IfcLightDistributionDataSourceSelect

BACnet MVD

#### IfcLightDistributionDataSourceSelect

Natural language names

| Light Distribution Data Source Select
| Sélection de la source de données sur la distribution lumineuse

##### Semantic definitions at the type

Type definition

A goniometric light gets its intensity distribution function (how much light goes in any one direction) from one of two sources: (i) an industry-standard file, (ii) from distribution data passed directly via the IfcLightIntensityDistribution.

The light distribution provides the luminous intensity distribution according to some standardized light distribution curves.

SELECT

Type | Definition
IfcExternalReference | Light distribution is represented by a standard photometric data file such as Eulumdat, IES, CIBSE TM14.
IfcLightIntensityDistribution | For representing a light distribution directly the following values needs to be given in a table like structure with column and row headings. These headings should contain the angles (C/γ or B/β ) and the table body contains the intensity values, (normally normalized to cd/Klm). The angles can be non- equidistant and the angle steps can be almost any value in the valid range, so a list of all available angles in both directions covers all cases.

> HISTORY New type in IFC2x2.

Select definition

Type | Description
--- | ---
IfcExternalReference |
IfcLightIntensityDistribution |

##### Formal representations

XML Specification
`<xs:group name="IfcLightDistributionDataSourceSelect">
<xs:choice>
<xs:element ref="ifc:IfcExternalReference"/>
<xs:element ref="ifc:IfcLightIntensityDistribution"/>
</xs:choice>
</xs:group>
`
EXPRESS Specification
`TYPE IfcLightDistributionDataSourceSelect = SELECT (
IfcExternalReference,
IfcLightIntensityDistribution);
END_TYPE;

EXPRESS-G diagram

`

References: IfcLightSourceGoniometric

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