IfcFixedReferenceSweptAreaSolid

Item	SPF	XML	Change	Description
IFC2x3 to IFC4
IfcFixedReferenceSweptAreaSolid			ADDED

Semantic definitions at the entity

Entity definition

An IfcFixedReferenceSweptAreaSolid is a type of swept area solid which is the result of sweeping an area along a Directrix. The swept area is provided by a subtype of IfcProfileDef. The profile is placed by an implicit cartesian transformation operator at the start point of the sweep, where the profile normal agrees to the tangent of the directrix at this point, and the profile's x-axis agrees to the FixedReference direction. The orientation of the curve during the sweeping operation is controlled by the FixedReference direction.

The SweptArea is swept along the Directrix in such a way that the origin of the local coordinate system used to define the SweptArea is on the Directrix and the local X axis is in the direction of the projection of FixedReference onto the normal plane to the directrix at this point. The resulting solid has the property that the cross section of the surface by the normal plane to the Directrix at any point is a copy of the SweptArea. The resulting swept solid is placed by the Position coordinate system.

The Directrix and the ReferenceSurface are positioned within the object coordinate system. The start of the sweeping operation is at the StartParam, the parameter value is provided based on the curve parameterization. If no StartParam is provided the start defaults to the begin of the directrix. The end of the sweeping operation is at the EndParam, the parameter value is provided based on the curve parameterization. If no EndParam is provided the end defaults to the end of the directrix.

NOTE The StartParam and the EndParam are not normalized by default, they depend upon the parameterization of the curve. However using the IfcReparametrisedCompositeCurveSegment within an IfcCompositeCurve as the directrix allows to explicitly reparameterize the underlying sweeping curve.

EXAMPLE The reference surface is any surface (plane, cylindric, composite) situated in 3D space and positioned in the object coordinate system. In many cases, it is a surface of extrusion. The directrix lies on the surface, often defined as a p-curve at this reference surface. At any point of the directrix, a plane can be constructed. The origin of the position coordinate system lies at the directrix. The Axis3 (the z-axis, or normal) of the position coordinate system is identical to the tangent of the directrix at this point, the Axis1 (the x axis, or u) of the position coordinate system is identical to the FixedReference direction. The Axis2 (the y axis, or v) is constructed. In this case the resulting swept solid is not repositioned.

The orientation of the SweptArea as it sweeps along the Directrix is precisely defined by a CartesianTransformationOperator3d with attributes:

LocalOrigin as point (0; 0; 0),
Axis1 as the FixedReference.
Axis3 as the direction of the tangent vector t at the point of the Directrix with parameter u.

The remaining attributes are defaulted to define a corresponding transformation matrix T(u), which varies with the Directrix parameter u.

NOTE The geometric shape of the solid is not dependent upon the curve parameterization; the volume depends upon the area swept and the length of the Directrix.

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

HISTORY New entity in IFC4.

Informal Propositions:

The SweptArea shall lie in the plane z = 0.
The FixedReference shall not be parallel to a tangent vector to the directrix at any point along this curve.
The Directrix curve shall be tangent continuous.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
3	Directrix	IfcCurve	[1:1]	The curve used to define the sweeping operation. The solid is generated by sweeping the SELF\IfcSweptAreaSolid.SweptArea along the Directrix.	X
4	StartParam	IfcParameterValue	[0:1]	The parameter value on the Directrix at which the sweeping operation commences. If no value is provided the start of the sweeping operation is at the start of the Directrix.	X
5	EndParam	IfcParameterValue	[0:1]	The parameter value on the Directrix at which the sweeping operation ends. < style="color:blue">If no value is provided the end of the sweeping operation is at the end of the Directrix.	X
6	FixedReference	IfcDirection	[1:1]	The direction providing the fixed axis1 (x-axis) direction for orienting the swept area during the sweeping operation along the Directrix.	X

Formal Propositions

Rule	Description
DirectrixBounded	If the values for StartParam or EndParam are omited, then the Directrix has to be a bounded or closed curve.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
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.	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.	X
IfcGeometricRepresentationItem
IfcSolidModel
	Dim :=3	IfcDimensionCount	[1:1]	The space dimensionality of this class, it is always 3.	X
IfcSweptAreaSolid
1	SweptArea	IfcProfileDef	[1:1]	The surface defining the area to be swept. It is given as a profile definition within the xy plane of the position coordinate system.	X
2	Position	IfcAxis2Placement3D	[0:1]	Position coordinate system for the resulting swept solid of the sweeping operation. The position coordinate system allows for re-positioning of the swept solid. If not provided, the swept solid remains within the position as determined by the cross section or by the directrix used for the sweeping operation.	X
IfcFixedReferenceSweptAreaSolid
3	Directrix	IfcCurve	[1:1]	The curve used to define the sweeping operation. The solid is generated by sweeping the SELF\IfcSweptAreaSolid.SweptArea along the Directrix.	X
4	StartParam	IfcParameterValue	[0:1]	The parameter value on the Directrix at which the sweeping operation commences. If no value is provided the start of the sweeping operation is at the start of the Directrix.	X
5	EndParam	IfcParameterValue	[0:1]	The parameter value on the Directrix at which the sweeping operation ends. < style="color:blue">If no value is provided the end of the sweeping operation is at the end of the Directrix.	X
6	FixedReference	IfcDirection	[1:1]	The direction providing the fixed axis1 (x-axis) direction for orienting the swept area during the sweeping operation along the Directrix.	X

Formal representations

XSD Specification

 <xs:element name="IfcFixedReferenceSweptAreaSolid" type="ifc:IfcFixedReferenceSweptAreaSolid" substitutionGroup="ifc:IfcSweptAreaSolid" nillable="true"/>

 <xs:complexType name="IfcFixedReferenceSweptAreaSolid">

  <xs:complexContent>

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

    <xs:sequence>

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

     <xs:element name="FixedReference" type="ifc:IfcDirection" nillable="true"/>

    </xs:sequence>

    <xs:attribute name="StartParam" type="ifc:IfcParameterValue" use="optional"/>

    <xs:attribute name="EndParam" type="ifc:IfcParameterValue" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcFixedReferenceSweptAreaSolid

 SUBTYPE OF (IfcSweptAreaSolid);

  Directrix : IfcCurve;

  StartParam : OPTIONAL IfcParameterValue;

  EndParam : OPTIONAL IfcParameterValue;

  FixedReference : IfcDirection;

 WHERE

  DirectrixBounded : (EXISTS(StartParam) AND EXISTS(EndParam)) OR 
(SIZEOF(['IFCGEOMETRYRESOURCE.IFCCONIC', 'IFCGEOMETRYRESOURCE.IFCBOUNDEDCURVE'] * TYPEOF(Directrix)) = 1);
END_ENTITY;

 EXPRESS-G diagram

	Festkörper - Entlang einer Leitlinie mit konstanter Richtung extrudiert
	Fixed Reference Swept Area Solid