From Roland Smeenk, "Attached you will find some changes to the dae plugin to improve light support.
-Changed the addition of lights to add the lightsource directly into the scenegraph (instead of below a switch node)
-All added lights are enabled in the root stateset and replace the head- or skylight.
(if no lights are available the head- or skylight will remain active)
-Ambient in osg::LightModel? is zeroed out. All ambient now comes from separate ambient only light sources.
-Lights can now be written properly
-Replaced strings by constants defined in the Collada DOM"
