IfcLightSourceSpot

注：根据ISO 10303-46的定义：

光源聚光灯图元是光源的子类型。聚光灯光源实体具有光源颜色、位置、方向、衰减系数、浓度指数和扩散角。如果一个点位于由光源位置、方向和扩散角确定的此类光源的影响锥之外，则其颜色不受该光源的影响。

注意，IfcLightSourceSpot添加了束宽角，定义了光源以均匀的全强度发射光的内锥。光源的发射强度从内立体角（束宽角）下降到外立体角（展开角）。

注：根据ISO/IEC 14772-1:1997的定义：

聚光灯节点定义一个光源，该光源从特定点沿特定方向矢量发射光，并受立体角约束。聚光灯可以照亮响应光源并与聚光灯定义的立体角相交的几何体节点。聚光灯节点在局部坐标系中指定，并受祖先变换的影响。图376显示了聚光灯的定义。

 

注：对应的ISO 10303实体：光源光斑。有关正式标准的最终定义，请参考ISO/IS 10303-46:1994，第33页。

注：除了ISO10303-46中定义的属性外，ISO/IEC 14772-1:1997（VRML）中的附加属性“半径”、“波束宽度”和“四向散射”被添加到该子类型中，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
IfcLightSourcePositional
5	Position	IfcCartesianPoint	[1:1]	Definition from ISO/CD 10303-46:1992: The Cartesian point indicates the position of the light source. Definition from VRML97 - ISO/IEC 14772-1:1997: A Point light node illuminates geometry within radius of its location.	X
6	Radius	IfcPositiveLengthMeasure	[1:1]	The maximum distance from the light source for a surface still to be illuminated. Definition from VRML97 - ISO/IEC 14772-1:1997: A Point light node illuminates geometry within radius of its location.	X
7	ConstantAttenuation	IfcReal	[1:1]	Definition from ISO/CD 10303-46:1992: This real indicates the value of the attenuation in the lighting equation that is constant.	X
8	DistanceAttenuation	IfcReal	[1:1]	Definition from ISO/CD 10303-46:1992: This real indicates the value of the attenuation in the lighting equation that proportional to the distance from the light source.	X
9	QuadricAttenuation	IfcReal	[1:1]	This real indicates the value of the attenuation in the lighting equation that proportional to the square value of the distance from the light source.	X
IfcLightSourceSpot
10	Orientation	IfcDirection	[1:1]	Definition from ISO/CD 10303-46:1992: This is the direction of the axis of the cone of the light source specified in the coordinate space of the representation being projected.. Definition from VRML97 - ISO/IEC 14772-1:1997: The direction field specifies the direction vector of the light's central axis defined in the local coordinate system.	X
11	ConcentrationExponent	IfcReal	[0:1]	Definition from ISO/CD 10303-46:1992: This real is the exponent on the cosine of the angle between the line that starts at the position of the spot light source and is in the direction of the orientation of the spot light source and a line that starts at the position of the spot light source and goes through a point on the surface being shaded. NOTE  This attribute does not exists in ISO/IEC 14772-1:1997.	X
12	SpreadAngle	IfcPositivePlaneAngleMeasure	[1:1]	Definition from ISO/CD 10303-46:1992: This planar angle measure is the angle between the line that starts at the position of the spot light source and is in the direction of the spot light source and any line on the boundary of the cone of influence. Definition from VRML97 - ISO/IEC 14772-1:1997: The cutOffAngle (name of spread angle in VRML) field specifies the outer bound of the solid angle. The light source does not emit light outside of this solid angle.	X
13	BeamWidthAngle	IfcPositivePlaneAngleMeasure	[1:1]	Definition from VRML97 - ISO/IEC 14772-1:1997: The beamWidth field specifies an inner solid angle in which the light source emits light at uniform full intensity. The light source's emission intensity drops off from the inner solid angle (beamWidthAngle) to the outer solid angle (spreadAngle).	X

EXPRESS Specification

ENTITY IfcLightSourceSpot
 SUBTYPE OF (IfcLightSourcePositional);
  Orientation : IfcDirection;
  ConcentrationExponent : OPTIONAL IfcReal;
  SpreadAngle : IfcPositivePlaneAngleMeasure;
  BeamWidthAngle : IfcPositivePlaneAngleMeasure;
END_ENTITY;