On Sun, Nov 11, 2012 at 1:42 PM, Andrew Dawson <daw...@atm.ox.ac.uk> wrote:
> Hi
>
> I'm trying to plot the trajectory of a particle in 3d using mplot3d. I
> tried to follow the example of an animated 3d plot on the matplotlib
> website but I'm having trouble with the updating of the data point being
> plotted at each frame. Does anyone know how to do this?
>
> So far I have:
>
> import numpy as np
> import matplotlib.pyplot as plt
> from mpl_toolkits.mplot3d.axes3d import Axes3D
> from matplotlib.animation import FuncAnimation
>
>
> def update_plot(num, data, sc):
> sc.set_array(data[num])
> return sc
>
>
> def main():
> numframes = 2
> data = np.random.rand(10, 3)# a (time, position) array
>
> fig = plt.figure()
> ax = fig.add_subplot(111, projection='3d')
>
> ix, iy, iz = data[0]
> sc = ax.scatter(ix, iy, iz, c='k')
>
> ani = FuncAnimation(fig, update_plot, frames=numframes,
> fargs=(data,sc))
> plt.show()
>
>
> if __name__ == '__main__':
> main()
>
>
> This just changes the color of the initial marker. I also tried to use
> sc.set_3d_properties but it is not clear to me what the arguments should be
> here, I kept getting an error... If anyone has done this before I'd love to
> see an example.
>
> Thanks,
> Andrew
>
>
Andrew,
For scatter objects (which are PatchCollection), the get/set_data() refers
to the scalar mappable part of things, which is why the color kept
changing. It does not seem to be an easy way to adjust the position data
for a Patch3DCollection (or a Line3DCollection for that matter...). I
would suggest filing a feature request about that on github. In coming up
with an example for your use-case, I have come across a couple of minor
bugs in mplot3d that I am going to need to resolve as well. In the
meantime, I think the following version of the code:
import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d.axes3d import Axes3D
from matplotlib.animation import FuncAnimation
def update_plot(num, data, sc):
print sc._offsets3d
sc._offsets3d = data[num]
return sc
def main():
numframes = 10
data = np.random.rand(numframes, 3, 1)# a (time, position) array
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ix, iy, iz = data[0]
sc = ax.scatter(ix, iy, iz, c='k')
ani = FuncAnimation(fig, update_plot, frames=numframes,
fargs=(data,sc))
plt.show()
if __name__ == '__main__':
main()
Essentially, there is no nice way to set the 3d position data, and the
easiest way is to just go to the internal _offsets3d variable. Second,
there seems to be an issue with array/scalar data in Patch3DCollection that
I had to make the random number generation be 3D, rather than 2D as you
originally had it.
Cheers!
Ben Root
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