IFC 4.3.1.0 (IFC4X3_ADD1) development

# 8.8.3.44 IfcTessellatedFaceSet

AbRV ⓘ
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ABSTRACT This definition may not be instantiated

## 8.8.3.44.1 Semantic definition

The IfcTessellatedFaceSet is a boundary representation topological model limited to planar faces and straight edges. It may represent an approximation of an analytical surface or solid that may be provided in addition to its tessellation as a separate shape representation. The IfcTessellatedFaceSet provides a compact data representation of an connected face set using indices into ordered lists of vertices, normals, colours, and texture maps.

The IfcTessellatedFaceSet is an abstract supertype of tessellated face sets each imposing specific constraints on face generation for tessellation, such as triangulation (with or without strip and fans), or quadrilaterals, or polygonal faces (with or without inner loops).

The following attributes apply to all subtypes:

• The Coordinates are the ordered list of Cartesian points representing the vertices of the tessellated item. An index list, defined at the level of subtypes, uses the points, identified by index position, to construct the polylines that represent the faces.
• The HasColours inverse relation provides an indexed colour map with an corresponding list of indices providing a colour for each face of the tessellated face set.
• The HasTextures inverse relation provides an indexed texture map with an corresponding list of indices providing texture coordinates that map to the geometric coordinates of the polylines representing the faces.

Each face of the tessellated face set shall have:

• at least three non-coincident vertices;
• vertices that define a planar polygon;
• vertices that define a non-self-intersecting polygon.

## 8.8.3.44.4 Formal representation

ENTITY IfcTessellatedFaceSet
ABSTRACT SUPERTYPE OF (ONEOF
(IfcPolygonalFaceSet
,IfcTriangulatedFaceSet))
SUBTYPE OF (IfcTessellatedItem);
Coordinates : IfcCartesianPointList3D;
DERIVE
Dim : IfcDimensionCount := 3;
INVERSE
HasColours : SET [0:1] OF IfcIndexedColourMap FOR MappedTo;
HasTextures : SET [0:?] OF IfcIndexedTextureMap FOR MappedTo;
END_ENTITY;

## 8.8.3.44.5 References

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