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 A.

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

{ .extDef}

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:

$$ \lambda(u) = C + (R_1\cos(u))x + (R_2\sin(u))y $$

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 Click to hide 4 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 B

8.9.3.32.4 Formal representation

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

8.9.3.32.5 References

IfcConic