Defining the Constructor

Implement the constructor for the class. Begin with the macro SO_ENGINE_CONSTRUCTOR(). Then use the macros SO_ENGINE_ADD_INPUT() and SO_ENGINE_ADD_OUTPUT() to add the engine inputs and outputs and to set default values for the outputs. Perform any other class-specific initialization, if needed. For example:

SoOnOff::SoOnOff()
{
  SO_ENGINE_CONSTRUCTOR( SoOnOff );
  SO_ENGINE_ADD_INPUT( on, () );     // no default value for
                                     // trigger fields
  SO_ENGINE_ADD_INPUT( off, () );    // no default value
  SO_ENGINE_ADD_INPUT( toggle, () ); // no default value
  SO_ENGINE_ADD_OUTPUT( isOn, SoSFBool );
  SO_ENGINE_ADD_OUTPUT( isOff, SoSFBool );
  state = FALSE; // engine is off by default
}

Notice that this is where the outputs are bound to a particular field type.