[osg-users] suggestions for performance using shadowed scenes

Joseanibal Colon Ramos jcolon at email.arc.nasa.gov
Tue Sep 2 13:52:38 PDT 2008


Hello Jean,

Thanks so much for the tips. For reference I am working on a 64-bit
Linux-86, with Nvidia Quadro 3450, and OSG 2.6.0. I don't think I am being
affected by exuberant resolutions on shadow map, since I am using whatever
is osg default (i'm not setting any resolutions, except the graphic
contexts). I don't know if my driver is rolling back to software
emulation, but I'll update my graphic card driver, to see if it helps.
Anyways, I started looking into PSSM by looking at the OSG osgshadow
example. The frame-rate gets worse using PSSM in that case. Are there any
settings that I should set to improve performance when making use of PSSM?
Thanks again!

-Jose


On Thu, August 28, 2008 5:34 pm, Jean-Sébastien Guay wrote:
> Hello Jose,
>
>> I have a HUGE terrain which uses paged LOD.
> ...
>> Using ShadowTexture technique drops my frame-rate from 60+ to
>> low 30's to high teens.
> ...
>> Finally, using ShadowMap puts OSG on its knees at ~6 fps.
>
> You neglected to tell us what kind of hardware you're using, and what
> version of OSG.
>
> I've only seen ShadowMap do so bad in two cases:
>
> 1. when the video card driver was falling back to software emulation for
> FBOs (for the shadowmap render to texture)
>
> 2. when the shadow map texture resolution is higher than the video card
> can support (most of the time, 4096x4096 or 8192x8192 is the limit on
> recent video cards)
>
> Perhaps one of those could be your problem?
>
> If you have a large terrain, using ShadowMap with a very large texture
> size is not a solution. Other shadow techniques are more adapted to
> large scenes, such as PSSM or LiSPSM (the former is already in OSG, the
> latter should be integrated soon).
>
> Hope this helps,
>
> J-S
> --
> ______________________________________________________
> Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com
>                                 http://www.cm-labs.com/
>                          http://whitestar02.webhop.org/
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