Scout
Registered: Dec 2002
Posts: 1568 |
Bresenham Circle Routine
Because Codebase64.org doesn't like me or something, I might as well post it here: a Bresenham Circle Routine.
This example is textmode (40x25) only but can easily be converted into any other mode.
Enjoy and don't forget to credit me if you use it ;-)
I hope those solid circle tunnels show up now in a demo.
; Draws a circle using the Bresenham algorithm in textmode
; [C]2006 Scout/Silicon Ltd.
Radius = 12
CenterX = 20
CenterY = 12
Char = 160
Cx = $50
Cy = $51
Cd = $52
*=$0810
circle
lda #Radius
sta Cy
asl ; 2 * radius
sta CalcD
lda #0
sta Cx
lda #3
sec
CalcD = *+1
sbc #$00
sta Cd
C_loop
lda Cx
cmp Cy
bmi C_Points
jmp E_rts
C_points
lda Cx
sta x1
sta y2
sta x4
sta y7
eor #$ff ; Maak
clc ; getal
adc #1 ; negatief
sta y3
sta x5
sta y6
sta x8
lda Cy
sta y1
sta x2
sta x3
sta y8
eor #$ff
clc
adc #1
sta y4
sta y5
sta x6
sta x7
y1=*+1
lda #0 ; y
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x1=*+1
lda #0 ; x
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;-----
y2=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x2=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;-----
y3=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x3=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;----
y4=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x4=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;----
y5=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x5=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
y6=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x6=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
y7=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x7=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
y8=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
x8=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
lda Cd
bpl D_pos ; d >= 0
lda Cx
asl
asl ; 4*x
clc
adc #6
adc Cd
sta Cd
inc Cx
jmp C_loop
D_pos
lda Cx
sec
sbc Cy
asl
asl ;4*(x-y)
clc
adc #10
clc
adc Cd
sta Cd
dec Cy
E_next
inc Cx
jmp C_loop
E_rts
lda Cx
sta xx1
sta yy2
sta xx4
sta yy7
eor #$ff
clc
adc #1
sta yy3
sta xx5
sta yy6
sta xx8
lda Cy
sta yy1
sta xx2
sta xx3
sta yy8
eor #$ff
clc
adc #1
sta yy4
sta yy5
sta xx6
sta xx7
yy1=*+1
lda #0 ; y
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx1=*+1
lda #0 ; x
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;-----
yy2=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx2=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;-----
yy3=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx3=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;----
yy4=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx4=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
;----
yy5=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx5=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
yy6=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx6=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
yy7=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx7=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
yy8=*+1
lda #0 ; x
clc
adc #CenterY
tax
lda screenlo,x
sta $f0
lda screenhi,x
sta $f1
xx8=*+1
lda #0 ; y
clc
adc #CenterX
tay
lda #Char
sta ($f0),y
rts
.align 256
screenlo
.byte <$0400+(40*0), <$0400+(40*1),<$0400+(40*2),<$0400+(40*3),<$0400+(40*4),<$0400+(40*5)
.byte <$0400+(40*6), <$0400+(40*7),<$0400+(40*8),<$0400+(40*9),<$0400+(40*10),<$0400+(40*11)
.byte <$0400+(40*12), <$0400+(40*13),<$0400+(40*14),<$0400+(40*15),<$0400+(40*16),<$0400+(40*17)
.byte <$0400+(40*18), <$0400+(40*19),<$0400+(40*20),<$0400+(40*21),<$0400+(40*22),<$0400+(40*23)
.byte <$0400+(40*24)
screenhi
.byte >$0400+(40*0), >$0400+(40*1),>$0400+(40*2),>$0400+(40*3),>$0400+(40*4),>$0400+(40*5)
.byte >$0400+(40*6), >$0400+(40*7),>$0400+(40*8),>$0400+(40*9),>$0400+(40*10),>$0400+(40*11)
.byte >$0400+(40*12), >$0400+(40*13),>$0400+(40*14),>$0400+(40*15),>$0400+(40*16),>$0400+(40*17)
.byte >$0400+(40*18), >$0400+(40*19),>$0400+(40*20),>$0400+(40*21),>$0400+(40*22),>$0400+(40*23)
.byte >$0400+(40*24)
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