Quote: "At first glance, the 3D coordinates don't relate at all to either of these, which would make "write once, deploy anywhere" problematic at best, at least for apps that use both 3D and 2D features."
With 3D [and this is likely one reason I find it easier than 2D] the 'aperture' of the 'viewport' IE... the screen that players see... is like the view you see when watching a DVD movie... the black borders control the view aspect...
In short my point is... with 3D the screen is irrelavent unless you are using menu items... which then returns to X,Y, coords... but then yeah % would likely be the way forward there...
But even having said that... your view port would still be in pixel form one way or another... so you would simply devide by that number [yes Menus are not my strong point ... yet]...
Ugh I leave it for others to debate... just wanted to tag in here as AppGameKit 3D + Video is what I have been waiting for...
Oh and regarding the distabt walls... I noticed current 3D games on say Android actually seldome have distant corridoors or distant objects... if they do I think there is some degree of optimisation going on... say increase camera range on the fly... or some form of culling...