POV-Ray will attempt to read the environment variable 'POVINI'. If found, the path&filename in it (IE "p3:include/povray.ini") will be used to load the default settings before anything else. If not found, it will attempt to load "povray.ini" from the same directory as the binary was executed from. Failing that, it will resort to internal defaults.
If the variable 'POVRAYTASKPRI' is found, it's integer content is used to set the task priority for the POV-Ray renderer. USE WITH CAUTION. If the priority is set much above zero, your system will slow tremendously, or even appear to lock up, and you may experience communication problems with the GUI if it is in use. The GUI will also read 'POVRAYTASKPRI', and set it's own priority to ONE HIGHER than that specified for POV-Ray.
If using the GUI, the ENV variable POVGUIINI is checked for the location and name of the settings file being passed from the GUI. If either the file specified or the variable are not located, "t:povray.ini" is used.
Also with the GUI, the ENV variable POVHELP is checked for the path and
name of the main pov-ray .guide file (NOT the one you are reading!) to
enable 'HELP' button links from the GUI to the guide.
**** Not enabled, since documents are HTML ****
If using OS3 display, the ENV variable 'POVRENDERSCREEEN' will be read,
and if found, it's contents used as the name for a public screen on which
to open the display preview.
**OS3 display is not yet implemented**
With Picasso96 display, if 'POVRENDERSCREEN' is found, POV-Ray will attempt to open a Picasso96 PIP window on the named screen. If the screen is not available, it will fallback to the default pubscreen. If that fails (which it should not) then it continues with the normal Picasso96 full-screen display opening, which will probably also fail, since the most likely reason for a PIP opening to fail on the default screen is from low memory.