Delete empty visibility layers
==============================

This script delete visibility layers (also called geometry layers) that contains
no surfaces.

.. literalinclude:: DeleteEmptyVisibilityLayers.py
   :linenos:

:download:`Download example <DeleteEmptyVisibilityLayers.py>`

:py:func:`delete_layer_if_empty` is a `post-order recursive`_ function.
It does the following:

* Recurse into direct sub layers of the layer.
* Delete the layer if it contains no surfaces and no sub layers (i.e. it is empty).
  The empty child layers are already removed by the recursive step.

.. _post-order recursive: https://en.wikipedia.org/wiki/Tree_traversal#Post-order_(LRN)