Hi John,
On 9 May 2012 15:52, John Kelso <ke...@nist.gov> wrote:
> Many thanks. This problem sure is beginning to smell like "driver and/or
> card" to me. I'd love to hear from other Linux users too.
I think there is probably a few issues going on here.
First up switching on/off subgraphs can cause problems on first
enabling a new subgraph in that OpenGL objects required to render the
subgraph may not have compiled and downloaded to the GPU so have to be
created, compiled and downloaded on the first frame that they appear -
this can cause a frame drop but it'll typically be just for the first
frame. The way to avoid this issue is to make sure you precompile the
whole subgraph prior to rendering. The OSG has a
osgUtil::GLObjectsVisitor written for the purpose of precompiling this
will be invoked in the realize of the graphics window - but will only
compile your subgraph if you have already assigned it to the view. If
you add you scene graph after realize you can invoke this
automatically for the next frame by calling
osgViewer::Renderer::setCompileOnNextDraw(true) for each viewer Camera
via:
osgViewer::Renderer* renderer =
dynamic_cast<osgViewer::Renderer*>(camera->getRenderer());
renderer->setCompileOnNextDraw(true);
If your NodeMask is set to 0x0 then the GLObjectVisitor won't traverse
the subgraphs so perhaps this might be causing problems, if so you
might need to use a draw callback to invoke your own GLObjectVistor
traversal with NodeVisitor::setNodeMaskOverride(uint) set so that the
compile traversal is able to ignore the 0x0 node masks during
traversal.
--
The odd frame rate cycling seen by Stephan is likely a whole different
issue related to the way the driver/os/OpenGL FIFO and the draw
dispatch are all interacting. Try disabling/enabling vsync to see if
that changes behaviour.
By co-incidence Today I'll be doing some work on using the new
ARB_sync functionality to sync frame loop, this should enable us to
control how many frames are dropped into the OpenGL FIFO and hold the
frame loop to be sync'd with vysnc so we don't end up over filling the
OpenGL FIFO and hopefully this will avoid the OpenGL FIFO blocking the
application periodically. I'll ping the list once I've checked this
functionality in.
Robert.
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