IfcLightSourceDirectional

BACnet MVD

#### IfcLightSourceDirectional

Natural language names

| Lichtquelle - gerichtet
| Light Source Directional
| Source de lumière directionnelle

##### Semantic definitions at the entity

Entity definition

> NOTE Definition according to ISO 10303-46:
> The light source directional is a subtype of light source. This entity has a light source direction. With a conceptual origin at infinity, all the rays of the light are parallel to this direction. This kind of light source lights a surface based on the surface's orientation, but not position.

> NOTE Definition according to ISO/IEC 14772-1:1997:
> The directional light node defines a directional light source that illuminates along rays parallel to a given 3-dimensional vector. Directional light nodes do not attenuate with distance. Directional light nodes are specified in the local coordinate system and are affected by ancestor transformations.

> NOTE Corresponding ISO 10303 entity: light_source_directional. Please refer to ISO/IS 10303-46:1994, p. 32 for the final definition of the formal standard.

> NOTE In addition to the attributes as defined in ISO 10303-46 the additional property from ISO/IEC 14772-1:1997 (VRML) AmbientIntensity and Intensity are inherited from the supertype.

> HISTORY New entity in IFC2x, renamed and enhanced in IFC2x2.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
5 | Orientation | IfcDirection |  | Definition from ISO/CD 10303-46:1992: This direction is the direction of the light source. Definition from VRML97 - ISO/IEC 14772-1:1997: The direction field specifies the direction vector of the illumination emanating from the light source in the local coordinate system. Light is emitted along parallel rays from an infinite distance away. |  | 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
IfcLightSource
1 | Name | IfcLabel | ? | The name given to the light source in presentation. |  | X
2 | LightColour | IfcColourRgb |  | Definition from ISO/CD 10303-46:1992: Based on the current lighting model, the colour of the light to be used for shading. Definition from VRML97 - ISO/IEC 14772-1:1997: The color field specifies the spectral color properties of both the direct and ambient light emission as an RGB value. |  | X
3 | AmbientIntensity | IfcNormalisedRatioMeasure | ? | Definition from VRML97 - ISO/IEC 14772-1:1997: The ambientIntensity specifies the intensity of the ambient emission from the light. Light intensity may range from 0.0 (no light emission) to 1.0 (full intensity). |  | X
4 | Intensity | IfcNormalisedRatioMeasure | ? | Definition from VRML97 - ISO/IEC 14772-1:1997: The intensity field specifies the brightness of the direct emission from the ligth. Light intensity may range from 0.0 (no light emission) to 1.0 (full intensity). |  | X
IfcLightSourceDirectional
5 | Orientation | IfcDirection |  | Definition from ISO/CD 10303-46:1992: This direction is the direction of the light source. Definition from VRML97 - ISO/IEC 14772-1:1997: The direction field specifies the direction vector of the illumination emanating from the light source in the local coordinate system. Light is emitted along parallel rays from an infinite distance away. |  | X

##### Formal representations

XML Specification
`<xs:element name="IfcLightSourceDirectional" type="ifc:IfcLightSourceDirectional" substitutionGroup="ifc:IfcLightSource" nillable="true"/>
<xs:complexType name="IfcLightSourceDirectional">
<xs:complexContent>
<xs:extension base="ifc:IfcLightSource">
<xs:sequence>
<xs:element name="Orientation" type="ifc:IfcDirection" nillable="true"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcLightSourceDirectional
SUBTYPE OF (IfcLightSource);
Orientation : IfcDirection;
END_ENTITY;

EXPRESS-G diagram

`

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