Hi Julien,
Thanks for porting the changes to svn/trunk.
I have now merged the changes with svn/trunk, albeit with a some tweaks to
parameter usage and addition/removal of spacing to make the code more
consistent with the rest of the OSG and more readable. I have also updated
the code to better use the new GLExtensions access, and put the new
serializer additions within a version checked block whilst updating the
SO_VERSION to pick up on this new version of the API.
I have reviewed the osgtransformfeedback example and have checked it in
with a few formatting tweaks but otherwise left as is. I'm not entirely
happy with the way the example is constructed. I'm hopeful that a cleaner
way of integrating the transform feedback functionality is possible but
don't yet have enough familiarity with extension to feel comfortable diving
in a re-factoring.
My initial feeling is that osgtransformfeedback example could be improved
by:
from a C++ perspective the C pointers usage is something I feel needs
removing as this the way it's done in the example could lead to
other users copying poor C++/OSG practices
There subclassing from osg::Geometry that look to me like they would be
better replaced with something more generic, perhaps using a
DrawCallback and usage of osg::StateSet.
The draw order isn't controlled in the example, so it would there is
nothing stopping the two osg::Geometry being passed to OpenGL in
the wrong order. The OSG has lots of different ways to control render
order, but which is most appropriate will depend on the needs of
the application. One can do high level control via placing the
pre-render stage into a subgraph below an osg::Camera and set it's
RenderOrder to pre render, a lower level way would be to use the
StateSet::setRenderBin("RenderBin", -1) to make sure it renders first.
The Uniform callback seems a bit overkill too - one can compute time
based variables all the vertex shader, this would be simpler and
faster.
I will leave further refinement of this example till others or yourself
chip in, or for when I get a chance to reflect more on how to better set up
transform feedback codes in the scene graph. The important thing right now
is we now have some working transform feedback code and example that can be
built upon going forward.
Thanks,
Robert.
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