mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-12-29 00:31:52 +00:00
398 lines
5.0 KiB
ArmAsm
398 lines
5.0 KiB
ArmAsm
; Hi-res Bresenham Lines
|
|
|
|
; by Vince `deater` Weaver <vince@deater.net>
|
|
|
|
; based on pseudo-code from
|
|
; https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm
|
|
|
|
; goal: ROM is 120 bytes 43c3/44a4/4599
|
|
|
|
; 361 bytes / D799/D23A/CE55 -- first working code
|
|
; 346 bytes / D7D6/D17C/CCE7 -- make X2 always > X1
|
|
; 347 bytes / D718/D0C6/CC39 -- make B_SY self modifying code
|
|
|
|
; D0+ used by HGR routines
|
|
|
|
HGR_COLOR = $E4
|
|
HGR_PAGE = $E6
|
|
|
|
X1_L = $A0
|
|
X1_H = $A1
|
|
Y1 = $A2
|
|
X2_L = $A3
|
|
X2_H = $A4
|
|
Y2 = $A5
|
|
B_ERR2_L = $EE
|
|
B_ERR2_H = $EF
|
|
B_X1_L = $F0
|
|
B_X1_H = $F1
|
|
B_Y1 = $F2
|
|
B_X2_L = $F3
|
|
B_X2_H = $F4
|
|
B_Y2 = $F5
|
|
B_DX_L = $F6
|
|
B_DX_H = $F7
|
|
B_DY_L = $F8
|
|
B_DY_H = $F9
|
|
;B_SX = $FA
|
|
;B_SY = $FB
|
|
B_ERR_L = $FC
|
|
B_ERR_H = $FD
|
|
COUNT = $FE
|
|
FRAME = $FF
|
|
|
|
; soft-switches
|
|
|
|
KEYPRESS = $C000
|
|
KEYRESET = $C010
|
|
|
|
; ROM routines
|
|
|
|
HGR2 = $F3D8 ; set hires page2 and clear $4000-$5fff
|
|
HGR = $F3E2 ; set hires page1 and clear $2000-$3fff
|
|
HPLOT0 = $F457 ; plot at (Y,X), (A)
|
|
HGLIN = $F53A ; line to (X,A),(Y)
|
|
HCOLOR1 = $F6F0 ; set HGR_COLOR to value in X
|
|
COLORTBL = $F6F6
|
|
PLOT = $F800 ; PLOT AT Y,A (A colors output, Y preserved)
|
|
NEXTCOL = $F85F ; COLOR=COLOR+3
|
|
SETCOL = $F864 ; COLOR=A
|
|
SETGR = $FB40 ; set graphics and clear LO-RES screen
|
|
BELL2 = $FBE4
|
|
WAIT = $FCA8 ; delay 1/2(26+27A+5A^2) us
|
|
|
|
|
|
lines:
|
|
jsr HGR2
|
|
|
|
reset:
|
|
ldx #0
|
|
stx COUNT
|
|
|
|
stx X1_H ; 0:0,0
|
|
stx X1_L
|
|
stx Y1
|
|
|
|
stx X2_H ; 0:0,191
|
|
stx X2_L
|
|
|
|
lda #191
|
|
sta Y2
|
|
|
|
left_lines_loop:
|
|
|
|
lda FRAME
|
|
and #$7
|
|
tax
|
|
; ldx #7
|
|
jsr HCOLOR1 ; set color
|
|
|
|
jsr draw_line
|
|
|
|
lda Y1
|
|
clc
|
|
adc #8
|
|
sta Y1
|
|
|
|
lda X2_L ; 280/24 = 140/12 = 70/6 = 11
|
|
clc
|
|
adc #11
|
|
sta X2_L
|
|
bcc noc
|
|
inc X2_H
|
|
noc:
|
|
inc COUNT
|
|
inc FRAME
|
|
|
|
lda COUNT
|
|
cmp #24
|
|
end:
|
|
bne left_lines_loop
|
|
|
|
;================
|
|
; right lines
|
|
;================
|
|
; at this point, count = 24
|
|
; X1, Y1 = 0,192
|
|
; X2, Y2 = 264,192
|
|
; want x1,y1 to go from 264,0 to 0,0
|
|
; want x2,y2 to go from 264,192 to 264,0
|
|
|
|
ldx #0
|
|
stx Y1
|
|
|
|
ldx X2_L
|
|
stx X1_L
|
|
ldx X2_H
|
|
stx X1_H
|
|
|
|
right_lines_loop:
|
|
|
|
jsr draw_line
|
|
|
|
lda Y2
|
|
sec
|
|
sbc #8
|
|
sta Y2
|
|
|
|
lda X1_L
|
|
sec
|
|
sbc #11
|
|
sta X1_L
|
|
bcs noc2
|
|
dec X1_H
|
|
noc2:
|
|
dec COUNT
|
|
inc FRAME
|
|
|
|
lda COUNT
|
|
|
|
beq reset
|
|
|
|
bne right_lines_loop
|
|
|
|
|
|
;=========================================
|
|
; draw line
|
|
; from x1,y1 to x2,y2
|
|
;=========================================
|
|
; note: x1,y1 points to x2,y2 at the end?
