while fiddling with old SCUMM games resources I noticed they often use a bitmask in order to describe which chunks of the backgrounds should stay in foreground.
I was surprised, since I imagined they had separate sprites for those "layers".
I'm wondering if they did image-cropping at run time and added the chunks depending on the z-order (seems pretty unlikely) or they used a "subtractive" approach, that is avoiding to display the pixels which were hidden by objects.
In any case I assume they actually had direct access to the pixel matrix to do something like this without separate sprites...
Am I missing something here?
Does anybody know how SCUMM did manage those chunks internally (or at least, how does ScummVM treat them?).
I also know AGS does something similar with bitmasks.
Just curious.
Thanks!
