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

[朱文武]

Darshan, thanks very much.  i will try it.

wenwu

2010/4/28 Darshan Pai <darshanpai at gmail.com>

> Now i get it . You need the projection . Try the vtkCoordinate class ,
> there is an example in the VTK Wiki. This will give you the answer in
> viewport coordinates.
>
> Regards
> Darshan
>
>
> On Tue, Apr 27, 2010 at 4:55 AM, 朱文武 <cool.wenwu at gmail.com> wrote:
>
>> 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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>>>
>>
>>
>> --
>> 祝
>> 工作愉快，身体健康！
>>
>
>


-- 
祝
工作愉快，身体健康！
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