Re: [wxVTK] screen coordinates to world coordinates

[Nigel N. <nN...@au...>]

Hi Andres,
Thanks for the details.  I'll try setting up such a pipeline
myself this weekend, then let you know what I find!
Nigel

-----Original Message-----
From: Andres Munarriz [mun...@gm...]
Sent: Thursday, 10 August 2006 8:02 AM
To: Nigel Nunn
Subject: Re: [wxVTK] screen coordinates to world coordinates


Hi Nigel,

Thank you for your reply.  I've loaded a single 2d DICOM image to a
vtkImageViewer2.  I wish to allow a user to double click a point on
this image (slice) and draw a "marker" in this case a sphere on the
point the user double clicked.  Later down the pipeline I will be
using this point as a seed for a connectivity filter.

I've created my own wxVTKInteractor derived class (ie.
MyVTKRenderWindowInteractor) where I've defined my own EVT_LEFT_DCLICK
handler (ie. void
MyVTKRenderWindowInteractor::OnButtonDouble(wxMouseEvent& p_Event) ).

I can obtain two sets of "display" coordinates (wx coordinates); one
by calling the p_Event.m_x, p_Event.m_y property or by calling the
wxVTKInteractor GetEventPosition method.

I'll pass whichever coordinate set to a vtkWorldPointPicker through
the Pick method
(ie.
 vtk_pointPicker->Pick(double(eventPosition[0]), double
(eventPosition[1]), 0.0, vtk_windowRenderer);
)

however when I retrieve the picked coordinates using the
vtk_pointPicker->GetPickPosition(pointCoordSet); call the coordinates
returned are not the coordinates I expect.  The x values are OK but
the Y coord is wrong.

Could you please help me?


Regards,
Andres


On 8/9/06, Nigel Nunn <nN...@au...> wrote:
>
>
> Andres Munarriz <mun...@gm...> wrote:
>
> > > Has someone come across the need of converting screen "display"
> > > corrdinates (ie. wxEvent ._x, ._y) to VTK world coordinates?
> > > I've read about a get event method in the VTKRenderWindowInteractor
> > > but wxVTKRenderWindowInteractor doesn't seem to support this method.
> > > If someone can help it'll be greatly appreciated.
>
> ...
>
>
> > I'm using the interactor->GetLastEventPosition(&event_x, &event_y);
> > method. event_x and event_y are both integers.
> >
> > Am I using the wrong method?
>
>
> Hi Andres,
>
> From file <vtkCoordinate.h>:
>
> The coordinate systems in vtk are as follows:
>
>   DISPLAY -             x-y pixel values in window
>   NORMALIZED DISPLAY -  x-y (0,1) normalized values
>   VIEWPORT -            x-y pixel values in viewport
>   NORMALIZED VIEWPORT - x-y (0,1) normalized value in viewport
>   VIEW -                x-y-z (-1,1) values in camera coordinates. (z is d=
epth)
>   WORLD -               x-y-z global coordinate values
>   USERDEFINED -         x-y-z in User defined space
>
>
> First question is what would you like to do?  Are you trying to convert a
> wxWindow "pick" position to vtk "world" or "viewport"?  Or are you trying=
 to
> go the other way, i.e. from Vtk to Wx?  Can you describe when and how you
> get the source coordinates, and what you would like to do with the target
> coordinates?
>
> A test for most possible conversions can be found here:
>
>   /VTK/Rendering/Testing/Cxx/otherCoordinate.cxx
>
>
> Nigel

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