[osg-users] Need advice for performance tweaks

Robert Osfield robert.osfield at gmail.com
Fri Nov 27 10:08:11 PST 2009


Hi Shayne,

You can use the osgTerrain::Terrain::setSampleRatio(float) to cut down
geometry complexity alone, and use osg::Camera::setLODScale(float) to
make the selection of LOD's more aggressive.

One thing you could do is implement an adaptive setting of
LODScale/SampleRatio by looking at the frame time of the previous
frame and it is looks close to breaking frame change the ratio's to
reduce the overhead, this way you might be able to get away with
better visuals when the hardware can cope such as looking downwards,
and only go for low high res visuals when you are looking at a shallow
angle to the horizontal when lots of tiles will be in view.

Robert.

On Fri, Nov 27, 2009 at 6:00 PM, Tueller, Shayne R Civ USAF AFMC 519
SMXS/MXDEC <Shayne.Tueller at hill.af.mil> wrote:
> All,
>
>
>
> I have a need to run my OSG app on some "marginal" hardware (single CPU with
>
> a GeForce 4800 for example) while still maintaining some decent frame rates
>
> (around 30fps). I want to use the same terrain database (built with VPB with
> the
>
> -terrain option) if possible.
>
> I've used the setSampleRatio() method in the osgTerrain class and culling
>
> backfaces to thin out the geometry with some success but I'm still not where
>
> I need to be. As a result, I'm wanting to optimize a bit more if possible.
>
> Does anyone have any suggestions for particular settings in the
>
> databasepager or pagedLOD that I could try to achieve better performance?
>
> I'm willing to sacrifice database fidelity to maintain decent frame rates if
>
> I must.
>
>
>
> Thanks for any suggestions in advance.
>
> Shayne
>
>
>
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