8.9.3.49 IfcPointByDistanceExpression

8.9.3.49.1 Semantic 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.

8.9.3.49.2 Entity inheritance

8.9.3.49.3 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. 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.
	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. IFC2x3-CHANGE The inverse attribute StyledByItem has been added.
Click to show 2 hidden inherited attributes Click to hide 2 inherited attributes
IfcPointByDistanceExpression (6)
1	DistanceAlong	IfcCurveMeasureSelect	The distance along the basis curve measured as either a IfcLengthMeasure or IfcParameterValue.
2	OffsetLateral	OPTIONAL 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.
3	OffsetVertical	OPTIONAL 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.
4	OffsetLongitudinal	OPTIONAL 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.
5	BasisCurve	IfcCurve	No description available.
*	Dim	IfcDimensionCount	This attribute is formally derived. `BasisCurve.Dim`

Table 8.9.3.49.B

8.9.3.49.4 Examples

Figure 8.9.3.49.A

LinearPlacement_2

8.9.3.49.5 Formal representation

ENTITY IfcPointByDistanceExpression
 SUBTYPE OF (IfcPoint);
	DistanceAlong : IfcCurveMeasureSelect;
	OffsetLateral : OPTIONAL IfcLengthMeasure;
	OffsetVertical : OPTIONAL IfcLengthMeasure;
	OffsetLongitudinal : OPTIONAL IfcLengthMeasure;
	BasisCurve : IfcCurve;
 DERIVE
	 Dim : IfcDimensionCount := BasisCurve.Dim;
END_ENTITY;