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

[Mark B. <ma...@gm...>]

Raymond,

The documentation says:

If blit=True, *func* and *init_func* should return an iterable of drawables
to clear.

But clearly, whatever is set by init_func is not cleared during animation
when blit=True, while it is cleared when blit=False.

Unless anybody knows what I am doing wrong I will file a bug report.

Thanks again, Mark


On Wed, Apr 23, 2014 at 4:25 PM, Raymond Smith <sm...@mi...> wrote:

> 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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>>
>