[osg-users] Big performance hit when using shadows

Robert Osfield robert.osfield at gmail.com
Wed Mar 25 05:47:26 PDT 2009


Hi Roger,

I haven't seen such great performance hits in my own testing, but I haven't
pushed things too hard on the shadows front so perhaps I just haven't tested
hard enough :-)

At your end you need to look into what the performance bottleneck is, bring
up the on screen stats and the look at the sizes of the update, cull, draw
and GPU draw costs, comparing between the scene with shadows and the one
without.

Also try the standard osgshadow example:

   osgshadow -4 --lispsm

For this scene I get a solid 60Hz, update and cull and GPU draw are all
pretty low, but curiously the draw dispatch is locked out at 16ms which
suggests that the draw is blocking on the OpenGL FIFO.

Robert.

2009/3/25 Roger James <roger at beardandsandals.co.uk>

>  Hi,
>
> I have been doing some tests using the minimal draw bounds LISPSM
> implementation. I find that when the shadow node is inserted in the graph my
> frame rates go from 60 fps (vsync) down to less then 10 fps. I have
> verfified this on a number of different machine configurations with varying
> levels of graphic card capability.  The original scene graph uses fixed
> pipeline functionality only, so the the introduction of the shadow node is
> turning on programmable functionality and some extra traverses of parts of
> the scene graph.
>
> Is anyone else experiencing these levels of performance hit.
>
> I am wondering if there is some kind of fundamental bottleneck in the way
> my graph is constructed that is really being exacerbated when the
> programmable pipeline is active. Is this a possibility? What sort of things
> should I be looking for?
>
> Any help or comments gratefully received!
>
> My apologies for the vagueness of the question, but I do not know where to
> start.
>
> Roger
>
>
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>
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