Hi Fred,
maybe have a look at this:
http://www.bricoworks.com/articles/stateset/stateset.html
I remember something like that state equality is only tested using
pointers and not internal data. So, maybe you'll have to explicitly
share state (that getOrCreate won't do).
Sorry I can't actually answer from more experience.
jp
On 06/04/11 15:14, Fred Smith wrote:
Hi,
I have a very large scene graph where I have many geodes.
Each of this geode has a stateset with a GPU program defined on it,
contianing a vertex and a fragment shader.
The GPU program instance is unique for my whole application - I am
not recreating the program over and over again for every geode. This
would be an easy, silly mistake.
I have done performance tests and having a StateSet assigned to each
Geode causes a MASSIVE performance drop. For a given model,
containing thousands of geodes, the framerate goes from 64 to 30 fps
just when you call getOrCreateStateSet on every geode, causing state
to be created on each individual geode.
An OpenGL trace shows that OSG is clever enough to avoid calling
glUseProgram(id) / glUseProgram(0) in between every geode being
rendered. Declaring the GPU program once, on the topmost graph node,
and not on every geode, results in the same GL trace, with no
performance degradation. This suggests OSG is very heavily using the
CPU to 'diff' the state changes across geodes.
Is there a way, maybe by fiddling with OVERRIDE/PROTECTED flags, to
improve the way OSG handles state changes, in order to keep good
performance?
Cheers, Fred
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