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

[Matthias Langer]

Matthias Langer wrote:

> John Platt wrote:
>
>> 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
>>
>>  
>>
> Thanks very much for your tipp; I thought that the view up vector is 
> updated automatically when calling Elevation(...). Following your 
> tipp, I wrote a routine which recalculates the the view-up vector 
> after Elevation(...), using the last camera position, the focal point 
> and the actual camera position. This worked fine and furthermore seems 
> complety contineous.

If I had found ' void vtkCamera::OrthogonalizeViewUp()' I bit earlier, 
maybe I wouldn't have implemented this routines myself :-).

> Matthias Langer
>
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