IfcSectionedSurface

Item	SPF	XML	Change	Description
IFC4x2 to IFC4x3_RC1
IfcSectionedSurface			ADDED
IFC4x3_RC1 to IFC4x3_RC2
IfcSectionedSurface
CrossSectionPositions	X	X	MODIFIED	Type changed from IfcDistanceExpression to IfcPointByDistanceExpression.
IFC4x3_RC3 to IFC4x3_RC4
IfcSectionedSurface			MOVED	Schema changed from IfcRoad to IfcGeometricModelResource.
IFC4x3_RC4 Update
IfcSectionedSurface
CrossSectionPositions	X	X	MODIFIED	Type changed from IfcPointByDistanceExpression to IfcAxis2PlacementLinear.
FixedAxisVertical	X		DELETED

Semantic definitions at the entity

Entity definition

A surface constructed by sweeping potentially varying open cross sections along a curve horizontally (or near horizontally). The surface is generated by sweeping the CrossSections between CrossSectionPositions; linear interpolation is assumed, unless transitions curves between cross section points are indicated by OpenCrossProfileDef.Tags.

The profile normal is derived from the associated IfcAxis2PlacementLinear, not necessarily the tangent of the Directrix. The profile Y axis is oriented according to Axis attribute of IfcAxis2PlacementLinear and the X is derived from the cross product of Directrix and the Axis attribute of IfcAxis2PlacementLinear.

Figure 500 illustrates an IfcSectionedSurface defined using IfcOpenCrossProfileDef

Figure 500 — Sectioned surface using IfcOpenCrossProfileDef

In case of branching longitudinal breaklines, the IfcSectionedSurface shall use IfcOpenCrossProfileDef instances with varying number of cross section points. In that case, the point in two consecutive cross sections that are connected are identified by the same tag value.

Figure 501 illustrates an IfcSectionedSurface featuring branching longitudinal breaklines

Figure 501 — Sectioned surface with branching longitudinal breaklines

Informal Propositions: No two consecutive sections shall intersect.

If the directrix is not tangent continuous, the resulting surface is created by a miter at half angle between the two segments.
Very sharp edges may result in nearly impossible miter; implementer agreements may define acceptable limits for tangent discontinuity or require the directrix to be tangent continuous.
The directrix shall not intersect

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
1	Directrix	IfcCurve		The curve used to define the sweeping operation	X
2	CrossSectionPositions	IfcAxis2PlacementLinear	L[2:?]	List of positions in sequentially increasing order paired with CrossSections, indicating the position of the corresponding section along the Directrix.	X
3	CrossSections	IfcProfileDef	L[2:?]	List of cross sections in sequential order along the Directrix	X

Formal Propositions

Rule	Description
DirectrixIs3D	The curve entity which is the underlying directrix shall have the dimensionality of 3.
AreaProfileTypes	Only open curve profile types are allowed as cross sections.
SectionsSameType	The entity type for each section must be the same.
CorrespondingSectionPositions	The set of cross sections and the set of cross section placements shall be of the same size.
NoOffsets	Distance expressions must not use longitudinal, laterial or vertical offsets.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcRepresentationItem
	LayerAssignment	IfcPresentationLayerAssignment @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
	StyledByItem	IfcStyledItem @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	IfcDimensionCount		The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item. IFC4 CHANGE Derived attribute promoted from subtypes.	X
IfcSectionedSurface
1	Directrix	IfcCurve		The curve used to define the sweeping operation	X
2	CrossSectionPositions	IfcAxis2PlacementLinear	L[2:?]	List of positions in sequentially increasing order paired with CrossSections, indicating the position of the corresponding section along the Directrix.	X
3	CrossSections	IfcProfileDef	L[2:?]	List of cross sections in sequential order along the Directrix	X

Formal representations

XML Specification

 <xs:element name="IfcSectionedSurface" type="ifc:IfcSectionedSurface" substitutionGroup="ifc:IfcSurface" nillable="true"/>

 <xs:complexType name="IfcSectionedSurface">

  <xs:complexContent>

   <xs:extension base="ifc:IfcSurface">

    <xs:sequence>

     <xs:element name="Directrix" type="ifc:IfcCurve" nillable="true"/>

     <xs:element name="CrossSectionPositions">

      <xs:complexType>

       <xs:sequence>

        <xs:element ref="ifc:IfcAxis2PlacementLinear" minOccurs="2" maxOccurs="unbounded"/>

       </xs:sequence>

       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcAxis2PlacementLinear"/>

       <xs:attribute ref="ifc:cType" fixed="list"/>

       <xs:attribute ref="ifc:arraySize" use="optional"/>

      </xs:complexType>

     </xs:element>

     <xs:element name="CrossSections">

      <xs:complexType>

       <xs:sequence>

        <xs:element ref="ifc:IfcProfileDef" minOccurs="2" maxOccurs="unbounded"/>

       </xs:sequence>

       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcProfileDef"/>

       <xs:attribute ref="ifc:cType" fixed="list"/>

       <xs:attribute ref="ifc:arraySize" use="optional"/>

      </xs:complexType>

     </xs:element>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcSectionedSurface

 SUBTYPE OF (IfcSurface);

  Directrix : IfcCurve;

  CrossSectionPositions : LIST [2:?] OF IfcAxis2PlacementLinear;

  CrossSections : LIST [2:?] OF IfcProfileDef;

 WHERE

  DirectrixIs3D : Directrix.Dim = 3;
  AreaProfileTypes : SIZEOF(QUERY(temp <* CrossSections | temp.ProfileType <> IfcProfileTypeEnum.CURVE)) = 0;
  SectionsSameType : SIZEOF(QUERY(temp <* CrossSections | TYPEOF(CrossSections[1]) :<>: TYPEOF(temp))) = 0;
  CorrespondingSectionPositions : SIZEOF(CrossSections) = SIZEOF(CrossSectionPositions);
  NoOffsets : SIZEOF(QUERY(temp <* CrossSectionPositions | EXISTS(temp.Location.OffsetLateral) OR EXISTS(temp.Location.OffsetVertical) OR EXISTS(temp.Location.OffsetLongitudinal))) = 0;
END_ENTITY;

 EXPRESS-G diagram