8.9.3.72 IfcThirdOrderPolynomialSpiral

AbV ⓘ

8.9.3.72.1 Semantic definition

The IfcThirdOrderPolynomialSpiral is a specialization of IfcSpiral. The curvature κ and radius of the curvature ρ, at any point of the curve, are related to the arc length s by the third order formulae:

Figure 8.9.3.72.A

Interpretation of the parameters:

C = SELF\IfcSpiral.Position.Location x = SELF\IfcSpiral.Position.P[1] y = SELF\IfcSpiral.Position.P[2] A₃ = CubicTerm A₂ = QuadraticTerm A₁ = LinearTerm A₀ = ContantTerm

and the third order polynomial spiral is parameterized as:

Figure 8.9.3.72.B

where:

Figure 8.9.3.72.C

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

8.9.3.72.2 Entity inheritance

8.9.3.72.3 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.
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	IfcAxis2Placement	No description available.
Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcThirdOrderPolynomialSpiral (4)
2	CubicTerm	IfcLengthMeasure	The constant that defines the cubic term in the equation which defines the relation between curvature and arc length for the curve.
3	QuadraticTerm	OPTIONAL IfcLengthMeasure	The constant that defines the quadratic term in the equation which defines the relation between curvature and arc length for the curve.
4	LinearTerm	OPTIONAL IfcLengthMeasure	The constant that defines the linear term in the equation which defines the relation between curvature and arc length for the curve.
5	ConstantTerm	OPTIONAL IfcLengthMeasure	The constant that defines the constant term in the equation which defines the relation between curvature and arc length for the curve.

Table 8.9.3.72.D

8.9.3.72.4 Formal representation

ENTITY IfcThirdOrderPolynomialSpiral
 SUBTYPE OF (IfcSpiral);
	CubicTerm : IfcLengthMeasure;
	QuadraticTerm : OPTIONAL IfcLengthMeasure;
	LinearTerm : OPTIONAL IfcLengthMeasure;
	ConstantTerm : OPTIONAL IfcLengthMeasure;
END_ENTITY;

8.9.3.72.5 References

IfcSpiral