# 3.3.3.57. NXcg_triangle_set¶

**Status**:

base class, extends NXobject

**Description**:

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

**Symbols**:

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

d: The dimensionality, which has to be at least 2.

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

n_unique: The number of unique vertices supporting the triangles.

**Groups cited**:NXcg_face_list_data_structure, NXcg_hexahedron_set, NXcg_unit_normal_set, NXtransformations

**Structure**:

dimensionality: (optional) NX_POSINT {units=NX_UNITLESS}

cardinality: (optional) NX_POSINT {units=NX_UNITLESS}

number_of_unique_vertices: (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 triangles. 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 triangles for explicit indexing.

area: (optional) NX_NUMBER (Rank: 1, Dimensions: [c]) {units=NX_AREA}

edge_length: (optional) NX_NUMBER (Rank: 2, Dimensions: [c, 3]) {units=NX_LENGTH}## Array of edge length values. For each triangle the edge length is ...

Array of edge length values. For each triangle the edge length is reported for the edges traversed according to the sequence in which vertices are indexed in triangles.

interior_angle: (optional) NX_NUMBER (Rank: 2, Dimensions: [c, 3]) {units=NX_ANGLE}## Array of interior angle values. For each triangle the angle is ...

Array of interior angle values. For each triangle the angle is reported for the angle opposite to the edges which are traversed according to the sequence in which vertices are indexed in triangles.

center: (optional) NX_NUMBER (Rank: 2, Dimensions: [c, d]) {units=NX_LENGTH}The center of mass of each polygon.

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

Reference to or definition of a coordinate system with which the qualifiers and primitive data are interpretable.

triangles: (optional) NXcg_face_list_data_structure## A simple approach to describe the entire set of triangles when the ...

A simple approach to describe the entire set of triangles when the main intention is to store the shape of the triangles for visualization.

vertex_normal: (optional) NXcg_unit_normal_set

edge_normal: (optional) NXcg_unit_normal_set

face_normal: (optional) NXcg_unit_normal_set

bounding_box: (optional) NXcg_hexahedron_setAxis-aligned or (approximate) (optimal) bounding boxes to each polygon.

## Hypertext Anchors¶

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