IfcPointByDistanceExpression

Item	SPF	XML	Change	Description
IFC4x3_RC1 to IFC4x3_RC2
IfcPointByDistanceExpression			MODIFIED	Name changed from IfcDistanceExpression to IfcPointByDistanceExpression.
DistanceAlong	X	X	MODIFIED	Type changed from IfcLengthMeasure to IfcCurveMeasureSelect.
BasisCurve	X	X	MODIFIED	Name changed from AlongHorizontal to BasisCurve. Type changed from IfcBoolean to IfcCurve. Instantiation changed from OPTIONAL.

Semantic definitions at the entity

Entity definition

An IfcPointByDistanceExpression describes a point relative to a basis curve according to distance along the basis curve. The offsets default to the initial context of the curve relative to it's tangent either specified in IfcProduct.Placement or in the case of a segmented curve to the IfcCurveSegment StartPlacement where the values correspond to the following:

lateral to the basis curve
offset vertical to the basis curve
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	IfcCurveMeasureSelect		The distance along the basis curve measured as either a IfcLengthMeasure or IfcParameterValue.	X
2	OffsetLateral	IfcLengthMeasure	?	Default offset horizontally is measured perpendicular to the basis curve, where positive values indicate to the left of the basis curve as facing in the positive parametrization 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	?	Default offset vertical to the basis curve where positive values indicate perpendicular to the tangent at DistanceAlong in the plane of the tangent perpendicular to the global XY plane.	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	BasisCurve	IfcCurve			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
IfcPoint
	Dim :=IfcPointDim(SELF)	IfcDimensionCount		The space dimensionality of this abstract class, handled by a function specific for concrete subtypes. Determined by the number of coordinate components in case of IfcCartesianPoint or by the dimensionality of the basis curve or surface in other cases.	X
IfcPointByDistanceExpression
1	DistanceAlong	IfcCurveMeasureSelect		The distance along the basis curve measured as either a IfcLengthMeasure or IfcParameterValue.	X
2	OffsetLateral	IfcLengthMeasure	?	Default offset horizontally is measured perpendicular to the basis curve, where positive values indicate to the left of the basis curve as facing in the positive parametrization 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	?	Default offset vertical to the basis curve where positive values indicate perpendicular to the tangent at DistanceAlong in the plane of the tangent perpendicular to the global XY plane.	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	BasisCurve	IfcCurve			X

Formal representations

XML Specification

 <xs:element name="IfcPointByDistanceExpression" type="ifc:IfcPointByDistanceExpression" substitutionGroup="ifc:IfcPoint" nillable="true"/>

 <xs:complexType name="IfcPointByDistanceExpression">

  <xs:complexContent>

   <xs:extension base="ifc:IfcPoint">

    <xs:sequence>

     <xs:element name="DistanceAlong">

      <xs:complexType>

       <xs:group ref="ifc:IfcCurveMeasureSelect"/>

      </xs:complexType>

     </xs:element>

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

    </xs:sequence>

    <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:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcPointByDistanceExpression

 SUBTYPE OF (IfcPoint);

  DistanceAlong : IfcCurveMeasureSelect;

  OffsetLateral : OPTIONAL IfcLengthMeasure;

  OffsetVertical : OPTIONAL IfcLengthMeasure;

  OffsetLongitudinal : OPTIONAL IfcLengthMeasure;

  BasisCurve : IfcCurve;

END_ENTITY;

 EXPRESS-G diagram