XdkWrl: Billboard Class Reference

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# Billboard Class Reference
[Standard Node Types]

`#include <billboard.h>`

Inherits Node.

List of all members.

## Public Member Functions
| Billboard (const char *name="")
virtual | ~Billboard ()
virtual unsigned int | nbFields () const
virtual FieldHandle | field (const std::string &n)
virtual FieldHandle | field (unsigned int i)
virtual bool | isSetToDefaultValue (unsigned int i) const
virtual unsigned int | nbEventsIn () const
virtual EventInHandle | eventIn (const std::string &n)
virtual EventInHandle | eventIn (unsigned int i)
virtual unsigned int | nbEventsOut () const
virtual EventOutHandle | eventOut (const std::string &n)
virtual EventOutHandle | eventOut (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

## Detailed Description

Here is the documentation for this node type, from the ISO standard.

## 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:

1. Compute the vector from the Billboard node's origin to the viewer's position. This vector is called the billboard-to-viewer vector.
2. Compute the plane defined by the axisOfRotation and the billboard-to-viewer vector.
3. 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:

4. Compute the billboard-to-viewer vector.
5. Rotate the Z-axis of the billboard to be collinear with the billboard-to-viewer vector and pointing towards the viewer's position.
6. 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);

~Billboard | ( |  | ) | `[virtual]`

Virtual destructor, does nothing

## Member Function Documentation

unsigned int nbFields | ( |  | ) | const`[inline, virtual]`

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

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.

wrl::Node::FieldHandle field | ( | 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.

bool isSetToDefaultValue | ( | 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.

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::EventInHandle eventIn | ( | 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.

unsigned int nbEventsOut | ( |  | ) | const`[inline, virtual]`

Returns the number of events out for this node type.

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::EventOutHandle eventOut | ( | 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.

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

Returns `"Billboard"`. Useful for printing.

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.

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

Implements Node.

## Member Data Documentation

SFVec3f axisOfRotation

See Detailed Description for meaning of this field. Default value is set to

           axisOfRotation.setXYZ(0,1,0);

MFNode children

See Detailed Description for meaning of this field. Default value is set to MFNode default value

SFVec3f bboxCenter

See Detailed Description for meaning of this field. Default value is set to

           bboxCenter.setXYZ(0,0,0);

SFVec3f bboxSize

See Detailed Description for meaning of this field. Default value is set to

           bboxSize.setXYZ(-1,-1,-1);

EventIn<MFNode> addChildren

See Detailed Description for meaning of this event.

EventIn<MFNode> removeChildren

See Detailed Description for meaning of this event.

EventIn<SFVec3f> set_axisOfRotation

Set event associated to exposedField axisOfRotation

EventIn<MFNode> set_children

Set event associated to exposedField children

EventOut<SFVec3f> axisOfRotation_changed

Changed event associated to exposedField axisOfRotation

EventOut<MFNode> children_changed

Changed event associated to exposedField children

Generated on 5 Jan 2007 with version 1.5.1. |