[osg-users] Update Optimization

Alan Harris alanosg at resoft.co.uk
Mon Jul 7 04:44:13 PDT 2008


Hi

I ran into the same speed problem and solved it using a height field. As 
I generate my own terrain and had a full resolution height field 
available it was the simplest and best solution.

Alan Harris

Robert Osfield wrote:
> Hi Joachim,
>
> One can use a HeightField for terrain, and have an O(1) look up into
> the height field, this is very fast, so it's a useful tool if it's
> appropriate to your problem.  However, it's not a general purpose
> solution, and not one that come from free when you create a database -
> you'd have to go an populate the height yourself from your source
> database, and if you are lucky this might just be a height field in
> the first place.
>
> More typical a database is polygonal based, using LOD's or PagedLOD,
> with lots of polygonal culutral data in it.  The data might even be
> whole earth database, so not even flat.  For this wide range of data
> the best we can do is make the standard intersection routines that
> work on polygonal dataset work faster, as this is just what I'm
> working on.  It won't get as fast as using a HeightField, but it'll
> close the gap substantially.
>
> Robert.
>
> On Mon, Jul 7, 2008 at 10:27 AM, Joachim E. Vollrath
> <vollrath at vis.uni-stuttgart.de> wrote:
>   
>> Hello to all in this thread,
>>
>> I have absolutely no terrain expertize and I don't know how OSG implements
>> this, but just out of curiosity:
>>
>> Suppose you have terrain elevation stored in an image (in CPU memory) as
>> well as normals.
>>
>> Given the 2d coordinate of an entity in elevation image space - wouldn't
>> calculating the height and normal (resp. orientation) merely reduce to a
>> bilinearly interpolated lookup in that image?
>>
>> I may be wrong, but shouldn't it be possible to get interactive update rates
>> that way?
>>
>> Best,
>> Joachim
>>
>> John Burgess wrote:
>>     
>>> Hi all,
>>> My viewer needs to support at least 400 entities running at 30 Hz.. My
>>> entities are all moving tanks and I need to clamp them to the terrain using
>>> an update call back in every frame, the frame rate will drop to 3 Hz when I
>>> load 300 tanks with the update cycle taking up a huge amount of time. How
>>> can I achieve 30 Hz for 400 entities and yet be able to clamp them to the
>>> terrain?
>>> Thanks,
>>> John
>>>
>>>
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
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>> --
>> Dipl. Inf. Joachim E. Vollrath
>> Visualisierungsinstitut der Universitaet Stuttgart (VISUS)
>> web:   http://www.vis.uni-stuttgart.de/~vollrajm/
>> mail:  vollrath at vis.uni-stuttgart.de
>> phone: 49.711.7816.403
>> fax:   49.711.7816.213
>>
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>>     
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