dos33fsprogs/games/peasant/hgr_7x28_sprite_mask.s

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;===============================================
; hgr 7x28 draw sprite, with bg mask in GR $400
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;===============================================
; SPRITE in INL/INH
; Location at CURSOR_X CURSOR_Y
; for now, BG mask is only all or nothing
; so we just skip drawing if behind
; left sprite AT INL/INH
; right sprite at INL/INH + 14
; left mask at INL/INH + 28
; right mask at INL/INH + 42
hgr_draw_sprite_7x28:
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lda #0
sta MASK_COUNTDOWN
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; set up pointers
lda INL
sta h728_smc1+1
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lda INH
sta h728_smc1+2
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clc
lda INL
adc #28
sta h728_smc3+1
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lda INH
adc #0
sta h728_smc3+2
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ldx #0 ; X is row counter
hgr_7x28_sprite_yloop:
lda MASK_COUNTDOWN
and #$3 ; only update every 4th
bne mask_good
txa
pha ; save X
; recalculate mask
txa
clc
adc CURSOR_Y
tax
ldy CURSOR_X
jsr update_bg_mask
pla ; restore X
tax
mask_good:
lda MASK
bne draw_sprite_skip
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txa ; X is current row
clc
adc CURSOR_Y ; add in cursor_y
; calc GBASL/GBASH
tay ; get output ROW into GBASL/H
lda hposn_low,Y
sta GBASL
lda hposn_high,Y
sta GBASH
ldy CURSOR_X
lda (GBASL),Y ; load background
h728_smc3:
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and $d000,X ; mask with sprite mask
h728_smc1:
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ora $d000,X ; or in sprite
sta (GBASL),Y ; store out
draw_sprite_skip:
inc MASK_COUNTDOWN
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inx
cpx #28
bne hgr_7x28_sprite_yloop
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rts
;======================
; save bg 7x28
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;======================
save_bg_7x28:
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ldx #0
save_yloop:
txa
pha
clc
adc CURSOR_Y
; calc GBASL/GBASH
tax
lda hposn_low,X
sta GBASL
lda hposn_high,X
sta GBASH
pla
tax
ldy CURSOR_X
lda (GBASL),Y
sta save_sprite_7x28,X
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inx
cpx #28
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bne save_yloop
rts
;======================
; restore bg 7x28
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;======================
restore_bg_7x28:
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ldx #0
restore_yloop:
txa ; current row
clc
adc CURSOR_Y ; add in y start point
; calc GBASL/GBASH using lookup table
tay
lda hposn_low,Y
sta GBASL
lda hposn_high,Y
sta GBASH
ldy CURSOR_X
lda save_sprite_7x28,X
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sta (GBASL),Y
inx
cpx #28
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bne restore_yloop
rts
;===================
; update_bg_mask
;===================
; newx/7 in Y
; newy in X
; updates MASK
update_bg_mask:
; calculate peasant priority
; based on head
; FIXME: only do this once at beginning
lda PEASANT_Y
sec
sbc #48 ; Y=48
lsr ; div by 8
lsr
lsr
clc
adc #2
sta PEASANT_PRIORITY
; rrrr rtii top 5 bits row, bit 2 top/bottom
txa
and #$04 ; see if odd/even
beq bg_mask_even
bg_mask_odd:
lda #$f0
bne bg_mask_mask ; bra
bg_mask_even:
lda #$0f
bg_mask_mask:
sta MASK
txa
lsr
lsr ; need to divide by 8 then * 2
lsr ; can't just div by 4 as we need to mask bottom bit
asl
tax
lda gr_offsets,X
sta BASL
lda gr_offsets+1,X
sta BASH
lda (BASL),Y
ldy MASK
cpy #$f0
bne mask_bottom
mask_top:
lsr
lsr
lsr
lsr
jmp mask_mask_mask
mask_bottom:
and #$0f
mask_mask_mask:
sta MASK
cmp PEASANT_PRIORITY
beq mask_false ; branch less than equal
bcc mask_false ; blt
mask_true:
lda #$ff
sta MASK
rts
mask_false:
lda #$00
sta MASK
rts
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; priorities
; 0 = collision
; 1 = bg = always draw ; Y-48
; 2 0-55
; 3 56-63 ; 8/8+2 = 3
; 4 64-71 ; 16/8+2 = 4
; 5 72-79
; 6 80-87 ; 32/8+2 = 6
; 7 88-95
; 8 96-103
; 9 104-111
; 10 112-119
; 11 120-127
; 12 128-135 ; 8
; 13 136-143
; 14 144-151
; 15 152-159
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;====================
; save area
;====================
save_sprite_7x28:
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.byte $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
.byte $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00