IFC (IFC4X3) development IfcCurveBoundedSurface Semantic definition

The IfcCurveBoundedSurface is a parametric surface with boundaries defined by p-curves, that is, a curve which lies on the basis of a surface and is defined in the parameter space of that surface. The p-curve is a special type of a composite curve segment and shall only be used to bound a surface.

The outer boundary shall be either defined by:

  • an IfcOuterBoundaryCurve a closed composite curve on surface for the definition of an outer boundary, in this case the attribute ImplicitOuter has to be set to FALSE, or
  • an implicit boundary of the bounded surface, e.g. the u1, u2, v1, v2 of IfcRectangularTrimmedSurface, in this case the attribute ImplicitOuter has to be set to TRUE.

Informal Propositions:

  1. Each curve in the set of Boundaries shall be closed.
  2. No two curves in the set of Boundaries shall intersect.
  3. At most one of the boundary curves may enclose any other boundary curve. If an IfcOuterBoundaryCurve is designated, only that curve may enclose any other boundary curve. Entity inheritance 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.

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.

IfcSurface (1)
* Dim IfcDimensionCount

This attribute is formally derived.


The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.

Click to show 3 hidden inherited attributes Click to hide 3 inherited attributes
IfcCurveBoundedSurface (3)
1 BasisSurface IfcSurface

The surface to be bounded.

2 Boundaries SET [1:?] OF IfcBoundaryCurve

The outer boundary of the surface.

3 ImplicitOuter IfcBoolean

No description available.

Table Formal representation

ENTITY IfcCurveBoundedSurface
 SUBTYPE OF (IfcBoundedSurface);
	BasisSurface : IfcSurface;
	Boundaries : SET [1:?] OF IfcBoundaryCurve;
	ImplicitOuter : IfcBoolean;
END_ENTITY; References

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