gr: lines: make it fit

This commit is contained in:
Vince Weaver 2021-03-28 00:27:06 -04:00
parent 244e0ea558
commit dc80cfdeb1
4 changed files with 272 additions and 35 deletions

View File

@ -7,13 +7,14 @@ EMPTYDISK = ../../../empty_disk/empty.dsk
all: lines.dsk
lines.dsk: HELLO LINES LINES_SMALL LINES_ROM LINES_WIKI
lines.dsk: HELLO LINES LINES_SMALL LINES_ROM LINES_WIKI LINES_BOT
cp $(EMPTYDISK) lines.dsk
$(DOS33) -y lines.dsk SAVE A HELLO
$(DOS33) -y lines.dsk BSAVE -a 0xC00 LINES
$(DOS33) -y lines.dsk BSAVE -a 0xC00 LINES_SMALL
$(DOS33) -y lines.dsk BSAVE -a 0xC00 LINES_ROM
$(DOS33) -y lines.dsk BSAVE -a 0xC00 LINES_WIKI
$(DOS33) -y lines.dsk BSAVE -a 0xC00 LINES_BOT
###
@ -52,8 +53,15 @@ LINES_WIKI: lines_wiki.o
lines_wiki.o: lines_wiki.s
ca65 -o lines_wiki.o lines_wiki.s -l lines_wiki.lst
###
LINES_BOT: lines_bot.o
ld65 -o LINES_BOT lines_bot.o -C $(LINKERSCRIPTS)/apple2_c00.inc
lines_bot.o: lines_bot.s
ca65 -o lines_bot.o lines_bot.s -l lines_bot.lst
###
clean:
rm -f *~ *.o *.lst HELLO LINES LINES_SMALL LINES_ROM LINES_WIKI
rm -f *~ *.o *.lst HELLO LINES LINES_SMALL LINES_ROM LINES_WIKI LINES_BOT

View File

@ -39,7 +39,7 @@ NORMAL = $F273
;; MONITOR ROUTINES
PLOT = $F800 ;; PLOT AT Y,A
PLOT = $F800 ;; PLOT AT Y,A (A colors output, Y preserved)
PLOT1 = $F80E ;; PLOT at (GBASL),Y (need MASK to be $0f or $f0)
SCRN2 = $F879 ;; set A to top or bottom nibble based on C
HLINE = $F819 ;; HLINE Y,$2C at A

View File

@ -0,0 +1,242 @@
; Bresenham Lines
; by Vince `deater` Weaver <vince@deater.net>
; based on pseudo-code from
; https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm
.include "zp.inc"
.include "hardware.inc"
; 174 -- initial
; 170 -- inline init
; 166 -- inline step
; 161 -- merge absolute_value/negative code
; 159 -- merging init X/Y paths
; 156 -- more merging X/Y init
; 154 -- note PLOT doesn't touch Y
; 152 -- merge into common_inc
; 151 -- share an RTS
; 150 -- use X when plotting
; 147 -- count down instead of up
; 144 -- mess around with how count set
; 142 -- who needs COUNT anyway
; 139 -- inline draw_line
B_X1 = $F0
B_Y1 = $F1
B_X2 = $F2
B_Y2 = $F3
B_DX = $F4
B_DY = $F5
B_SX = $F6
B_SY = $F7
B_ERR = $F8
lines_bot:
jsr SETGR ; set lo-res 40x40 mode
; A=$D0 afterward
restart:
lda #36
sta B_Y2
lines_loop:
pha
sta B_X2
sta B_Y1
jsr NEXTCOL
lda #0
sta B_X1
;====================================
; inline draw_line
;====================================
;============================
; draw line
; from x1,y1 to x2,y2
;============================
draw_line:
; 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
tax ; know this is zero from above
; ldx #0
jsr do_abs
; dy = -abs(y2-y1)
; sy = y1 < y2 ? 1 : -1
inx
jsr do_abs
jsr neg ; dy = -abs(y2-y1)
; err = dx+dy
; B_DY is in A already
clc
adc B_DX
sta B_ERR
;======================
; iterative plot points
line_loop:
; plot X1,Y1
ldy B_X1
ldx B_Y1
txa
jsr PLOT ; PLOT AT Y,A (A colors output, Y preserved)
; check if hit end
; ldy B_X1
cpy B_X2
bne line_no_end
; lda B_Y1
cpx B_Y2
beq end_inline_draw_line
line_no_end:
;========================
; step bresenham
;========================
; err2 = 2*err
lda B_ERR
asl
pha ; save err2 for later
ldx #0 ; setup for common_inc
; if err2 >= dy:
; err = err + dy
; x1 = x1 + sx
; B_ERR already in A
cmp B_DY ; check equal first
beq do_x
clc ; signed compare
sbc B_DY
bvc blah2
eor #$80
blah2:
bmi skip_x ; ble
do_x:
lda B_DY
jsr common_inc
skip_x:
inx ; setup common inc
; if err2 <= dx:
; err = err + dx
; y1 = y1 + sy
pla ; restore err2
clc ; signed compare
sbc B_DX
bvc blah
eor #$80
blah:
bpl skip_y
do_y:
lda B_DX
jsr common_inc
skip_y:
jmp line_loop
;=============================
;end inline draw_line
;=============================
; jsr draw_line
end_inline_draw_line:
pla
sec
sbc #4 ; update count
bpl lines_loop
bmi restart
;=====================================
; common increment
;=====================================
common_inc:
clc
adc B_ERR
sta B_ERR
lda B_X1,X
clc
adc B_SX,X
sta B_X1,X
done_line:
rts
;=====================================
; init, do the abs and sx calculations
; x=0, for X
; x=1, for Y
;=====================================
do_abs:
sec
lda B_X1,X
sbc B_X2,X ; A = x1 - x2
bmi is_neg
ldy #$ff
bmi neg_done
is_neg:
ldy #$1
neg:
eor #$ff
clc
adc #1
neg_done:
sty B_SX,X
sta B_DX,X
rts
jmp lines_bot

