IfcEllipse

BACnet MVD

#### IfcEllipse

Natural language names

| Ellipse
| Ellipse
| Ellipse

##### Semantic definitions at the entity

Entity 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.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 317. It is placed within the object coordinate system of an element of which it is a representation.
Figure 317 — 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:

> 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

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

> NOTE Entity adapted from ellipse defined in ISO 10303-42

> HISTORY New entity in IFC1.0

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
2 | SemiAxis1 | IfcPositiveLengthMeasure |  | The first radius of the ellipse which shall be positive. Placement.Axes[1] gives the direction of the SemiAxis1. |  | X
3 | SemiAxis2 | IfcPositiveLengthMeasure |  | The second radius of the ellipse which shall be positive. |  | X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcRepresentationItem

LayerAssignment

IfcPresentationLayerAssignment
@AssignedItems

S[0:1]

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.

X

StyledByItem

IfcStyledItem
@Item

S[0:1]

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.

X

X

IfcGeometricRepresentationItem
IfcCurve
| Dim :=IfcCurveDim(SELF) | IfcDimensionCount |  | The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve. | X | X
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." |  | X
IfcEllipse
2 | SemiAxis1 | IfcPositiveLengthMeasure |  | The first radius of the ellipse which shall be positive. Placement.Axes[1] gives the direction of the SemiAxis1. |  | X
3 | SemiAxis2 | IfcPositiveLengthMeasure |  | The second radius of the ellipse which shall be positive. |  | X

##### Formal representations

XML Specification
`<xs:element name="IfcEllipse" type="ifc:IfcEllipse" substitutionGroup="ifc:IfcConic" nillable="true"/>
<xs:complexType name="IfcEllipse">
<xs:complexContent>
<xs:extension base="ifc:IfcConic">
<xs:attribute name="SemiAxis1" type="ifc:IfcPositiveLengthMeasure" use="optional"/>
<xs:attribute name="SemiAxis2" type="ifc:IfcPositiveLengthMeasure" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcEllipse
SUBTYPE OF (IfcConic);
SemiAxis1 : IfcPositiveLengthMeasure;
SemiAxis2 : IfcPositiveLengthMeasure;
END_ENTITY;

EXPRESS-G diagram

`

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