IFC 4.3.x development IfcClothoid

Change log


added Semantic definitions at the entity

A clothoid is a planar curve in the form of a spiral. This curve has the property that the curvature varies linearly with the arc length.

NOTE Definition according to ISO 10303-42:2003

Interpretation of the data shall be as follows:

C = SELF\IfcSpiral.Position.Location x = SELF\IfcSpiral.Position.P[1] y = SELF\IfcSpiral.Position.P[2] A = ClothoidConstant and the clothoid is parameterized as:


and the parametric range is: -∞ < u < ∞

The arc length s of the curve, from the point C, is given by the formula:


The curvature κ and radius of the curvature ρ, at any point of the curve, are related to the arc length s by the formulae:


NOTE Formulae adapted from clothoid defined in ISO 10303-42 Attributes

# Attribute Type Description
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.
Dim INVALID The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.
1 Position OPTIONAL IfcAxis2Placement
2 ClothoidConstantIfcLengthMeasure The constant which defines the relationship between curvature and arc length for the curve. Entity inheritance

dot_inheritance IfcClothoid IfcClothoid IfcSpiral IfcSpiral IfcClothoid->IfcSpiral IfcSpiral_children 5 more... IfcSpiral_children->IfcSpiral IfcCurve IfcCurve IfcSpiral->IfcCurve IfcCurve_children 7 more... IfcCurve_children->IfcCurve IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcCurve->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem Formal representations

ENTITY IfcClothoid
 SUBTYPE OF (IfcSpiral);
	ClothoidConstant : IfcLengthMeasure;