8.9.3.24 IfcCosineSpiral

AbV ⓘ

8.9.3.24.1 Semantic definition

IfcCosineSpiral is a type of spiral curve for which the curvature change is dependent on the cosine function.

The cosine spiral curve is parameterized by its curve length and for a given parameter $s$ , the heading angle $θ (s)$ and the curvature $κ (s)$ are defined as follows. Here, $A_{0}$ corresponds to the ConstantTerm and $A_{1}$ to the CosineTerm.

Heading Angle:

The Heading Angle $θ (s)$ represents the orientation of the tangent to the curve at a given arc length. It indicates the direction in which the curve is "pointing" at that point. As you move along the curve, $θ (s)$ changes, showing how the curve’s direction evolves.

$θ (s) = \frac{1}{A_{0}} s + \frac{L}{π A_{1}} \sin! (\frac{π}{L} s)$

Curvature:

The Curvature $κ (s)$ describes how quickly the heading angle changes with respect to the arc length $s$ . It reflects the "tightness" of the curve. Higher curvature values correspond to sharper bends, and lower curvature values correspond to straighter segments.

$κ (s) = \frac{L}{A_{0}} + \frac{L}{A_{1}} \cos! (\frac{π}{L} s)$

8.9.3.24.2 Entity inheritance

8.9.3.24.3 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
IfcCosineSpiral (2)
2	CosineTerm	IfcLengthMeasure	No description available.
3	ConstantTerm	OPTIONAL IfcLengthMeasure	No description available.

Table 8.9.3.24.A

8.9.3.24.4 Formal representation

 ENTITY IfcCosineSpiral
 SUBTYPE OF (IfcSpiral);
	CosineTerm : IfcLengthMeasure;
	ConstantTerm : OPTIONAL IfcLengthMeasure;
END_ENTITY;

8.9.3.24.5 References

IfcSpiral