dos33fsprogs/games/peasant/hgr_sprite_bg_mask.s
2024-09-11 20:29:06 -04:00

392 lines
6.2 KiB
ArmAsm

;===============================================
; hgr draw sprite, with bg mask in GR $400
;===============================================
; used primarily to draw Rather Dashing
;===============================================
; *cannot* handle sprites bigger than 256 bytes
;
; attempts to shift for odd/even column
; ideally sprite palette has precedence over background
; if completely transparent then let bg keep palette
; Location at CURSOR_X CURSOR_Y
; for now, BG mask is only all or nothing (from LORES)
; so we just skip drawing if behind
; this version handles arbitrary width sprites, which complicates
; things
; X is sprite to draw
; Y is save slot
hgr_draw_sprite_bg_mask:
; ldy #4 ; FIXME, should be proper save slot
; save info on background to restore
lda CURSOR_X
sta save_xstart,Y
lda CURSOR_Y
sta save_ystart,Y
; calculate end of sprite on screen for Xpos loop
; also save for background restore
lda peasant_sprites_xsize,X
clc
adc CURSOR_X
sta hdsb_width_smc+1
sta save_xend,Y
; calculate bottom of sprite for Ypos loop
; also save for background restore
lda peasant_sprites_ysize,X
sta hdsb_ysize_smc+1
clc
adc CURSOR_Y
sta save_yend,Y
; set up mask countdown value
lda #0
sta MASK_COUNTDOWN
; calculate peasant priority
; based on head location
; see chart later
lda CURSOR_Y
sec
sbc #48 ; Y=48
lsr ; div by 8
lsr
lsr
clc
adc #2
sta PEASANT_PRIORITY
; set up sprite pointers
lda peasant_sprites_data_l,X
sta h728_smc1+1
sta h728_smc2+1
lda peasant_sprites_data_h,X
sta h728_smc1+2
sta h728_smc2+2
; set up mask pointers
lda peasant_mask_data_l,X
sta h728_smc3+1
sta h728_smc4+1
lda peasant_mask_data_h,X
sta h728_smc3+2
sta h728_smc4+2
;===============================
; main loop
; X = row counter at times (CURRENT_ROW is real one)
; Y = col counter
ldx #0 ; X is sprite counter
stx CURRENT_ROW ; zero row counter
hgr_sprite_bm_yloop:
lda MASK_COUNTDOWN ; FIXME is this same as CURRENT_ROW
and #$3 ; only update every 4th
bne mask_good
;======================
; recalculate mask
txa
pha ; save sprite counter
lda CURRENT_ROW
clc
adc CURSOR_Y
tax ; X has row
ldy CURSOR_X ; Y has column
; FIXME: we have multi-width now
jsr update_bg_mask
pla ; restore sprite counter
tax
mask_good:
lda 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 ; always page2
;============================
; set up inner loop
ldy CURSOR_X
lda #0
sta SPRITE_TEMP
sta MASK_TEMP
hsbm_inner_loop:
lda MASK
bne draw_sprite_skip
;============================
; not masked so actually draw
;=========================
; pick if even or odd
lda CURSOR_X
ror
bcs hsbm_draw_sprite_odd
;============================
hsbm_draw_sprite_even:
h728_smc1:
lda $d000,X ; load sprite value
sta TEMP_SPRITE
h728_smc3:
lda $d000,X ; load mask value
jmp hsbm_draw_sprite_both
hsbm_draw_sprite_odd:
h728_smc2:
lda $f000,X ; load sprite data
; PSSS SSSS
; rol C=P, SSSS SSST
; want to set bit7 to C?
rol SPRITE_TEMP
rol
sta SPRITE_TEMP
bcc hsbm_pal0
hsbm_pal1:
ora #$80 ; set pal bit
bne hsbm_pal_done
hsbm_pal0:
and #$7f ; clear pal bit
hsbm_pal_done:
sta TEMP_SPRITE
h728_smc4:
lda $f000,X ; load sprite data
rol MASK_TEMP
rol
sta MASK_TEMP
hsbm_draw_sprite_both:
eor #$FF
and #$7F
sta TEMP_MASK
; if mask is $7f then skip drawing
cmp #$7f
beq draw_sprite_skip
; do actual sprite-ing
lda (GBASL),Y ; load background
and TEMP_MASK
ora TEMP_SPRITE
sta (GBASL),Y ; store out
draw_sprite_skip:
inx ; increment sprite pointer
iny ; increment column
hdsb_width_smc:
cpy #6
bne hsbm_inner_loop
inc MASK_COUNTDOWN ; increment row
inc CURRENT_ROW
lda CURRENT_ROW
hdsb_ysize_smc:
cmp #28
bne hgr_sprite_bm_yloop
rts
;===================
; update_bg_mask
;===================
; Column (xpos/7) in Y
; Row in X
; updates MASK
update_bg_mask:
; ?????????
; rrrr rtii top 5 bits row, bit 2 top/bottom
sty xsave
mask_try_again:
stx ysave
txa
and #$04 ; see if odd/even in the lo-res lookup
beq bg_mask_even
; setup mask based on odd/even
bg_mask_odd:
lda #$f0
bne bg_mask_mask ; bra
bg_mask_even:
lda #$0f
bg_mask_mask:
sta MASK
; X is current row here
; converting to which row in lores
; 0 -> 0 low
; 4 -> 0 high
; 8 -> 1 low
; ....
; 191 -> 23 high
txa
lsr
lsr ; need to divide by 8 then * 2
lsr ; can't just div by 4 as we need to mask bottom bit
asl ; because our lookup is multiple of two
tax
; set up row for mask lookup
lda gr_offsets,X
sta BASL
lda gr_offsets+1,X
sta BASH
; read out current mask color
lda (BASL),Y
; get high/low properly
ldy MASK
cpy #$f0
bne mask_bottom
mask_top:
lsr
lsr
lsr
lsr
jmp mask_mask_mask
mask_bottom:
and #$0f
mask_mask_mask:
sta MASK
; special cases?
cmp #$0 ; 0 means collision, find mask
bne mask_not_zero ; by iteratively going down till
; mask 0 here, which means can't walk there but doesn't give
; prioirty. This can happen if there's a don't walk spot
; above you even if not on it. In this case, find the actual
; mask by looking down the screen until we find an actual
; proper mask value
ldy xsave
ldx ysave ; move to next lower lookup value
inx
inx
inx
inx
jmp mask_try_again
mask_not_zero:
cmp #$f ; priority F means always on top
beq mask_true
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 = fg = always hide
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;====================
; save area
;====================
ysave:
.byte $00
xsave:
.byte $00