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 $\theta(s)$ and the curvature $\kappa(s)$ are defined as follows. Here, $A_0$ corresponds to the ConstantTerm and $A_1$ to the CosineTerm.

Heading Angle:

The Heading Angle $\theta(s)$ 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, $\theta(s)$ changes, showing how the curve’s direction evolves.

$$\theta(s) = \frac{1}{A_0} s \;+\; \frac{L}{\pi A_1} \sin!\biggl(\frac{\pi}{L}s\biggr)$$

Curvature:

The Curvature $\kappa(s)$ 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.

$$\kappa(s) = \frac{L}{A_0} \;+\; \frac{L}{A_1}\cos!\biggl(\frac{\pi}{L}s\biggr)$$

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 Click to hide 4 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