Creating an Arbitrary Custom Transform Orientation in Python

Question

Is there a way to create an arbitrary transform orientation in Python?

The API function bpy.ops.transform.create_orientation() only allows the orientation to be created from the current view or the selected object. In my particular case, I want it along the line between two objects.

My initial thought is to create the transform orientation (call it 'mytransform') with bpy.ops.transform.create_orientation(), and then directly set bpy.context.scene.orientations['mytransform'].matrix. But:

1. I don't know if this is kosher (I try to avoid mucking directly with the data structures when possible).
2. It has some disadvantages, mainly that I can't run it from the Python console for testing (create_orientation() only works in a 3DView context).

Answer 1

Test code to create orientation and use in all 3d views in the current (context) screen.

import bpy
from math import radians
from mathutils import Matrix
context = bpy.context
scene = context.scene

# create view

bpy.ops.transform.create_orientation(name="Frank", overwrite=True)
orientation = scene.orientations.get("Frank")
print(orientation)

# make up some matrix
# rotated 45 degrees on (1, 1, 1) axis
m = Matrix.Rotation(radians(45), 3, (1, 1, 1))
orientation.matrix = m

# find 3d views to set to "Frank"
screen = context.screen
views = [area.spaces.active for area in screen.areas if area.type == 'VIEW_3D']
for view in views:
    view.transform_orientation = orientation.name

Note you can override operators to "trick" them into thinking they are running in another area.