Adding a new modifier

The concept of a modifier is relatively simple. Their only function is to change the data stored in variables in the corresponding component, for example to add noise to the information, or by applying some generic geometric transformation.

A modifier is defined by a Python script. The Python script is responsible for altering the data by directly changing the information stored in each component’s local_data dictionary.


Be aware that once the data has been changed, there is no way to get the original information back. If there is a need to have both the clean and the modified data for a particular sensor, the recommended method is to add two sensors of the same type, and only bind one of them to the modifier.

Adding a new modifier

Adding a new modifier is a matter of implementing a new class which derives from morse.modifiers.abstract_modifier.AbstractModifier.

The only mandatory method to specialize is the modify method which contains the actual modification of component data. In this method, you can use to access to the local_data field of the associated component.

It can also be useful to override the initialize and finalize methods, that contain the initialization code, and the finalization code. Do not override __init__ and __del__.

If you want to add some parameters to your modifier and to get their value during initialization, you can use the parameter method.

Let see an example with a custom modifier that switches x and y and the puts z to a constant value (set from a parameter).

from morse.modifiers.abstract_modifier import AbstractModifier

class MyModifier(AbstractModifier):
    def initialize(self):
        """ initialization of parameters ... """
        self.z = self.parameter("z", default=0)

    def modify(self):
        """" modify the data in this method """
        x =['x']['x'] =['y']['y'] = x['z'] = self.z

Now, you can test your new modifier directly in the builder:

from morse.builder import *

atrv = ATRV()

pose = Pose()
pose.alter('', '')

env = Environment('empty', fastmode=True)

Lastly, if you want to use it more easily, you can add some entries in


morse.modifiers.ned shows a simple example for a modifier.