IFC 4.3.x development

8.9.3.19 IfcClothoid

Change log

IFC4X3_RC3

added

8.9.3.19.1 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:

formula

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

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

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:

formula

NOTE Formulae adapted from clothoid defined in ISO 10303-42

8.9.3.19.1 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
IfcCurve
Dim INVALID The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.
IfcSpiral
1 Position OPTIONAL IfcAxis2Placement
IfcClothoid
2 ClothoidConstantIfcLengthMeasure The constant which defines the relationship between curvature and arc length for the curve.

8.9.3.19.2 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

8.9.3.19.3 Formal representations

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