BillBoard Node

Billboard is a special grouping node. All children nodes will turn to face you, as a sunflower to turns to face the sun as it moves. The children nodes will rotate in a user defined axis.

The following fields are present:

children which contains all the nodes included in the group.

axisOfRotation specifies a 3D vector which will be used for the rotation. If a null vector is specified, (0,0,0), then the object rotates to always face the user.

bboxCenter specifies the center of a box that encloses the nodes in the group. The value for this field is a 3D point.

bboxSize specifies where the size of a box that encloses the nodes in the group. By default this field has a value of -1 -1 -1, which implies that no box is defined. The values for this field must be greater than or equal to zero. If the children nodes do not fit inside the box defined the results are undefined.

The latter two fields are optional. They can be used by the browser for optimization purposes.

Syntax:

Billboard {

children [ ]

axisOfRotation 0 1 0

bboxCenter 0 0 0

bboxSize -1 -1 -1

}

If an axisOfRotation different from the null vector is specified then there is one case where results are undefined, this occurs when the user is aligned with the axis of rotation.