Quote - Two sided materials can be done by appropriate use of the N node. There's a thread at RDNA and/or here.

Correct.  Last time I saw the topic, the results could be effective under certain conditions and were fiddley to set up.  Using the N node, you have to get the normal from the surface to the camera, IIRC, and plug those numbers in for each frame as the camera moves relative to that surface.  Unless something has changed, it's something that fits into the category of things that Poser can kinda-sorta do, but not completely.  Actual real support for two-sidedness would be nice!  :D

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.