.. auto-generated by script ../../../../utils/nxdl2rst.py from the NXDL source NXcylindrical_geometry.nxdl.xml
.. index::
! NXcylindrical_geometry (base class)
! cylindrical_geometry (base class)
see: cylindrical_geometry (base class); NXcylindrical_geometry
.. _NXcylindrical_geometry:
======================
NXcylindrical_geometry
======================
**Status**:
base class, extends :ref:`NXobject`
**Description**:
Geometry description for cylindrical shapes.
This class can be used in place of ``NXoff_geometry`` when an exact
representation for cylinders is preferred.
For example, for Helium-tube, neutron detectors.
It can be used to describe the shape of any beamline component, including detectors.
In the case of detectors it can be used to define the shape of a single pixel, or,
if the pixel shapes are non-uniform, to describe the shape of the whole detector.
**Symbols**:
These symbols will be used below.
**i**: number of vertices required to define all cylinders in the shape
**j**: number of cylinders in the shape
**k**: number cylinders which are detectors
**Groups cited**:
none
**Structure**:
.. index:: vertices (field)
**vertices[i, 3]**: (optional) :ref:`NX_NUMBER ` {units=\ :ref:`NX_LENGTH `}
List of x,y,z coordinates for vertices.
The origin of the coordinates is the position of the parent component, for
example the NXdetector which the geometry describes.
If the shape describes a single pixel for a detector with uniform pixel shape
then the origin is the position of each pixel as described by the
``x/y/z_pixel_offset`` datasets in ``NXdetector``.
.. index:: cylinders (field)
**cylinders[j, 3]**: (optional) :ref:`NX_INT `
List of indices of vertices in the ``vertices`` dataset to form each cylinder.
Each cylinder is described by three vertices A, B, C.
First vertex A lies on the cylinder axis and circular face, second point B
on edge of the same face as A, and third point C at the other face and on axis.
.. index:: detector_number (field)
**detector_number[k]**: (optional) :ref:`NX_INT `
Maps cylinders in ``cylinder``, by index, with a detector id.
**NXDL Source**:
https://github.com/nexusformat/definitions/blob/master/base_classes/NXcylindrical_geometry.nxdl.xml