195 lines
2.9 KiB
ArmAsm
195 lines
2.9 KiB
ArmAsm
; this is a pretty effect during sierpinski zoom
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; accidentally discovered when loading at the wrong address
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; so TL/TH was on text page1 and full of $a0 (space characters) in TL/TH
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; sierpinski-like demo
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; based on the code from Hellmood's Memories demo
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; by Vince `deater` Weaver <vince@deater.net>
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; zero page
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HGR_BITS = $1C
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GBASH = $27
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MASK = $2E
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COLOR = $30
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HGR_X = $E0
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HGR_Y = $E2
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HGR_COLOR = $E4
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;XX = $F7
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XX_TH = $F8
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XX_TL = $F9
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;YY = $FA
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YY_TH = $FB
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YY_TL = $FC
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;T_L = $FD
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;T_H = $FE
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SAVED = $FF
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; Soft switches
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FULLGR = $C052
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PAGE1 = $C054
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PAGE2 = $C055
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LORES = $C056 ; Enable LORES graphics
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; ROM routines
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HGR = $F3E2
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HGR2 = $F3D8
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HPLOT0 = $F457
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PLOT1 = $F80E ;; PLOT at (GBASL),Y (need MASK to be $0f or $f0)
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GBASCALC= $F847 ;; take Y-coord/2 in A, put address in GBASL/H ( a trashed, C clear)
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SETGR = $FB40
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;================================
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; Clear screen and setup graphics
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;================================
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sier:
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jsr HGR2 ; set FULLGR, sets A=0
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sier_outer:
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ldy #0 ; YY starts at 0
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sty YY_TL
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sty YY_TH
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sier_yloop:
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; calc YY_T (8.8 fixed point add)
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; save space by skipping clc as it's only a slight variation w/o
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; clc
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lda YY_TL
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adc T_L
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sta YY_TL
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lda YY_TH
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adc T_H
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sta YY_TH
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; txa ; YY ; plot call needs Y/2
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; lsr
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; php
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; bcc even_mask
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; ldy #$f0
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; .byte $2C ; bit hack
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;even_mask:
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; ldy #$0f
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; sty MASK
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; jsr GBASCALC ; take Y-coord/2 in A, put address in GBASL/H ( a trashed, C clear)
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; lda GBASH
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;draw_page_smc:
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; adc #0
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; sta GBASH ; adjust for PAGE1/PAGE2 ($400/$800)
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; plp
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; jsr $f806 ; trick to calculate MASK by jumping
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; into middle of PLOT routine
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; reset XX to 0
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ldx #0 ; XX
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stx XX_TL
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stx XX_TH
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sier_xloop:
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; want (YY-(XX*T)) & (XX+(YY*T)
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; SAVED = XX+(Y*T)
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; clc
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txa ; XX
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adc YY_TH
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sta SAVED
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; calc XX*T
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; clc
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lda XX_TL
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adc T_L
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sta XX_TL
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lda XX_TH
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adc T_H
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sta XX_TH
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; calc (YY-X_T)
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tya ; lda YY
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sec
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sbc XX_TH
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; want (YY-(XX*T)) & (XX+(YY*T)
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and SAVED
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and #$f0
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beq white
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black:
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lda #00 ; black
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.byte $2C ; bit trick
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white:
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lda #$ff ; green
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sta HGR_COLOR
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tya ; YY in A
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ldy #0
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; XX in X
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jsr HPLOT0 ; plot at (Y,X), (A)
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; at begin, stores A to HGR_Y
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; X to HGR_X and Y to HGR_X+1
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; destroys X,Y,A
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; Y is XX/7
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ldy HGR_Y
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ldx HGR_X
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inx ; XX
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cpx #255
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bne sier_xloop
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iny ; YY
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cpy #192
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bne sier_yloop
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; inc T
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; clc
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lda T_L
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blah_smc:
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adc #1
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sta T_L
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bcc no_carry
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inc T_H
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no_carry:
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; speed up the zoom as it goes
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; inc blah_smc+1
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; x is 48
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;flip_pages:
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; lda draw_page_smc+1 ; DRAW_PAGE
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; beq done_page
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; inx
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;done_page:
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; X=48 ($30) PAGE1=$C054-$30=$C024
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; ldy $C024,X ; set display page to PAGE1 or PAGE2
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; eor #$4 ; flip draw page between $400/$800
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; sta draw_page_smc+1 ; DRAW_PAGE
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jmp sier_outer ; what can we branch on?
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T_L: .byte $A0
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T_H: .byte $A0
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