OSGEarth绘制Geometry：画线（一）

在OSGEarth中绘制线，首先考虑osgEarth::Annotation::FeatureNode。
功能描述如下：
1. 鼠标两次点击的点之间连线，为黄色的实线；
2. 最近一次点击的点和鼠标move到的点之间连线，为红色的虚线。
代码如下：drawline.h

class DrawLine : public HandleAdapter
{
public:
    DrawLine(GraphicsView* view);
    ~DrawLine();

protected:
    // 只需要经纬度
    virtual void slotPicked(osg::Vec3d pos);
    virtual void slotMoveing(osg::Vec3d pos);
    virtual void slotRightHandle();

private:
    // 实线的style，Node
    osgEarth::Symbology::Style m_lineStyle;
    osgEarth::Features::Feature* m_pFeature;
    osgEarth::Annotation::FeatureNode* m_pFeatureNode;

    // 虚线的style，Node
    osgEarth::Symbology::Style m_stippleLineStyle;
    osgEarth::Features::Feature* m_pStippleFeature;
    osgEarth::Annotation::FeatureNode* m_pStippleFeatureNode;

    std::vector<osg::Vec3d> m_vecPoint;
};

功能实现如下：drawline.cpp

DrawLine::DrawLine(GraphicsView* view)
: HandleAdapter(view)
{
    m_pFeature = NULL;
    m_pFeatureNode = NULL;
    m_pStippleFeature = NULL;
    m_pStippleFeatureNode = NULL;

    m_vecPoint.clear();

    // 初始化实线的style
    m_lineStyle.getOrCreate<osgEarth::Symbology::LineSymbol>()
        ->stroke()->color() = osgEarth::Symbology::Color::Yellow;
    m_lineStyle.getOrCreate<osgEarth::Symbology::LineSymbol>()
        ->stroke()->width() = 2.0;
    m_lineStyle.getOrCreate<osgEarth::Symbology::LineSymbol>()
        ->tessellation() = 20.0;
    m_lineStyle.getOrCreate<osgEarth::Symbology::AltitudeSymbol>()
        ->clamping() = osgEarth::Symbology::AltitudeSymbol::CLAMP_TO_TERRAIN;
    m_lineStyle.getOrCreate<osgEarth::Symbology::AltitudeSymbol>()
        ->technique() = osgEarth::Symbology::AltitudeSymbol::TECHNIQUE_MAP;
    m_lineStyle.getOrCreate<osgEarth::Symbology::AltitudeSymbol>()
        ->verticalOffset() = 0.1;

    // 初始化实线的style
    m_stippleLineStyle.getOrCreate<osgEarth::Symbology::LineSymbol>()
        ->stroke()->color() = osgEarth::Symbology::Color::Red;
    m_stippleLineStyle.getOrCreate<osgEarth::Symbology::LineSymbol>()
        ->stroke()->width() = 2.0;
    m_stippleLineStyle.getOrCreate<osgEarth::Symbology::LineSymbol>()
        ->tessellation() = 20.0;
    m_stippleLineStyle.getOrCreate<osgEarth::Symbology::AltitudeSymbol>()
        ->clamping() = osgEarth::Symbology::AltitudeSymbol::CLAMP_TO_TERRAIN;
    m_stippleLineStyle.getOrCreate<osgEarth::Symbology::AltitudeSymbol>()
        ->technique() = osgEarth::Symbology::AltitudeSymbol::TECHNIQUE_MAP;
    m_stippleLineStyle.getOrCreate<osgEarth::Symbology::AltitudeSymbol>()
        ->verticalOffset() = 0.1;
    m_stippleLineStyle.getOrCreate<osgEarth::Symbology::LineSymbol>()
        ->stroke()->stipple() = 255;
}

DrawLine::~DrawLine()
{

}

void DrawLine::slotPicked(osg::Vec3d pos)
{
    m_vecPoint.push_back(pos);
    if (m_vecPoint.size() <= 1)
    {
        return;
    }

    if (m_pFeatureNode == NULL)
    {
        m_pFeature = new osgEarth::Features::Feature(
            new osgEarth::Annotation::LineString,
            m_pMap3D->getMapNode()->getMapSRS(), m_lineStyle);
        m_pFeatureNode = new osgEarth::Annotation::FeatureNode(
            m_pMap3D->getMapNode(), m_pFeature);

        m_pLayerGroup->addChild(m_pFeatureNode);
    }

    m_pFeature->getGeometry()->clear();
    m_pFeatureNode->setStyle(m_lineStyle);
    for (int i = 0; i < m_vecPoint.size(); ++i)
    {
        m_pFeature->getGeometry()->push_back(m_vecPoint[i]);
    }

    m_pFeatureNode->init();

    if (m_pStippleFeatureNode != NULL)
    {
        m_pStippleFeature->getGeometry()->clear();
    }
}

void DrawLine::slotMoveing(osg::Vec3d pos)
{
    if (m_vecPoint.size() <= 0)
    {
        return;
    }
    if (m_pStippleFeatureNode == NULL)
    {
        m_pStippleFeature = new osgEarth::Features::Feature(
            new osgEarth::Annotation::LineString,
            m_pMap3D->getMapNode()->getMapSRS(), m_lineStyle);
        m_pStippleFeatureNode = new osgEarth::Annotation::FeatureNode(
            m_pMap3D->getMapNode(), m_pStippleFeature);

        m_pLayerGroup->addChild(m_pStippleFeatureNode);
    }

    m_pStippleFeature->getGeometry()->clear();
    m_pStippleFeatureNode->setStyle(m_stippleLineStyle);
    m_pStippleFeature->getGeometry()->push_back(m_vecPoint[m_vecPoint.size() - 1]);
    m_pStippleFeature->getGeometry()->push_back(pos);

    m_pStippleFeatureNode->init();
}

void DrawLine::slotRightHandle()
{
    m_vecPoint.clear();
    if (m_pStippleFeatureNode != NULL)
    {
        m_pStippleFeature->getGeometry()->clear();
    }
}

关于osgEarth::Features::Feature*，并不需要写成成员的，可以再需要使用的时候直接new一个就好，在后面的篇章中展示此方式。