Very old adventure games (such as Sierra quests from the 80s) used to actually maintain a separate bitmap image of the entire screen, representing z-depth and materials, to determine where your character can go and where it will be hidden. They will use a pixel selection to check where their small sprites will go.
, , , . .
- "" , . , (, ), (, ). IMHO zelda- , -.
- . , , , (, , ).
, 2D-, , 3D-, . 3D- 2D.