|
|
; x2,y2 unchanged
|
|
draw_line:
|
|
|
|
lda X1_L
|
|
sta B_X1_L
|
|
lda X1_H
|
|
sta B_X1_H
|
|
lda Y1
|
|
sta B_Y1
|
|
|
|
lda X2_L
|
|
sta B_X2_L
|
|
lda X2_H
|
|
sta B_X2_H
|
|
lda Y2
|
|
sta B_Y2
|
|
|
|
; from wikipedia
|
|
|
|
; dx = abs(x2 - x1)
|
|
; sx = x1 < x2 ? 1 : -1
|
|
; dy = -abs(y2 - y1)
|
|
; sy = y1 < y2 ? 1 : -1
|
|
; err = dx+dy
|
|
|
|
init_bresenham:
|
|
|
|
; dx = abs(x2-x1)
|
|
; sx = x1<x2 ? 1 : -1
|
|
|
|
; we force x2 to always be greater than x1
|
|
; now dx=x2-x1, sx fixed at 1
|
|
|
|
; 16 bit unsigned compare x1 vs x2
|
|
|
|
ldx B_X1_H
|
|
ldy B_X1_L
|
|
|
|
cpx B_X2_H ; compare high bytes
|
|
bne dx_done_check
|
|
cpy B_X2_L
|
|
dx_done_check:
|
|
|
|
bcc calc_dx ; blt skip swap if x1<x2
|
|
|
|
; swap X1/X2, Y1/Y2
|
|
|
|
lda B_X2_H
|
|
sta B_X1_H
|
|
|
|
lda B_X2_L
|
|
sta B_X1_L
|
|
|
|
stx B_X2_H
|
|
sty B_X2_L
|
|
|
|
ldx B_Y1
|
|
ldy B_Y2
|
|
stx B_Y2
|
|
sty B_Y1
|
|
|
|
calc_dx:
|
|
sec
|
|
lda B_X2_L
|
|
sbc B_X1_L ; x2 - x1
|
|
sta B_DX_L
|
|
lda B_X2_H
|
|
sbc B_X1_H
|
|
sta B_DX_H
|
|
|
|
|
|
; dy = -abs(y2-y1)
|
|
; sy = y1 < y2 ? 1 : -1
|
|
|
|
do_abs_y:
|
|
ldy #$1
|
|
|
|
sec
|
|
lda B_Y1
|
|
sbc B_Y2 ; A = y1 - y2
|
|
sta B_DY_L
|
|
lda #0 ; need to sign extend?
