dos33fsprogs/graphics/hgr/tiny_triangles/sier_hplot.s

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2021-04-12 18:47:49 +00:00
; sierpinski-like demo
; based on the code from Hellmood's Memories demo
; by Vince `deater` Weaver <vince@deater.net>
; the simple sierpinski you more or less just plot
; X AND Y
; Hellmood's you plot something more or less like
; COLOR = ( (Y-(X*T)) & (X+(Y*T) ) & 0xf0
; where T is an incrementing frame value
; to get speed on 6502/Apple II we change the multiplies to
; a series of 16-bit 8.8 fixed point adds
; TODO:
; HPLOT timing
; MOVERIGHT timing
; MOVERIGHT MOVEDOWN timing
; LOOKUP TABLE timing
; zero page
HGR_BITS = $1C
GBASH = $27
MASK = $2E
COLOR = $30
HGR_X = $E0
HGR_Y = $E2
HGR_COLOR = $E4
;XX = $F7
XX_TH = $F8
XX_TL = $F9
;YY = $FA
YY_TH = $FB
YY_TL = $FC
;T_L = $FD
;T_H = $FE
SAVED = $FF
; Soft switches
FULLGR = $C052
PAGE1 = $C054
PAGE2 = $C055
LORES = $C056 ; Enable LORES graphics
; ROM routines
HGR = $F3E2
HGR2 = $F3D8
HPLOT0 = $F457
PLOT1 = $F80E ;; PLOT at (GBASL),Y (need MASK to be $0f or $f0)
GBASCALC= $F847 ;; take Y-coord/2 in A, put address in GBASL/H ( a trashed, C clear)
SETGR = $FB40
;.zeropage
;.globalzp T_L,T_H
;================================
; Clear screen and setup graphics
;================================
sier:
jsr HGR2 ; set FULLGR, sets A=0
; lda #0 ; start with multiplier 0
; sta T_L
; sta T_H
sier_outer:
ldy #0 ; YY starts at 0
sty YY_TL
sty YY_TH
sier_yloop:
; calc YY_T (8.8 fixed point add)
; save space by skipping clc as it's only a slight variation w/o
; clc
lda YY_TL
adc T_L
sta YY_TL
lda YY_TH
adc T_H
sta YY_TH
; txa ; YY ; plot call needs Y/2
; lsr
; php
; bcc even_mask
; ldy #$f0
; .byte $2C ; bit hack
;even_mask:
; ldy #$0f
; sty MASK
; jsr GBASCALC ; take Y-coord/2 in A, put address in GBASL/H ( a trashed, C clear)
; lda GBASH
;draw_page_smc:
; adc #0
; sta GBASH ; adjust for PAGE1/PAGE2 ($400/$800)
; plp
; jsr $f806 ; trick to calculate MASK by jumping
; into middle of PLOT routine
; reset XX to 0
ldx #0 ; XX
stx XX_TL
stx XX_TH
sier_xloop:
; want (YY-(XX*T)) & (XX+(YY*T)
; SAVED = XX+(Y*T)
; clc
txa ; XX
adc YY_TH
sta SAVED
; calc XX*T
; clc
lda XX_TL
adc T_L
sta XX_TL
lda XX_TH
adc T_H
sta XX_TH
; calc (YY-X_T)
tya ; lda YY
sec
sbc XX_TH
; want (YY-(XX*T)) & (XX+(YY*T)
and SAVED
and #$f0
beq white
black:
lda #00 ; black
.byte $2C ; bit trick
white:
lda #$ff ; green
sta HGR_COLOR
tya ; YY in A
ldy #0
; XX in X
jsr HPLOT0 ; plot at (Y,X), (A)
; at begin, stores A to HGR_Y
; X to HGR_X and Y to HGR_X+1
; destroys X,Y,A
; Y is XX/7
ldy HGR_Y
ldx HGR_X
inx ; XX
cpx #255
bne sier_xloop
iny ; YY
cpy #192
bne sier_yloop
; inc T
; clc
lda T_L
blah_smc:
adc #1
sta T_L
bcc no_carry
inc T_H
no_carry:
; speed up the zoom as it goes
inc blah_smc+1
; x is 48
;flip_pages:
; lda draw_page_smc+1 ; DRAW_PAGE
; beq done_page
; inx
;done_page:
; X=48 ($30) PAGE1=$C054-$30=$C024
; ldy $C024,X ; set display page to PAGE1 or PAGE2
; eor #$4 ; flip draw page between $400/$800
; sta draw_page_smc+1 ; DRAW_PAGE
jmp sier_outer ; what can we branch on?
T_L: .byte $00
T_H: .byte $00