[vtkusers] How to map the point in 3D coordinate to 2D coordinate locates in 2D image by using vtkCellPicker?

[朱文武]

hi all,

      i encounter a problem, and need your kind help ! I get 3D global
coordinate by using vtkCellPicker, then i want to know the 2D coordinate of
point which is picked in the 3D scene.  However, the 2D coordiante i
transformed was not accurate. Could anyone give some suggestion or better
methods? thanks in advance!

All related code is as follows:
    vtkBMPReader *m_read=... // read bmp image

m_read->SetDataSpacing(CReadBmp::m_Dx,CReadBmp::m_Dy,CReadBmp::m_Dz);//


m_read->SetDataExtentCReadBmp::m_Xmin,CReadBmp::m_Xmax,CReadBmp::m_Ymin,CReadBmp::m_Ymax,CReadBmp::m_Zmin,CReadBmp::m_Zmax);//


    vtkInteractorStyleTrackballCamera *style;
    vtkRenderWindowInteractor *iren;
    vtkCellPicker *picker;
    iren->SetInteractorStyle(style);

    style->AddObserver(vtkCommand::MiddleButtonReleaseEvent, cmd);
    cmd->SetCallback(MyExecute);
    picker->SetTolerance(0.0001);
    iren->SetPicker(picker);

void MyExecute(vtkObject *caller, unsigned long eid, void *clientdata, void
*calldata)
{
    double globalCoordinate[3]; //
    double selPt[2];

picker->Pick(psurface->iren->GetEventPosition()[0],psurface->iren->GetEventPosition()[1],0,
psurface->aRenderer);
    picker->GetPickPosition(globalCoordinate);

     int _2DCoor[3];
// this is the map formula
      _2DCoor[0] = static_cast<int>(globalCoordinate[0] / CReadBmp::m_Dx);
//2D x Coordinate

    _2DCoor[1] = CReadBmp::m_Ymax + 1 - static_cast<int>(globalCoordinate[1]
/ CReadBmp::m_Dy);//2D y Coordinate

    _2DCoor[2] = static_cast<int>(globalCoordinate[2] / CReadBmp::m_Dz +
0.5) +  CReadBmp::m_Zmin ; // the index of image

}


wenwu
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