Class Ifc4::IfcGeometricRepresentationItem

Nested Relationships

This class is a nested type of Struct Ifc4.

Inheritance Relationships

Base Type

Derived Types

Class Documentation

class Ifc4::IfcGeometricRepresentationItem : public Ifc4::IfcRepresentationItem

Definition from ISO/CD 10303-43:1992: 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:

being a Cartesian point or a direction

referencing directly a Cartesian point or direction

referencing indirectly a Cartesian point or direction

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.

EXAMPLE: 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).

EXAMPLE: 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).

The derivation of the dimensionality of the IfcGeometricRepresentationItem is different to ISO 10303; there is a specific derived attribute at each class that defines the dimensionality, whereas ISO 10303 does it for the representation_context and requires all geometric_representation_item’s to have the same dimensionality therein.

The definition of swept area solids as geometric representation items is different to ISO 10303; it is based on a set of predefined profiles (or cross sections), that is, a set of parameterized geometric primitives widely supported in the industry. Those profiles are used to create volumes through extrusion, revolution and cross section based sweep operations.

NOTE: Corresponding ISO 10303 entity: geometric_representation_item. Please refer to ISO/IS 10303-42:1994, p. 22 for the final definition of the formal standard. The following changes have been made: It does not inherit from ISO/IS 10303-43:1994 entity representation_item. The derived attribute Dim is demoted to the appropriate subtypes. The WR1 has not been incorporated. Not all subtypes that are in ISO/IS 10303-42:1994 have been added to the current IFC Release.

HISTORY: New entity in IFC Release 1.5

Subclassed by Ifc4::IfcAnnotationFillArea, Ifc4::IfcBooleanResult, Ifc4::IfcBoundingBox, Ifc4::IfcCartesianPointList, Ifc4::IfcCartesianTransformationOperator, Ifc4::IfcCompositeCurveSegment, Ifc4::IfcCsgPrimitive3D, Ifc4::IfcCurve, Ifc4::IfcDirection, Ifc4::IfcFaceBasedSurfaceModel, Ifc4::IfcFillAreaStyleHatching, Ifc4::IfcFillAreaStyleTiles, Ifc4::IfcGeometricSet, Ifc4::IfcHalfSpaceSolid, Ifc4::IfcLightSource, Ifc4::IfcPlacement, Ifc4::IfcPlanarExtent, Ifc4::IfcPoint, Ifc4::IfcSectionedSpine, Ifc4::IfcShellBasedSurfaceModel, Ifc4::IfcSolidModel, Ifc4::IfcSurface, Ifc4::IfcTessellatedItem, Ifc4::IfcTextLiteral, Ifc4::IfcVector

Public Types

typedef IfcTemplatedEntityList<IfcGeometricRepresentationItem> list

Public Functions

const IfcParse::entity &declaration() const
IfcGeometricRepresentationItem(IfcEntityInstanceData *e)
IfcGeometricRepresentationItem()

Public Static Functions

const IfcParse::entity &Class()