XdkWrl: Billboard Class Reference

6.6 Billboard

The Billboard node is a grouping node which modifies its coordinate system so that the Billboard node's local Z-axis turns to point at the viewer. The Billboard node has children which may be other children nodes.

The axisOfRotation field specifies which axis to use to perform the rotation. This axis is defined in the local coordinate system.

When the axisOfRotation field is not (0, 0, 0), the following steps describe how to rotate the billboard to face the viewer:

Compute the vector from the Billboard node's origin to the viewer's position. This vector is called the billboard-to-viewer vector.
Compute the plane defined by the axisOfRotation and the billboard-to-viewer vector.
Rotate the local Z-axis of the billboard into the plane from b., pivoting around the axisOfRotation.

When the axisOfRotation field is set to (0, 0, 0), the special case of viewer-alignment is indicated. In this case, the object rotates to keep the billboard's local Y-axis parallel with the Y-axis of the viewer. This special case is distinguished by setting the axisOfRotation to (0, 0, 0). The following steps describe how to align the billboard's Y-axis to the Y-axis of the viewer:

Compute the billboard-to-viewer vector.
Rotate the Z-axis of the billboard to be collinear with the billboard-to-viewer vector and pointing towards the viewer's position.
Rotate the Y-axis of the billboard to be parallel and oriented in the same direction as the Y-axis of the viewer.

If the axisOfRotation and the billboard-to-viewer line are coincident, the plane cannot be established and the resulting rotation of the billboard is undefined. For example, if the axisOfRotation is set to (0,1,0) (Y-axis) and the viewer flies over the billboard and peers directly down the Y-axis, the results are undefined.

Multiple instances of Billboard nodes (DEF/USE) operate as expected: each instance rotates in its unique coordinate system to face the viewer.

Subclause 4.6.5, Grouping and children nodes, provides a description of the children, addChildren, and removeChildren fields and eventIns.

The bboxCenter and bboxSize fields specify a bounding box that encloses the Billboard node's children. This is a hint that may be used for optimization purposes. The results are undefined if the specified bounding box is smaller than the actual bounding box of the children at any time. A default bboxSize value, (-1, -1, -1), implies that the bounding box is not specified and if needed shall be calculated by the browser. A description of the bboxCenter and bboxSize fields is contained in 4.6.4, Bounding boxes.

Constructor & Destructor Documentation

Billboard ( const char * name = "" )

Construct a node with all its fields set to default value, which is equivalent to the code below:

  axisOfRotation.setXYZ(0,1,0);
  bboxCenter.setXYZ(0,0,0);
  bboxSize.setXYZ(-1,-1,-1);

Member Function Documentation

wrl::Node * duplicate ( std::map< const Node *, Node * > & ) const [virtual]

Implements Node.

wrl::Node * duplicate ( ) const [virtual]

Returns a deep copy of this node, that is a fully independant node with all children (if any) also copied. This is mainly useful for instanciating protos.

Implements Node.

wrl::Node::EventInHandle eventIn ( const unsigned int n ) [virtual]

Return a handle on the i th event in of the node or a "unknown" typed handle if there is no such node. Here is how i is related to fields:

0 : addChildren
1 : removeChildren
2 : set_axisOfRotation
3 : set_children

This function is useful, with nbEventsIn() if you want to traverse all events in of a Node.

Implements Node.

wrl::Node::EventInHandle eventIn ( const std::string & n ) [virtual]

Return a handle on the event in named n of the node or a "unknown" typed handle if there is no such event. Valid names are:

addChildren
removeChildren
set_axisOfRotation
set_children

Implements Node.

wrl::Node::EventOutHandle eventOut ( const unsigned int n ) [virtual]

Return a handle on the i th event out of the node or a "unknown" typed handle if there is no such node. Here is how i is related to fields:

0 : axisOfRotation_changed
1 : children_changed This function is useful, with nbEventsOut() if you want to traverse all events in of a Node.

Implements Node.

wrl::Node::EventOutHandle eventOut ( const std::string & n ) [virtual]

Return a handle on the event out named n of the node or a "unknown" typed handle if there is no such event. Valid names are:

axisOfRotation_changed
children_changed

Implements Node.

wrl::Node::FieldHandle field ( const unsigned int n ) [virtual]

Return a handle on the i th field of the node or a "unknown" typed handle if there is no such node. Here is how i is related to fields:

0 : axisOfRotation
1 : children
2 : bboxCenter
3 : bboxSize This function is useful, with nbFields() if you want to traverse all fields of a Node.

Implements Node.

wrl::Node::FieldHandle field ( const std::string & n ) [virtual]

Return a handle on the field named n of the node or a "unknown" typed handle if there is no such field. Valid names are:

axisOfRotation
children
bboxCenter
bboxSize

Implements Node.

bool isSetToDefaultValue ( const unsigned int i ) const [virtual]

Implements Node.

unsigned int nbEventsIn ( ) const [inline, virtual]

Returns the number of events in for this node type.

Implements Node.

unsigned int nbEventsOut ( ) const [inline, virtual]

Returns the number of events out for this node type.

Implements Node.

unsigned int nbFields ( ) const [inline, virtual]

Returns the number of fields (exposed or not) for this node type.

Implements Node.

const char * typeName ( ) const [inline, virtual]

Returns "Billboard". Useful for printing.

Implements Node.


Public Member Functions
	Billboard (const char *name="")
virtual	~Billboard ()
virtual unsigned int	nbFields () const
virtual FieldHandle	field (const std::string &n)
virtual FieldHandle	field (const unsigned int i)
virtual bool	isSetToDefaultValue (const unsigned int i) const
virtual unsigned int	nbEventsIn () const
virtual EventInHandle	eventIn (const std::string &n)
virtual EventInHandle	eventIn (const unsigned int i)
virtual unsigned int	nbEventsOut () const
virtual EventOutHandle	eventOut (const std::string &n)
virtual EventOutHandle	eventOut (const unsigned int i)
const char *	typeName () const
virtual Node *	duplicate () const
virtual Node *	duplicate (std::map< const Node , Node > &) const
Public Attributes
Exposed Fields
A field that is capable of receiving events via an eventIn to change its value(s), and generating events via an eventOut when its value(s) change.
SFVec3f	axisOfRotation
MFNode	children
Fields
A property or attribute of a node. Each node type has a fixed set of fields. Fields may contain various kinds of data and one or many values. Each field has a default value.
SFVec3f	bboxCenter
SFVec3f	bboxSize
Events In
EventIn< MFNode >	addChildren
EventIn< MFNode >	removeChildren
EventIn< SFVec3f >	set_axisOfRotation
EventIn< MFNode >	set_children
Events Out
EventOut< SFVec3f >	axisOfRotation_changed
EventOut< MFNode >	children_changed

Billboard Class Reference
[Standard Node Types]

Public Member Functions

Public Attributes

Detailed Description

6.6 Billboard

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation

Billboard Class Reference [Standard Node Types]

Public Member Functions

Public Attributes

Detailed Description

6.6 Billboard

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation

Billboard Class Reference
[Standard Node Types]