用OpenSceneGraph实现的NeHe OpenGL教程 - 第四十三课
2014-06-03 11:22
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简介
这节课NeHe教我们怎么使用FreeType字体库来创建字体,在OSG中通过FreeType的插件已经支持FreeType字体了,前面很多课程中的字体就是使用FreeType字体库创建的。实现
本课的实现过程十分的简单,创建字体,然后再回调中修改字体显示:创建字体代码如下:
osg::Node* createFont1() { osg::MatrixTransform *zoomMT = new osg::MatrixTransform; zoomMT->setMatrix(osg::Matrix::translate(-3.0f,3.0f,-10.0f)); osgText::Text *textWords = new osgText::Text; textWords->setColor(osg::Vec4(0,0,1,1)); textWords->setText("Active WGL Bitmap Text With NeHe"); textWords->setFont("Fonts/Arial.ttf"); textWords->setCharacterSize(0.3f); textWords->setUpdateCallback(new Font1UpdateCallback); osg::Geode *fontGeode = new osg::Geode; fontGeode->addDrawable(textWords); zoomMT->addChild(fontGeode); return zoomMT; }
在字体回调中不断修改字体的显示内容:
class Font1UpdateCallback : public osg::Drawable::UpdateCallback { public: virtual void update(osg::NodeVisitor*, osg::Drawable* draw) { static float cnt1 = 0.0; osgText::Text *text = dynamic_cast<osgText::Text*>(draw); if (!text) return; std::stringstream os; std::string str; os.precision(2); os << std::fixed << "Active WGL Bitmap Text With NeHe - " << cnt1; str = os.str(); text->setText(str); cnt1 += 0.01; } };
将两部分添加到场景根节点中:
osg::Group *root = new osg::Group; root->addChild(createFont1()); root->addChild(createFont2()); return root;
编译运行程序:
附:本课源码(源码中可能存在错误和不足之处,仅供参考)
#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 <osgText/Text>
#include <osg/AnimationPath>
//////////////////////////////////////////////////////////////////////////
class Font1UpdateCallback : public osg::Drawable::UpdateCallback { public: virtual void update(osg::NodeVisitor*, osg::Drawable* draw) { static float cnt1 = 0.0; osgText::Text *text = dynamic_cast<osgText::Text*>(draw); if (!text) return; std::stringstream os; std::string str; os.precision(2); os << std::fixed << "Active WGL Bitmap Text With NeHe - " << cnt1; str = os.str(); text->setText(str); cnt1 += 0.01; } };
class Font2UpdateCallback : public osg::Drawable::UpdateCallback
{
public:
virtual void update(osg::NodeVisitor*, osg::Drawable* draw)
{
static float cnt1 = 0.0;
osgText::Text *text = dynamic_cast<osgText::Text*>(draw);
if (!text)
return;
std::stringstream os;
std::string str;
os.precision(2);
os << std::fixed << "Active FreeType Text - " << cnt1;
str = os.str();
text->setText(str);
cnt1 += 0.02;
}
};
//////////////////////////////////////////////////////////////////////////
osg::Node* createFont1() { osg::MatrixTransform *zoomMT = new osg::MatrixTransform; zoomMT->setMatrix(osg::Matrix::translate(-3.0f,3.0f,-10.0f)); osgText::Text *textWords = new osgText::Text; textWords->setColor(osg::Vec4(0,0,1,1)); textWords->setText("Active WGL Bitmap Text With NeHe"); textWords->setFont("Fonts/Arial.ttf"); textWords->setCharacterSize(0.3f); textWords->setUpdateCallback(new Font1UpdateCallback); osg::Geode *fontGeode = new osg::Geode; fontGeode->addDrawable(textWords); zoomMT->addChild(fontGeode); return zoomMT; }
osg::Node* createFont2()
{
osg::MatrixTransform *zoomMT = new osg::MatrixTransform;
zoomMT->setMatrix(osg::Matrix::translate(0.0f,-2.0f,-1.0f));
osg::MatrixTransform *rotZ = new osg::MatrixTransform;
rotZ->setMatrix(osg::Matrix::rotate(0, osg::Z_AXIS));
rotZ->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::Z_AXIS, 0.5));
osg::MatrixTransform *transMT = new osg::MatrixTransform;
transMT->setMatrix(osg::Matrix::translate(-5, 0, -10));
zoomMT->addChild(rotZ);
rotZ->addChild(transMT);
osgText::Text *textWords = new osgText::Text;
textWords->setColor(osg::Vec4(1,0,0,1));
textWords->setText("Active FreeType Text");
textWords->setFont("Fonts/Arial.ttf");
textWords->setCharacterSize(0.6f);
textWords->setUpdateCallback(new Font2UpdateCallback);
osg::Geode *fontGeode = new osg::Geode;
fontGeode->addDrawable(textWords);
transMT->addChild(fontGeode);
return zoomMT;
}
//////////////////////////////////////////////////////////////////////////
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, 0), osg::Vec3d(0, 0, -1), osg::Vec3d(0, 1, 0));
this->setSceneData( scene );
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; root->addChild(createFont1()); root->addChild(createFont2()); 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();
}
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