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Troubleshooting
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Some common problems people may run into when using drivers.


Scripted Expression
===================

.. figure:: /images/animation_drivers_troubleshooting_autorun-graph-editor.png

   :menuselection:`Graph Editor --> Properties --> Drivers`

.. figure:: /images/animation_drivers_troubleshooting_autorun-info-header.png

   Info Header.


By default Blender will not autorun Python scripts.

If using a *Scripted Expression* Driver Type, you will have to open the file as *Trusted Source*,
or set *Auto Run Python Scripts* in :menuselection:`User Preferences --> File --> Auto Execution`.

.. list-table::
   :widths: 40 60

   * - .. figure:: /images/animation_drivers_troubleshooting_autorun-file-browser.png

          File Browser.

     - .. figure:: /images/animation_drivers_troubleshooting_autorun-user-preference.png

          :menuselection:`User Preference --> File --> Auto Execution`


Rotational Properties are Radians
=================================

Parts of the User Interface may use different units of measurements for angles, rotation.
In the Graph Editor, while working with Drivers, all angles are Radians.


Intra-armature Bone Drivers Can Misbehave
=========================================

There is a `well-known limitation <https://developer.blender.org/T40301>`__
with drivers on bones that refer to another bone in the same armature. Their values can be
incorrectly calculated based on the position of the other bone as it was *before* you adjust
the current_frame. This can lead to obvious shape glitches when the rendering of frames has
a jump in the frame number (either because the blend-file is currently on a different frame
number or because you are skipping already rendered frames).