OpenSceneGraph实现的NeHe OpenGL教程 - 第十二课

简介

本课NeHe教程主要是使用了OpenGL中的显示列表。OpenGL的显示列表是加速OpenGL性能的一种重要的手段。OpenGl的几何体绘制方法主要包括立即模式、顶点数组、显示列表和VBO。在OSG中显示列表是大部分OSG程序所使用的默认绘制优化行为，因此不需要我们去像OpenGL那样进行设置。

实现

首先创建整个场景，本课中我使用了OSG中预定义的几种基本形体，(osg::Box)来绘制立方体

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osg::Node* buildScene()

{

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

for (int yloop=1;yloop<6;yloop++)

{

osg::Group *cubeGroup = new osg::Group;

for (int xloop=0;xloop<yloop;xloop++)

{

osg::MatrixTransform *posMT = new osg::MatrixTransform;

posMT->setMatrix(osg::Matrix::translate(1.4f+(float(xloop)*2.8f)-(float(yloop)*1.4f),((6.0f-float(yloop))*2.4f)-7.0f,-20.0f));

cubeGroup->addChild(posMT);

osg::MatrixTransform *rotXMT = new osg::MatrixTransform;

rotXMT->setName("XRotMT");

posMT->addChild(rotXMT);

XRotCallback* xrot = new XRotCallback(osg::DegreesToRadians(45.0f-(2.0f*yloop)));

rotXMT->setUpdateCallback(xrot);

osg::MatrixTransform *rotYMT = new osg::MatrixTransform;

rotXMT->addChild(rotYMT);

rotYMT->setName("YRotMT");

YRotCallback* yrot = new YRotCallback(osg::DegreesToRadians(45.0f));

rotYMT->setUpdateCallback(yrot);

osg::Geode *cube = createCube(yloop-1);

rotYMT->addChild(cube);

}

root->addChild(cubeGroup);

}

return root;

}

参照NeHe教程中平移量进行(glTranslate对应一个osg::MatrixTransform)，对于每一个几何体叶节点，通过不同的颜色索引值创建它

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osg::Geode* createCube(int colorIndex)

{

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

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

texture2D->setImage(textureImage);

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

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

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

sd->setColor(osg::Vec4d(boxcol[colorIndex][0], boxcol[colorIndex][1], boxcol[colorIndex][2], 1));

osg::Geode *cubeGeode = new osg::Geode;

cubeGeode->addDrawable(sd);

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

return cubeGeode;

}

可以看到场景中对每一个MatrixTransform均设置了UpdateCallback，为的是通过键盘对它们进行操作。首先先通过名字找到所有这些节点

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class FindNamedNodeVisitor : public osg::NodeVisitor

{

public:

FindNamedNodeVisitor(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.push_back(&node);

}

traverse(node);

}

std::string _name;

std::vector<osg::Node*> _foundNode;

};

在EventHandler交互类中进行设置如下：

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

{

FindNamedNodeVisitor fnnv("YRotMT");

root->accept(fnnv);

for (unsigned i = 0; i < fnnv._foundNode.size(); ++i)

{

yrot = dynamic_cast<YRotCallback*>(fnnv._foundNode.at(i)->getUpdateCallback());

if (yrot)

{

yrot->setAngle(yrot->getAngle() - osg::DegreesToRadians(2.0));

}

}

}

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 <osgDB/ReadFile>

#include <osg/Texture2D>

#include <osg/ShapeDrawable>

#include <osg/NodeVisitor>

static GLfloat boxcol[5][3]=

{

{1.0f,0.0f,0.0f},{1.0f,0.5f,0.0f},{1.0f,1.0f,0.0f},{0.0f,1.0f,0.0f},{0.0f,1.0f,1.0f}

};

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

//RotCallback

class XRotCallback : public osg::NodeCallback

{

public:

XRotCallback(double angle) : _angle(angle){}

virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)

{

if (dynamic_cast<osg::MatrixTransform*>(node))

{

osg::MatrixTransform *rot = dynamic_cast<osg::MatrixTransform*>(node);

rot->setMatrix(osg::Matrix::rotate(_angle, osg::X_AXIS));

}

traverse(node, nv);

}

void setAngle(double angle)

{

_angle = angle;

}

double getAngle() const

{

return _angle;

}

double _angle;

};

class YRotCallback : public osg::NodeCallback

{

public:

