本节课实现了在场景中添加雾效，在OpenGL中添加雾效使用glFog函数来设置，在OSG中也十分的简单，雾效作为一个StateAttribute来添加到节点的。
本节课在第七课的基础上添加少量代码，主要是设置雾效
[cpp] view plain copy osg::Fog *fog = new osg::Fog; fog->setMode(osg::Fog::EXP); fog->setColor(osg::Vec4(0.5f,0.5f,0.5f,1.0f)); fog->setDensity(0.35f); fog->setStart(1.0f); fog->setEnd(5.0f); 雾的参数设置和NeHe教程中的完全一致，接下来在响应键盘G键的时候修改雾效计算方式，通过切换LINEAR、EXP、EXP2来修改场景中雾的浓密程度。
[cpp] view plain copy if (ea.getKey()== osgGA::GUIEventAdapter::KEY_G) { static int i = 0; if (i % 3 == 0) { g_fog->setMode(osg::Fog::EXP2); } else if (i % 3 == 1) { g_fog->setMode(osg::Fog::LINEAR); } else { g_fog->setMode(osg::Fog::EXP); } ++i; } 余下代码和第七课相同。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)
[cpp] view plain copy #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/NodeVisitor> #include <osg/Texture2D> #include <osgGA/GUIEventAdapter> #include <osg/Light> #include <osg/LightModel> #include <osg/LightSource> #include <osg/Fog> osg::Fog *g_fog; float textureVertices[][2] = { //Front Face {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f}, // Back Face {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f}, {0.0f, 0.0f}, // Top Face {0.0f, 1.0f}, {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, // Bottom Face {1.0f, 1.0f}, {0.0f, 1.0f}, {0.0f, 0.0f}, {1.0f, 0.0f}, // Right face {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f}, {0.0f, 0.0f}, // Left Face {0.0f, 0.0f}, {1.0f, 0.0f}, {1.0f, 1.0f}, {0.0f, 1.0f} }; float QuadVertices[][3] = { {-1.0f, -1.0f, 1.0f}, { 1.0f, -1.0f, 1.0f}, { 1.0f, 1.0f, 1.0f}, {-1.0f, 1.0f, 1.0f}, {-1.0f, -1.0f, -1.0f}, {-1.0f, 1.0f, -1.0f}, { 1.0f, 1.0f, -1.0f}, { 1.0f, -1.0f, -1.0f}, {-1.0f, 1.0f, -1.0f}, {-1.0f, 1.0f, 1.0f}, { 1.0f, 1.0f, 1.0f}, { 1.0f, 1.0f, -1.0f}, {-1.0f, -1.0f, -1.0f}, { 1.0f, -1.0f, -1.0f}, { 1.0f, -1.0f, 1.0f}, {-1.0f, -1.0f, 1.0f}, { 1.0f, -1.0f, -1.0f}, { 1.0f, 1.0f, -1.0f}, { 1.0f, 1.0f, 1.0f}, { 1.0f, -1.0f, 1.0f}, {-1.0f, -1.0f, -1.0f}, {-1.0f, -1.0f, 1.0f}, {-1.0f, 1.0f, 1.0f}, {-1.0f, 1.0f, -1.0f} }; float normalVertics[][3] = { // Front Face { 0.0f, 0.0f, 1.0f}, // Back Face { 0.0f, 0.0f,-1.0f}, // Top Face { 0.0f, 1.0f, 0.0f}, // Bottom Face { 0.0f,-1.0f, 0.0f}, // Right face { 1.0f, 0.0f, 0.0f}, // Left Face {-1.0f, 0.0f, 0.0f} }; // //FindFirstNamedNodeVisitor用来遍历寻找与指定名称相同的节点 class FindFirstNamedNodeVisitor : public osg::NodeVisitor { public: FindFirstNamedNodeVisitor(const std::string& name): osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN), _name(name), _foundNode(NULL) {} virtual void apply(osg::Node& node) { if (node.getName()==_name) { _foundNode = &node; return; } traverse(node); } std::string _name; osg::Node *_foundNode; }; // //RotateCallback class RotateCallback : public osg::NodeCallback { public: RotateCallback(osg::Vec3d rotateAxis, double rotateSpeed) : osg::NodeCallback(), _rotateAxis(rotateAxis), _rotateSpeed(rotateSpeed), _rotateAngle(0.0) { //Nop } void setRotateSpeed(double speed) { _rotateSpeed = speed; } double getRotateSpeed() const { return _rotateSpeed; } virtual void operator()(osg::Node* node, osg::NodeVisitor* nv) { osg::MatrixTransform *currentMT = dynamic_cast<osg::MatrixTransform*>(node); if (currentMT) { //获取当前的平移位置 osg::Vec3d currentTranslate = currentMT->getMatrix().getTrans(); osg::Matrix newMatrix = osg::Matrix::rotate(_rotateAngle, _rotateAxis) * osg::Matrix::translate(currentTranslate); currentMT->setMatrix(newMatrix); _rotateAngle += _rotateSpeed; } traverse(node, nv); } private: osg::Vec3d _rotateAxis; //旋转轴 double _rotateSpeed; //旋转速度 double _rotateAngle; //当前旋转的角度 }; // class ManipulatorSceneHandler : public osgGA::GUIEventHandler { public: ManipulatorSceneHandler() { } 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; osg::Group *root = viewer->getSceneData()->asGroup(); switch(ea.getEventType()) { case(osgGA::GUIEventAdapter::KEYDOWN): { if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Left) { FindFirstNamedNodeVisitor fnv("yRotMT"); root->accept(fnv); osg::Node *mtNode = fnv._foundNode; osg::MatrixTransform *yRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode); if (!yRotMT) return false; RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(yRotMT->getUpdateCallback()); if (!rotCallback) return false; double speed = rotCallback->getRotateSpeed(); speed += 0.02; rotCallback->setRotateSpeed(speed); } if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Right) { FindFirstNamedNodeVisitor fnv("yRotMT"); root->accept(fnv); osg::Node *mtNode = fnv._foundNode; osg::MatrixTransform *yRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode); if (!yRotMT) return false; RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(yRotMT->getUpdateCallback()); if (!rotCallback) return false; double speed = rotCallback->getRotateSpeed(); speed -= 0.02; rotCallback->setRotateSpeed(speed); } if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Up) { FindFirstNamedNodeVisitor fnv("xRotMT"); root->accept(fnv); osg::Node *mtNode = fnv._foundNode; osg::MatrixTransform *xRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode); if (!xRotMT) return false; RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(xRotMT->getUpdateCallback()); if (!rotCallback) return false; double speed = rotCallback->getRotateSpeed(); speed += 0.02; rotCallback->setRotateSpeed(speed); } if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Down) { FindFirstNamedNodeVisitor fnv("xRotMT"); root->accept(fnv); osg::Node *mtNode = fnv._foundNode; osg::MatrixTransform *xRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode); if (!xRotMT) return false; RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(xRotMT->getUpdateCallback()); if (!rotCallback) return false; double speed = rotCallback->getRotateSpeed(); speed -= 0.02; rotCallback->setRotateSpeed(speed); } if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Page_Up) { FindFirstNamedNodeVisitor fnv("zoomMT"); root->accept(fnv); osg::Node *mtNode = fnv._foundNode; osg::MatrixTransform *zoomMT = dynamic_cast<osg::MatrixTransform*>(mtNode); if (!zoomMT) return false; osg::Vec3 trans = zoomMT->getMatrix().getTrans(); trans.set(trans.x(), trans.y(), trans.z() + 0.2); zoomMT->setMatrix(osg::Matrix::translate(trans)); } if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Page_Down) { FindFirstNamedNodeVisitor fnv("zoomMT"); root->accept(fnv); osg::Node *mtNode = fnv._foundNode; osg::MatrixTransform *zoomMT = dynamic_cast<osg::MatrixTransform*>(mtNode); if (!zoomMT) return false; osg::Vec3 trans = zoomMT->getMatrix().getTrans(); trans.set(trans.x(), trans.y(), trans.z() - 0.2); zoomMT->setMatrix(osg::Matrix::translate(trans)); } if (ea.getKey()== osgGA::GUIEventAdapter::KEY_L) { static int i = 0; if (i % 2 == 0) { root->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF); } else { root->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::ON); } ++i; } if (ea.getKey()== osgGA::GUIEventAdapter::KEY_F) { FindFirstNamedNodeVisitor fnv("quadGeode"); root->accept(fnv); osg::Node *mtNode = fnv._foundNode; osg::Geode *quadGeode = dynamic_cast<osg::Geode*>(mtNode); if (!quadGeode) return false; osg::Texture2D *texture2D = dynamic_cast<osg::Texture2D*>(quadGeode->getOrCreateStateSet()->getTextureAttribute(0, osg::StateAttribute::TEXTURE)); static int i = 0; if (i % 3 == 0) { texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR); texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR); } else if (i % 3 == 1) { texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR); texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR_MIPMAP_NEAREST); } else { texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::NEAREST); texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::NEAREST); } ++i; } if (ea.getKey()== osgGA::GUIEventAdapter::KEY_G) { static int i = 0; if (i % 3 == 0) { g_fog->setMode(osg::Fog::EXP2); } else if (i % 3 == 1) { g_fog->setMode(osg::Fog::LINEAR); } else { g_fog->setMode(osg::Fog::EXP); } ++i; } } 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(0.5, 0.5, 0.5, 1.0) ); 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)); osg::StateSet* globalStateset = camera->getStateSet(); if (globalStateset) { osg::LightModel* lightModel = new osg::LightModel; lightModel->setAmbientIntensity(osg::Vec4(0,0,0,0)); globalStateset->setAttributeAndModes(lightModel, osg::StateAttribute::ON); } 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::Light* light = new osg::Light(); light->setLightNum(0); light->setAmbient(osg::Vec4(0.5f, 0.5f, 0.5f, 1.0f)); light->setDiffuse(osg::Vec4(1.0f, 1.0f, 1.0f, 1.0f)); light->setPosition(osg::Vec4(0.0f, 0.0f, 2.0f, 1.0f)); osg::LightSource* lightsource = new osg::LightSource(); lightsource->setLight (light); root->addChild (lightsource); osg::MatrixTransform *quadMT = new osg::MatrixTransform; quadMT->setName("zoomMT"); quadMT->setMatrix(osg::Matrix::translate(0.0, 0.0, -5.0)); osg::MatrixTransform *quadXRotMT = new osg::MatrixTransform; quadXRotMT->setName("xRotMT"); RotateCallback *xRotCallback = new RotateCallback(osg::X_AXIS, 0.0); quadXRotMT->setUpdateCallback(xRotCallback); osg::MatrixTransform *quadYRotMT = new osg::MatrixTransform; quadYRotMT->setName("yRotMT"); RotateCallback *yRotCallback = new RotateCallback(osg::Y_AXIS, 0.0); quadYRotMT->setUpdateCallback(yRotCallback); osg::Geometry *quadGeometry = new osg::Geometry; osg::Vec3Array *quadVertexArray = new osg::Vec3Array; for (unsigned i = 0; i < sizeof(QuadVertices); ++i) { quadVertexArray->push_back(osg::Vec3(QuadVertices[i][0], QuadVertices[i][1], QuadVertices[i][2])); } quadGeometry->setVertexArray(quadVertexArray); osg::Vec2Array* texcoords = new osg::Vec2Array; for (unsigned i = 0; i < sizeof(textureVertices); ++i) { texcoords->push_back(osg::Vec2(textureVertices[i][0], textureVertices[i][1])); } quadGeometry->setTexCoordArray(0,texcoords); osg::Vec3Array *quadNormalArray = new osg::Vec3Array; for (unsigned i = 0; i < sizeof(normalVertics); ++i) { quadNormalArray->push_back(osg::Vec3(normalVertics[i][0], normalVertics[i][1], normalVertics[i][2])); } quadGeometry->setNormalArray(quadNormalArray, osg::Array::BIND_PER_PRIMITIVE_SET); int first = 0; for (unsigned i = 0; i < 6; ++i) { osg::DrawArrays *vertexIndices = new osg::DrawArrays(osg::PrimitiveSet::QUADS, first, 4); first += 4; quadGeometry->addPrimitiveSet(vertexIndices); } osg::Image *textureImage = osgDB::readImageFile("Data/Crate.bmp"); osg::Texture2D *texture2D = new osg::Texture2D; texture2D->setImage(textureImage); texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::NEAREST); texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::NEAREST); osg::Fog *fog = new osg::Fog; fog->setMode(osg::Fog::EXP); fog->setColor(osg::Vec4(0.5f,0.5f,0.5f,1.0f)); fog->setDensity(0.35f); fog->setStart(1.0f); fog->setEnd(5.0f); g_fog = fog; osg::Geode *quadGeode = new osg::Geode; quadGeode->setName("quadGeode"); quadGeode->getOrCreateStateSet()->setTextureAttributeAndModes(0, texture2D); quadGeode->getOrCreateStateSet()->setAttributeAndModes(fog); quadGeode->addDrawable(quadGeometry); quadYRotMT->addChild(quadGeode); quadXRotMT->addChild(quadYRotMT); quadMT->addChild(quadXRotMT); root->addChild(quadMT); 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(); }
