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 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 B

where:

Figure 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 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