.5f,-15.0f));  

        textureArray->push_back(osg::Vec2(0.0f, 0.0f));  

        textureArray->push_back(osg::Vec2(1.0f, 0.0f));  

        textureArray->push_back(osg::Vec2(1.0f, 1.0f));  

        textureArray->push_back(osg::Vec2(0.0f, 1.0f));  

        fogArray->push_back(1.0f);  

        fogArray->push_back(1.0f);  

        fogArray->push_back(1.0f);  

        fogArray->push_back(1.0f);  

        ......  

接着读取纹理：

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osg::Texture2D *texture2D = new osg::Texture2D;  

texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);  

texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);  

texture2D->setImage(osgDB::readImageFile("Data/Wall.bmp"));  

geometry->getOrCreateStateSet()->setTextureAttributeAndModes(0, texture2D);  

启用雾效特效：

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osg::Fog *fog = new osg::Fog;  

fog->setMode(osg::Fog::LINEAR);  

fog->setColor(osg::Vec4(fogColor[0], fogColor[1],fogColor[2],fogColor[3]));  

fog->setStart(0.0f);  

fog->setEnd(1.0f);  

fog->setFogCoordinateSource(osg::Fog::FOG_COORDINATE);  

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）

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#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/Texture2D>  

#include <osg/Fog>  

  

  

GLfloat fogColor[4] = {0.6f, 0.3f, 0.0f, 1.0f};  

  

osg::MatrixTransform *g_Trans = NULL;  

  

class ManipulatorSceneHandler : public osgGA::GUIEventHandler  

{  

public:  

    ManipulatorSceneHandler()  

    {  

    }  

  

public:  

    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_Up)  

                {  

                    if (!g_Trans)  

                        return false;  

  

                    osg::Vec3 trans = g_Trans->getMatrix().getTrans();  

                    if(trans.z() < 14.0f)  

                        trans += osg::Vec3(0,0,1);  

  

                    g_Trans->setMatrix(osg::Matrix::translate(trans));  

                }  

  

                if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Down)  

                {  

                    if (!g_Trans)  

                        return false;  

  

                    osg::Vec3 trans = g_Trans->getMatrix().getTrans();  

                    if(trans.z() >-19.0f)  

                        trans -= osg::Vec3(0,0,1);  

  

                    g_Trans->setMatrix(osg::Matrix::translate(trans));  

                }  

            }  

            break;  

  

        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, 0.5) );  

        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, 0), osg::Vec3d(0, 0, -1), osg::Vec3d(0, 1, 0));  

  

        this->setSceneData( scene );  

        this->addEventHandler(new ManipulatorSceneHandler);  

        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;  

};  

  

  

  

osg::Node*  buildScene()  

{  

    osg::Group *root = new osg::Group;  

  

    osg::MatrixTransform *zoomMT = new osg::MatrixTransform;  

    zoomMT->setMatrix(osg::Matrix::translate(0,0,-19.0));  

    g_Trans = zoomMT;  

  

    osg::Geode *geode = new osg::Geode;  

    osg::Geometry *geometry = new osg::Geometry;  

    osg::Vec3Array *vertexArray = new osg::Vec3Array;  

    osg::FloatArray *fogArray = new osg::FloatArray;  

    osg::Vec2Array *textureArray = new osg::Vec2Array;  

  

    vertexArray->push_back(osg::Vec3(-2.5f,-2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,-2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(-2.5f,2.5f,-15.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 1.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 1.0f));  

    fogArray->push_back(1.0f);  

    fogArray->push_back(1.0f);  

    fogArray->push_back(1.0f);  

    fogArray->push_back(1.0f);  

  

    vertexArray->push_back(osg::Vec3(-2.5f,-2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,-2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,-2.5f,15.0f));  

    vertexArray->push_back(osg::Vec3(-2.5f,-2.5f,15.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 1.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 1.0f));  

    fogArray->push_back(1.0f);  

    fogArray->push_back(1.0f);  

    fogArray->push_back(0.0f);  

    fogArray->push_back(0.0f);  

  

    vertexArray->push_back(osg::Vec3(-2.5f,2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,2.5f,15.0f));  

    vertexArray->push_back(osg::Vec3(-2.5f,2.5f,15.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 1.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 1.0f));  

    fogArray->push_back(1.0f);  

    fogArray->push_back(1.0f);  

    fogArray->push_back(0.0f);  

    fogArray->push_back(0.0f);  

  

    vertexArray->push_back(osg::Vec3(2.5f,-2.5f,15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,2.5f,15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(2.5f,-2.5f,-15.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 1.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 1.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 0.0f));  

    fogArray->push_back(0.0f);  

    fogArray->push_back(0.0f);  

    fogArray->push_back(1.0f);  

    fogArray->push_back(1.0f);  

  

    vertexArray->push_back(osg::Vec3(-2.5f,-2.5f,15.0f));  

    vertexArray->push_back(osg::Vec3(-2.5f,2.5f,15.0f));  

    vertexArray->push_back(osg::Vec3(-2.5f,2.5f,-15.0f));  

    vertexArray->push_back(osg::Vec3(-2.5f,-2.5f,-15.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 0.0f));  

    textureArray->push_back(osg::Vec2(0.0f, 1.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 1.0f));  

    textureArray->push_back(osg::Vec2(1.0f, 0.0f));  

    fogArray->push_back(0.0f);  

    fogArray->push_back(0.0f);  

    fogArray->push_back(1.0f);  

    fogArray->push_back(1.0f);  

  

    geometry->setVertexArray(vertexArray);  

    geometry->setTexCoordArray(0, textureArray);  

    geometry->setFogCoordArray(fogArray, osg::Array::BIND_PER_VERTEX);  

    geometry->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF);  

      

    osg::Texture2D *texture2D = new osg::Texture2D;  

    texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);  

    texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);  

    texture2D->setImage(osgDB::readImageFile("Data/Wall.bmp"));  

    geometry->getOrCreateStateSet()->setTextureAttributeAndModes(0, texture2D);  

  

    osg::Fog *fog = new osg::Fog;  

    fog->setMode(osg::Fog::LINEAR);  

    fog->setColor(osg::Vec4(fogColor[0], fogColor[1],fogColor[2],fogColor[3]));  

    fog->setStart(0.0f);  

    fog->setEnd(1.0f);  

    fog->setFogCoordinateSource(osg::Fog::FOG_COORDINATE);  

      

    geometry->getOrCreateStateSet()->setAttributeAndModes(fog);  

  

    geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, vertexArray->size()));  

    geode->addDrawable(geometry);  

  

    zoomMT->addChild(geode);  

    root->addChild(zoomMT);  

  

    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();  

}