|
|
sbc #0
|
|
sta B_DY_H
|
|
|
|
bmi yis_neg
|
|
|
|
ldy #$ff
|
|
yneg:
|
|
lda B_DY_L
|
|
eor #$ff
|
|
clc
|
|
adc #1
|
|
sta B_DY_L
|
|
lda B_DY_H
|
|
eor #$ff
|
|
adc #0
|
|
sta B_DY_H
|
|
|
|
yis_neg:
|
|
sty b_sy_smc+1 ; B_SY
|
|
|
|
|
|
; err = dx+dy
|
|
|
|
clc
|
|
lda B_DY_L
|
|
adc B_DX_L
|
|
sta B_ERR_L
|
|
lda B_DY_H
|
|
adc B_DX_H
|
|
sta B_ERR_H
|
|
|
|
;======================
|
|
; iterative plot points
|
|
|
|
line_loop:
|
|
|
|
; hplot X1,Y1
|
|
|
|
ldy B_X1_H
|
|
ldx B_X1_L
|
|
lda B_Y1
|
|
|
|
jsr HPLOT0 ; plot at (Y,X), (A)
|
|
|
|
; check if hit end
|
|
|
|
ldy B_X1_H
|
|
cpy B_X2_H
|
|
bne line_no_end
|
|
|
|
ldy B_X1_L
|
|
cpy B_X2_L
|
|
bne line_no_end
|
|
|
|
lda B_Y1
|
|
cmp B_Y2
|
|
beq done_line
|
|
|
|
line_no_end:
|
|
|
|
;========================
|
|
; step bresenham
|
|
;========================
|
|
|
|
; err2 = 2*err
|
|
lda B_ERR_L
|
|
sta B_ERR2_L
|
|
lda B_ERR_H
|
|
sta B_ERR2_H
|
|
|
|
clc
|
|
rol B_ERR2_L
|
|
rol B_ERR2_H
|
|
|
|
; if err2 >= dy:
|
|
; err = err + dy
|
|
; x1 = x1 + sx
|
|
|
|
; http://6502.org/tutorials/compare_beyond.html#5
|
|
; 16 bit signed compare
|
|
lda B_ERR2_L ; ERR2-DY
|
|
cmp B_DY_L
|
|
lda B_ERR2_H
|
|
sbc B_DY_H
|
|
bvc blah
|
|
eor #$80 ; N eor V
|
|
blah:
|
|
bmi check_dx ; branch if less than
|
|
|
|
; err = err + dy
|
|
|
|
clc
|
|
lda B_ERR_L
|
|
adc B_DY_L
|
|
sta B_ERR_L
|
|
lda B_ERR_H
|
|
adc B_DY_H
|
|
sta B_ERR_H
|
|
|
|
; SX is always 1
|
|
; x1 = x1 + sx
|
|
|
|
inc B_X1_L
|
|
bne done_inc_x1
|
|
inc B_X1_H
|
|
done_inc_x1:
|
|
|
|
check_dx:
|
|
; if err2 <= dx:
|
|
; err = err + dx
|
|
; y1 = y1 + sy
|
|
|
|
lda B_DX_L
|
|
cmp B_ERR2_L
|
|
bne check_less
|
|
lda B_DX_H
|
|
cmp B_ERR2_H
|
|
beq doit
|
|
|
|
check_less:
|
|
|
|
; 16 bit signed compare
|
|
lda B_DX_L
|
|
cmp B_ERR2_L
|
|
lda B_DX_H
|
|
sbc B_ERR2_H
|
|
bvc blah2
|
|
eor #$80 ; N eor V
|
|
blah2:
|
|
bmi skip_y ; if minus than dx<err2 (i.e. err2>=dx)
|
|
|
|
; err = err + dx
|
|
doit:
|
|
clc
|
|
lda B_ERR_L
|
|
adc B_DX_L
|
|
sta B_ERR_L
|
|
lda B_ERR_H
|
|
adc B_DX_H
|
|
sta B_ERR_H
|
|
|
|
; y1 = y1 + sy
|
|
clc
|
|
lda B_Y1
|
|
b_sy_smc:
|
|
adc #0
|
|
sta B_Y1
|
|
|
|
skip_y:
|
|
|
|
jmp line_loop
|
|
|
|
done_line:
|
|
rts
|
|
|
|
|