IFC 4.3.x development

8.9.3.49 IfcPointByDistanceExpression

Change log

IFC4X3_RC3

added

8.9.3.49.1 Semantic definitions at the entity

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.

8.9.3.49.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.
IfcGeometricRepresentationItem
IfcPoint
IfcPointByDistanceExpression
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 OffsetLongitudinalOPTIONAL 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
Dim INVALID

8.9.3.49.2 Entity inheritance

dot_inheritance IfcPointByDistanceExpression IfcPointByDistanceExpression IfcPoint IfcPoint IfcPointByDistanceExpression->IfcPoint IfcPoint_children 3 more... IfcPoint_children->IfcPoint IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcPoint->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.9.3.49.3 Formal representations

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;