dos33fsprogs/games/tfv/gr_putsprite_mask.s
2021-01-18 14:00:30 -05:00

169 lines
3.6 KiB
ArmAsm

;=============================================
; put_sprite_mask
;=============================================
; put an outline of the sprite, using non-transparent ($AA)
; pixels with a solid color in COLOR
; Sprite to display in INH,INL
; Location is XPOS,YPOS
; Note, only works if YPOS is multiple of two
; transparent color is $A (grey #2)
; this means we can have black ($0) in a sprite
; FIXME: force YPOS to be even?
; A, X, Y trashed
put_sprite_mask:
ldy #0 ; byte 0 is xsize ; 2
lda (INL),Y ; 5
sta CH ; xsize is in CH ; 3
iny ; 2
clc
adc XPOS
sta XMAX
lda (INL),Y ; byte 1 is ysize ; 5
sta CV ; ysize is in CV ; 3
iny ; 2
lda YPOS ; make a copy of ypos ; 3
sta TEMPY ; as we modify it ; 3
;===========
; 28
psm_put_sprite_loop:
sty TEMP ; save sprite pointer ; 3
ldy TEMPY ; 3
bpl psm_put_sprite_pos ; if < 0, skip to next
clc ; skip line in sprite too
lda TEMP
adc CH
tay
bne psm_increment_y
psm_put_sprite_pos:
psm_smc1:
cpy #48 ; bge if >= 48, done sprite
bcs psm_sprite_done
lda gr_offsets,Y ; lookup low-res memory address ; 4
clc ; 2
adc XPOS ; add in xpos ; 3
sta OUTL ; store out low byte of addy ; 3
clc ; never wraps, handle negative
lda gr_offsets+1,Y ; look up high byte ; 4
adc DRAW_PAGE ; ; 3
sta OUTH ; and store it out ; 3
ldy TEMP ; restore sprite pointer ; 3
; OUTH:OUTL now points at right place
ldx XPOS ; load xposition into x ; 3
;===========
; 34
psm_put_sprite_pixel:
lda (INL),Y ; get sprite colors ; 5
iny ; increment sprite pointer ; 2
sty TEMP ; save sprite pointer ; 3
cpx #0 ; if off-screen left, skip draw
bmi psm_skip_drawing
cpx #40
bcs psm_skip_drawing ; if off-screen right, skip draw
ldy #$0 ; 2
; check if completely transparent
; if so, skip
cmp #$AA ; if all zero, transparent ; 2
beq psm_put_sprite_done_draw ; don't draw it ; 2nt/3
;==============
; 16/17
sta COLOR2 ; save color for later ; 3
; check if top pixel transparent
and #$f0 ; check if top nibble zero ; 2
cmp #$a0
bne psm_put_sprite_bottom ; if not skip ahead ; 2nt/3
;==============
; 7/8
lda COLOR
and #$0f
sta COLOR2
lda #$f0 ; setup mask ; 2
sta MASK ; 3
bmi psm_put_sprite_mask ; always? ; 3
;=============
; 8
psm_put_sprite_bottom:
lda COLOR2 ; re-load color ; 3
and #$0f ; check if bottom nibble zero ; 2
cmp #$0a
bne psm_put_sprite_all ; if not, skip ahead ; 2nt/3
;=============
; 7/8
lda COLOR
and #$f0
sta COLOR2
lda #$0f ; 2
sta MASK ; setup mask ; 3
;===========
; 5
psm_put_sprite_mask:
lda (OUTL),Y ; get color at output ; 5
and MASK ; mask off unneeded part ; 3
ora COLOR2 ; or the color in ; 3
sta (OUTL),Y ; store it back ; 6
jmp psm_put_sprite_done_draw ; we are done ; 3
;===========
; 20
psm_put_sprite_all:
lda COLOR ; load color ; 3
sta (OUTL),Y ; and write it out ; 6
;============
; 9
psm_put_sprite_done_draw:
psm_skip_drawing:
ldy TEMP ; restore sprite pointer ; 3
inc OUTL ; increment output pointer ; 5
inx ; increment x counter ; 2
cpx XMAX
bne psm_put_sprite_pixel ; if not done, keep looping ; 2nt/3
;==============
; 12/13
psm_increment_y:
inc TEMPY ; each line has two y vars ; 5
inc TEMPY ; 5
dec CV ; decemenet total y count ; 5
bne psm_put_sprite_loop ; loop if not done ; 2nt/3
;==============
; 17/18
psm_sprite_done:
rts ; return ; 6