dos33fsprogs/hellmood_memories/plane.s
2020-05-12 14:58:40 -04:00

129 lines
1.9 KiB
ArmAsm

; Tilted Plane, based on the code in Hellmood's Memories
; by deater (Vince Weaver) <vince@deater.net>
; Zero Page
BASL = $28
BASH = $29
H2 = $2C
COLOR = $30
X1 = $F0
X2 = $F1
Y1 = $F2
Y2 = $F3
M1 = $F7
M2 = $F8
TEMP = $FA
TEMPY = $FB
FRAME = $FC
TEMPX = $FD
SCALED = $FE
; Soft Switches
KEYPRESS= $C000
KEYRESET= $C010
SET_GR = $C050 ; Enable graphics
FULLGR = $C052 ; Full screen, no text
PAGE0 = $C054 ; Page0
PAGE1 = $C055 ; Page1
LORES = $C056 ; Enable LORES graphics
; ROM routines
PLOT = $F800 ; plot, horiz=y, vert=A (A trashed, XY Saved)
SETCOL = $F864
TEXT = $FB36 ;; Set text mode
BASCALC = $FBC1
SETGR = $FB40
HOME = $FC58 ;; Clear the text screen
WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
HLINE = $F819
tilted_plane:
;===================
; init screen
jsr SETGR ; 3
bit FULLGR ; 3
jsr init_multiply_tables
plane_forever:
inc FRAME ; 2
ldx #47 ; yy ; 2
yloop:
ldy #39 ; xx ; 2
xloop:
; clc
; adc #$10 ; adjust top of screen
lda division,X ; scaled=((0x3d5/yy)&0xff);
; reverse divide AL=C/Y'
sta M1
sta SCALED
; color=((signed char)((xprime-20)&0xff))*((signed char)(scaled&0xff));
tya
sec
sbc #20
sta M2
jsr multiply_s8x8
lda M1
rol
rol M2
rol
rol M2
lda M2
sta COLOR
; fedcba9876543210
; dcba9876
; color=(color>>6)&0xff;
sec
lda SCALED
sbc FRAME ; scaled-=frame;
eor COLOR ; color^=(scaled&0xff);
and #$1C ; color&=0x1c; // map colors
jsr SETCOL
txa ; A==Y1 ; 1
jsr PLOT ; (X2,Y1) ; 3
dey ; 1
bpl xloop ; 2
dex ; 1
bpl yloop ; 2
bmi plane_forever ; 2
division:
.byte $62,$59,$51,$4B,$46,$41,$3D,$39,$36,$33
.byte $31,$2E,$2C,$2A,$28,$27,$25,$24,$23,$21
.byte $20,$1F,$1E,$1D,$1C,$1C,$1B,$1A,$19,$19
.byte $18,$17,$17,$16,$16,$15,$15,$14,$14,$14
.byte $13,$13,$12,$12,$12,$11,$11,$11
.include "multiply_tables.s"
.include "multiply_s8x8.s"
.include "multiply_u8x8.s"