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Spirograph Demo
REBOL [
Title: "Simple Spirograph"
Author: "Gregg Irwin"
EMail: greggirwin@acm.org
Comment: {
Set max number of lines
Generate random start point and velocity
at each iteration
for each set
calculate next set of end-points from previous end-points
append line command to draw effect, wrap if at max-lines
TBD
Allow for multiple line "sets".
Figure out why it's so slow for large canvases.
Use color-shifting lines, rather than restarting with a new color.
}
]
num-lines: 30 ; change this for longer, or shorter, line sets.
end-points: make block! 128
pt-1: pt-2: 0x0
delta-1: delta-2: 0x0
direction-1: direction-2: 'SE
color: 0.0.0
directions: [
SE 1x1
NW -1x-1
NE 1x-1
SW -1x1
]
initialize: func [
"Initialize starting coordinates, directions, and colors."
face
i [integer!]
][
random/seed now
; Starting locations for line end points
pt-1: random face/size
pt-2: random face/size
change/only at end-points i [pt-1 pt-2]
; Direction of travel
direction-1: pick [SE NW NE SW] random 4
direction-2: pick [SE NW NE SW] random 4
; Angle of travel. Bigger numbers move things faster.
;delta-1: 2 + (random 3x3)
;delta-2: 2 + (random 3x3)
delta-1: random 3x3
delta-2: random 3x3
; Colors. The + 32 keeps it from being too dark.
color: (random 200.200.200) + 32
]
move-points: func [face] [
; direction-1 = Direction of Travel for Point 1
; direction-2 = Direction of Travel for Point 2
;TBD Should be able to map these so the code isn't duped for each point.
pt-1: pt-1 + (delta-1 * (select directions direction-1))
switch direction-1 [
NE [if pt-1/x > face/size/x [direction-1: 'NW]
if pt-1/y < 1 [direction-1: 'SE]]
SE [if pt-1/x > face/size/x [direction-1: 'SW]
if pt-1/y > face/size/y [direction-1: 'NE]]
SW [if pt-1/x < 1 [direction-1: 'SE]
if pt-1/y > face/size/y [direction-1: 'NW]]
NW [if pt-1/x < 1 [direction-1: 'NE]
if pt-1/y < 1 [direction-1: 'SW]]
]
pt-2: pt-2 + (delta-2 * (select directions direction-2))
switch direction-2 [
NE [if pt-2/x > face/size/x [direction-2: 'NW]
if pt-2/y < 1 [direction-2: 'SE]]
SE [if pt-2/x > face/size/x [direction-2: 'SW]
if pt-2/y > face/size/y [direction-2: 'NE]]
SW [if pt-2/x < 1 [direction-2: 'SE]
if pt-2/y > face/size/y [direction-2: 'NW]]
NW [if pt-2/x < 1 [direction-2: 'NE]
if pt-2/y < 1 [direction-2: 'SW]]
]
]
do-spiro: func [
face
max-interval [time!]
/local i t interval
][
i: j: 0
t: now/time/precise
interval: 0:0:3 + random max-interval
initialize face i
forever [
if now/time/precise > (t + interval) [
clear draw-cmds
interval: 0:0:3 + random max-interval
t: now/time/precise
initialize face i
wait .05
]
append draw-cmds compose [pen (color) line (pt-1) (pt-2)]
; Erase oldest line
if (length? draw-cmds) > (num-lines * 5) [
remove/part head draw-cmds 5
]
;print mold draw-cmds
move-points face
i: either i < 127 [i + 1][0]
j: either j < 127 [j + 1][0]
show face
; wait 0 isn't as system friendly as wait .001, but it's faster.
wait 0 ;.001
]
]
lay: layout [
origin 0x0
backdrop black
; Using a larger canvas really slows things down
;canvas: image black 640x480
canvas: image black 320x240
across
button "go" [do-spiro canvas 0:0:10]
button "quit" [quit]
]
canvas/effect: reduce ['draw draw-cmds: make block! (num-lines * 5)]
view lay
;view/offset lay 0x0
