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Diffstat (limited to 'hacks/images/m6502/sierpinsky.asm')
| -rw-r--r-- | hacks/images/m6502/sierpinsky.asm | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/hacks/images/m6502/sierpinsky.asm b/hacks/images/m6502/sierpinsky.asm new file mode 100644 index 0000000..6a67906 --- /dev/null +++ b/hacks/images/m6502/sierpinsky.asm @@ -0,0 +1,131 @@ +; 6502 assembler Sierpinsky Triangle ver.2 +; by Magnus Wedmark 2007-05-02 +; This program is especially written for +; the 6502asm.com competition and +; uses the 32*32 pixel display used in that +; virtual platform. The sierpinsky +; fractal is one of the simplest to +; implement. Here is a walk-through: +; 1) Specify 3 points that form a triangle +; 2) Choose one of them as a starting point +; 3) Choose one of them as targetpoint randomly +; 4) Set the new current position half-way +; between the current point and the target +; point. +; 5) Goto 3 + + LDX #0 + LDY #0 +new_rnd: + LDA $FE ; random 0-255 + AND #3 ; only 0-3 left + CMP #3 + BNE good_rnd + JMP new_rnd +good_rnd: +; random = 0-2 + PHA +; transform X and Y values according to: +; X=X/2+(P*8) and Y=Y/2+(P*16) + ASL + ASL + ASL + STA $F3 ; P*8 + PLA + AND #1 + ASL + ASL + ASL + ASL + STA $F4 ; (P AND 1)*16 + TXA + LSR + ADC $F3 + TAX + TYA + LSR + ADC $F4 + TAY + JSR set_point ; use and restore regs + JMP new_rnd + +set_point: ; uses both X,Y,A and restores them + PHA ; backup all reg-value (X,Y,A) + TXA + PHA + TYA + PHA + PHA + PHA ; triple Y push, two for int. use + STX $F2 ; transfer X to Y using $F2 + LDY $F2 + LDA #0 + STA $F0 + LDA #$2 + STA $F1 ; set base vector to $200 + LDA #0 + PLA ; transfer the pushed Y-coord to A + AND #$07 ; the value %0000'0111 + ASL + ASL + ASL + ASL + ASL + CLC + ADC $F0 + STA $F0 + BCC no_carry + INC $F1 +no_carry: + CLC + PLA ; transfer the pushed Y-coord to A + AND #$18 + LSR + LSR + LSR + ADC $F1 + STA $F1 + + CLC + TYA + ADC $F0 + ADC $F1 + + LDA #1 ;1 = white for trouble-shooting + JSR set_toning_point ; use for shading + STA ($F0),Y ; set pixel + PLA ; restore all reg-value (X,Y,A) + TAY + PLA + TAX + PLA + RTS + +; sub routine to shade the current pixel ($F0),Y +; lighter on a scale: $0, $B, $C, $F, $1 +; Black, DarkGrey, Grey, LightGrey, White +set_toning_point: + LDA ($F0),Y + CMP #$00 + BNE not_black + LDA #$0B + RTS +not_black: + CMP #$0B + BNE not_dgrey + LDA #$0C + RTS +not_dgrey: + CMP #$0C + BNE not_grey + LDA #$0F + RTS +not_grey: + CMP #$0F + BNE not_lgrey + LDA #$01 + RTS +not_lgrey: +; white stays white + RTS + |