[osg-users] Slow optimization and OpenFlight

[Robert Osfield]

HI Andreas,

I haven't had a chance to dig further.

One curious thing I noticed is that when I enabled verbose debug
output there was lots of buffer objects being created and destroyed
during the optimisation step.  osg::Drawable now assigns
VetextArrayState and VBO's by default for osg::Geometry - this is
required to make VAO support possible.  The large number of these
operations suggest lots of creation and merging of osg::Geometry for
this dataset.  There is chance tthat this change alone may be causing
a performance slow down.

However, I don't think creation/deletion of osg::Geometry is the crux
of the problem, and may not even be the optimization step - it could
well be down to the nature of the scene graph being created by the
OpenFlight plugin for this dataset.  I suspect the source data is
stored in a way that is really inefficient to handle for real-time.
It might be that the OpenFlight plugin just isn't handling the data
well.

As a general rule, running the Optimizer is a last resort for fixing
really bad datasets, ideally datasets should be created in a form that
is appropriate for decent performance right from the start.

Robert.