dos33fsprogs/mode7_demo/rasterbars.s
2018-01-31 01:15:47 -05:00

245 lines
4.2 KiB
ArmAsm

; Not quite a raster-bar, but why not
;===========
; CONSTANTS
;===========
ELEMENTS EQU 64
NUM_ROWS EQU 20
;=====================
; Rasterbars
;=====================
;===========================
;===========================
; Main Loop
;===========================
;===========================
draw_rasters:
; clear rows
ldy #(NUM_ROWS-1) ; 2
lda #0 ; 2
init_rows:
sta row_color,Y ; 5
dey ; 2
bpl init_rows ; 2nt/3
;================
; set colors
lda #COLOR_BOTH_AQUA ; aqua
ldy SCREEN_Y
jsr set_row_color
lda #COLOR_BOTH_MEDIUMBLUE ; medium blue
jsr set_row_color
lda #COLOR_BOTH_LIGHTGREEN ; light green
jsr set_row_color
lda #COLOR_BOTH_DARKGREEN ; green
jsr set_row_color
lda #COLOR_BOTH_YELLOW ; yellow
jsr set_row_color
lda #COLOR_BOTH_ORANGE ; orange
jsr set_row_color
lda #COLOR_BOTH_PINK ; pink
jsr set_row_color
lda #COLOR_BOTH_RED ; red
jsr set_row_color
;=================
; draw rows
ldy #(NUM_ROWS-1) ; 2
draw_rows_loop:
lda row_color,Y ; 5
beq draw_rows_skip ; skip if black ; 2nt/3
sta COLOR ; 3
tya ; 2
pha ; 3
asl ; 2
ldy #39 ; 2
sty V2 ; 3
ldy #0 ; 2
jsr hlin_double ; hlin y,V2 at A ; 63+(X*16)
pla ; 4
tay ; 2
draw_rows_skip:
dey ; 2
bpl draw_rows_loop ; 2
;==================
; update y pointer
;==================
ldy SCREEN_Y
iny
cpy #ELEMENTS
bne not_there
ldy #0
not_there:
sty SCREEN_Y
rts
;===================
;===================
; set_row_color
;===================
;===================
; color in A
; Y=offset
; Y incremented
; A, X trashed
set_row_color:
sta COLOR
tya ; wrap y offset
and #(ELEMENTS-1)
tax
lda fine_sine,X ; lookup sine value
; pre-shifted right by 4, sign-extended
clc
adc #18 ; add in 18 to center on screen
sin_no_more:
pha ; save row value
jsr put_color ; put color at row
pla ; restore row value
clc ; increment row value
adc #1
jsr put_color ; put color at row
iny ; increment for next time
rts
;==================
; put_color
;==================
; A = row to set color of
; A trashed
put_color:
clc
ror ; row/2, with even/odd in carry
tax ; put row/2 in X
bcc even_line ; if even, skip to even
odd_line:
lda #$f0 ; load mask for odd
bcs finish_line
even_line:
lda #$0f ; load mask for even
finish_line:
sta MASK
and COLOR ; mask off color
sta COLOR2 ; store for later
lda MASK
eor #$ff ; invert mask
and row_color,X ; load existing color
ora COLOR2 ; combine
sta row_color,X ; store back
rts
;======================
; some arrays
;======================
row_color:
.byte $00,$00,$00,$00,$00, $00,$00,$00,$00,$00
.byte $00,$00,$00,$00,$00, $00,$00,$00,$00,$00
; arithmatically shifted right by 4
; FIXME: exploit symmetry and get rid of 3/4 of this table
; possibly not worth the extra code
fine_sine:
.byte $00 ; 0.000000
.byte $01 ; 0.098017
.byte $03 ; 0.195090
.byte $04 ; 0.290285
.byte $06 ; 0.382683
.byte $07 ; 0.471397
.byte $08 ; 0.555570
.byte $0A ; 0.634393
.byte $0B ; 0.707107
.byte $0C ; 0.773010
.byte $0D ; 0.831470
.byte $0E ; 0.881921
.byte $0E ; 0.923880
.byte $0F ; 0.956940
.byte $0F ; 0.980785
.byte $0F ; 0.995185
.byte $0F ; 1.000000
.byte $0F ; 0.995185
.byte $0F ; 0.980785
.byte $0F ; 0.956940
.byte $0E ; 0.923880
.byte $0E ; 0.881921
.byte $0D ; 0.831470
.byte $0C ; 0.773010
.byte $0B ; 0.707107
.byte $0A ; 0.634393
.byte $08 ; 0.555570
.byte $07 ; 0.471397
.byte $06 ; 0.382683
.byte $04 ; 0.290285
.byte $03 ; 0.195090
.byte $01 ; 0.098017
.byte $00 ; 0.000000
.byte $FE ; -0.098017
.byte $FC ; -0.195090
.byte $FB ; -0.290285
.byte $F9 ; -0.382683
.byte $F8 ; -0.471397
.byte $F7 ; -0.555570
.byte $F5 ; -0.634393
.byte $F4 ; -0.707107
.byte $F3 ; -0.773010
.byte $F2 ; -0.831470
.byte $F1 ; -0.881921
.byte $F1 ; -0.923880
.byte $F0 ; -0.956940
.byte $F0 ; -0.980785
.byte $F0 ; -0.995185
.byte $F0 ; -1.000000
.byte $F0 ; -0.995185
.byte $F0 ; -0.980785
.byte $F0 ; -0.956940
.byte $F1 ; -0.923880
.byte $F1 ; -0.881921
.byte $F2 ; -0.831470
.byte $F3 ; -0.773010
.byte $F4 ; -0.707107
.byte $F5 ; -0.634393
.byte $F7 ; -0.555570
.byte $F8 ; -0.471397
.byte $F9 ; -0.382683
.byte $FB ; -0.290285
.byte $FC ; -0.195090
.byte $FE ; -0.098017