IFC 4.3.0.1 (IFC4X3) development

8.14.2.3 IfcLightDistributionDataSourceSelect

8.14.2.3.1 Semantic 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.

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.
Table 8.14.2.3.A

8.14.2.3.2 Type values

Type
IfcExternalReference
IfcLightIntensityDistribution
Table 8.14.2.3.B

8.14.2.3.3 Formal representation

TYPE IfcLightDistributionDataSourceSelect = SELECT
	(IfcExternalReference
	,IfcLightIntensityDistribution);
END_TYPE;

8.14.2.3.4 References

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