IfcDistanceExpression

Item	SPF	XML	Change	Description
IFC4x1 Release Candidate 3
IfcDistanceExpression			ADDED

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

#	Attribute	Type	Cardinality	Description	G
1	DistanceAlong	IfcLengthMeasure		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
2	OffsetLateral	IfcLengthMeasure	?	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
3	OffsetVertical	IfcLengthMeasure	?	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
4	OffsetLongitudinal	IfcLengthMeasure	?	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
5	AlongHorizontal	IfcBoolean	?	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

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
IfcDistanceExpression
1	DistanceAlong	IfcLengthMeasure		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
2	OffsetLateral	IfcLengthMeasure	?	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
3	OffsetVertical	IfcLengthMeasure	?	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
4	OffsetLongitudinal	IfcLengthMeasure	?	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
5	AlongHorizontal	IfcBoolean	?	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;

 EXPRESS-G diagram