The Default Medium

The default medium is the medium which surrounds and encompasses all of the objects in the scene; it is the ``air'' through which eye rays usually travel before hitting an object. The properties of the default medium may be modified through the use of the <#630#>atmosphere<#630#> keyword.

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<#1463#>atmosphere<#1463#> [<#1464#>N<#1464#>] [<#1465#>atmospheric effects<#1465#>]
If given, <#635#>N<#635#> specifies the index of refraction of the default medium. The default is 1.0. Any atmospheric effects listed are applied to rays that are exterior to every object in the scene (e.g., rays emanating from the camera).

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