concentric circles

Hi, I'm new in nodebox, and I'm trying to draw concentric circles but I don't know how to center objects in the screen (align center). Can anybody help me?

Thanks!

SK,

Circle in nodebox are defined from their top-left corner so you need to go through an extra step of moving them up and to the left by the amount of the radius to have them centered where you want.

Here's a short example:

stroke(.2)
nofill()
 
#set up some constants you change to fit your needs
center_x, center_y = (200, 200)
gap_between_circles = 14
 
for diameter in range(1,20):
    diameter *= gap_between_circles
    radius = diameter/2.0
    oval(center_x-radius, center_y-radius, diameter, diameter)

if you define:

def centeredOval(x, y, radius, other = None):
    if other == None:
        other = radius
    return oval(x-radius*0.5, y-other*0.5, radius, other)

# centered in 10, 10 with radius 20
# other is None, so it's a circle
centeredOval(10, 10, 20)

Thanks for your help!