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PrepareOAMData:
; Determine OAM data for currently visible
; sprites and write it to wOAMBuffer.
ld a, [wUpdateSpritesEnabled]
dec a
jr z, .updateEnabled
cp -1
ret nz
ld [wUpdateSpritesEnabled], a
jp HideSprites
.updateEnabled
xor a
ld [hOAMBufferOffset], a
.spriteLoop
ld [hSpriteOffset2], a
ld d, wSpriteStateData1 / $100
ld a, [hSpriteOffset2]
ld e, a
ld a, [de] ; c1x0
and a
jp z, .nextSprite
inc e
inc e
ld a, [de] ; c1x2 (facing/anim)
ld [wd5cd], a
cp $ff ; off-screen (don't draw)
jr nz, .visible
call GetSpriteScreenXY
jr .nextSprite
.visible
cp $a0 ; is the sprite unchanging like an item ball or boulder?
jr c, .usefacing
; unchanging
and $f
add $10 ; skip to the second half of the table which doesn't account for facing direction
jr .next
.usefacing
and $f
.next
ld l, a
; get sprite priority
push de
inc d
ld a, e
add $5
ld e, a
ld a, [de] ; c2x7
and $80
ld [hSpritePriority], a ; temp store sprite priority
pop de
; read the entry from the table
ld h, 0
ld bc, SpriteFacingAndAnimationTable
add hl, hl
add hl, hl
add hl, bc
ld a, [hli]
ld c, a
ld a, [hli]
ld b, a
ld a, [hli]
ld h, [hl]
ld l, a
call GetSpriteScreenXY
ld a, [hOAMBufferOffset]
ld e, a
ld d, wOAMBuffer / $100
.tileLoop
ld a, [hSpriteScreenY] ; temp for sprite Y position
add $10 ; Y=16 is top of screen (Y=0 is invisible)
add [hl] ; add Y offset from table
ld [de], a ; write new sprite OAM Y position
inc hl
ld a, [hSpriteScreenX] ; temp for sprite X position
add $8 ; X=8 is left of screen (X=0 is invisible)
add [hl] ; add X offset from table
inc e
ld [de], a ; write new sprite OAM X position
inc e
ld a, [bc] ; read pattern number offset (accommodates orientation (offset 0,4 or 8) and animation (offset 0 or $80))
inc bc
push bc
ld b, a
ld a, [wd5cd] ; temp copy of c1x2
swap a ; high nybble determines sprite used (0 is always player sprite, next are some npcs)
and $f
; Sprites $a and $b have one face (and therefore 4 tiles instead of 12).
; As a result, sprite $b's tile offset is less than normal.
cp $b
jr nz, .notFourTileSprite
ld a, $a * 12 + 4
jr .next2
.notFourTileSprite
; a *= 12
sla a
sla a
ld c, a
sla a
add c
.next2
add b ; add the tile offset from the table (based on frame and facing direction)
pop bc
ld [de], a ; tile id
inc hl
inc e
ld a, [hl]
bit 1, a ; is the tile allowed to set the sprite priority bit?
jr z, .skipPriority
ld a, [hSpritePriority]
or [hl]
.skipPriority
inc hl
ld [de], a
inc e
bit 0, a ; OAMFLAG_ENDOFDATA
jr z, .tileLoop
ld a, e
ld [hOAMBufferOffset], a
.nextSprite
ld a, [hSpriteOffset2]
add $10
cp $100 % $100
jp nz, .spriteLoop
; Clear unused OAM.
ld a, [hOAMBufferOffset]
ld l, a
ld h, wOAMBuffer / $100
ld de, $4
ld b, $a0
ld a, [wd736]
bit 6, a ; jumping down ledge or fishing animation?
ld a, $a0
jr z, .clear
; Don't clear the last 4 entries because they are used for the shadow in the
; jumping down ledge animation and the rod in the fishing animation.
ld a, $90
.clear
cp l
ret z
ld [hl], b
add hl, de
jr .clear
GetSpriteScreenXY:
inc e
inc e
ld a, [de] ; c1x4
ld [hSpriteScreenY], a
inc e
inc e
ld a, [de] ; c1x6
ld [hSpriteScreenX], a
ld a, 4
add e
ld e, a
ld a, [hSpriteScreenY]
add 4
and $f0
ld [de], a ; c1xa (y)
inc e
ld a, [hSpriteScreenX]
and $f0
ld [de], a ; c1xb (x)
ret
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