[vtkusers] vtkCamera::Elevation(...)

[John Platt]

Hi Matthias,

Elevation() rotates the camera about the cross product of the negative
of the direction of projection and the view-up vector centered on the
focal
point. Singularities exist at the north & south poles where the view-up
vector becomes parallel to the view plane normal. This can be avoided by
orthogonalising the view-up vector after each Elevation() but this flips
direction at the poles and the camera motion is not continuous. The
elevation is therefore best restricted to (-90, +90).

HTH

John.
-----Original Message-----
From: vtkusers-bounces+jcplatt=lineone.net at vtk.org
[mailto:vtkusers-bounces+jcplatt=lineone.net at vtk.org] On Behalf Of
Matthias Langer
Sent: 24 August 2005 17:15
To: vtkusers at vtk.org
Subject: Re: [vtkusers] vtkCamera::Elevation(...)

Matthias Langer wrote:

> I'm a complete newbe in using the vtk library. So my question may be 
> trivial ...
> However: I use the c++ api of vtk-4.2.6. When trying to rotate a cone 
> by somthing like
>
> unsigned count = 0;
> while(true)
> {
>     p_renderer->GetActiveCamera()->Elevation(1);

        // of course render
       p_renderWin->Render();
       /////////////////////////////

>    ++count;
> }
>
> the image starts to flicker the moment count reaches 90.
>
> Maybe anybody here in the list can explain me why ...
>
> Thanks,
> Matthias Langer
>
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