鼠标单击点在世界坐标系中的射线 计算原理

鼠标单击点在世界坐标系中的射线 计算原理

参考osgManipulator/Dragger.cpp：

求鼠标单击射线在世界坐标系中Znear、Zfar的交点：

bool PointerInfo::projectWindowXYIntoObject(const osg::Vec2d& windowCoord, osg::Vec3d& nearPoint, osg::Vec3d& farPoint)const

{    nearPoint = osg::Vec3d(windowCoord.x(),windowCoord.y(),0.0)*_inverseMVPW;

    farPoint = osg::Vec3d(windowCoord.x(),windowCoord.y(),1.0)*_inverseMVPW;

    return true;

}

 

窗口坐标值(winx，winy，深度值)＝世界坐标点 * 视图矩阵 *投影矩阵 * 视口矩阵＝V世界 * VM * PM * WM。故V世界＝(winx，winy，深度值)* (VM * PM * WM)的逆

Znear对应的深度值为0，Zfar对应的深度值为1，故：

Znear对应点坐标为(winx，winy，0)* (VM * PM * WM)的逆，

Zfar对应点坐标为(winx，winy，1)* (VM * PM * WM)的逆。

 

获取(VM * PM * WM)的逆的代码如下：

           osg::ref_ptr<osg::Camera> cameraMaster = viewer->getCamera();

           osg::Matrix mvpw = cameraMaster->getViewMatrix() * cameraMaster->getProjectionMatrix();

           if ( cameraMaster->getViewport()) mvpw.postMult( cameraMaster->getViewport()->computeWindowMatrix());

 

           osg::Matrix _inverseMVPW;

           _inverseMVPW.invert( mvpw);

 

参考代码如下：

/*OSG中的HUD实时显示视点坐标*/

#include <osgDB/ReadFile>

#include <osgViewer/Viewer>

#include <osg/Geode>

#include <osg/Depth>

#include <osg/CameraNode>

#include <osgText/Text>

#include <osgGA/TrackballManipulator>

#include <osg/LineWidth>

#include <osg/Point>

 

#include <iostream>

#include <sstream>

 

#pragma comment( lib, "osgd.lib"); //.在Debug版本下的库名都加d,如"osgd.lib"

#pragma comment( lib, "osgDBd.lib")

#pragma comment( lib, "osgViewerd.lib");

#pragma comment( lib, "osgTextd.lib");

#pragma comment( lib, "osgGAd.lib");

 

osg::ref_ptr<osg::Group> g_grpMouse;

 

using namespace std;

 

//事件类

class CHUD_viewPoint: public osgGA::GUIEventHandler  

{

public:  

 

    /**构造函数*/

      CHUD_viewPoint(osgText::Text* updateText):

      m_text(updateText) {}

 

      ~CHUD_viewPoint(){}

 

      virtual bool handle(const osgGA::GUIEventAdapter& ea,osgGA::GUIActionAdapter& aa);

      void UpdateText(osgViewer::Viewer* viewer,const osgGA::GUIEventAdapter&);

 

      /**LABEL*/

      void setLabel(const std::string& name)

      {

         if ( m_text.get())

         {

             m_text->setText(name); 

         }

      }

 

protected: 

    osg::Vec2 m_vPosWindowMouse;//鼠标单击处的窗口坐标

 

    osg::ref_ptr<osgText::Text>  m_text;//视点信息，会动态改变

};

 

bool CHUD_viewPoint::handle(const osgGA::GUIEventAdapter& ea,osgGA::GUIActionAdapter& aa)

{

    switch(ea.getEventType())

    {

    //case(osgGA::GUIEventAdapter::FRAME):

    //  {

    //     osgViewer::Viewer* viewer = dynamic_cast<osgViewer::Viewer*>(&aa);

 

    //     if (viewer)

    //     {

    //         osg::Vec3 vCenter, vUp;

    //         viewer->getCamera()->getViewMatrixAsLookAt( m_vPosEye, vCenter, vUp);//获取视点信息

    //         UpdateText( viewer, ea);//更新文字信息       

 

    //     }

 

    //     return true; 

    //  }    

    case( osgGA::GUIEventAdapter::PUSH):

    {

       m_vPosWindowMouse.set( ea.getX(), ea.getY());//鼠标单击处的窗口坐标

 

       osgViewer::Viewer* viewer = dynamic_cast< osgViewer::Viewer*>( &aa);

      

       if (viewer)

       {

           UpdateText( viewer, ea);//更新文字信息

 

