dos33fsprogs/demos/lores_escape/gr_putsprite_fast.s

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2019-10-09 03:04:26 +00:00
;=============================================
; put_sprite_fast
;=============================================
; Sprite to display in INH,INL
; Assumes sprite size is 3x2
; Location is SPRITE_XPOS,SPRITE_YPOS
; Note, only works if SPRITE_YPOS is multiple of two
; NO TRANSPARENCY
; 13+ Y*(33+17+X*(18+13) + 5
; 18 + Y*(50+31*X)
; so if 3*2 = 304 cycles??
put_sprite_fast:
ldy #0 ; 2
lda #2 ; ysize is 2 ; 2
sta CV ; ysize is in CV ; 3
lda SPRITE_YPOS ; make a copy of ypos ; 3
sta TEMPY ; as we modify it ; 3
;===========
; 13
put_sprite_loop_fast:
sty TEMP ; save sprite pointer ; 3
ldy TEMPY ; 3
lda gr_offsets,Y ; lookup low-res memory address ; 4
clc ; 2
adc SPRITE_XPOS ; add in xpos ; 3
sta OUTL ; store out low byte of addy ; 3
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 #3 ; load xsize into x ; 2
;===========
; 33
put_sprite_pixel_fast:
lda (INL),Y ; get sprite colors ; 5
iny ; increment sprite pointer ; 2
sty TEMP ; save sprite pointer ; 3
ldy #$0 ; 2
sta (OUTL),Y ; and write it out ; 6
;============
; 18
put_sprite_done_draw_fast:
ldy TEMP ; restore sprite pointer ; 3
inc OUTL ; increment output pointer ; 5
dex ; decrement x counter ; 2
bne put_sprite_pixel_fast ; if not done, keep looping ; 3
;==============
; 13
; -1
inc TEMPY ; each line has two y vars ; 5
inc TEMPY ; 5
dec CV ; decemenet total y count ; 5
bne put_sprite_loop_fast ; loop if not done ; 3
;==============
; 17
; -1
rts ; return ; 6