[Graphics] [pokeemerald] How Do Subsprites Work?

[WiserVisor]

I've been trying to use the subsprites in pokeemerald, located in src/data/object_events/object_event_subsprites.h to have an object event's sprite be half cut-off vertically, meaning the left half is visible while the right half is invisible. I see that a similar process is used in regards to entering long grass, though it's a horizonal cut-off, making the bottom half invisible while keeping the top half visible. I've tried creating a new subsprite, using a similar pattern as the subsprite that is applied when walking in long grass, but changing the SPRITE_SHAPE and SPRITE_SIZE to be vertically oriented and having .x change instead of .y:

static const struct Subsprite sOamTable_32x32_5[] = {
    {
        .x = -16,
        .y = -16,
        .shape = SPRITE_SHAPE(16x32),
        .size = SPRITE_SIZE(16x32),
        .tileOffset = 0,
        .priority = 2
    },
    {
        .x = 0,
        .y = -16,
        .shape = SPRITE_SHAPE(16x32),
        .size = SPRITE_SIZE(16x32),
        .tileOffset = 8,
        .priority = 3
    }
};

This does not produce any kind of desirable result, unless you're goal was to make a corrupted-looking sprite. If anyone can point me to a subsprite tutorial, or at least explain to me how to accomplish my goal, I would be greatly appreciative.