View File

@ -19,6 +19,7 @@
; 154 -- note PLOT doesn't touch Y
; 152 -- merge into common_inc
; 151 -- share an RTS
; 150 -- use X when plotting
B_X1 = $F0
B_Y1 = $F1
@ -36,7 +37,7 @@ lines:
jsr SETGR ; set lo-res 40x40 mode
; A=$D0 afterward
restart:
lda #0
sta COUNT
lines_loop:
@ -50,8 +51,8 @@ lines_loop:
lda COUNT
cmp #10
end:
beq end
;end:
beq restart
asl
asl
@ -109,7 +110,8 @@ line_loop:
; plot X1,Y1
ldy B_X1
lda B_Y1
ldx B_Y1
txa
jsr PLOT ; PLOT AT Y,A (A colors output, Y preserved)
; check if hit end
@ -118,52 +120,51 @@ line_loop:
cpy B_X2
bne line_no_end
lda B_Y1
cmp B_Y2
; lda B_Y1
cpx B_Y2
beq done_line
line_no_end:
;========================
; step
; step bresenham
;========================
step_bresenham:
; err2 = 2*err
lda B_ERR
asl
pha ; push err2
pha ; save err2 for later
ldx #0 ; setup for common_inc
; if err2 >= dy:
; err = err + dy
; x1 = x1 + sx
; signed compare
ldx #0
clc
cmp B_DY
; B_ERR already in A
cmp B_DY ; check equal first
beq do_x
clc ; signed compare
sbc B_DY
bvc blah2
eor #$80
blah2:
bmi skip_x ; ble
do_x:
lda B_DY
jsr common_inc
skip_x:
inx ; setup common inc
; if err2 <= dx:
; err = err + dx
; y1 = y1 + sy
pla ; pop err2
inx
pla ; restore err2
clc ; signed compare
sbc B_DX
@ -226,17 +227,3 @@ neg_done:
rts
;B_X1 = $F0 00
;B_Y1 = $F1 00
;B_X2 = $F2 00
;B_Y2 = $F3 $23 = 35
;B_DX = $F4 $00
;B_DY = $F5 $DD = -35
;B_SX = $F6 $FF = -1
;B_SY = $F7 $01 = 1
;B_ERR = $F8 $DD = -35
; E2=2*ERR = 1101 1101 1011 1010 = 0100 0110 = $46 = -70
; if -70 >= -35 .... no
; if -70 <= 0 ... yes, err=err+dx, -35+0=-35