Bindable Nodes


Bindable nodes are a special type of node in the sense that only one of each can be active at a certain type. Bindable nodes provide information about the environment and the user. The following nodes are bindable nodes:
  • Viewpoint: specifies the position of the user
  • NavigationInfo: specifies features of the user
  • Fog: adds atmosphere to the scene
  • Background: provides a sky, and background images that can enhance dramatically the scene.


  • When the scene is loaded the first of each of these nodes to be found becomes active, i.e. is bound (nodes within inlined files do not count). The bound nodes are put on the top of a stack. There is a stack for each type of node.

    When a node is bound it generates the boolean event isBound with the value TRUE.

    In order to bound a node, for instance to change the background, an event set_Bind with the value TRUE should be routed to the node. The newly bounded node goes to the top of the respective stack. The previously bound node sends an event isBound with value FALSE, and the newly bound node sends an isBound event with value TRUE.

    In order to unbind a node an event set_Bind with the value FALSE should be sent to the respective node. The unbounded node sends an event isBound with value FALSE and  is pushed from the top of the stack. The node which is now in the top of the stack becomes the active node, i.e. it becomes bounded, and it sends an event isBound with value TRUE.

    If a node which is not bound but is in the stack receives an event set_Bind with the value FALSE, the node is removed from the stack. If the node is not in the stack the event is ignored.