dos33fsprogs/games/duke/draw_tilemap.s
Vince Weaver b1238af49d re-arranged the entire directory structure
this will probably upset people
2021-01-05 15:29:31 -05:00

144 lines
2.2 KiB
ArmAsm

;================================
; draw local tilemap to screen
;================================
draw_tilemap:
ldy #0 ; Y on screen currently drawing
sty tiley ; we draw two at a time
ldx #1 ; offset in current screen
stx tilemap_offset ; tilemap
lda #0 ; init odd/even
sta tile_odd
tilemap_outer_loop:
ldy tiley ; setup pointer to current Y
lda gr_offsets,Y
sta GBASL
lda gr_offsets+1,Y
clc
adc DRAW_PAGE
sta GBASH
ldy #6 ; we draw in window 6->34
tilemap_loop:
ldx tilemap_offset ; get actual tile
lda TILEMAP,X
asl ; *4 ; get offset in tile
asl
tax
lda tile_odd
beq not_odd_line
inx
inx
not_odd_line:
lda TILES,X ; draw two tiles
cmp #$AA ; transparency
beq skip_tile1
sta (GBASL),Y
skip_tile1:
iny
lda TILES+1,X
cmp #$AA
beq skip_tile2
sta (GBASL),Y
skip_tile2:
iny
inc tilemap_offset
cpy #34 ; until done
bne tilemap_loop
; move to next line
lda tile_odd ; toggle odd/even
eor #$1 ; (should we just add/mask?)
sta tile_odd
bne move_to_odd_line
move_to_even_line:
lda tilemap_offset
clc
adc #2
jmp done_move_to_line
move_to_odd_line:
lda tilemap_offset
sec
sbc #14
done_move_to_line:
sta tilemap_offset
ldy tiley ; move to next line
iny
iny
sty tiley
cpy #40 ; check if at end
bne tilemap_outer_loop
rts
; these should probably be in the zero page
tilemap_offset: .byte $00
tile_odd: .byte $00
tiley: .byte $00
;===================================
; copy tilemap
;===================================
; want to copy a 16x10 area from global tileset to local
; default at first we want to start at 128,88
; which is 13, 20???
copy_tilemap_subset:
; set start
lda TILEMAP_Y
clc
adc #>BIG_TILEMAP
sta cptl1_smc+2 ; set proper row in big tilemap
adc #$10
sta cptl3_smc+1 ; set loop limit
; reset row
lda #<TILEMAP
sta cptl2_smc+1 ; set small tilemap to row0
cp_tilemap_outer_loop:
ldx TILEMAP_X
ldy #0
cp_tilemap_inner_loop:
cptl1_smc:
lda $9400,X
cptl2_smc:
sta $BC00,Y
iny
inx
cpy #16
bne cp_tilemap_inner_loop
; next line
inc cptl1_smc+2 ; incremement page
clc
lda cptl2_smc+1 ; increment row
adc #$10
sta cptl2_smc+1
lda cptl1_smc+2
cptl3_smc:
cmp #$a
bne cp_tilemap_outer_loop
rts