The Ellipsoid is an example object that implements the kDirectModeling object property.  

The ellipsoid object contains a new resource of type 'PXpr'.  

With this resource the application calls the ellipsoid's definition procedure with the kObjOnInitXProperties action/event.  

The ellipsoid's kObjOnInitXProperties event handler installs the kDirectModeling property.  With the kDirectModeling property installed, the 3D Reshape tool will call the ellipsoid's definition procedure with direct modeling events.   By handling these events, the ellipsoid is able to be reshaped interactively by the tool.