注：根据ISO 10303-46的定义：
“光源方向”是光源的子类型。此实体具有光源方向。当概念原点在无穷远处时，所有光线都与这个方向平行。这种光源根据曲面的方向而不是位置来照亮曲面。
注：根据ISO/IEC 14772-1:1997的定义：
平行光节点定义一个平行于给定三维向量的光线照明的平行光源。平行光节点不随距离衰减。平行光节点在局部坐标系中指定，并受祖先变换的影响。
注：相应的ISO 10303实体：光源方向。有关正式标准的最终定义，请参考ISO/IS 10303-46:1994，第32页。
注：除了ISO 10303-46中定义的属性外，ISO/IEC 14772-1:1997（VRML）的附加属性“模糊度”和“强度”继承自父类型。
IFC2x中增加的新实体，在IFC2x2中重命名和增强。
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| 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. | 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. | X | |
| IfcGeometricRepresentationItem | |||||
| IfcLightSource | |||||
| 1 | Name | IfcLabel | [0:1] | The name given to the light source in presentation. | X |
| 2 | LightColour | IfcColourRgb | [1:1] | 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 | [0:1] | 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 | [0:1] | 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 | [1:1] | 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 |
EXPRESS Specification
ENTITY IfcLightSourceDirectional
SUBTYPE OF (IfcLightSource);
Orientation : IfcDirection;
END_ENTITY;