IfcShapeRepresentation

Definition from ISO/CD 10303-42:1992: The shape representation is a specific kind of representation that represents a shape.

Definition from IAI: The IfcShapeRepresentation represents the concept of a particular geometric representation of a product or a product component within a specific geometric representation context. The inherited attribute RepresentationType is used to define the geometric model used for the shape representation, the inherited attribute RepresentationIdentifier is used to denote the part of the representation captured by the IfcShapeRepresentation (e.g. Axis, Body, etc.).

Several representation types for shape representation are included as predefined types:

Curve2D		2 dimensional curves
GeometricSet		points, curves, surfaces (2 or 3 dimensional)
	GeometricCurveSet	points, curves (2 or 3 dimensional)
SurfaceModel		face based and shell based surface model
SolidModel		including swept solid, Boolean results and Brep bodies more specific types are:
	SweptSolid	swept area solids, by extrusion and revolution
	Brep	faceted Brep's with and without voids
	CSG	Boolean results of operations between solid models, half spaces and Boolean results
	Clipping	Boolean differences between swept area solids, half spaces and Boolean results
	AdvancedSweptSolid	swept area solids created by sweeping a profile along a directrix
additional types		some additional representation types are given:
	BoundingBox	simplistic 3D representation by a bounding box
	SectionedSpine	cross section based representation of a spine curve and planar cross sections. It can represent a surface or a solid and the interpolations of the between the cross sections is not defined
	MappedRepresentation	representation based on mapped item(s), referring to a representation map. Note: it can be seen as an inserted block reference. The shape representation of the mapped item has a representation type declaring the type of its representation items.

Table 1: string values for the inherited attribute 'RepresentationType'.

NOTE: The definition of this entity relates to the STEP entity shape_representation. Please refer to ISO/IS 10303-41:1994 for the final definition of the formal standard.

HISTORY: New entity in IFC Release 1.5.

EXPRESS specification:

ENTITY IfcShapeRepresentation

SUBTYPE OF (

IfcShapeModel);

WHERE

WR21	:	'IFCREPRESENTATIONRESOURCE.IFCGEOMETRICREPRESENTATIONCONTEXT' IN TYPEOF(SELF\IfcRepresentation.ContextOfItems);
WR22	:	SIZEOF(QUERY(temp <* Items \| ('IFCTOPOLOGYRESOURCE.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp)) AND (NOT(SIZEOF( ['IFCTOPOLOGYRESOURCE.IFCVERTEXPOINT', 'IFCTOPOLOGYRESOURCE.IFCEDGECURVE', 'IFCTOPOLOGYRESOURCE.IFCFACESURFACE'] * TYPEOF(temp)) = 1)) )) = 0;
WR23	:	EXISTS(SELF\IfcRepresentation.RepresentationType);
WR24	:	IfcShapeRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);

END_ENTITY;

Formal Propositions:

WR21	:	The context to which the IfcShapeRepresentation is assign, shall be of type IfcGeometricRepresentationContext.
WR22	:	No topological representation item shall be directly used for shape representations, with the exception of IfcVertexPoint, IfcEdgeCurve, IfcFaceSurface.
WR23	:	A representation type should be given to the shape representation.
WR24	:	Checks the proper use of Items according to the RepresentationType.

Inheritance graph

ENTITY IfcShapeRepresentation;

ENTITY IfcRepresentation;

ContextOfItems

IfcRepresentationContext;

RepresentationIdentifier

OPTIONAL IfcLabel;

RepresentationType

OPTIONAL IfcLabel;

Items

SET [1:?] OF IfcRepresentationItem;

INVERSE

RepresentationMap

SET [0:1] OF IfcRepresentationMap FOR MappedRepresentation;

LayerAssignments

SET OF IfcPresentationLayerAssignment FOR Assigneditems;

OfProductRepresentation

SET [0:1] OF IfcProductRepresentation FOR Representations;

ENTITY IfcShapeModel;

INVERSE

OfShapeAspect

SET [0:1] OF IfcShapeAspect FOR ShapeRepresentations;

ENTITY IfcShapeRepresentation;

END_ENTITY;