[Matplotlib-users] better plotting of magnetic field lines

[Slavin, Jonathan]

Hi Nathan,

That's interesting but not quite what I had in mind.  See the attached
figure to see what I'm looking for.  I created that by using uniformly
spaced start_points along the upper boundary of the plot.  The only problem
then is that I need to use the negative of Bx and By to get the field lines
to get propagated in the correct directions.  And then the arrows are in
the wrong direction.

One thought I had was to do this, get the output streamlines and then use
the end points of those streamlines for start points.  However it's not
clear to me how to get those end points from the LineCollection that is
part of the StreamplotSet container that's returned by streamplot.  I can
get segments from the LineCollection, but I don't know how to get the line
endpoint out of those.  Do you know how to do that?

Jon

On Thu, Dec 15, 2016 at 12:00 PM, Slavin, Jonathan <jslavin at cfa.harvard.edu>
wrote:

> Thanks Nathan.  I'll check it out.
>
> Jon
>
> On Thu, Dec 15, 2016 at 11:41 AM, Nathan Goldbaum <nathan12343 at gmail.com>
> wrote:
>
>> yt uses an implementation of the line integral convolution recipe from
>> scipy that works very nicely (IMO):
>>
>> http://yt-project.org/docs/dev/visualizing/callbacks.html#
>> overplot-line-integral-convolution
>>
>> I don't think there's an easy way to do this with pure matplotlib right
>> now, but you can take a look at yt's implementation if you're curious:
>>
>> https://bitbucket.org/yt_analysis/yt/src/011cd19563215cefb3f
>> acfd5d6f575b6b38de0db/yt/visualization/plot_
>> modifications.py?at=yt&fileviewer=file-view-default#plot_
>> modifications.py-2347
>>
>> https://bitbucket.org/yt_analysis/yt/src/011cd19563215cefb3f
>> acfd5d6f575b6b38de0db/yt/utilities/lib/line_integral_
>> convolution.pyx?at=yt&fileviewer=file-view-default
>>
>> On Thu, Dec 15, 2016 at 10:38 AM, Slavin, Jonathan <
>> jslavin at cfa.harvard.edu> wrote:
>>
>>> Hi all,
>>>
>>> I would like to plot the magnetic field lines for a simulation and am
>>> finding that streamplot is in adequate in a few ways.  First, it breaks
>>> lines when they get too close together.  I think this can be configured
>>> with the density parameter.  More fundamentally, one usually wants the
>>> density of field lines to indicate the strength of the magnetic field.  So
>>> a clever selection of start_points could in principle accomplish this, I
>>> think.  That may be the way I go, but I wonder if someone hasn't already
>>> come up with a solution for this.  If so, I'd love to hear about it.
>>>
>>> Regards,
>>> Jon
>>>
>>> --
>>> ________________________________________________________
>>> Jonathan D. Slavin                 Harvard-Smithsonian CfA
>>> jslavin at cfa.harvard.edu       60 Garden Street, MS 83
>>> phone: (617) 496-7981       Cambridge, MA 02138-1516
>>> cell: (781) 363-0035             USA
>>> ________________________________________________________
>>>
>>>
>>> _______________________________________________
>>> Matplotlib-users mailing list
>>> Matplotlib-users at python.org
>>> https://mail.python.org/mailman/listinfo/matplotlib-users
>>>
>>>
>>
>
>
> --
> ________________________________________________________
> Jonathan D. Slavin                 Harvard-Smithsonian CfA
> jslavin at cfa.harvard.edu       60 Garden Street, MS 83
> phone: (617) 496-7981       Cambridge, MA 02138-1516
> cell: (781) 363-0035             USA
> ________________________________________________________
>
>


-- 
________________________________________________________
Jonathan D. Slavin                 Harvard-Smithsonian CfA
jslavin at cfa.harvard.edu       60 Garden Street, MS 83
phone: (617) 496-7981       Cambridge, MA 02138-1516
cell: (781) 363-0035             USA
________________________________________________________
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/matplotlib-users/attachments/20161216/9e8d8bd9/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Bmag_w_fieldlines.png
Type: image/png
Size: 261372 bytes
Desc: not available
URL: <http://mail.python.org/pipermail/matplotlib-users/attachments/20161216/9e8d8bd9/attachment-0001.png>