The OIV.Inventor.Nodes.SoBillboard 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 children of an OIV.Inventor.Nodes.SoBillboard node may include other grouping nodes as well as shape nodes.

Performance:

• OIV.Inventor.Nodes.SoBillboard nodes recompute the screen alignment transformation on every render traversal. A large number of billboard nodes will reduce performance.

• The orientation of an OIV.Inventor.Nodes.SoBillboard depends on the current camera settings, so this node should not be render cached.

• OIV.Inventor.Nodes.SoBillboard nodes prohibit auto-caching, so no OIV.Inventor.Nodes.SoSeparator (or other render caching node) above an OIV.Inventor.Nodes.SoBillboard in the scene graph will automatically create a render cache. This can significantly reduce performance and applications should put nodes that can be render cached (especially geometry nodes) under their own OIV.Inventor.Nodes.SoSeparator below the OIV.Inventor.Nodes.SoBillboard.

• We recommend leaving the OIV.Inventor.Nodes.SoBillboard.useSphereBBox field set to true. This will significantly improve performance when using billboard nodes.

Export limitations:

• OIV.Inventor.Nodes.SoBillboard can be exported to PDF3D/U3D (OIV.HardCopy.SoToPDFAction) as a group node, but due to limitations of that file format, it will not act as a billboard. In other words, the geometry will not be "screen locked".

The OIV.Inventor.Nodes.SoBillboard.axisOfRotation field specifies which axis to use to perform the rotation. This axis is defined in the local coordinates of the OIV.Inventor.Nodes.SoBillboard node. The default (0,1,0) is useful for objects such as images of trees and lamps positioned on a ground plane. But when an object is oriented at an angle, for example, on the incline of a mountain, then the OIV.Inventor.Nodes.SoBillboard.axisOfRotation may also need to be oriented at a similar angle.

A special case of billboarding is screen-alignment the object rotates to always stay aligned with the viewer even when the viewer elevates, pitches and rolls. This special case is distinguished by setting the OIV.Inventor.Nodes.SoBillboard.axisOfRotation to (0, 0, 0).

To rotate the OIV.Inventor.Nodes.SoBillboard to face the viewer, determine the line between the OIV.Inventor.Nodes.SoBillboard's origin and the viewer's position; call this the billboard-to-viewer line. The OIV.Inventor.Nodes.SoBillboard.axisOfRotation and the billboard-to-viewer line define a plane. The local z-axis of the OIV.Inventor.Nodes.SoBillboard is then rotated into that plane, pivoting around the OIV.Inventor.Nodes.SoBillboard.axisOfRotation.

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

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

FILE FORMAT/DEFAULT

Billboard {

axisOfRotation	0 1 0
useSphereBBox	true

}

Note
Node available since Open Inventor 10.0

Reference