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242 lines
4.3 KiB
ArmAsm
242 lines
4.3 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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; only write 1/7 of time roughly 3s / frame
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; only draw 128 lines roughly 2s / 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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SEVEN = $F6
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NEXTCOL = $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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; 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 = $1100
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;.zeropage
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;.globalzp T_L,T_H
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;================================
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; Clear screen and setup graphics
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;================================
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sier:
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jsr HGR2 ; set FULLGR, sets A=0
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sta T_L ; start with multiplier 0
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sta T_H
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sier_outer:
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ldx #0 ; get X 0 for later
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stx YY ; YY starts at 0
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; create XX_T and YY_T lookup tables
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stx XX_TL ; always start at 0
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stx XX_TH
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; calc XX*T
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; only really care about XX_TH
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xt_table_loop:
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clc ; 2
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lda XX_TL ; 3
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adc T_L ; 2
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sta XX_TL ; 3
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lda XX_TH ; 3
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adc T_H ; 3
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sta XX_TH ; 3
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sta YT_LOOKUP_TABLE,X ; 5
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eor #$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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; inc T
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; clc
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lda T_L
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speed_smc:
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adc #2
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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 speed_smc+1
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; set initial position on screen at line 32
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lda #$0 ;
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sta GBASL
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lda #$42 ; start on page2 line 32 ($4200)
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sta GBASH
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sier_yloop:
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; GBASH is in A here
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; lda GBASH ; update output pointer
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sta gb_smc+2
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lda GBASL ; adjust so centered
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clc
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adc #$1
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sta gb_smc+1
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; YY*T only needs to be updated once per line
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; so do it here and then self-modify into place
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ldx YY ; 3
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stx add_yy_smc+1 ; 4
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lda YT_LOOKUP_TABLE,X ; 4
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sta yy_th_smc+1 ; 4
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; reset XX to 0
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ldx #0 ; XX
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seven_loop:
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ldy #7 ; apple ii 7 pixels per byte
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sier_xloop:
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; want (YY-(XX*T)) & (XX+(YY*T)
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; SAVED = XX+(Y*T)
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clc ; needed for proper colors ; 2
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txa ; XX ; 2
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yy_th_smc:
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adc #$dd ; 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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add_yy_smc:
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adc #$dd ; 2
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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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; 20
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clc ; 2
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beq black ; 2/3
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white:
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sec ; 2
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black:
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;=====
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; 5/6
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ror NEXTCOL ; rotate in next bit ; 5
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inx ; increment x ; 2
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dey ; dec seven count ; 2
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bne sier_xloop ; 2/3
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;===========================================================
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lda NEXTCOL ; sign extend top bit, ; 3
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cmp #$80 ; matches earlier cool colors ; 2
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ror ; 2
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gb_smc:
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sta $4000 ; write to hi-res display ; 4
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inc gb_smc+1 ; increase GBASL ; 6
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cpx #248 ; 2
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bcc seven_loop ; 3/2
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;=================
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; total roughly ???
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; full screen each inner cycle is done 256*192 = 49152
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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 ; ROM routine to skip the next line
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; as this is non-trivial on Apple II
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; X/Y left alone
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; returns with GBASH in A
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inc YY ; repeat until YY=128
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bpl sier_yloop
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;flip_pages:
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; TODO if frame rate ever gets fast enough
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bmi sier_outer ; branch always
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