8.9.3.64 IfcSineSpiral

AbV ⓘ

8.9.3.64.1 Semantic definition

IfcSineSpiral is a type of spiral curve for which the curvature change is dependent on the sine function.

The sine 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, $A_1$ to the LinearTerm, and $A_2$ to the SineTerm.

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. By following changes in $\theta(s)$ along the curve, one can understand how the curve rotates and changes direction as it progresses.

$$\theta(s) = \frac{1}{A_0} s \;+\; \frac{1}{2}\left(\frac{A_1}{|A_1|}\right)\left(\frac{s}{|A_1|}\right)^2\;-\; \frac{L}{2\pi A_2}\biggl(\cos\bigl(\frac{2\pi}{L}s\bigr)-1\biggr)$$

Curvature:

The Curvature $\kappa(s)$ describes how quickly the heading angle changes with respect to the arc length. In other words, curvature indicates how "tight" a curve is turning at any point. A larger curvature corresponds to a sharper bend, while a smaller curvature corresponds to a straighter segment of the curve.

$$ \kappa(s) = \frac{L}{A_0} \;+\; \frac{A_1}{|A_1|}\left(\frac{L}{|A_1|}\right)^2 \frac{s}{L} \;+\; \frac{L}{A_2}\sin\left(\frac{2\pi}{L}s\right) $$

8.9.3.64.2 Entity inheritance

8.9.3.64.3 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
IfcSineSpiral (3)
2	SineTerm	IfcLengthMeasure	No description available.
3	LinearTerm	OPTIONAL IfcLengthMeasure	No description available.
4	ConstantTerm	OPTIONAL IfcLengthMeasure	No description available.

Table 8.9.3.64.A

8.9.3.64.4 Formal representation

ENTITY IfcSineSpiral
 SUBTYPE OF (IfcSpiral);
	SineTerm : IfcLengthMeasure;
	LinearTerm : OPTIONAL IfcLengthMeasure;
	ConstantTerm : OPTIONAL IfcLengthMeasure;
END_ENTITY;

8.9.3.64.5 References

IfcSpiral