Added a factory for a constant magnetic field.

imagine/magnetic_fields/constant_field_factory.py

+# -*- coding: utf-8 -*-
+
+import numpy as np
+
+from magnetic_field_factory import MagneticFieldFactory
+
+
+class ConstantFieldFactory(MagneticFieldFactory):
+    @property
+    def descriptor(self):
+        return 'CONSTANT_FIELD'
+
+    @staticmethod
+    def _create_array(self):
+        result_array = np.empty(tuple(self.resolution) + (3,))
+        result_array[:, :, :] = [self.parameters['b_x'],
+                                 self.parameters['b_y'],
+                                 self.parameters['b_z']]
+        return result_array
+
+    def _initialize_parameter_defaults(self):
+        self._parameter_defaults = {'b_x': 0,
+                                    'b_y': 0,
+                                    'b_z': 0}
+
+    def _initialize_variable_to_parameter_mappings(self):
+        self._variable_to_parameter_mappings = {'b_x': [-np.inf, 0, np.inf],
+                                                'b_y': [-np.inf, 0, np.inf],
+                                                'b_z': [-np.inf, 0, np.inf]}

imagine/observers/hammurapy/__init__.py

+# -*- coding: utf-8 -*-
+