enlighten me with Polish term for "projective sphere" ?
Hmmm. At first sight it's a trivial task: one has to look up a dictionary and... here comes a difficulty. Having learnt Polish equivalents of "projective" and "sphere" doesn't mean you know the equivalent of "projective sphere".
There are many Anglo-Polish jokes what happens if one translates a phrase word by word. Here's one: In Polish we say "dziękuję z góry", "płacę z góry" etc. (where "z góry" means "in advance"). However, lame translators would write "thank you from the mountain", "I pay from the mountain". :-)))
What I'm saying here is that I simply have never heard "projective sphere" in Polish. So I would be very cautious here. Maybe it *is* actually "sfera rzutowana" but it's just my guess and it may happen that "sfera rzutowana" is something like "thank you from the mountain".
-- Andrzej