Deformers are implemented by deriving from the MPxDeformerNode class. Any deformer that is derived from this class also acquires the full benefits of Maya’s internal deformer functionality. Please see the API description of MPxDeformerNode for more detailed and updated information.
Deformers often require a helper node such as a locator in order to control the change of deformation. These helper nodes are called Accessories. Accessory nodes are optional and not required for deformers. The input attributes of the MPxDeformerNode class are sufficient to perform the deformation. You should implement the accessoryNodeSetup() and accessoryAttribute() methods only if you want to deform geometry using an accessory.
As MPxDeformerNode derives from MPxNode, a compute() method can be implemented in the class. You do not need to implement the compute() method for simple deformers. Only implement the compute() method if you need to modify the input geometry. Please see the API descriptions for an example of compute() method implementation.