Polyplanes could be completely wrong, for all I know.  I have had to cobble together that first part of the line-plane intersection code (before the edge bounds check) from hints and fragments gathered from svdl's posts on page 1, a bit of Ockham's NoPoke (now reduced to the "center method"), and a method outline offered on a Game Maker forum.  The math to calculate the plane of the polygon is gathered from the GM forum, but I have seen it repeated elsewhere online.  I plug that plane value into svdl's outlined code, assuming I've assembled his outlined code effectively.  As you may have noted, my record for correctly assembling such things isn't so great, thus far.  :-P

I was looking into Numeric both in hopes of reducing the memory issues and of speeding things up a bit.  All of this is quite slow, on my system, and I don't see reason to expect greater speed as the code becomes more complex to accomodate more situations.  I tried using Numeric for the various coordinate and normals lists used during the main linecasting process, but that really did nothing to help.  I think pulling Numeric in at that point may actually serve to complicate matters.  Hmm.

WorldNormals?  Are you testing using your worldspace additions, or have you re-tooled the script to use world coordinates instead of local coordinates?  I guess I should take a look for myself, eh?  :)

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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.