SH3 can almost be played as any 3rd person adventure game with completely free camera as long as you hold R2 all the time while moving your character. Camera will follow behind your back constanly. Camera angles simply have nothing to do with shadow calculations in SH3.
Chap, it's a stupid argument really - Dreamcast could do that kind of shadowing, PS2 and GC certainly can do it, as games on them clearly demonstrate (Luigi on GC, SH3 on PS2) It just happens that SH3 does those shadows in a really dramatic way (and they're everywhere), to make a horror atmosphere, just as D3 does, so that makes people bring it up as an example. Shadows alone would simply be a non-isue in some kind of possible Doom 3 port, no matter what that ID guy said. It's the massive use of normal maps and huge amounts of 'regular' textures that would pose a real problem, and wolud make a reasonably close port impossible on PS2. I don't really see what would be a technical limitation to make a GC version if not for the memory alone, but that I think is going to be a huge problem on Xbox too.
I think that some kind of tech demo that would utilize D3 technology could be made on PS2 (maybe even on DC, although it's small fillrate limits the usage of DOT3 operation even more than on PS2 - we're talking the full scene bumpmapping here) but as noone is ever going to bother making something like that, it's all just speculation.
