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 elliptical arc segment is defined by using the IfcTrimmedCurve with BasisCurve being an IfcEllipse. Definition according to ISO/CD 10303-42:1992An 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
$$ T = (-C_y,C_x,0) $$
New entity in IFC1.08.9.3.32.2 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
8.9.3.32.3 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. The inverse attribute LayerAssignments has been added. 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. The inverse attribute StyledByItem has been added. |
|
| 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. |
8.9.3.32.4 Examples
8.9.3.32.5 Formal representation
ENTITY IfcEllipse
SUBTYPE OF (IfcConic);
SemiAxis1 : IfcPositiveLengthMeasure;
SemiAxis2 : IfcPositiveLengthMeasure;
END_ENTITY;