IFC 4.3.x development

8.14.3.5 IfcLightSourceDirectional

8.14.3.5.1 Semantic definitions at the entity

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.

8.14.3.5.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignment SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment 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.
StyledByItem SET [0:1] OF IfcStyledItem FOR Item 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.
IfcGeometricRepresentationItem
IfcLightSource
1 Name OPTIONAL IfcLabel The name given to the light source in presentation.
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.
3 AmbientIntensityOPTIONAL 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).
4 Intensity OPTIONAL 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).
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.

8.14.3.5.2 Entity inheritance

dot_inheritance IfcLightSourceDirectional IfcLightSourceDirectional IfcLightSource IfcLightSource IfcLightSourceDirectional->IfcLightSource IfcLightSource_children 3 more... IfcLightSource_children->IfcLightSource IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcLightSource->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.14.3.5.3 Formal representations

ENTITY IfcLightSourceDirectional
 SUBTYPE OF (IfcLightSource);
	Orientation : IfcDirection;
END_ENTITY;