mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-12-27 02:31:00 +00:00
365 lines
6.9 KiB
ArmAsm
365 lines
6.9 KiB
ArmAsm
; Lo-res fire animation, size-optimized
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; by deater (Vince Weaver) <vince@deater.net>
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; based on code described here http://fabiensanglard.net/doom_fire_psx/
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FIRE_YSIZE=20
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;=======================
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; fire_init
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;=======================
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; call at beginning to clear out framebuffer
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fire_init:
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lda #<fire_framebuffer
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sta FIRE_FB_L
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lda #>fire_framebuffer
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sta FIRE_FB_H
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ldx #FIRE_YSIZE
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clear_fire_loop:
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lda #0
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ldy #39
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clear_fire_line_loop:
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sta (FIRE_FB_L),Y
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dey
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bpl clear_fire_line_loop
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done_fire_line_loop:
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clc
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lda FIRE_FB_L
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adc #40
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sta FIRE_FB_L
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bcc skip_inc_hi
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inc FIRE_FB_H
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skip_inc_hi:
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dex
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bne clear_fire_loop
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lda #7
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;fall through
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;jsr fire_setline
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;rts
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;======================================
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; set bottom line to color in A
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;======================================
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; Set to 7 to init, Set to 0 to have fire go out
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fire_setline:
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ldx #<(fire_framebuffer+(FIRE_YSIZE-1)*40)
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stx FIRE_FB_L
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ldx #>(fire_framebuffer+(FIRE_YSIZE-1)*40)
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stx FIRE_FB_H
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ldy #39
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set_fire_line:
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sta (FIRE_FB_L),Y
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dey
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bpl set_fire_line
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done_set_fire_line:
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rts
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;===============================
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;===============================
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; Draw fire frame
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;===============================
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;===============================
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draw_fire_frame:
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;===============================
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; Update fire frame
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;===============================
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; Unroll x 2
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; set up working line (to store to)
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lda #<fire_framebuffer ; 2
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sta fire_smc5_fb+1 ; 4
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lda #>fire_framebuffer ; 2
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sta fire_smc5_fb+2 ; 4
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; set up input line, one below, (to load from)
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lda #<(fire_framebuffer+40) ; 2
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sta fire_smc5_fb2+1 ; 4
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lda #>(fire_framebuffer+40) ; 2
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sta fire_smc5_fb2+2 ; 4
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; loop X (ypos) from 0 - FIRE_YSIZE-1
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ldx #0 ; 2
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fire_fb_update:
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; FIXME: optimize
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; original = ??? (complex)
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; TODO: unroll once and combine with the lores copy on even lines?
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; Loop Y (xpos) from 39 to 0
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ldy #39 ; 2
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fire_fb_update_loop:
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; Get random 16-bit number
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jsr random16 ; 40
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; A randomly has either SEEDL or SEEDH here, I guess that's enough?
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; get random number Q 0..3
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; Q used to see if whether we grab same lower value or if decrement
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and #$3 ; 2
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sta FIRE_Q ; 3
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; 0..12 = A volume, 13-25 = B volume, 26-39 = C volume
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lda A_VOLUME ; 3
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cpy #13 ; 2
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bcc fire_vol ; blt ; 2/3
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lda B_VOLUME ; 3
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cpy #26 ; 2
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bcc fire_vol ; blt ; 2/3
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lda C_VOLUME ; 3
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fire_vol:
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and #$f ; 2
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; adjust fire height with volume
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cmp #$8 ; 2
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bcs fire_medium ; bge ; 2/3
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fire_low:
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; Q=1 3/4 of time
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lda FIRE_Q ; 3
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bne fire_one ; 0-3, is not 0 3/4 of time ; 2/3
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beq fire_set ; 3
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fire_medium:
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cmp #$d ; 2
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lda FIRE_Q ; 3
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bcs fire_high ; bge ; 2/3
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; Q=1 1/2 of time
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and #$1 ; 2
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bcc fire_set ; branch always ; 3
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fire_high:
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; Q=1 1/4 of time
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;;lda FIRE_Q ; is 0 1/4 of time ; 3
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bne fire_zero ; 2/3
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fire_one:
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lda #1 ; 2
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bne fire_set ; 3
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fire_zero:
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lda #0 ; 2
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fire_set:
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sta FIRE_Q ; 3
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;=================
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; check if flame from left/right
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; store Y as we over-write it
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sty FIRE_Y ; 3
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; bounds check
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; on edges, don't wrap
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tya ; 2
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beq fire_r_same ; 2/3
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cpy #39 ; 2
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beq fire_r_same ; 2/3
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; RAND_R
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; 50% chance fire comes from below
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; 25% chance comes from right
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; 25% change comes from left
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lda SEEDH ; 3
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lsr ; 2
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and #$1 ; 2
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bne fire_r_same ; 2/3
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bcc r_up ; 2/3
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r_down:
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dey ; 2
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.byte $a9 ; 2
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r_up:
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iny ; 2
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fire_r_same:
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; get next line color
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fire_smc5_fb2:
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lda $1234,Y ; 4+
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; restore saved Y
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ldy FIRE_Y ; 3
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; have value, subtract Q
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sec ; 2
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sbc FIRE_Q ; 3
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; saturate to 0
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bpl fb_positive ; 2/3
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lda #0 ; 2
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fb_positive:
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; store out
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fire_smc5_fb:
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sta $1234,Y ; store out ; 5
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dey ; 2
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bpl fire_fb_update_loop ; 2/3
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done_fire_fb_update_loop:
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; if just finished odd line, we are already set up
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; to do the framebuffer copy for the prev two lines?
