OpenSceneGraph CullVisitor::apply(Geode&) detected NaN - openscenegraph

Question

I am trying to use OSG for displaying some cubes on the screen.
at some runs it works perfectly but sometimes it does not display anything, just prints this in the virtual console:
CullVisitor::apply(Geode&) detected NaN,
depth=nan, center=(0 0 0),
matrix={
-1 0 0 0
0 0 1 0
0 1 0 0
-nan -nan -nan -nan
}
the reason why it sometimes works and other times doesn't is probably that the cubes are positioned randomly, and some positions apparently do not work.
The question is:
what does it mean and how do I avoid it?
note: you may be tempted to downvote this question right away, but please note that google only provides miserably useless results and I see no way of solving this problem other than asking for help.

Answer 1

Did you search your code for the usual list of suspects?
see:
http://en.wikipedia.org/wiki/NaN#Operations_generating_NaN
It's also possible you're trying to cull your scene before an object is fully initialized (no position yet) - the fix would be to not add it to your scene until you've initialized it. But we're really just guessing unless you post some of your relevant code.

Answer 2

The point is the view matrix is not correctly initialized.
Perform a check and, if the view matrix is invalid, replace it by the identity matrix:
// if the view matrix is invalid (NaN), use the identity
osg::ref_ptr<osg::Camera> camera = _viewer->getCamera();
if (camera->getViewMatrix().isNaN())
camera->setViewMatrix(osg::Matrix::identity());