Posted 31 August 2012 - 09:13 AM
It's only a little trigonometry, and it has nothing to do with "resolution independent" coordinates.
Apart from changing the camera projection matrix. the only thing that changes with camera movement is the selection of mipmaps, but it is automatic: texture coordinates remain constant.
You don't know how large the tiles are on screen? Hard to believe, as even in a 3D engine with an arbitrarily moving and zooming camera you can easily compute the worst case scaling of your tiles: the longest tile edge that can appear in screen coordinates is presumably one that lies on the near clipping plane (as close as possible, with no foreshortening) and is parallel to either side of the screen (depending on vertical and horizontal stretching), measured at the shortest "focal length" of your zoom and at the highest screen resolution.