Am 20.07.2014 15:37, schrieb Bald Eagle:

> I didn't really understand this from the documentation:
> "In the PLAIN_TEXTURE, each of the items are optional but if they are present
> the TEXTURE_IDENTIFIER must be first. If no texture identifier is given, then
> POV-Ray creates a copy of the default texture. See "The #default Directive" for
> details.
> Next are optional pigment, normal, and/or finish identifiers which fully
> override any pigment, normal and finish already specified in the previous
> texture identifier or default texture. Typically this is used for backward
> compatibility to allow things like: texture { MyPigment } where MyPigment is a
> pigment identifier."
>
> Not assigning a texture gives a default texture (black), which looks like it CAN
> be textured in a union. It would be useful to be able to have access to that
> default texture, or to be able to assign NO texture WITH a texture statement.

The default texture mentioned here is the thing you can set via:

     default {
       texture { ... }
     }

Whenever you specify a texture without a TEXTURE_IDENTIFYER to "inherit" 
from, POV-Ray plugs in whatever this default texture is /currently/ set 
to; thus, the following are perfectly equivalent:

     // (A)
     default { texture {
        ... // some default texture settings
     }}
     #declare Foo = texture { ... }
     default { texture {
        ... // some other default texture settings
     }}
     #declare Bar = texture { ... }


     // (B)
     #declare DEFAULT = texture {
        ... // some default texture settings
     }
     #declare Foo = texture { DEFAULT ... }
     #declare DEFAULT = texture {
        DEFAULT
        ... // some other default texture settings
     }
     #declare Bar = texture { DEFAULT ... }

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