[vtkusers] How to set camera so that the image fill up the screen horizontally

[David Gobbi]

Hi Chris,

The ResetCamera method is only meant to be approximate.
Do not use it if you need to exactly fit an image to the window,
that is not what it is for.

To fit an image to the window, compute the height of the
image, and use that to set the ParallelScale.  Or if you need
to fit the width, then use the aspect ratio to compute the
ParallelScale you need from the width.

If you need to do the same thing for perspective, then you
can use a bit of trigonometry and compute the ViewAngle
that is needed to exactly fit the image.

  - David


On Wed, Mar 9, 2011 at 10:31 AM, chrisyeshi <chrisyeshi at gmail.com> wrote:
> So, I need the image the fit the width of the screen. It doesn't matter if
> the image is too high for the screen.
> It needs to be done both in Parallel and Perspective modes.
>
> I have read the vtkRenderer::ResetCamera() method. There are two places I
> don't understand.
>
> 1)   double w1 = bounds[1] - bounds[0];
>  double w2 = bounds[3] - bounds[2];
>  double w3 = bounds[5] - bounds[4];
>  w1 *= w1;
>  w2 *= w2;
>  w3 *= w3;
>  double radius = w1 + w2 + w3;
>
> Why do we get the radius this way? What is it?
>
> 2) this->ActiveCamera->SetParallelScale(radius);
>
> Why is the radius the ParallelScale? And why there is no perspective zoom
> settings?
>
> Thanks in advance!
>
> --
> View this message in context: http://vtk.1045678.n5.nabble.com/How-to-set-camera-so-that-the-image-fill-up-the-screen-horizontally-tp3415966p3415966.html
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