This is pretty weird. If instead of Mark's original script, if I move the
add_patch out of init and have the init simply return an empty tuple, it
_mostly_ works as expected. But -- at least on my computer -- on some runs,
it has the moving circle, but also leaves a circle at the "top", starting
point, whereas on other runs it simply has the desired moving circle with
no 'background' circle. Usually, it will happen at least once if I start
the animation script 10 times. So still, the init function is a bit of a
mystery to me.
import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
fig = plt.figure()
fig.set_dpi(100)
fig.set_size_inches(7, 6.5)
ax = plt.axes(xlim=(0, 10), ylim=(0, 10))
patch = plt.Circle((5, -5), 0.75, fc='y')
ax.add_patch(patch)
def init():
return tuple()
def animate(i):
x, y = patch.center
patch.set_facecolor('y')
patch.set_edgecolor('k')
x = 5 + 3 * np.sin(np.radians(i))
y = 5 + 3 * np.cos(np.radians(i))
patch.center = (x, y)
return patch,
anim = animation.FuncAnimation(fig, animate,
init_func=init,
frames=360,
interval=20,
blit=True)
plt.show()
On Wed, Apr 23, 2014 at 10:29 AM, Benjamin Root <ben.r...@ou.edu> wrote:
> Working off of very faded memory, try not to return any objects in your
> init function that you intend to be animated. If I remember correctly, when
> blitting is True, the animator treats any object returned by the init()
> function as background objects, and any objects returned by the animation
> function as blittable. Since your patch is returned in both functions, I
> think it is getting confused.
>
> Again, very rusty memory here...
>
> Ben Root
>
>
>
> On Wed, Apr 23, 2014 at 9:34 AM, Raymond Smith <smit...@mit.edu> wrote:
>
>> Hi Mark,
>>
>> I can't say this is the 'proper' solution or the correct interpretation,
>> but it should work.
>>
>> I think when blitting that the init function serves as a something of a
>> "background" for the rest of the animation. So try changing
>>
>>
>> def init():
>> *patch.center = (5, 5)*
>> ax.add_patch(patch)
>> return patch,
>>
>> to
>>
>> def init():
>> *patch.center = (5, -5)*
>> ax.add_patch(patch)
>> return patch,
>>
>> Cheers,
>> Ray
>>
>>
>> On Wed, Apr 23, 2014 at 5:44 AM, Mark Bakker <mark...@gmail.com> wrote:
>>
>>> Hello list,
>>>
>>> I am trying to animate a patch. The animation should show a circle
>>> orbiting around a point. I took the code from
>>> http://nickcharlton.net/posts/drawing-animating-shapes-matplotlib.html
>>>
>>> Problem is that when I run the code, the animation doesn't remove the
>>> initial position of the circle (blit is True) while it works correctly on
>>> the website referenced above.
>>>
>>> Does anybody else see this behavior? Here's the code:
>>>
>>> import numpy as np
>>> from matplotlib import pyplot as plt
>>> from matplotlib import animation
>>>
>>> fig = plt.figure()
>>> fig.set_dpi(100)
>>> fig.set_size_inches(7, 6.5)
>>>
>>> ax = plt.axes(xlim=(0, 10), ylim=(0, 10))
>>> patch = plt.Circle((5, -5), 0.75, fc='y')
>>>
>>> def init():
>>> patch.center = (5, 5)
>>> ax.add_patch(patch)
>>> return patch,
>>>
>>> def animate(i):
>>> x, y = patch.center
>>> x = 5 + 3 * np.sin(np.radians(i))
>>> y = 5 + 3 * np.cos(np.radians(i))
>>> patch.center = (x, y)
>>> return patch,
>>>
>>> anim = animation.FuncAnimation(fig, animate,
>>> init_func=init,
>>> frames=360,
>>> interval=20,
>>> blit=True)
>>>
>>> plt.show()
>>>
>>> Thanks, Mark
>>>
>>>
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