8.8.3.20 IfcFixedReferenceSweptAreaSolid
8.8.3.20.1 Semantic 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 start tangent of the directrix at this point, and the profile's xaxis agrees to the orthogonal projection of the FixedReference direction within the plane of start tangent and Fixed_Reference. 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 xaxis 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, being either the parameter value based on the curve parameterization, or by a length measured along the directrix from its beginning. If no StartParam is provided the start defaults to the begin of the directrix. The end of the sweeping operation is at the EndParam, being either the parameter value based on the curve parameterization, or by a length measured along the directrix from its beginning. If no EndParam is provided the end defaults to the end of the directrix.
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 orthogonal projection of the FixedReference onto the normal plane defined by Axis3.
 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.
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.
8.8.3.20.2 Entity inheritance

 IfcSolidModel
 IfcAnnotationFillArea
 IfcBooleanResult
 IfcBoundingBox
 IfcCartesianPointList
 IfcCartesianTransformationOperator
 IfcCsgPrimitive3D
 IfcCurve
 IfcDirection
 IfcFaceBasedSurfaceModel
 IfcFillAreaStyleHatching
 IfcFillAreaStyleTiles
 IfcGeometricSet
 IfcHalfSpaceSolid
 IfcLightSource
 IfcPlacement
 IfcPlanarExtent
 IfcPoint
 IfcSectionedSpine
 IfcSegment
 IfcShellBasedSurfaceModel
 IfcSurface
 IfcTessellatedItem
 IfcTextLiteral
 IfcVector
8.8.3.20.3 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. 

IfcSolidModel (1)  
*  Dim  IfcDimensionCount 
This attribute is formally derived.
The space dimensionality of this class, it is always 3. 
IfcSweptAreaSolid (2)  
1  SweptArea  IfcProfileDef 
The surface defining the area to be swept. It is given as a profile definition within the xy plane of the position coordinate system. 
2  Position  OPTIONAL IfcAxis2Placement3D 
Position coordinate system for the resulting swept solid of the sweeping operation. The position coordinate system allows for repositioning 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. 
IfcDirectrixCurveSweptAreaSolid (3)  
3  Directrix  IfcCurve 
The curve used to define the sweeping operation. The solid is generated by sweeping the SELF\IfcSweptAreaSolid.SweptArea along the Directrix. 
4  StartParam  OPTIONAL IfcCurveMeasureSelect 
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. 
5  EndParam  OPTIONAL IfcCurveMeasureSelect 
The parameter value on the Directrix at which the sweeping operation ends. If no value is provided the end of the sweeping operation is at the end of the Directrix. 
Click to show 8 hidden inherited attributes Click to hide 8 inherited attributes  
IfcFixedReferenceSweptAreaSolid (1)  
6  FixedReference  IfcDirection 
No description available. 
8.8.3.20.4 Examples
8.8.3.20.5 Formal representation
ENTITY IfcFixedReferenceSweptAreaSolid
SUPERTYPE OF (ONEOF
(IfcDirectrixDerivedReferenceSweptAreaSolid))
SUBTYPE OF (IfcDirectrixCurveSweptAreaSolid);
FixedReference : IfcDirection;
END_ENTITY;