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

[朱文武]

hey, Darshan, thanks for your kind help. From my point of view, the function
of the GetSelectionPoint() of vtkAbstractPicker is "get the selection point
in screen (pixel) coordinates".   And my condition is that user can pick
point  on the 3D model(surface), then i need to calculate the 2D coordinate
of this point. The mean of 2D coordinate is the 3D point projected into
original 2D image.  So, i think the point coordinate which i want  does not
equalize the screen point coordinate. But, thank your all the same.
Could anyone provide suggestion? thanks very much!



On Tue, Apr 27, 2010 at 3:12 AM, Darshan Pai <darshanpai at gmail.com> wrote:

> I think GetSelection() should be the function of choice
>
> On Mon, Apr 26, 2010 at 10:17 AM, 朱文武 <cool.wenwu at gmail.com> wrote:
>
>> 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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