IfcSurfaceStyleRefraction
IfcSurfaceStyleRefraction通过添加很少使用的特性，扩展了用于计算物理精确照度的特性的曲面样式照明或曲面样式渲染定义。目前，这包括折射率（光线通过棱镜时的折射率）和色散因子（或阿贝常数），其中考虑了折射的波长依赖性。
注意：如果使用了此类折射特性，则IfcSurfaceStyle应在其样式集（取决于是否使用渲染或照明）中包含IfcSurfaceStyleLighting和IfcSurfaceStyleRefraction的实例，或IfcSurfaceStyleRendering和IfcSurfaceStyleRefraction的实例。
IFC2x2中增加的新实体。
Attribute inheritance
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcPresentationItem | |||||
| IfcSurfaceStyleRefraction | |||||
| 1 | RefractionIndex | IfcReal | [0:1] | The index of refraction for all wave lengths of light. The refraction index is the ratio between the speed of light in a vacuum and the speed of light in the medium. E.g. glass has a refraction index of 1.5, whereas water has an index of 1.33 | X |
| 2 | DispersionFactor | IfcReal | [0:1] | The Abbe constant given as a fixed ratio between the refractive indices of the material at different wavelengths. A low Abbe number means a high dispersive power. In general this translates to a greater angular spread of the emergent spectrum. | X |
EXPRESS Specification
ENTITY IfcSurfaceStyleRefraction
SUBTYPE OF (IfcPresentationItem);
RefractionIndex : OPTIONAL IfcReal;
DispersionFactor : OPTIONAL IfcReal;
END_ENTITY;
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