           //主相机

           osg::ref_ptr<osg::Camera> cameraMaster = viewer->getCamera();

 

           osg::Matrix mvpw = cameraMaster->getViewMatrix() * cameraMaster->getProjectionMatrix();

           if ( cameraMaster->getViewport()) mvpw.postMult( cameraMaster->getViewport()->computeWindowMatrix());

 

           osg::Matrix _inverseMVPW;

           _inverseMVPW.invert( mvpw);

 

           osg::Vec3d nearPoint = osg::Vec3d( ea.getX(), ea.getY(), 0.0)* _inverseMVPW;//透视投影中Znear平面的交点

           osg::Vec3d farPoint = osg::Vec3d( ea.getX(), ea.getY(), 1.0)* _inverseMVPW;//透视投影中Zfar平面的交点

 

           osg::Vec3 vPosEye, vCenter, vUp;

           cameraMaster->getViewMatrixAsLookAt( vPosEye, vCenter, vUp);//获取视点信息

 

           osg::Vec3d dir1= farPoint- nearPoint;

           dir1.normalize();

 

           osg::Vec3d dir2= farPoint- vPosEye;

           dir2.normalize();

 

           osg::Vec3d delta= dir1- dir2;

 

           //看视点、Znear平面的交点、Zfar平面的交点是否在同一直线上。经验证，确定在同一直线上

           if ( delta.length()< 1e-8)

           {

              cout<< "yes,line\n";

           }

 

 

           osg::Geode* geode= new osg::Geode();

           osg::Geometry* pyramidGeometry = new osg::Geometry();

 

           geode->addDrawable( pyramidGeometry);

 

           osg::Vec3Array* pyramidVertices = new osg::Vec3Array;

           pyramidVertices->push_back( nearPoint);

           pyramidVertices->push_back( farPoint);

   

           pyramidGeometry->setVertexArray( pyramidVertices );

 

           //颜色

           osg::Vec4Array* colors = new osg::Vec4Array;

           colors->push_back( osg::Vec4(  1.0f, 0.0f, 0.0f, 1.0f) );//红色

           pyramidGeometry->setColorArray( colors);

           pyramidGeometry->setColorBinding( osg::Geometry::BIND_OVERALL);

          

           //红点表示透视投影中Znear平面的交点

          pyramidGeometry->addPrimitiveSet(  new osg::DrawArrays( osg::PrimitiveSet::POINTS, 0, 1/*3*/));

           //红线表示鼠标点击的线，其起点为Znear平面交点，终点为Zfar平面交点。

           pyramidGeometry->addPrimitiveSet(  new osg::DrawArrays( osg::PrimitiveSet::LINES, 0, 2));/**/

 

           ////设置线宽

           //osg::ref_ptr <osg::LineWidth> LineSize = new osg::LineWidth;

           //LineSize ->setWidth( 12.0) ;      

           //geode->getOrCreateStateSet()->setAttributeAndModes( LineSize.get (),osg::StateAttribute::ON);

 

           //设置点大小

           osg::ref_ptr <osg::Point> ptSize = new osg::Point;

           ptSize->setSize( 12.0) ;      

           geode->getOrCreateStateSet()->setAttributeAndModes( ptSize.get (),osg::StateAttribute::ON);          

          

           /*当只有一个点时，包围球半径为，所以可能看不到这个点，故需要重新设置包围球大小，可把包围球半径设大点。

           如对glider、cow等小模型，半径取.1可以，对fountain.osg则.1太小。为统一，可大些，如*/

           osg::Vec3d ptCnt= geode->getBound().center();

           double dRadius= geode->getBound().radius();

           //重新设置包围球的半径（可调用setInitialBound()）

           osg::BoundingSphere bs( ptCnt, 100);

           geode->setInitialBound( bs);

 

           g_grpMouse->removeChildren( 0, g_grpMouse->getNumChildren());

           g_grpMouse->addChild( geode);

 

       }

       return true;

    }

    default:     

       return false; 

 

    }

}

 

void CHUD_viewPoint::UpdateText(osgViewer::Viewer* viewer,const osgGA::GUIEventAdapter&)

{

    std::string gdlist=""; 

 

    std::ostringstream os;

    os<<"MousePos(X: "<< m_vPosWindowMouse.x()<<",Y: "<< m_vPosWindowMouse.y()<<")";

   

    gdlist = os.str(); 

 

    setLabel(gdlist); 

}

 

osg::Node* createHUD_viewPoint( osgText::Text* text)

