[vtkusers] vtkImageActor and scaling

[David Gobbi]

Hi Mark,

The camera method you want is SetParallelScale(), it sets the height of
viewport when ParallelProjection is on.

  David

On Mon, Nov 29, 2010 at 8:24 AM, endlosschleife1 <
endlosschleife1 at googlemail.com> wrote:

> Hi all,
>
> I'm a bit confused about how cameras are initialized. I would like to scale
> a 2D image (scale a DICOM image to best fit a viewport size). I first did
> this via vtkImageResample and that works fine, but now I would like to try
> this with accelarated scaling and so I wanted to do that as part of the
> visualization pipeline (I hope that means that it is actually using OpenGL).
> I replaced my original vtkActor2D/vtkImageMapper with a vtkImageActor. The
> following works (pseudo code):
>
> Variant 1:
> - add imageActor to renderer, and renderer to renderwindow. Then call
> Render() on renderwindow.
> -> The image displays as expected in the original size.
>
> Variant 2:
> - same as in Variant 1 (including Render() call)
> - renderer->GetActiveCamera()->ParallelProjectionOn()
> - renderer->GetActiveCamera()->Zoom(zoomFactor);
> -> The image displays with the desired scaling.
>
> But variant 2 only works because I called Render() first. I assume this
> somehow initializes the camera of the renderer with exactly the attributes
> that I need, but when I call GetActiveCamera without rendering first this
> (just calling the getter-method) will already) will give a different result
> (in my case a grey box in the upper right corner of the viewport). I'm now
> about to reverse engineer the camera settings after variant 1 was executed
> and set all the camera attributes to the desired initial values (position,
> viewUp, clipping range etc.), but I'm wondering if I'm just missing the more
> appropriate and convenient way to do this (after all the vtkImageActor seems
> to be all about convenience).
>
> Thank you.
>
> Mark
>
>
>
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