When you create a new node, you probably also want to create an alternate representation for it that can be written to a file. For example, a good alternate representation for the Glow node would be an SoMaterial SoMaterial SoMaterial node with all fields ignored except for emissiveColor. The alternate representation is in the form of a field called alternateRep, of type SoSFNode SoSFNode SoSFNode . If your node is later read into an Inventor application that is not linked with this new node, Inventor will be able to render the node using this alternate representation even though the node has not been initialized with the database. (See Chapter 11 in The Inventor Mentor on reading in extender nodes and engines.)

Within your program, when a change is made to the original node, you may want the alternate representation to change as well. In this case, override the write() method on SoNode SoNode SoNode to update the alternate representation, and then have it call the write() method of the base class.