osg::TransferFunction1D* tf(new osg::TransferFunction1D());
tf->allocate(18);
tf->setColor(-10000,osg::Vec4( 1.0, 1.0, 1.0,1.0));
tf->setColor(-1e-6,osg::Vec4( 1.0, 1.0, 1.0,1.0));
tf->setColor( 0,osg::Vec4( 0.0, 0.0, 1.0,1.0));
Remark: The value -1e-6 may be added (falsely) because of a rounding error.
The attached fix prevents assigning NaN values to the image.
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