IFC 4.3.x development

8.9.3.33 IfcEllipse

8.9.3.33.1 Semantic definitions at the entity

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.

ellipse

Definition of the IfcEllipse within the a three-dimensional position coordinate system is shown in Figure 1.

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

Figure 1 — Ellipse placement and parameterization

 

NOTE  An elliptical arc segment is defined by using the IfcTrimmedCurve with BasisCurve

NOTE Definition according to ISO/CD 10303-42:1992
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 = position.location x = position.p[1] y = position.p[2] z = position.p[3] R1 = semi axis 1 R2 = semi axis 2 and the ellipse is parameterized as:

formula 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

formula

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

formula

NOTE  Entity adapted from ellipse defined in ISO 10303-42

HISTORY  New entity in IFC1.0

8.9.3.33.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignmentSET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.
IfcGeometricRepresentationItem
IfcCurve
Dim INVALID The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.
IfcConic
1 Position IfcAxis2Placement The location and orientation of the conic. Further details of the interpretation of this attribute are given for the individual subtypes."
IfcEllipse
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.

8.9.3.33.2 Entity inheritance

dot_inheritance IfcEllipse IfcEllipse IfcConic IfcConic IfcEllipse->IfcConic IfcCircle IfcCircle IfcCircle->IfcConic IfcCurve IfcCurve IfcConic->IfcCurve IfcCurve_children 7 more... IfcCurve_children->IfcCurve IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcCurve->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.9.3.33.3 Formal representations

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