Quote - @millighost

yeah, I know all that. BG Color, BG Picture and BG Movie show up in the preview when connected to the Color parameter in the Background node, in various cases BG Color even shows up in preview when not connected to the Color parameter, and BG Picture can show up when connected indirectly - via intermediate nodes like color_math.

Most varieties make sense when selecting the Render over... options in the Render settings, even the other parameters in the background node become active then.

Hm, i used poser2010, where the background setting does what is supposed to do (like described earlier). Does not show in the preview, though, but they fiddled with the preview rendering in 2012. Anyway, i think as far as the rendering goes, it should do the same as 2010.

Quote - But whatever I do, the Use Background Shader Node option in the Display menu has no effect at all, nor on preview, nor on render. So I still keep longing to an answer to precisely the question I stated: what does this menu option really do? Who knows?

Note that the option does not come up in the manual, and is only mentioned vagely in the Poser 6 (7, 8) Revealed book. Also Google does not reveal more interesting references.

But it is in the reference manual. It is in a section called "Firefly Options Settings" (page 304 in the 2010 manual). What do you mean, btw, by "no effect at all"? Does it mean, it simply uses the setting you used before?