8.9.3.32 IfcEllipse

8.9.3.32.1 Semantic definition

An IfcEllipse is a curve consisting of a set of points whose distances to two fixed points add to the same constant.

The inherited SELF\IfcConic.Position.Location is the center of the IfcEllipse, and the inherited SELF\IfcConic.Position.P[1] is the direction of the SemiAxis1.

Definition of the IfcEllipse within the a three-dimensional position coordinate system is shown in Figure 8.9.3.32.A.

It is placed within the object coordinate system of an element of which it is a representation.

An ellipse is a conic section defined by the lengths of the semi-major and semi-minor diameters and the position (center or mid point of the line joining the foci) and orientation of the curve. Interpretation of the data shall be as follows:

 C = SELF\IfcConic.Position.Location
x = SELF\IfcConic.Position.P[1]
y = SELF\IfcConic.Position.P[2]
z = SELF\IfcConic.Position.P[3]
R1 = SemiAxis1
R2 = SemiAxis2

The ellipse is parameterized as:

$λ (u) = C + (R_{1} \cos (u)) x + (R_{2} \sin (u)) y$

The parameterization range is 0 ≤ u <≤ 2π (0 ≤ u ≤ 360 degree). In the placement coordinate system defined above, the ellipse is the equation C = 0, where

$C (x, y, z) = \frac{x^{2}}{R_{1}^{2}} + \frac{y^{2}}{R_{2}^{2}} - 1$

The positive sense of the ellipse at any point is in the tangent direction, T, to the curve at the point, where

$T = (- C_{y}, C_{x}, 0)$

8.9.3.32.2 Entity inheritance

8.9.3.32.3 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.
IfcConic (1)
1	Position	IfcAxis2Placement	The location and orientation of the conic. Further details of the interpretation of this attribute are given for the individual subtypes."
Click to show 4 hidden inherited attributes
IfcEllipse (2)
2	SemiAxis1	IfcPositiveLengthMeasure	The first radius of the ellipse which shall be positive. Placement.Axes[1] gives the direction of the SemiAxis1.
3	SemiAxis2	IfcPositiveLengthMeasure	The second radius of the ellipse which shall be positive.

Table 8.9.3.32.D

8.9.3.32.4 Examples

Figure 8.9.3.32.B

Curve Parameters In Degrees
Figure 8.9.3.32.C

Curve Parameters In Radians

8.9.3.32.5 Formal representation

 ENTITY IfcEllipse
 SUBTYPE OF (IfcConic);
	SemiAxis1 : IfcPositiveLengthMeasure;
	SemiAxis2 : IfcPositiveLengthMeasure;
END_ENTITY;

8.9.3.32.6 References

IfcConic

	C = SELF\IfcConic.Position.Location
	x = SELF\IfcConic.Position.P[1]
	y = SELF\IfcConic.Position.P[2]
	z = SELF\IfcConic.Position.P[3]
	R1 = SemiAxis1
	R2 = SemiAxis2

	ENTITY IfcEllipse
	SUBTYPE OF (IfcConic);
	SemiAxis1 : IfcPositiveLengthMeasure;
	SemiAxis2 : IfcPositiveLengthMeasure;
	END_ENTITY;