# 3.3.1.11. NXcylindrical_geometry¶

**Status**:

base class, extends NXobject

**Description**:

## Geometry description for cylindrical shapes. ...

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**:

@default: (optional) NX_CHAR## Declares which child group contains a path leading ...

Declares which child group contains a path leading to a NXdata group.

It is recommended (as of NIAC2014) to use this attribute to help define the path to the default dataset to be plotted. See https://www.nexusformat.org/2014_How_to_find_default_data.html for a summary of the discussion.

vertices: (optional) NX_NUMBER (Rank: 2, Dimensions: [i, 3]) {units=NX_LENGTH}## List of x,y,z coordinates for vertices. ...

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`

.

cylinders: (optional) NX_INT (Rank: 2, Dimensions: [j, 3])## List of indices of vertices in the ``vertices`` dataset to form each cylinder. ...

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.

detector_number: (optional) NX_INT (Rank: 1, Dimensions: [k])Maps cylinders in

`cylinder`

, by index, with a detector id.

## Hypertext Anchors¶

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.