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243 lines
4.1 KiB
ArmAsm
243 lines
4.1 KiB
ArmAsm
; 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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; the simple sierpinski you more or less just plot
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; X AND Y
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; Hellmood's you plot something more or less like
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; COLOR = ( (Y-(X*T)) & (X+(Y*T) ) & 0xf0
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; where T is an incrementing frame value
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; to get speed on 6502/Apple II we change the multiplies to
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; a series of 16-bit 8.8 fixed point adds
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; TODO:
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; HPLOT: roughly 30s / frame
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; MOVERIGHT: roughly 14s / frame
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; MOVERIGHT NO COLORSHIFT:roughly 11s / frame
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; MOVERIGHT MOVEDOWN roughly 11s / frame
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; INLINE HPLOT roughly 9s / frame
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; INLINE EVERYTHING roughly 7s / frame
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; XT/YT lookup tables roughly 6s / frame
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; zero page
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HGR_BITS = $1C
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GBASL = $26
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GBASH = $27
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MASK = $2E
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COLOR = $30
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HGR_HMASK = $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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HGR_HORIZ = $E5
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SAVEX = $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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HPOSN = $F411
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HPLOT0 = $F457
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HPLOT1 = $F45A ; skip the HPOSN call
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COLOR_SHIFT = $F47E ; shift color for odd/even Y (0..7 or 7..13)
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MOVE_RIGHT = $F48A ; move next plot location one to the right
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MOVE_DOWN = $F504 ; clc at f504, needed?
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; f505 is applesoft entry point but assumes c?
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; move next plot location one to the right
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; note moveright/movedown respect HGR_PAGE
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COLORTBL = $F6F6
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XT_LOOKUP_TABLE = $1000
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YT_LOOKUP_TABLE = $1100
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;.zeropage
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;.globalzp T_L,T_H
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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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sta T_L ; start with multiplier 0
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sta T_H
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sier_outer:
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lda #$40 ; start on page2 ($4000)
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sta GBASH
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ldx #0 ; get X 0 for later
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stx YY ; YY starts at 0
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stx GBASL ; GBASL is $00
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; create XX_T lookup table
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; note, same as YY_T lookup table?
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stx XX_TL ; start at 0
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stx XX_TH
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; calc XX*T
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; only really care about XX_TH
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xt_table_loop:
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clc
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lda XX_TL ; 3
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tl_smc:
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adc T_L ; 2
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sta XX_TL ; 3
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lda XX_TH ; 3
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th_smc:
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adc T_H ; 3
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sta XX_TH ; 3
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sta YT_LOOKUP_TABLE,X ; 5
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eor #$ff ; negate, as we subtract ; 2
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sta XT_LOOKUP_TABLE,X ; 5
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inx ; 2
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bne xt_table_loop ; 3/2
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sier_yloop:
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lda #$C0 ; 192 reset hmask at begin of line
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sta HGR_HMASK
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ldx YY ; 3
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lda YT_LOOKUP_TABLE,X ; 4
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sta yy_th_smc+1 ; 4
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; reset XX to 0
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ldy #0 ; y is x/7
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ldx #0 ; XX
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sier_xloop:
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; want (YY-(XX*T)) & (XX+(YY*T)
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; SAVED = XX+(Y*T)
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; clc
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txa ; XX ; 2
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yy_th_smc:
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adc #00 ; 2
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sta SAVED ; 3
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lda XT_LOOKUP_TABLE,X ; ~(XX*T) ; 4
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; calc (YY-XX*T)
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sec ; 2
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adc YY ; 3
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; want (YY-(XX*T)) & (XX+(YY*T)
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and SAVED ; 3
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;============
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; 19
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; and #$f8
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beq black ; 2/3
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white:
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lda #$ff ; white ; 2
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; .byte $2C ; bit trick
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black:
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;=====
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; 4?
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color_ready:
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; sta HGR_BITS
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no_shift:
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; inline HPLOT1 (starting at $F45C)
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eor (GBASL),Y ; 5+
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and HGR_HMASK ; 3
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eor (GBASL),Y ; 5+
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sta (GBASL),Y ; 6
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;=======
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; 19
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; inline MOVE_RIGHT
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lda HGR_HMASK ; get mask ; 3
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asl ; adjust ; 2
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eor #$80 ; toggle top bit ; 2
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bmi lr_1 ; if set, done? ; 3/2
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lda #$81 ; otherwise set to $81 ; 2
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iny ; and move to next mult of 7 ; 2
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; no need to check for
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; right boundary
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; as we do that separately
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lr_1:
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sta HGR_HMASK ; 3
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;======
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; 16
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;==================================
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inx ; 2
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bne sier_xloop ; 3/2
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;=================
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; total roughly 19+4+19+16+5 = 63
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; 49152 per inside *80 = 3,145,728
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; apple II cyles/frame = 17,030
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; 1FPS = 1,021,800
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;==================================
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jsr MOVE_DOWN ; X/Y left alone
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inc YY ; repeat until Y=192
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ldy 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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;flip_pages:
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; TODO if frame rate ever gets fast enough
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jmp sier_outer ; what can we branch on?
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