IfcLightSourcePositional

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注:根据ISO 10303-46的定义:

光源位置实体是光源的子类型。此实体具有光源位置和衰减系数。位置光源基于曲面的方向和位置影响曲面。

注:根据ISO/IEC 14772-1:1997的定义:

“点光源”节点在局部坐标系中的三维位置指定点光源。点光源在所有方向上均匀地发射光;也就是说,它是全向的。点光源节点在局部坐标系中指定,并受祖先变换的影响。

点光源节点的照明随距离衰减,由三个衰减系数指定。衰减系数为

1/max(衰减[0]+衰减[1]×r+衰减[2]×r2,1),

式中,r是从灯光到被照明表面的距离。默认设置为“无衰减”。衰减值(0,0,0)与(1,0,0)相同。衰减值应大于或等于零。

注:对应的ISO 10303实体:光源位置。有关正式标准的最终定义,请参考ISO/IS 10303-46:1994,第32页。

注:除ISO10303-46中定义的属性外,ISO/IEC 14772-1:1997(VRML)半径和四边形的附加属性添加到该子类型中,模糊度和强度从父类型继承。

IFC2x中增加的新实体,在IFC2x2中重命名和增强。

技术图片

 

 

#AttributeTypeCardinalityDescriptionC
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
EXPRESS Specification
ENTITY IfcLightSourcePositional
 SUPERTYPE OF(IfcLightSourceSpot)
 SUBTYPE OF (IfcLightSource);
  Position : IfcCartesianPoint;
  Radius : IfcPositiveLengthMeasure;
  ConstantAttenuation : IfcReal;
  DistanceAttenuation : IfcReal;
  QuadricAttenuation : IfcReal;
END_ENTITY;

 

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