Billboard {
MFNode children [ ] # {node, PROTO}
}
A Billboard node contains children nodes that rotate and translate automatically to follow the viewpoint and face it. It could be use to display information in the main view regardless of the position and orientation of the viewpoint, like a cockpit or the score of a soccer match.
It is otherwise similar to a Group node.
When a node is added to the children list of a Billboard, it is placed in the world relatively to the viewpoint position and orientation.
To see the newly added nodes, they should be translated positively along their x-axis.
The objects contained in the Billboard are not visible by Cameras.
Shapes that are inside a Billboard cannot cast or receive shadows.