OpenSceneGraph实现的NeHe OpenGL教程 - 第二十三课

简介

这节课我们将学习使用环境纹理映射。这种映射方式可以让物体表面看上去像镜子一样反射周围的环境。这节课的代码是在前面第十八节课程的基础上修改的。

实现

本课的实现过程十分的简单，在几何体的生成中添加一个环境纹理osg::TexGen属性即可。

首先创建背景几何体

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osg::Group* createBackGroup()

{

osg::Group *backGroup = new osg::Group;

osg::Geode* bgGeode = new osg::Geode;

osg::Geometry *bgGeometry = new osg::Geometry;

osg::Vec3Array *verticesArray = new osg::Vec3Array;

verticesArray->push_back(osg::Vec3(-13.3f, -10.0f, 10.0f));

verticesArray->push_back(osg::Vec3(13.3f, -10.0f, 10.0f));

verticesArray->push_back(osg::Vec3(13.3f, 10.0f, 10.0f));

verticesArray->push_back(osg::Vec3(-13.3f, 10.0f, 10.0f));

osg::Vec3Array *verticesNormal = new osg::Vec3Array;

verticesNormal->push_back(osg::Vec3(0.0f, 0.0f, 1.0f));

osg::Vec2Array *texArray = new osg::Vec2Array;

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

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

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

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

osg::Texture2D *texture = new osg::Texture2D;

texture->setImage(osgDB::readImageFile("Data/BG.bmp"));

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

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

bgGeometry->setVertexArray(verticesArray);

bgGeometry->setNormalArray(verticesNormal, osg::Array::BIND_OVERALL);

bgGeometry->setTexCoordArray(0, texArray);

bgGeometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));

bgGeometry->getOrCreateStateSet()->setTextureAttributeAndModes(0, texture);

bgGeode->addDrawable(bgGeometry);

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

zoomMT->setMatrix(osg::Matrix::translate(0, 0, -24));

backGroup->addChild(zoomMT);

zoomMT->addChild(bgGeode);

return backGroup;

}

接着给几何体添加TexGen的属性，按照NeHe课程中的设置：

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osg::TexGen *texGen = new osg::TexGen;

texGen->setMode(osg::TexGen::SPHERE_MAP);

g_Switch->getOrCreateStateSet()->setTextureAttributeAndModes(0, texGen);

这里我们将节点的属性设置给它的父节点，默认情况下子节点会继承父节点的属性，我们也可以强制使用osg::StateAttribute::OVERRIDE设置。

接下来将两个节点添加到场景中：

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quadYRotMT->addChild(g_Switch);

quadXRotMT->addChild(quadYRotMT);

quadMT->addChild(quadXRotMT);

root->addChild(quadMT);

root->addChild(createBackGroup());

编译运行程序：



附：本科源码(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/NodeVisitor>

#include <osg/Texture2D>

#include <osgGA/GUIEventAdapter>

#include <osg/Light>

#include <osg/LightModel>

#include <osg/LightSource>

#include <osg/ShapeDrawable>

#include <osg/Switch>

#include <osg/TexGen>

//////////////////////////////////////////////////////////////////////////

//开关节点

osg::Switch *g_Switch;

//////////////////////////////////////////////////////////////////////////

//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_Space)

{

static int index = 0;

g_Switch->setSingleChildOn(++index % 4);

}

}

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, 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::Group* createBackGroup()

{

osg::Group *backGroup = new osg::Group;

osg::Geode* bgGeode = new osg::Geode;

osg::Geometry *bgGeometry = new osg::Geometry;

osg::Vec3Array *verticesArray = new osg::Vec3Array;

verticesArray->push_back(osg::Vec3(-13.3f, -10.0f, 10.0f));

verticesArray->push_back(osg::Vec3(13.3f, -10.0f, 10.0f));

verticesArray->push_back(osg::Vec3(13.3f, 10.0f, 10.0f));

verticesArray->push_back(osg::Vec3(-13.3f, 10.0f, 10.0f));

osg::Vec3Array *verticesNormal = new osg::Vec3Array;

verticesNormal->push_back(osg::Vec3(0.0f, 0.0f, 1.0f));

osg::Vec2Array *texArray = new osg::Vec2Array;

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

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

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

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

osg::Texture2D *texture = new osg::Texture2D;

texture->setImage(osgDB::readImageFile("Data/BG.bmp"));

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

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

bgGeometry->setVertexArray(verticesArray);

bgGeometry->setNormalArray(verticesNormal, osg::Array::BIND_OVERALL);

bgGeometry->setTexCoordArray(0, texArray);

bgGeometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, 4));

bgGeometry->getOrCreateStateSet()->setTextureAttributeAndModes(0, texture);

bgGeode->addDrawable(bgGeometry);

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

zoomMT->setMatrix(osg::Matrix::translate(0, 0, -24));

backGroup->addChild(zoomMT);

zoomMT->addChild(bgGeode);

return backGroup;

}

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);

//////////////////////////////////////////////////////////////////////////

//新增代码，使用开关节点管理

g_Switch = new osg::Switch;

//添加立方体

osg::Geode *box = new osg::Geode;

osg::ShapeDrawable *boxDrawable = new osg::ShapeDrawable;

osg::Box *boxShape = new osg::Box(osg::Vec3(0, 0,0), 2);

boxDrawable->setShape(boxShape);

box->addDrawable(boxDrawable);

g_Switch->addChild(box);

//添加圆柱体

osg::Geode *cylinder = new osg::Geode;

osg::ShapeDrawable *cylinderDrawable = new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0,0,0), 0.5, 2.0));

cylinder->addDrawable(cylinderDrawable);

g_Switch->addChild(cylinder);

//添加圆球

osg::Geode *sphere = new osg::Geode;

osg::ShapeDrawable *sphereDrawable = new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(0,0,0), 1.3));

sphere->addDrawable(sphereDrawable);

g_Switch->addChild(sphere);

//添加圆锥

osg::Geode *cone = new osg::Geode;

osg::ShapeDrawable *coneDrawable = new osg::ShapeDrawable(new osg::Cone(osg::Vec3(0,0,0), 0.5, 2));

cone->addDrawable(coneDrawable);

g_Switch->addChild(cone);

g_Switch->setSingleChildOn(0);

//////////////////////////////////////////////////////////////////////////

osg::Image *textureImage = osgDB::readImageFile("Data/Reflect.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);

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

osg::TexGen *texGen = new osg::TexGen;

texGen->setMode(osg::TexGen::SPHERE_MAP);

g_Switch->getOrCreateStateSet()->setTextureAttributeAndModes(0, texGen);

quadYRotMT->addChild(g_Switch);

quadXRotMT->addChild(quadYRotMT);

quadMT->addChild(quadXRotMT);

root->addChild(quadMT);

root->addChild(createBackGroup());

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();

}