IfcSurfaceStyleRefraction

BACnet MVD

#### IfcSurfaceStyleRefraction

Natural language names

| Oberflächenstil - Lichtbrechung
| Surface Style Refraction
| Style de réfraction de surface

##### Semantic definitions at the entity

Entity definition

IfcSurfaceStyleRefraction extends the surface style lighting, or the surface style rendering definition for properties for calculation of physically exact illuminance by adding seldomly used properties. Currently this includes the refraction index (by which the light ray refracts when passing through a prism) and the dispersion factor (or Abbe constant) which takes into account the wavelength dependency of the refraction.

> NOTE If such refraction properties are used, the IfcSurfaceStyle should include within its set of Styles (depending on whether rendering or lighting is used) an instance of IfcSurfaceStyleLighting and IfcSurfaceStyleRefraction, or an instance of IfcSurfaceStyleRendering and IfcSurfaceStyleRefraction.

> HISTORY New entity in IFC2x2.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
1 | RefractionIndex | IfcReal | ? | 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 | ? | 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

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcPresentationItem
IfcSurfaceStyleRefraction
1 | RefractionIndex | IfcReal | ? | 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 | ? | 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

##### Formal representations

XML Specification
`<xs:element name="IfcSurfaceStyleRefraction" type="ifc:IfcSurfaceStyleRefraction" substitutionGroup="ifc:IfcPresentationItem" nillable="true"/>
<xs:complexType name="IfcSurfaceStyleRefraction">
<xs:complexContent>
<xs:extension base="ifc:IfcPresentationItem">
<xs:attribute name="RefractionIndex" type="ifc:IfcReal" use="optional"/>
<xs:attribute name="DispersionFactor" type="ifc:IfcReal" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcSurfaceStyleRefraction
SUBTYPE OF (IfcPresentationItem);
RefractionIndex : OPTIONAL IfcReal;
DispersionFactor : OPTIONAL IfcReal;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcSurfaceStyleElementSelect

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