Re: [Matplotlib-users] problem with patches in animation

[Raymond S. <sm...@mi...>]

Well, the intended behavior of init() isn't completely clear to me after
reading over some of the docs <http://matplotlib.org/contents.html> and
examples <http://matplotlib.org/examples/animation/index.html>, so I'm not
sure if it's a bug or not. Either way, it could be a request for
documentation, perhaps.


On Wed, Apr 23, 2014 at 10:08 AM, Mark Bakker <ma...@gm...> wrote:

> I thought about that. I even thought about changing the initial color to
> white or radius to zero.
>
> But I am thinking this is a bug. When blitting, whatever is created with
> the init function is not removed. That is why lines that are animated
> initially have no data. For a Patch object this is a bit harder, as it
> needs something to begin with.
>
>  It seems that this used to work in a previous version.
>
> Should I file a bug report?
>
> Mark
>
>
> On Wed, Apr 23, 2014 at 3:34 PM, Raymond Smith <sm...@mi...> 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 <ma...@gm...> 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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>