vtkInteractorStyleTrackballCamera renders unnecessarily

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vtkInteractorStyleTrackballCamera renders unnecessarily

Christoph Kolb
Hi All,

In several events defined in vtkInteractorStyleTrackballCamera which are
rerendering the scene (zooming, panning...), an additional render call
is issued within StopState() at the end of an Interaction.
For example if the mouseWheelEvent is processed, the 3D scene is zoomed
for one step but two consecutive render calls are started. There seems
to be no difference between both renderings.
Can you please explain the need for the rendering in StopState()? Is it
possible to avoid the second rendering without subclassing the
vtkInteractorStyle?

Thank you for your help!

Regards
Christoph
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Re: vtkInteractorStyleTrackballCamera renders unnecessarily

David Cole-2
> ... an additional render call
> is issued within StopState() at the
> end of an Interaction.

The second-to-last rendering is done while the interactor is still in
an interactive state, and will therefore possibly be at a lower
resolution/level-of-detail for volume rendering, or for level of detail
actors. (Fast, interactive speed renderings, but possibly of lower
quality...)

The last rendering, issued during the StopState call, is made after the
interactor is taken out of its interactive state, and will therefore be
a full rendering, at highest level of detail. (Best quality rendering
possible, but might be much slower...)

If you are not taking advantage of any fast interactive renders with
any actors in your scene, then you will not appreciate the difference.
But for those of us who use the level of detail functionality, with
lower quality fast renderings when interacting, and higher quality
slower renderings when not interacting, *both* Render calls are
definitely required.


HTH,
David C.

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Re: vtkInteractorStyleTrackballCamera renders unnecessarily

Christoph Kolb
Thank you for your reply!
We are actually not using the level of detail rendering and I see now
the advantage of the two rendering steps. But still, in the case of a
mousewheel event both steps are performed directly consecutively. This
is what makes zooming particularly slow for us, because using the
mousewheel triggers several events with two renderings each.

Is this also fixed if we would use the level of detail rendering ? Or
would it be best in our case to override the TrackballInteractor?

Regards
Christoph

On 04/23/2014 05:11 PM, David Cole wrote:

>> ... an additional render call
>> is issued within StopState() at the
>> end of an Interaction.
> The second-to-last rendering is done while the interactor is still in
> an interactive state, and will therefore possibly be at a lower
> resolution/level-of-detail for volume rendering, or for level of detail
> actors. (Fast, interactive speed renderings, but possibly of lower
> quality...)
>
> The last rendering, issued during the StopState call, is made after the
> interactor is taken out of its interactive state, and will therefore be
> a full rendering, at highest level of detail. (Best quality rendering
> possible, but might be much slower...)
>
> If you are not taking advantage of any fast interactive renders with
> any actors in your scene, then you will not appreciate the difference.
> But for those of us who use the level of detail functionality, with
> lower quality fast renderings when interacting, and higher quality
> slower renderings when not interacting, *both* Render calls are
> definitely required.
>
>
> HTH,
> David C.
>
>

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