IFC 4.3.x development

8.8.3.47 IfcTriangulatedIrregularNetwork

Change log

IFC4X1

added

8.8.3.47.1 Semantic definitions at the entity

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.

8.8.3.47.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.

> IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE  The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
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.



> IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
IfcGeometricRepresentationItem
IfcTessellatedItem
IfcTessellatedFaceSet
1 Coordinates IfcCartesianPointList3D An ordered list of Cartesian points used by the coordinate index defined at the subtypes of IfcTessellatedFaceSet.
Dim INVALID The space dimensionality of this geometric representation item, it is always 3.
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.
IfcTriangulatedFaceSet
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 IfcTriangulatedFaceSet is a closed shell or not. If omited no such information can be provided.
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).

> NOTE  The coordinates of the vertices are provided by the indexed list of _SELF\IfcTessellatedFaceSet.Coordinates.CoordList_.
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.
NumberOfTrianglesINVALID Derived number of triangles used for this triangulation.
IfcTriangulatedIrregularNetwork
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.

8.8.3.47.2 Entity inheritance

dot_inheritance IfcTriangulatedIrregularNetwork IfcTriangulatedIrregularNetwork IfcTriangulatedFaceSet IfcTriangulatedFaceSet IfcTriangulatedIrregularNetwork->IfcTriangulatedFaceSet IfcTessellatedFaceSet IfcTessellatedFaceSet IfcTriangulatedFaceSet->IfcTessellatedFaceSet IfcPolygonalFaceSet IfcPolygonalFaceSet IfcPolygonalFaceSet->IfcTessellatedFaceSet IfcTessellatedItem IfcTessellatedItem IfcTessellatedFaceSet->IfcTessellatedItem IfcIndexedPolygonalFace IfcIndexedPolygonalFace IfcIndexedPolygonalFace->IfcTessellatedItem IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcTessellatedItem->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.8.3.47.3 Formal representations

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