IfcDirection

BACnet MVD

#### IfcDirection

Natural language names

| Richtung
| Direction
| Direction

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC4 Addendum 1
IfcDirection |  |  |  |
DirectionRatios |  |  | MODIFIED | Type changed from REAL to IfcReal.

##### Semantic definitions at the entity

Entity definition

The IfcDirection provides a direction in two or three dimensional space depending on the number of DirectionRatio's provided. The IfcDirection does not imply a vector length, and the direction ratios does not have to be normalized.

> NOTE Definition according to ISO/CD 10303-42:1992
> This entity defines a general direction vector in two or three dimensional space. The actual magnitudes of the components have no effect upon the direction being defined, only the ratios X:Y:Z or X:Y are significant.

> NOTE The components of this entity are not normalized. If a unit vector is required it should be normalized before use.

> NOTE Entity adapted from direction defined in ISO 10303-42.

> HISTORY New entity in IFC1.0

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
1 | DirectionRatios | IfcReal | L[2:3] | The components in the direction of X axis (DirectionRatios[1]), of Y axis (DirectionRatios[2]), and of Z axis (DirectionRatios[3]) | X | X
| Dim :=HIINDEX(DirectionRatios) | IfcDimensionCount |  | The space dimensionality of this class, defined by the number of real in the list of DirectionRatios. | X | X

Formal Propositions

Rule | Description
--- | ---
MagnitudeGreaterZero | The magnitude of the direction vector shall be greater than zero.

##### 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
IfcDirection
1 | DirectionRatios | IfcReal | L[2:3] | The components in the direction of X axis (DirectionRatios[1]), of Y axis (DirectionRatios[2]), and of Z axis (DirectionRatios[3]) | X | X
| Dim :=HIINDEX(DirectionRatios) | IfcDimensionCount |  | The space dimensionality of this class, defined by the number of real in the list of DirectionRatios. | X | X

##### Formal representations

XML Specification
`<xs:element name="IfcDirection" type="ifc:IfcDirection" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>
<xs:complexType name="IfcDirection">
<xs:complexContent>
<xs:extension base="ifc:IfcGeometricRepresentationItem">
<xs:attribute name="DirectionRatios" use="optional">
<xs:simpleType>
<xs:restriction>
<xs:simpleType>
<xs:list itemType="ifc:IfcReal"/>
</xs:simpleType>
<xs:minLength value="2"/>
<xs:maxLength value="3"/>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcDirection
SUBTYPE OF (IfcGeometricRepresentationItem);
DirectionRatios : LIST [2:3] OF IfcReal;
DERIVE
Dim : IfcDimensionCount := HIINDEX(DirectionRatios);
WHERE
MagnitudeGreaterZero : SIZEOF(QUERY(Tmp <* DirectionRatios | Tmp <> 0.0)) > 0;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcStructuralCurveConnection IfcStructuralCurveMember IfcGridPlacementDirectionSelect IfcExtrudedAreaSolid IfcFixedReferenceSweptAreaSolid IfcAxis1Placement IfcAxis2Placement2D IfcAxis2Placement3D IfcCartesianTransformationOperator IfcCartesianTransformationOperator2D IfcCartesianTransformationOperator3D IfcOffsetCurve3D IfcSurfaceOfLinearExtrusion IfcVector IfcVectorOrDirection IfcLightSourceDirectional IfcLightSourceSpot IfcGeometricRepresentationContext IfcGeometricRepresentationSubContext

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