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8.9.3.33 IfcGeometricRepresentationItem

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ABSTRACT This definition may not be instantiated

8.9.3.33.1 Semantic definition

An IfcGeometricRepresentationItem is the common supertype of all geometric items used within a representation. It is positioned within a geometric coordinate system, directly or indirectly through intervening items.

Definition according to ISO/CD 10303-42:1992 An geometric representation item is a representation item that has the additional meaning of having geometric position or orientation or both. This meaning is present by virtue of:

An indirect reference to a Cartesian point or direction means that a given geometric item references the Cartesian point or direction through one or more intervening geometry or topology items.

1 Consider a circle. It gains its geometric position and orientation by virtue of a reference to axis2_placement (IfcAxis2Placement) that is turn references a cartesian_point (IfcCartesianPoint) and several directions (IfcDirection). 2 Consider a manifold brep. A manifold_solid_brep (IfcManifoldSolidBrep) is a geometric_representation_item (IfcGeometricRepresentationItem) that through several layers of topological_representation_item's (IfcTopologicalRepresentationItem) references poly loops (IfcPolyLoop). Through additional intervening entities poly loops reference cartesian_point's (IfcCartesianPoint). Entity adapted from geometric_representation_item defined in ISO 10303-42. New entity in IFC1.5

8.9.3.33.2 Entity inheritance

8.9.3.33.3 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.

The inverse attribute LayerAssignments has been added. 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.

The inverse attribute StyledByItem has been added.
Table 8.9.3.33.A

8.9.3.33.4 Formal representation 

ENTITY IfcGeometricRepresentationItem
 ABSTRACT SUPERTYPE OF (ONEOF
	(IfcAnnotationFillArea
	,IfcBooleanResult
	,IfcBoundingBox
	,IfcCartesianPointList
	,IfcCartesianTransformationOperator
	,IfcCsgPrimitive3D
	,IfcCurve
	,IfcDirection
	,IfcFaceBasedSurfaceModel
	,IfcFillAreaStyleHatching
	,IfcFillAreaStyleTiles
	,IfcGeometricSet
	,IfcHalfSpaceSolid
	,IfcLightSource
	,IfcPlacement
	,IfcPlanarExtent
	,IfcPoint
	,IfcSectionedSpine
	,IfcSegment
	,IfcShellBasedSurfaceModel
	,IfcSolidModel
	,IfcSurface
	,IfcTessellatedItem
	,IfcTextLiteral
	,IfcVector))
 SUBTYPE OF (IfcRepresentationItem);
END_ENTITY;

8.9.3.33.5 References

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