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

[Rahul Jain]

Hi Ralph,
Basically the object in my case is a terrain generated by using VPB. I
checked for the LOD ranges and they are  Min : 1408.8Max : 1e+10 and Min
: 0 Max : 1408.8. Reordering them makes the terrain disappear.
RJ


Ralph Kern wrote:
> hi Rahul,
>
> did you take care of the inverse effect of distance and pixel size?
>
> An object far away (large distance) has a small pixel size on screen.
> So you perhaps have to reorder your LOD range.
>
> regards Ralph
>
> Rahul Jain schrieb:
>> 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
>>> _______________________________________________
>>> osg-users mailing list
>>> osg-users at lists.openscenegraph.org
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>>>
>>>
>>>
>>>   
>>
>
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