8.9.3.33 IfcEllipse
8.9.3.33.1 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 S_ELF\IfcConic.Position.Position.P[1] is the direction of the _SemiAxis1.
Definition of the IfcEllipse within the a threedimensional position coordinate system is shown in Figure 8.9.3.33.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 semimajor and semiminor 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 = position.location
x = position.p[1]
y = position.p[2]
z = position.p[3]
R1 = semi axis 1
R2 = semi axis 2
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
$$ T = (C_y,C_x,0) $$
8.9.3.33.2 Entity inheritance

 IfcCurve
 IfcAnnotationFillArea
 IfcBooleanResult
 IfcBoundingBox
 IfcCartesianPointList
 IfcCartesianTransformationOperator
 IfcCsgPrimitive3D
 IfcDirection
 IfcFaceBasedSurfaceModel
 IfcFillAreaStyleHatching
 IfcFillAreaStyleTiles
 IfcGeometricSet
 IfcHalfSpaceSolid
 IfcLightSource
 IfcPlacement
 IfcPlanarExtent
 IfcPoint
 IfcSectionedSpine
 IfcSegment
 IfcShellBasedSurfaceModel
 IfcSolidModel
 IfcSurface
 IfcTessellatedItem
 IfcTextLiteral
 IfcVector
8.9.3.33.3 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. 

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. 

IfcCurve (1)  
*  Dim  IfcDimensionCount 
This attribute is formally derived.
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. 
8.9.3.33.4 Formal representation
ENTITY IfcEllipse
SUBTYPE OF (IfcConic);
SemiAxis1 : IfcPositiveLengthMeasure;
SemiAxis2 : IfcPositiveLengthMeasure;
END_ENTITY;