There are at least two problems with the present circle function. 1)
Gregor has pointed out the oddity of the filling. (As I understand it,
it's odd in that the filling occurs inside the circle that is drawn and
you may have been trying to draw a figure with circle segments and you
actually wanted the bounded region to be filled but the bounded region
is actually on the exterior of a circle that was used--see the yin()
function of Gregor's recent post.) 2) From a pedagogical point of
view, the fact that the circle is drawn without respect to speed is not
good. It's instructive, for example, to see how Gregor's yin-yang image
is drawn, but by using the present circle() you can't really follow the
progress.
Here's a prototype (less smart than the present circle, but heading in
the right direction, I hope) that fixes both of these issues. It draws
a circle as approximated by a polygon. Since it only uses forward() and
turns, it responds to the speed setting. If you run Gregor's yin()
demo, you will see it fill properly, too.
###
def circle(r, xtnt=360.0, segs=30):
'''use the forward() and turn primitives to draw a circle as a
polygon'''
th=xtnt/float(segs)
h=2*abs(r)*sin(th*pi/180) #would be better to compute segs
#so that h is some fraction of
window size
forward(h/2.0)
if r<0:
turn=right
else:
turn=left
for i in xrange(segs-1):
turn(th)
forward(h)
turn(th)
forward(h/2.0)
###
/chris
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