Volume bounding box
===================

.. _fig_volume_bbox_actor:
.. figure:: ./figs/volume_bbox/actorref_volumebbox.webp
    :figwidth: 100%
    :align: left
    :alt: A figure should appear here

    Volume bounding box actor.


Description
-----------

The volume bounding box actor draws a 3-D box into the scene. It can be used
to mark the spatial extent of a data volume, or to provide a spatial reference
frame for other actors. The edges of the box are rendered as shaded 3-D tubes.

The spatial extent of the box is controlled by the shared bounding box
assigned in the **Bounding box** group.


Appearance
----------

**Frame thickness**
    Controls the radius of the tube used to draw each edge of the box. At
    small values the tubes appear as thin lines.

**Colour**
    Sets the colour applied to the frame and the vertical tick marks.

Label font size and colour, and an optional background box behind the tick
labels, are configurable in the **Labels** group inherited from the actor
base class.


Vertical tick marks
-------------------

Enable **Tick settings** to draw short horizontal tick lines on the vertical
edges of the bounding box and label them with their pressure or flight level
values. Sub-properties:

**Tick length**
    Length of the tick lines extending outward from each vertical edge corner.

**Tick unit**
    Whether levels are specified in *Pressure (hPa)* or *Flight level (FL)*.

**Tick levels**
    Comma-separated list of levels, or a range formatted as
    ``[start, end, step]``.

**Label every n-th tick**
    Only every n-th tick is labelled, to avoid crowding.

**Display unit**
    When enabled, the unit string is appended to each label.