Hi Jan,
On Wed, 2005-09-14 at 19:42 +0200, Jan Wurster wrote:
> Dear list,
>
> Since a bit of time, I'm running into strange performance problems
> with OpenSG. For me, it looks like graphics card memory being eaten up
> quite fast and the system swapping in from main memory, but I can't
> confirm that since - correct me if I'm wrong - there's no way to
> determine the actual amount of graphics card memory used.
Nope, there isn't, at least not easily. There are performance tools from
the manufacturers that can do it, but not many and not in a general way.
> I've put a testfile up:
>
> http://www.syrophenium.de/files/tmp/opensg/2bmw.bin (sorry, it's quite
> big at 130something mb ..)
I tried loading that but couldn't. Can you save that as an .osb? .bin is
tied to a specific OpenSG version and is very brittle, osb is more
tolerant.
> On big iron complete with a quadro fx 3400 graphics card this renders
> at a whopping 0.9 to 2 fps when viewed full. If I let the view frustum
> gradually cull parts of the geometry away, it suddenly jumps up to 60+
> fps. The geometry isn't too complex and I wouldn't consider the amount
> of texture data (opensg shows 34 megs) as a challenge for a 256 MB card.
By default OpenSG uses Display Lists for everything, those will rpobably
eat up more memory.
> I can render the same situation with different scenegraphs (perf**mer,
> OpenSceneGraph) at 20 fps on a much lower-spec system and at near 40 fps
> on the system mentioned above.
Not sure what they are doing.
> Perhaps somebody could confirm this? It seems that both windows and
> linux suffer from this problem, however I mainly tried linux. I've used
> stock OpenSG optimized libs 1.4.0 and 1.6.0 together with unmodified
> osgSceneViewer, no FSAA, no anisotropic mapping (if enabled, these make
> things worse).
>
> What surprises me the most are the sudden changes in fps, the trigger
> in between about 1 fps and 60 fps seems to be only at < 50 triangles
> drawn more or less.
That sounds very much like memory thrashing.
> nvidia drivers used are 77.56 for win32, 7676 for linux (older driver
> versions exhibited the same behaviour, though).
>
> Could this be attributed to non power-of-two textures? I though these
> would now be supported (and they do work out of the box in opensg), but
> for the other rendering systems I do some re-scaling on the textures.
I don't think so. They are supported (and have been forever), but by
default OpenSG scales them up to the next power of two, we don't use the
NPOT textures as they have some constraints on most hardware.
Yours
Dirk
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