IFC 4.3.x development

8.9.3.68 IfcSurface

8.9.3.68.1 Semantic definitions at the entity

An IfcSurface is a 2-dimensional representation item positioned in 3-dimensional space. 2-dimensional means that each point at the surface can be defined by a 2-dimensional coordinate system, usually by u and v coordinates.

NOTE  Definition according to ISO/CD 10303-42:1992
A surface can be envisioned as a set of connected points in 3-dimensional space which is always locally 2-dimensional, but need not be a manifold.

NOTE  Entity adapted from surface defined in ISO 10303-42.

HISTORY  New entity in IFC1.5

Informal Propositions:

  1. A surface has non zero area.
  2. A surface is arcwise connected.

8.9.3.68.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignmentSET [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
IfcSurface
Dim INVALID The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.

> IFC4 CHANGE Derived attribute promoted from subtypes.

8.9.3.68.2 Entity inheritance

dot_inheritance IfcSurface_children 3 more... IfcSurface IfcSurface IfcSurface_children->IfcSurface IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcSurface->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.9.3.68.3 Formal representations

ENTITY IfcSurface
 ABSTRACT SUPERTYPE OF (ONEOF
	(IfcBoundedSurface
	,IfcElementarySurface
	,IfcSectionedSurface
	,IfcSweptSurface))
 SUBTYPE OF (IfcGeometricRepresentationItem);
 DERIVE
	Dim : IfcDimensionCount := 3;
END_ENTITY;