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