Great read and I learned a lot. Just curious about the inactivate/activate use of parametricplot3d. Why do you use that. I'll read your post more because there's a lot to digest.
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Thank you for your kind words! The (* foreground - blue column: *) part, which is an "iconized" Sequence[...], seems to cause some warning messages, so I inactivate ParametricPlot3D to allow the iconized form expanding first.
(* foreground - blue column: *)
A simple demonstration:
I did it wrong on the color and alpha blending in this post. Please refer to
[Notebook] [GIF] Color Notes - Alpha blending done properly for more details!