Hi, I've been very happy developing using OSG but unfortunately, even “simple” graphics¹ tend to result in very low performance on Intel GPUs (which happen to be very common on wide-spread desktops and laptops); while I ACK that well, there are better GPUs available, it'd still be nice to be able to somehow run the app I've developed on other machines without having to upgrade them, so I've been wondering whether there are some guidelines to help getting things “easier” on the GPU.
Random thoughts:
- dimensions/resolutions (maybe some “native” screen/window size are
better than others in order to limit resizing overhead)?
- texture blending modes (how transparency is handled, etc.)?
- level of detail (there is even osg::LOD for that)?
- use a tree-like scene-graph (rather than a flat one) to ensure osg
will do its job properly?
- checking compositing on X's side (forgot to mention: running Linux
machines)? acceleration type (EXA et al.)?
I know there's also the “stats” display that might be of some help,
and it indeed shows that most of the time is spent during “Draw”.
I should mention I've tested with both OSG 2.4 and 2.8 on both
desktops and laptops, and it looks like versions don't have much
impact on performances, only GPUs do. (To give an idea, I'm at
100-150+ FPS with Nvidia, limited to either 60 or 75 via vblanc sync,
and around 10-15 FPS with Intel.)
Hardware is like Intel Core 2 Duo, 2 GB RAM. The application isn't
eating more than a few MB so RAM clearly isn't the bottleneck. A
single CPU out of 2 seems to be used, around 50%, so that probably
isn't the bottleneck either.
So, if you have any rules of thumb to share about how to get a better
framerate on low-end GPUs, I'll be very pleased to read them. :)
Cheers,
--
Cyril Brulebois
Details:
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¹: That is some dozens/hundreds of geometrical forms (boxes, spheres
with uniform textures), a few of them being transparent somehow,
only colours/sphere radius/positions of some spheres change; using
a single camera; and with some texts as overlay, HUD-like.
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