create_sub_zbuffer (3) - Linux Manuals
create_sub_zbuffer: Creates a sub-z-buffer. Allegro game programming library.
NAME
create_sub_zbuffer - Creates a sub-z-buffer. Allegro game programming library.SYNOPSIS
#include <allegro.h>
ZBUFFER *create_sub_zbuffer(ZBUFFER *parent, int x, int y, int width, int height);
DESCRIPTION
Creates a sub-z-buffer, ie. a z-buffer sharing drawing memory with a pre-existing z-buffer, but possibly with a different size. The same rules as for sub-bitmaps apply: the sub-z-buffer width and height can extend beyond the right and bottom edges of the parent (they will be clipped), but the origin point must lie within the parent region.When drawing z-buffered to a bitmap, the top left corner of the bitmap is always mapped to the top left corner of the current z-buffer. So this function is primarily useful if you want to draw to a sub-bitmap and use the corresponding sub-area of the z-buffer. In other cases, eg. if you just want to draw to a sub-bitmap of screen (and not to other parts of screen), then you would usually want to create a normal z-buffer (not sub-z-buffer) the size of the visible screen. You don't need to first create a z-buffer the size of the virtual screen and then a sub-z-buffer of that.