## 6.6 Interior

Introduced in POV-Ray 3.1 is an object modifier statement called `interior`. The syntax is:

    INTERIOR:
        interior { [INTERIOR_IDENTIFIER] [INTERIOR_ITEMS...] }
    INTERIOR_ITEM:
        ior Value | caustics Value | dispersion Value |
        dispersion_samples Samples | fade_distance Distance |
        fade_power Power | fade_color <Color>
        MEDIA...

Interior default values:

    ior                : 1.0
    caustics           : 0.0
    dispersion         : 1.0
    dispersion_samples : 7
    fade_distance      : 0.0
    fade_power         : 0.0
    fade_color         : <0,0,0>

The `interior` contains items which describe the properties of the interior of the object. This is in contrast to the `texture` and `interior_texture` which describe the surface properties only. The interior of an object is only of interest if it has a transparent texture which allows you to see inside the object. It also applies only to solid objects which have a well-defined inside/outside distinction.

Note: the `open` keyword, or `clipped_by` modifier also allows you to see inside but interior features may not render properly. They should be avoided if accurate interiors are required.

Interior identifiers may be declared to make scene files more readable and to parameterize scenes so that changing a single declaration changes many values. An identifier is declared as follows.

    INTERIOR_DECLARATION:
        #declare IDENTIFIER = INTERIOR |
        #local IDENTIFIER = INTERIOR

Where IDENTIFIER is the name of the identifier up to 40 characters long and INTERIOR is any valid `interior` statement. See "#declare vs. #local" for information on identifier scope.

In 'Interior' ...
6.6.1 | Why are Interior and Media Necessary?
6.6.2 | Empty and Solid Objects
6.6.3 | Scaling objects with an interior.
6.6.4 | Refraction
6.6.5 | Dispersion
6.6.6 | Attenuation
6.6.7 | Faked Caustics
6.6.8 | Object-Media