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; complicated adjustment
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clc ; 2
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lda fire_smc5_fb+1 ; 4
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adc #40 ; 2
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sta fire_smc5_fb+1 ; 4
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bcc skip_fb_inc1 ; 2/3
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inc fire_smc5_fb+2 ; 4
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clc ; 2
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skip_fb_inc1:
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lda fire_smc5_fb2+1 ; 4
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adc #40 ; 2
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sta fire_smc5_fb2+1 ; 4
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bcc skip_fb2_inc1 ; 2/3
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inc fire_smc5_fb2+2 ; 4
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skip_fb2_inc1:
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inx ; 2
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cpx #(FIRE_YSIZE-1) ; 2
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;beq fire_update_done ; 2/3
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bne fire_fb_update ; 3
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fire_update_done:
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;===================================
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; copy framebuffer to low-res screen
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;===================================
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lda #<fire_framebuffer ; 2
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sta fire_smc_fb+1 ; 5
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lda #<(fire_framebuffer+40) ; 2
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sta fire_smc_fb2+1 ; 5
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lda #>fire_framebuffer ; 2
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sta fire_smc_fb+2 ; 5
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;this lda could be omitted if values match
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lda #>(fire_framebuffer+40) ; 2
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sta fire_smc_fb2+2 ; 5
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lda #16 ; 2
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sta FIRE_FB_LINE ; 3
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ldx #(FIRE_YSIZE/2) ; 2
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fire_fb_copy:
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ldy FIRE_FB_LINE ; 3
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iny ; 2
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iny ; 2
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sty FIRE_FB_LINE ; 3
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; Set up output, self-modifying code
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lda gr_offsets,Y ; 4+
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sta fire_smc_outl+1 ; 4
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lda gr_offsets+1,Y ; 4+
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clc ; 2
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adc DRAW_PAGE ; 3
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sta fire_smc_outl+2 ; 4
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; FIXME: below, can we do this better?
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; 50: original code
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; 39: move to big lookup table
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; 33: move save/restore X outside inner loop
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; 30: self-modifying code
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ldy #39 ; 2
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stx FIRE_X ; 3
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fire_fb_copy_loop:
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; get top byte
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; note, seems backwards, apple II LORES bottom byte is on top
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fire_smc_fb2:
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lda $1234,Y ; 4+
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asl ; 2
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asl ; 2
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asl ; 2
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; get bottom byte
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fire_smc_fb:
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ora $1234,Y ; 4+
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tax ; 2
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lda fire_colors,X ; 4+
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fire_smc_outl:
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sta $1234,Y ; store out ; 5
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dey ; 2
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bpl fire_fb_copy_loop ; 2/3
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done_fire_fb_copy_loop:
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ldx FIRE_X ; 3
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; complicated adjustment
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clc ; 2
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lda fire_smc_fb+1 ; 4
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adc #80 ; 2
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sta fire_smc_fb+1 ; 5
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bcc skip_fb_inc2 ; 2/3
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inc fire_smc_fb+2 ; 5
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clc ; 2
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skip_fb_inc2:
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lda fire_smc_fb2+1 ; 4
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adc #80 ; 2
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sta fire_smc_fb2+1 ; 5
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bcc skip_fb2_inc2 ; 2/3
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inc fire_smc_fb2+2 ; 5
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skip_fb2_inc2:
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dex ; 2
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bne fire_fb_copy ; 2/3
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rts ; 6
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;fire_colors_low: .byte $00,$00,$03,$02,$06,$07,$0E,$0F
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;fire_colors_high: .byte $00,$00,$30,$20,$60,$70,$E0,$F0
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fire_colors:
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; 0 1 2 3 4 5 6 7
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; 0 0 3 2 6 7 e f
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.byte $00,$00,$03,$02,$06,$07,$0e,$0f ; 0
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.byte $00,$00,$03,$02,$06,$07,$0e,$0f ; 0
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.byte $30,$30,$33,$32,$36,$37,$3e,$3f ; 3
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.byte $20,$20,$23,$22,$26,$27,$2e,$2f ; 2
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.byte $60,$60,$63,$62,$66,$67,$6e,$6f ; 6
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.byte $70,$70,$73,$72,$76,$77,$7e,$7f ; 7
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.byte $e0,$e0,$e3,$e2,$e6,$e7,$ee,$ef ; e
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.byte $f0,$f0,$f3,$f2,$f6,$f7,$fe,$ff ; f
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; FIXME: just reserve space in our memory map
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fire_framebuffer:
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.res 40*FIRE_YSIZE, $00
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