mirror of
https://github.com/deater/dos33fsprogs.git
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234 lines
4.6 KiB
ArmAsm
234 lines
4.6 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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; 611 bytes at first
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; 601 bytes -- strip out some unused code
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; 592 bytes -- don't init screen
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; 443 bytes -- remove more dead code
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; 206 bytes -- no need to clear screen
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; 193 bytes -- un-cycle exact the random16 code
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; 189 bytes -- more optimization of random16 code
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; 161 bytes -- move to 8-bit RNG
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; 152 bytes -- reduce lookup to top half colors (had to remove brown)
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; also changed maroon to pink
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; 149 bytes -- use monitor GR
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; 149 bytes -- load into zero page
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; 140 bytes -- start using zero-page addressing
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; 139 bytes -- rotate instead of mask for low bit
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; 138 bytes -- bcs instead of jmp
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; 137 bytes -- BIT nop trick to get rid of jump
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; 135 bytes -- push/pull instead of saving to zero page
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; 134 bytes -- replace half of lookup table with math
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; 119 bytes -- replace that half of lookup table with better math
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; 134 bytes -- replace other half of lookup table with math
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; 132 bytes -- replace stack with zp loads
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; 129 bytes -- use Y instead of X
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; 125 bytes -- optimize low byte generationw with branch
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; 113 bytes -- make get_row a subroutine
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; Zero Page
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SEEDL = $4E
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TEMP = $00
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TEMPY = $01
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LOW = $02
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; 100 = $64
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; Soft Switches
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SET_GR = $C050 ; Enable graphics
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FULLGR = $C052 ; Full screen, no text
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LORES = $C056 ; Enable LORES graphics
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; monitor routines
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GR = $F390
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fire_demo:
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; GR part
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jsr GR ; 3
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bit FULLGR ; 3
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;==========
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; 6
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; Setup white line on bottom
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lda #$ff ; 2
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ldy #39 ; 2
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white_loop:
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sta $7d0,Y ; hline 24 (46+47) ; 3
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dey ; 1
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bpl white_loop ; 2
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;============
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; 10
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fire_loop:
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ldx #22 ; 22 ; 2
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yloop:
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stx TEMPY ; txa/pha not any better ; 2
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; Self-modify the inner loop so it loads/stores from proper
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; low-res address. Generate the proper row memory address
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jsr get_row ; 3
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sty <smc_sta+1 ; 2
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sta <smc_sta+2 ; 2
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inx ; 1
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jsr get_row ; 3
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sty <smc_lda+1 ; 2
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sta <smc_lda+2 ; 2
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; low byte of store address:
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; 000X X00X
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; 0000 XX00 C
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; txa ; 1
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; and #$19 ; 2
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; lsr ; 1
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; bcs odd_sta ; 2
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; .byte $2C ; bit, nop ; 1
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;odd_sta:
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; ora #$2 ; 2
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; lsr ; 1
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; tay ; 1
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; lda <low_offsets,Y ; 2
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; sta <smc_sta+1 ; 2
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;===========
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; 15
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; high byte of store address
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; txa ; 1
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; and #$7 ; 2
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; lsr ; 1
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; ora #$4 ; 2
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; sta <smc_sta+2 ; 2
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;===========
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; 8
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; low byte of load address (one row more than store)
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; inx ; 1
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; txa ; 1
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; and #$19 ; 2
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; lsr ; 1
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; bcs odd_lda ; 2
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; .byte $2C ; bit, nop ; 1
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;odd_lda:
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; ora #$2 ; 2
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; lsr ; 1
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; tay ; 1
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; lda <low_offsets,Y ; 2
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; sta <smc_lda+1 ; 2
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; high byte of load address
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; txa ; 1
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; and #$7 ; 2
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; lsr ; 1
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; ora #$4 ; 2
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; sta <smc_lda+2 ; 2
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ldy #39 ; 2
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xloop:
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smc_lda:
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lda $8d0,Y ; 3
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pha ; save on stack ; 1
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and #$7 ; mask off ; 2
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tax ; 1
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;=============================
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; random8
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;=============================
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; 8-bit 6502 Random Number Generator
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; Linear feedback shift register PRNG by White Flame
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; http://codebase64.org/doku.php?id=base:small_fast_8-bit_prng
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random8:
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lda SEEDL
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beq doEor
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asl
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beq noEor ; if the input was $80, skip the EOR
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bcc noEor
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doEor: eor #$1d
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noEor: sta SEEDL
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; end inlined RNG
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ror ; shift into carry ; 1
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pla ; 1
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bcs no_change ; 2
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.byte $2c ; BIT trick, nops out next instruction
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no_change:
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lda <color_progression,X ; 2
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smc_sta:
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sta $750,Y ; 3
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dey ; 1
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bpl xloop ; 2
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ldx TEMPY
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dex
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bpl yloop
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bmi fire_loop
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color_progression:
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.byte $00 ; 8->0 ; 1000 0101
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.byte $bb ; 9->11 ; 1001 0001
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.byte 0 ; 10->0 ; 1010 0000
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.byte $aa ; 11->10 ; 1011 0000
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.byte 0 ; 12->0 ; 1100 0000
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.byte $99 ; 13->9 ; 1101 1001
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.byte $00 ; 14->0 ; 1110 0000
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.byte $dd ; 15->13 ; 1111 1101
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; Take row X and convert to address A:Y
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get_row:
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; get low byte
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txa ; 1
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and #$19 ; 2
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lsr ; 1
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bcs odd_row ; 2
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.byte $2C ; bit, nop ; 1
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odd_row:
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ora #$2 ; 2
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lsr ; 1
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tay ; 1
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lda <low_offsets,Y ; 2
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tay ; 1
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;===========
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; 14
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; high byte of store address
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txa ; 1
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and #$7 ; 2
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lsr ; 1
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ora #$4 ; 2
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;===========
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; 6
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rts ; 1
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low_offsets:
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.byte $00,$80,$28,$a8,$50,$d0
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