IFC 4.3.0.1 (IFC4X3) development

8.8.3.47 IfcTriangulatedIrregularNetwork

8.8.3.47.1 Semantic definition

The IfcTriangulatedIrregularNetwork is a triangulated face set for representing horizontal surfaces (one unique Z coordinate for all X and Y coordinates within domain) with additional flags for each face indicating breaklines between faces or designation as a hole or void. Triangles shall be defined with vertices in counterclockwise order as viewing from above (following right-hand rule).

For visualization, applications should not display faces where flags are set as negative (either a hole, void, or possible future extension).

The flag Void shall be used to indicate that faces are to be excluded without falling back on any other geometry. Such designation could be used for portions of a site beneath a building or other structure.

The flag Hole shall be used to indicate that faces are to be excluded but may fall back on other geometry. Such designation could be used for portions of a proposed site that are to remain unchanged (conforming to an existing site that may also be defined)

For scenarios where multiple surfaces used as input are to be combined, any triangles marked Void shall be retained as voids, while any triangles marked as Hole shall be overridden if another surface has visible geometry defined within the same horizontal location.

8.8.3.47.2 Entity inheritance

8.8.3.47.3 Attributes

# Attribute Type Description
IfcRepresentationItem (2)
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems

Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.

StyledByItem SET [0:1] OF IfcStyledItem FOR Item

Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.

IfcTessellatedFaceSet (4)
1 Coordinates IfcCartesianPointList3D

An ordered list of Cartesian points used by the coordinate index defined at the subtypes of IfcTessellatedFaceSet.

HasColours SET [0:1] OF IfcIndexedColourMap FOR MappedTo

Reference to the indexed colour map providing the corresponding colour RGB values to the faces of the subtypes of IfcTessellatedFaceSet.

HasTextures SET [0:?] OF IfcIndexedTextureMap FOR MappedTo

Reference to the indexed texture map providing the corresponding texture coordinates to the vertices bounding the faces of the subtypes of IfcTessellatedFaceSet.

* Dim IfcDimensionCount

This attribute is formally derived.

3

The space dimensionality of this geometric representation item, it is always 3.

IfcTriangulatedFaceSet (5)
2 Normals OPTIONAL LIST [1:?] OF LIST [3:3] OF IfcParameterValue

An ordered list of three directions for normals. It is a two-dimensional list of directions provided by three parameter values. * The first dimension corresponds to the vertex indices of the Coordindex * The second dimension has exactly three values, [1] the x-direction, [2] the y-direction and [3] the z-directions

3 Closed OPTIONAL IfcBoolean

Indication whether the face set is a closed shell (TRUE) or an open shell (FALSE). If omitted no such information can be asserted.

4 CoordIndex LIST [1:?] OF LIST [3:3] OF IfcPositiveInteger

Two-dimensional list for the indexed-based triangles, where * The first dimension represents the triangles (from 1 to N) * The second dimension has exactly three values representing the indices to three vertex points (from 1 to 3).

5 PnIndex OPTIONAL LIST [1:?] OF IfcPositiveInteger

The list of integers defining the locations in the IfcCartesianPointList3D to obtain the point coordinates for the indices withint the CoordIndex. If the PnIndex is not provided the indices point directly into the IfcCartesianPointList3D.

* NumberOfTriangles IfcInteger

This attribute is formally derived.

SIZEOF(CoordIndex)

Derived number of triangles used for this triangulation.

Click to show 11 hidden inherited attributes Click to hide 11 inherited attributes
IfcTriangulatedIrregularNetwork (1)
6 Flags LIST [1:?] OF IfcInteger

Indicates attributes of each triangle in a compact form as follows: -2 = invisible void; -1 = invisible hole; 0 = no breaklines; 1 = breakline at edge 1; 2 = breakline at edge 2; 3 = breakline at edges 1 and 2; 4 = breakline at edge 3; 5 = breakline at edges 1 and 3; 6 = breakline at edges 2 and 3; 7 = breakline at edges 1, 2, and 3.

Table 8.8.3.47.J

8.8.3.47.4 Formal propositions

Name Description
NotClosed

The triangulated face set shall not be closed.

SELF\IfcTriangulatedFaceSet.Closed = FALSE
Table 8.8.3.47.K

8.8.3.47.5 Examples

8.8.3.47.6 Formal representation

ENTITY IfcTriangulatedIrregularNetwork
 SUBTYPE OF (IfcTriangulatedFaceSet);
	Flags : LIST [1:?] OF IfcInteger;
 WHERE
	NotClosed : SELF\IfcTriangulatedFaceSet.Closed = FALSE;
END_ENTITY;

8.8.3.47.7 References

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8.8.3.47.8 Changelog

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