{

    //设置字体

    std::string font("fonts/arial.TTF");//此处设置的是汉字字体 "fonts/STCAIYUN.TTF"

    text->setFont( font); 

    //设置文字显示的位置(左下为(0,0),X正向朝右，Y正向朝上)

    osg::Vec3 position( 100.0f, 10.0f,0.0f);

    text->setPosition(position);   

    text->setColor( osg::Vec4( 1, 1, 0, 1));

    text->setText(L"");//设置显示的文字

    text->setCharacterSize(15);

    text->setDataVariance(osg::Object::DYNAMIC);//一定要设置字体为动态，否则程序会卡住，死在那里。（参照osgcatch）

 

    //几何体节点

    osg::Geode* geode = new osg::Geode();

    geode->addDrawable( text );//将文字Text作这drawable加入到Geode节点中

    //设置状态

    osg::StateSet* stateset = geode->getOrCreateStateSet(); 

    stateset->setMode(GL_LIGHTING,osg::StateAttribute::OFF);//关闭灯光

    stateset->setMode(GL_DEPTH_TEST,osg::StateAttribute::OFF);//关闭深度测试

    //打开GL_BLEND混合模式（以保证Alpha纹理正确）

    stateset->setMode(GL_BLEND,osg::StateAttribute::ON);

 

    //相机

    osg::Camera* camera = new osg::Camera;

    //设置透视矩阵

    camera->setProjectionMatrix(osg::Matrix::ortho2D(0,600,0,600));//正交投影   

    //设置绝对参考坐标系，确保视图矩阵不会被上级节点的变换矩阵影响

    camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);

    //视图矩阵为默认的

    camera->setViewMatrix(osg::Matrix::identity());

 

    //设置背景为透明，否则的话可以设置ClearColor 

    camera->setClearMask(GL_DEPTH_BUFFER_BIT);

    camera->setAllowEventFocus( false);//不响应事件，始终得不到焦点

 

    //设置渲染顺序，必须在最后渲染

    camera->setRenderOrder(osg::CameraNode::POST_RENDER); 

 

    camera->addChild(geode);//将要显示的Geode节点加入到相机

 

    return camera; 

};

 

 

int main( int argc, char **argv )

{

    osgViewer::Viewer viewer; 

 

    osg::ref_ptr<osg::Node> model = osgDB::readNodeFile("fountain.osg");// glider nathan

 

    osg::ref_ptr<osg::Group> root= new osg::Group; 

    root->addChild( model.get());//加入某个模型

 

 

    osgText::Text* text = new osgText::Text; 

    root->addChild( createHUD_viewPoint( text));//加入HUD文字

   

    osg::ref_ptr< CHUD_viewPoint> pHUD= new CHUD_viewPoint( text);

    viewer.addEventHandler( pHUD.get());

 

 

    //GraphicsContext设备上下文关键参数

    osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits ;

    traits->x = 200; 

    traits->y = 200; 

    traits->width = 600;

    traits->height = 600; 

    traits->windowDecoration = true; 

    traits->doubleBuffer = true;

    traits->sharedContext = 0; 

 

    osg::ref_ptr<osg::GraphicsContext> gc = osg::GraphicsContext::createGraphicsContext(traits.get());

    //gc->setClearColor( osg::Vec4f( 0.2f,0.2f,0.2f,1.0f));

    gc->setClearColor( osg::Vec4f( 0.0f, 1.0f, 0.0f, 1.0f)); //设置整个windows窗口颜色

    gc->setClearMask( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   

    //主相机

    osg::ref_ptr<osg::Camera> cameraMaster = viewer.getCamera();

    cameraMaster->setGraphicsContext(gc.get());//设置GraphicsContext设备上下文

    //相机视口设置

    cameraMaster->setViewport(new osg::Viewport( 100, 100, traits->width, traits->height));/**/

 

   

    g_grpMouse= new osg::Group();

    //设置状态

    osg::StateSet* stateset = g_grpMouse->getOrCreateStateSet(); 

    stateset->setMode( GL_LIGHTING,osg::StateAttribute::OFF);//关闭灯光

    //stateset->setMode( GL_DEPTH_TEST,osg::StateAttribute::OFF);//关闭深度测试

    root->addChild( g_grpMouse.get());

 

    //viewer.setUpViewInWindow( 0, 0, 600, 600);//设置窗口大小

          

 

    viewer.setSceneData( root.get());

    viewer.realize();

    viewer.run() ;  

   

    return 0;

}