YRotCallback(double angle) : _angle(angle){}

virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)

{

if (dynamic_cast<osg::MatrixTransform*>(node))

{

osg::MatrixTransform *rot = dynamic_cast<osg::MatrixTransform*>(node);

rot->setMatrix(osg::Matrix::rotate(_angle, osg::Y_AXIS));

}

traverse(node, nv);

}

void setAngle(double angle)

{

_angle = angle;

}

double getAngle() const

{

return _angle;

}

double _angle;

};

//End

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

class FindNamedNodeVisitor : public osg::NodeVisitor

{

public:

FindNamedNodeVisitor(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.push_back(&node);

}

traverse(node);

}

std::string _name;

std::vector<osg::Node*> _foundNode;

};

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

//EventHandler

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):

{

XRotCallback *xrot;

YRotCallback *yrot;

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

{

FindNamedNodeVisitor fnnv("YRotMT");

root->accept(fnnv);

for (unsigned i = 0; i < fnnv._foundNode.size(); ++i)

{

yrot = dynamic_cast<YRotCallback*>(fnnv._foundNode.at(i)->getUpdateCallback());

if (yrot)

{

yrot->setAngle(yrot->getAngle() - osg::DegreesToRadians(2.0));

}

}

}

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

{

FindNamedNodeVisitor fnnv("YRotMT");

root->accept(fnnv);

for (unsigned i = 0; i < fnnv._foundNode.size(); ++i)

{

yrot = dynamic_cast<YRotCallback*>(fnnv._foundNode.at(i)->getUpdateCallback());

if (yrot)

{

yrot->setAngle(yrot->getAngle() + osg::DegreesToRadians(2.0));

}

}

}

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

{

FindNamedNodeVisitor fnnv("XRotMT");

root->accept(fnnv);

for (unsigned i = 0; i < fnnv._foundNode.size(); ++i)

{

xrot = dynamic_cast<XRotCallback*>(fnnv._foundNode.at(i)->getUpdateCallback());

if (xrot)

{

xrot->setAngle(xrot->getAngle() - osg::DegreesToRadians(2.0));

}

}

}

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

{

FindNamedNodeVisitor fnnv("XRotMT");

root->accept(fnnv);

for (unsigned i = 0; i < fnnv._foundNode.size(); ++i)

{

xrot = dynamic_cast<XRotCallback*>(fnnv._foundNode.at(i)->getUpdateCallback());

if (xrot)

{

xrot->setAngle(xrot->getAngle() + osg::DegreesToRadians(2.0));

}

}

}

}

default: break;

}

return false;

}

};

//End

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

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));

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::Geode* createCube(int colorIndex)

{

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

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

texture2D->setImage(textureImage);

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

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

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

sd->setColor(osg::Vec4d(boxcol[colorIndex][0], boxcol[colorIndex][1], boxcol[colorIndex][2], 1));

osg::Geode *cubeGeode = new osg::Geode;

cubeGeode->addDrawable(sd);

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

return cubeGeode;

}

osg::Node* buildScene()

{

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

for (int yloop=1;yloop<6;yloop++)

{

osg::Group *cubeGroup = new osg::Group;

for (int xloop=0;xloop<yloop;xloop++)

{

osg::MatrixTransform *posMT = new osg::MatrixTransform;

posMT->setMatrix(osg::Matrix::translate(1.4f+(float(xloop)*2.8f)-(float(yloop)*1.4f),((6.0f-float(yloop))*2.4f)-7.0f,-20.0f));

cubeGroup->addChild(posMT);

osg::MatrixTransform *rotXMT = new osg::MatrixTransform;

rotXMT->setName("XRotMT");

posMT->addChild(rotXMT);

XRotCallback* xrot = new XRotCallback(osg::DegreesToRadians(45.0f-(2.0f*yloop)));

rotXMT->setUpdateCallback(xrot);

osg::MatrixTransform *rotYMT = new osg::MatrixTransform;

rotXMT->addChild(rotYMT);

rotYMT->setName("YRotMT");

YRotCallback* yrot = new YRotCallback(osg::DegreesToRadians(45.0f));

rotYMT->setUpdateCallback(yrot);

osg::Geode *cube = createCube(yloop-1);

rotYMT->addChild(cube);

}

root->addChild(cubeGroup);

}

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();

}