To simplify implementation there are two base Drawables that can be used as parent classes for derivation:
osg::Drawable and
osg::MaterialDrawable.
The simple Drawable is the root class of all renderable NodeCores. It contains the Statistics element descriptors that can be used to collect information about renderable geometry.
The MaterialDrawable contains a pointer to a
osg::Material that is used to render the node. It is abstract, but the base for most renderable classes.
