POV-Ray : Documentation : Restrictions Affect all Core File I/O
  POV-Ray 3.6 Documentation Online View Restrict Read/Write Additional Options Restrictions Affect all Core File I/O

Note that the above settings do not just affect scripted file I/O; they also affect things like include files, output files, and input .POV files. Basically any file-related input or output by the rendering engine. You should take careful note of this statement if you are in the habit of writing your output files to anywhere other than the same directory as the scene file is in (see below). Restrict Read/Write Additional Options

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