IfcCurveBoundedSurface

Natural language names
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Curve Bounded Surface
Change log
ItemSPFXMLChangeDescription
IFC2x3 to IFC4 4.0.0.0
    IfcCurveBoundedSurfaceADDED
IFC4 Addendum 1 4.0.1.0
    IfcCurveBoundedSurface
      ImplicitOuterMODIFIEDType changed from BOOLEAN to IfcBoolean.
Semantic definitions at the entity
Entity 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:

NOTE  Some surfaces, like IfcCylindricalSurface does not have identifiable implicit boundaries.

NOTE  Definition according to ISO/CD 10303-42:1992
The curve bounded surface is a parametric surface with curved boundaries defined by one or more boundary curves. One of the boundary curves may be the outer boundary; any number of inner boundaries is permissible. The region of the curve bounded surface in the basis surface is defined to be the portion of the basis surface in the direction of N x T from any point on the boundary, where N is the surface normal and T the boundary curve tangent vector at this point. The region so defined shall be arcwise connected.

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

HISTORY  New entity in IFC4.

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.
Attribute definitions
#AttributeTypeCardinalityDescription G
1BasisSurfaceIfcSurface The surface to be bounded. X
2BoundariesIfcBoundaryCurveS[1:?] The outer boundary of the surface. X
3ImplicitOuterIfcBoolean X
Inherited definitions from supertypes
Entity inheritance IfcBoundedSurface IfcSurface IfcGeometricRepresentationItem IfcRepresentationItem
Attribute inheritance
#AttributeTypeCardinalityDescriptionG
IfcRepresentationItem
LayerAssignmentIfcPresentationLayerAssignment
@AssignedItems
S[0:1]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.
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.
X
StyledByItemIfcStyledItem
@Item
S[0:1]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.
X
IfcGeometricRepresentationItem
IfcSurface
Dim
:=3
IfcDimensionCountThe space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.
IFC4 CHANGE Derived attribute promoted from subtypes.
X
IfcBoundedSurface
IfcCurveBoundedSurface
1BasisSurfaceIfcSurface The surface to be bounded. X
2BoundariesIfcBoundaryCurveS[1:?] The outer boundary of the surface. X
3ImplicitOuterIfcBoolean X
Formal representations
XML Specification
 <xs:element name="IfcCurveBoundedSurface" type="ifc:IfcCurveBoundedSurface" substitutionGroup="ifc:IfcBoundedSurface" nillable="true"/>
 <xs:complexType name="IfcCurveBoundedSurface">
  <xs:complexContent>
   <xs:extension base="ifc:IfcBoundedSurface">
    <xs:sequence>
     <xs:element name="BasisSurface" type="ifc:IfcSurface" nillable="true"/>
     <xs:element name="Boundaries">
      <xs:complexType>
       <xs:sequence>
        <xs:element ref="ifc:IfcBoundaryCurve" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcBoundaryCurve"/>
       <xs:attribute ref="ifc:cType" fixed="set"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>
      </xs:complexType>
     </xs:element>
    </xs:sequence>
    <xs:attribute name="ImplicitOuter" type="ifc:IfcBoolean" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
EXPRESS Specification
ENTITY IfcCurveBoundedSurface
 SUBTYPE OF (IfcBoundedSurface);
  BasisSurface : IfcSurface;
  Boundaries : SET [1:?] OF IfcBoundaryCurve;
  ImplicitOuter : IfcBoolean;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

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