REBOL [
	title:	"Barnsley formula"
	author:	cyphre@rebol.com
	type:	'graphic
	Purpose: {
		Michael Barnsley generated the fractal pattern that's now known 
		as Barnsley's Fern. It's supposed to resemble the Black Spleenwort, 
		Asplenium adiantum-nigrum. 
	}
]

time: func [b /local start] [
	start: now/precise
	do b
	print ["Time:" difference now/precise start]
]

img-size: 512x384

oftx: 200
isx: img-size/x

img: make image! img-size
img/rgb: 72.96.120

view/new layout [origin 0 ii: image img]

barnsley: rebcode [/local x y nb t px py ry pxi pyi idx1 idx2][
	
	set x 64.0
	set y 0.0
	set px 0.0
	set py 0.0
	set ry 0.0
	set nb 10000

	

	repeat k nb [
		set t 100
		randz t
		to-dec t 
		div.d t 100.0

		gteq.d t 0.3

		either [
			set.d px x
			mul.d px 0.781
			set.d ry y
			mul.d ry 0.034
			add.d px ry
			add.d px 13.76
		
			set.d py x
			mul.d py -0.032
			set.d ry y
			mul.d ry 0.739
			add.d py ry
			add.d py 70.2

			;draw
			set.d x px
			set.d y py

			set pxi x			
			to-int pxi 
			set pyi y
			to-int pyi 

			set idx1 320
			sub.i idx1 pyi
			mul.i idx1 isx
			add.i idx1 pxi
			add.i idx1 oftx

			set idx2 320
			sub.i idx2 pyi
			add.i idx2 4
			mul.i idx2 isx
			add.i idx2 4
			add.i idx2 pxi
			add.i idx2 oftx


			poke img idx1 16777215
			poke img idx2 2043711
			
			;end draw
		][
			gteq.d t 0.17
			either [

				set.d px x
				mul.d px 0.17
				set.d ry y
				mul.d ry 0.215
				sub.d px ry
				add.d px 52.224

				set.d py x
				mul.d py 0.222
				set.d ry y
				mul.d ry 0.176
				add.d py ry 
				add.d py 23.218

				;draw
				set.d x px
				set.d y py

				set pxi x				
				to-int pxi 
				set pyi y
				to-int pyi 
	
				set idx1 320
				sub.i idx1 pyi
				mul.i idx1 isx
				add.i idx1 pxi
				add.i idx1 oftx
				
				set idx2 320
				sub.i idx2 pyi
				add.i idx2 4
				mul.i idx2 isx
				add.i idx2 4
				add.i idx2 pxi
				add.i idx2 oftx
	
				poke img idx1 16777215
				poke img idx2 2043711
	
				;end draw
			][
				gteq.d t 0.02
				either [

					set.d px x
					mul.d px -0.139
					set.d ry y
					mul.d ry 0.263
					add.d px ry
					add.d px 72.96

					set.d py x
					mul.d py 0.246
					set.d ry y
					mul.d ry 0.224
					add.d py ry
					sub.d py 9.36

				;draw
				set.d x px
				set.d y py
				
				set pxi x				
				to-int pxi 
				set pyi y
				to-int pyi 
	
				set idx1 320
				sub.i idx1 pyi
				mul.i idx1 isx
				add.i idx1 pxi
				add.i idx1 oftx
				
				set idx2 320
				sub.i idx2 pyi
				add.i idx2 4
				mul.i idx2 isx
				add.i idx2 4
				add.i idx2 pxi
				add.i idx2 oftx
	
				poke img idx1 16777215
				poke img idx2 2043711
	
				;end draw
				][
					set.d px 64.0
					set.d py 0.27
					mul.d py y
				]			
			]
		]

			;draw
			set.d x px
			set.d y py
			
			set pxi x				
			to-int pxi 
			set pyi y
			to-int pyi 

			set idx1 320
			sub.i idx1 pyi
			mul.i idx1 isx
			add.i idx1 pxi
			add.i idx1 oftx
			
			set idx2 320
			sub.i idx2 pyi
			add.i idx2 4
			mul.i idx2 isx
			add.i idx2 4
			add.i idx2 pxi
			add.i idx2 oftx

			poke img idx1 16777215
			poke img idx2 2043711

			;end draw
		
;			apply r show [ii]
;			apply r wait [0]
	]

]

time [barnsley]
show ii
wait []
;halt