IFC 4.3.0.1 (IFC4X3) development

8.9.3.19 IfcClothoid

8.9.3.19.1 Semantic definition

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.

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

The clothoid is parameterized as:

$$\lambda(u)=C+A\sqrt{\pi}(\int_{0}^{u}\cos(\pi\frac{At^2}{2|A|})dt\ x+\int_{0}^{u}\sin(\pi\frac{At^2}{2|A|})dt\ y)$$

The parametric range is: -∞ < u < ∞

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

$$s=Au\sqrt{\pi}$$

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:

$$\kappa=\frac{As}{|A^3|}, \rho=\frac{1}{\kappa}$$

8.9.3.19.2 Entity inheritance

8.9.3.19.3 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.

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.

IfcCurve (1)
* Dim IfcDimensionCount

This attribute is formally derived.

IfcCurveDim(SELF)

The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.

IfcSpiral (1)
1 Position OPTIONAL IfcAxis2Placement

No description available.

Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcClothoid (1)
2 ClothoidConstant IfcLengthMeasure

The constant which defines the relationship between curvature and arc length for the curve.

Table 8.9.3.19.A

8.9.3.19.4 Formal representation

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

8.9.3.19.5 References

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8.9.3.19.6 Changelog

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