IFC 4.3.x development

8.9.3.67 IfcSpiral

Change log

IFC4X3_RC3

added

8.9.3.67.1 Semantic definitions at the entity

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.

8.9.3.67.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignmentSET [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

8.9.3.67.2 Entity inheritance

dot_inheritance IfcSpiral_children 5 more... IfcSpiral IfcSpiral 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

8.9.3.67.3 Formal representations

ENTITY IfcSpiral
 ABSTRACT SUPERTYPE OF (ONEOF
	(IfcClothoid
	,IfcCosine
	,IfcSecondOrderPolynomialSpiral
	,IfcSeventhOrderPolynomialSpiral
	,IfcSine
	,IfcThirdOrderPolynomialSpiral))
 SUBTYPE OF (IfcCurve);
	Position : OPTIONAL IfcAxis2Placement;
END_ENTITY;