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

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

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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>