'
' Christmas tree.
' See https://github.com/anvaka/atree for explanation.
'


#define yScreenOffset 160
#define xScreenOffset 140
#define yScreenScale 230 ' 192
#define xScreenScale 180

	yCamera = 2
	zCamera = -3

	pi = 3.14159
	'pi4 = pi/4

	rate = 1 / (2 * pi)
	factor = rate/3

	'minx=100
	'max=0
	'miny=100
	'maxy=0


	home
	hgr2

	'theta = 0
	angleOffset = 0
	hcolor 1 ' green
	for theta=0 to 14 step .1
		gosub update
	next



	'theta = 0
	angleOffset = pi
	hcolor 5 ' orange
	for theta=0 to 14 step .1
		gosub update
	next

	'print "x=";minx;"..";maxx
	'print "y=";miny;"..";maxy
	end




update:
	ta = theta + angleOffset
	tf = theta * factor
	x = tf * cos(ta) 'theta + angleOffset
	z = - tf * sin(ta) 'theta + angleOffset
	y = rate * theta


	'if x>maxx then maxx=x
	'if y>maxy then maxy=y
	'if x<minx then minx=x
	'if y<miny then miny=y

	z = z - zCamera
	if z<2.9 then return

	x = int(xScreenOffset + xScreenScale * (x / z))
	y = int(yScreenOffset + yScreenScale * ((y - yCamera) / z))
	hplot x,y
	'print "x=";x;" y=";y;" z=";z
	return