# 3.3.3.50. NXcg_point_set¶

**Status**:

base class, extends NXobject

**Description**:

## Computational geometry description of a set of points in Euclidean space. ...

Computational geometry description of a set of points in Euclidean space.

The relevant coordinate system should be referred to in the NXtransformations instance. Points may have an associated time value; however users are advised to store time data of point sets rather as instances of time events, where for each point in time there is an NXcg_point_set instance which specifies the points locations. This is a frequent situation in experiments and computer simulations, where positions of points are taken at the same point in time; and therefore an additional time array would demand to store redundant pieces of information for each point.

**Symbols**:

The symbols used in the schema to specify e.g. dimensions of arrays.

d: The dimensionality, which has to be at least 1.

c: The cardinality of the set, i.e. the number of points.

**Groups cited**:

**Structure**:

dimensionality: (optional) NX_POSINT {units=NX_UNITLESS}

cardinality: (optional) NX_POSINT {units=NX_UNITLESS}

identifier_offset: (optional) NX_INT {units=NX_UNITLESS}## Integer which specifies the first index to be used for distinguishing ...

Integer which specifies the first index to be used for distinguishing identifiers for points. Identifiers are defined either implicitly or explicitly. For implicit indexing the identifiers are defined on the interval [identifier_offset, identifier_offset+c-1]. For explicit indexing the identifier array has to be defined.

The identifier_offset field can for example be used to communicate if the identifiers are expected to start from 1 (referred to as Fortran-/Matlab-) or from 0 (referred to as C-, Python-style index notation) respectively.

identifier: (optional) NX_INT (Rank: 1, Dimensions: [c]) {units=NX_UNITLESS}Integer used to distinguish points for explicit indexing.

position: (optional) NX_NUMBER (Rank: 2, Dimensions: [c, d]) {units=NX_LENGTH}The array of point coordinates.

time: (optional) NX_NUMBER (Rank: 1, Dimensions: [c]) {units=NX_TIME}The optional array of time for each vertex.

TRANSFORMATIONS: (optional) NXtransformations## Reference to or definition of a coordinate system with ...

Reference to or definition of a coordinate system with which the positions and directions are interpretable.

## Hypertext Anchors¶

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