[osg-users] how to zoom in and out in orthographic projection

[Rahul Jain]

Hi Mew,
For the perspective projection i am moving the eye (camera) in negative
z direction for zooming in to the scene. For the orthographic projection
i am reducing the viewport (frustum) for zooming in to the scene.

RJ

Mike Weiblen wrote:
> Could you pls answer Paul's question of "how did you implement the
> zoom in your projection"?
> What exactly do you mean by "zoom" in an orthographic projection?
>
> -- mew
>
>
>
>
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> On Sun, May 4, 2008 at 9:28 AM, Rahul Jain <rahulj at darshan3d.com> wrote:
>   
>> Hi Paul,
>>  Thanks for the answer and sorry for being so desperate last time.
>>  We tried the approach you mentioned by writing a node visitor and
>>  setting the range node(PIXEL_SIZE_ON_SCREEN)  for  LOD nodes. But the
>>  effect i am getting is completely opposite, as i zoom in the high
>>  resolution data disappears and when i zoom out high resolution data is
>>  loaded. I tried the same thing with perspective projection also and i am
>>  getting the same effect. I am not able to understand what am i doing wrong.
>>  cheers
>>  RJ
>>
>>
>>
>>
>>  Paul Melis wrote:
>>  > Posting your question just once and waiting a bit for an answer would be
>>  > nice...
>>  >
>>  > santosh wrote:
>>  >
>>  >> how to do zoom in and out in orthographic projection?
>>  >> As I zoom in  the detailed geometry should be loaded .
>>  >>
>>  >> Right now I am scaling the  geometry but in this method the details are
>>  >> not getting loaded.
>>  >>
>>  >
>>  > How did you implement the zoom in your projection, just by changing the
>>  > viewport to be smaller? In that case the distance from the viewpoint to
>>  > your objects doesn't change and therefore the same LOD-level will
>>  > continue to be selected, as the default RangeMode for an osg::LOD is
>>  > DISTANCE_FROM_EYE_POINT. Changing it to PIXEL_SIZE_ON_SCREEN should make
>>  > your LODs switch to more detailed models if you zoom in.
>>  >
>>  > Paul
>>  > _______________________________________________
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>>  >
>>  >
>>  >
>>
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