Civ4 uses Gamebryo-Engine for terrain/units (same engines as Elder Scrolls Oblivion btw) which is not realy fast
However usually only the visible parts are calculated (in most engines at least) and since Details Scale down as you Zoom out ... I dont think it will be a problem with the video card
However usually only the visible parts are calculated (in most engines at least) and since Details Scale down as you Zoom out ... I dont think it will be a problem with the video card