IfcDistanceExpression

Natural language names
Distance Expression
Change log
ItemSPFXMLChangeDescription
IFC4x1 Final 4.1.0.0
    IfcDistanceExpressionADDED
IFC4x1 Final 4.1.0.0
    IfcDistanceExpressionADDED
Semantic definitions at the entity
Entity definition

An IfcDistanceExpression describes a point relative to a basis curve according to distance along the basis curve in 3D or as projected onto the horizontal plane, offset lateral to the basis curve according to the horizontal orientation at the specified distance, offset vertical to the basis curve, and an optional additional offset parallel to the basis curve that may be used to address locations otherwise unreachable where the basis curve is tangentially discontinuous.

Attribute definitions
#AttributeTypeCardinalityDescription G
1DistanceAlongIfcLengthMeasure The distance along the basis curve, measured according to projection in the horizontal plane if AlongHorizontal is True, or according to 3D distance otherwise. If the basis curve refers to IfcAlignmentCurve and AlongHorizontal is True, then this measurement directly corresponds to IfcAlignment2DHorizontal. X
2OffsetLateralIfcLengthMeasure? Offset horizontally perpendicular to the basis curve, where positive values indicate to the left of the basis curve as facing in the direction of the basis curve, and negative values indicate to the right. If DistanceAlong coincides with a point of tangential discontinuity (within precision limits), then the tangent of the previous segment governs. X
3OffsetVerticalIfcLengthMeasure? Offset vertical to the basis curve where positive values indicate vertically upwards in global coordinates at DistanceAlong, regardless of the slope of the basis curve at such point. X
4OffsetLongitudinalIfcLengthMeasure? Offset parallel to the basis curve after applying DistanceAlong, OffsetLateral, and OffsetVertical to reach locations for the case of a tangentially discontinuous basis curve. X
5AlongHorizontalIfcBoolean? Indicates whether DistanceAlong is measured according to horizontal projection of distance (if True), or 3D distance (if False or unset). X
Inherited definitions from supertypes
Entity inheritance 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
IfcDistanceExpression
1DistanceAlongIfcLengthMeasure The distance along the basis curve, measured according to projection in the horizontal plane if AlongHorizontal is True, or according to 3D distance otherwise. If the basis curve refers to IfcAlignmentCurve and AlongHorizontal is True, then this measurement directly corresponds to IfcAlignment2DHorizontal. X
2OffsetLateralIfcLengthMeasure? Offset horizontally perpendicular to the basis curve, where positive values indicate to the left of the basis curve as facing in the direction of the basis curve, and negative values indicate to the right. If DistanceAlong coincides with a point of tangential discontinuity (within precision limits), then the tangent of the previous segment governs. X
3OffsetVerticalIfcLengthMeasure? Offset vertical to the basis curve where positive values indicate vertically upwards in global coordinates at DistanceAlong, regardless of the slope of the basis curve at such point. X
4OffsetLongitudinalIfcLengthMeasure? Offset parallel to the basis curve after applying DistanceAlong, OffsetLateral, and OffsetVertical to reach locations for the case of a tangentially discontinuous basis curve. X
5AlongHorizontalIfcBoolean? Indicates whether DistanceAlong is measured according to horizontal projection of distance (if True), or 3D distance (if False or unset). X
Formal representations
XML Specification
 <xs:element name="IfcDistanceExpression" type="ifc:IfcDistanceExpression" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>
 <xs:complexType name="IfcDistanceExpression">
  <xs:complexContent>
   <xs:extension base="ifc:IfcGeometricRepresentationItem">
    <xs:attribute name="DistanceAlong" type="ifc:IfcLengthMeasure" use="optional"/>
    <xs:attribute name="OffsetLateral" type="ifc:IfcLengthMeasure" use="optional"/>
    <xs:attribute name="OffsetVertical" type="ifc:IfcLengthMeasure" use="optional"/>
    <xs:attribute name="OffsetLongitudinal" type="ifc:IfcLengthMeasure" use="optional"/>
    <xs:attribute name="AlongHorizontal" type="ifc:IfcBoolean" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
EXPRESS Specification
ENTITY IfcDistanceExpression
 SUBTYPE OF (IfcGeometricRepresentationItem);
  DistanceAlong : IfcLengthMeasure;
  OffsetLateral : OPTIONAL IfcLengthMeasure;
  OffsetVertical : OPTIONAL IfcLengthMeasure;
  OffsetLongitudinal : OPTIONAL IfcLengthMeasure;
  AlongHorizontal : OPTIONAL IfcBoolean;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcDirectrixDistanceSweptAreaSolid IfcSectionedSurface IfcLinearPlacement IfcSectionedSolidHorizontal IfcOffsetCurveByDistances

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