Spirals are curves that revolve around a point while increasing its length. In general, these curves are parameterized in the following way: x = r(φ) cosφ y = r(φ) sinφ
In the case of the clothoid and higher order transition spirals, the parametrization is: x = ∫cos &Theta dl y = ∫sin &Theta dl
where &Theta is the deflection or bearing angle and dl the differential of the spiral length.
|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.
|Dim||INVALID||The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.|
ENTITY IfcSpiral ABSTRACT SUPERTYPE OF (ONEOF (IfcClothoid ,IfcCosine ,IfcSecondOrderPolynomialSpiral ,IfcSeventhOrderPolynomialSpiral ,IfcSine ,IfcThirdOrderPolynomialSpiral)) SUBTYPE OF (IfcCurve); Position : OPTIONAL IfcAxis2Placement; END_ENTITY;