[yt-dev] Making a particle density plot

[Christopher Moody]

Thanks John! This is perfect.

chris


On Sat, Dec 1, 2012 at 7:21 PM, John ZuHone <jzuhone at gmail.com> wrote:

> Chris,
>
> Try something like this script:
>
> http://paste.yt-project.org/show/2947/
>
> Which produces these images:
>
> http://i.imgur.com/g4Q7B.png (slice)
> http://i.imgur.com/2UYdY.png (projection)
>
> Basically I generate particle x and y positions to be fed into the uniform
> grid field data, and I define a "ParticleNumberDensity" field that
> histograms this data. The grid has dimensions of (64,64,1).
>
> Notice I defined the bounding box 'bbox' oddly--it's because I wanted all
> of the cells to be cubical. You could probably just get away with defining
> the bbox as (0,1) along all three axes, but this would mean the cells are
> long and rectangular along the z-axis. I'm not sure how yt would handle
> this (my guess is just fine, but I've seen code that seems to assume
> cubical cells).
>
> Best,
>
> John
>
> On Dec 1, 2012, at 6:33 PM, Christopher Moody <cemoody at ucsc.edu> wrote:
>
> Thanks John!
>
> chris
>
>
>
>
> On Sat, Dec 1, 2012 at 12:18 PM, John ZuHone <jzuhone at gmail.com> wrote:
>
>> Chris,
>>
>> You could probably use the uniform grid stream for what you want. You
>> could just flatten the particle position along the axis you're projecting
>> along and then define a 2D uniform grid with shape, say, (nx, ny, 1) if you
>> were projecting along Z. Then you could use the normal yt stuff to make
>> plots, but the particles would only be on one grid.
>>
>> When I'm able to get back to a real keyboard I will write an example
>> script if this sounds good to you.
>>
>> John
>>
>> John ZuHone
>> Laboratory for High-Energy Astrophysics
>> NASA/Goddard Space Flight Center
>> 8800 Greenbelt Rd., Code 662
>> Greenbelt, MD 20771
>> (w) 301-286-2531
>> (m) 773-758-0172
>> jzuhone at gmail.com
>> john.zuhone at nasa.gov
>>
>> On Dec 1, 2012, at 2:57 PM, Christopher Moody <cemoody at ucsc.edu> wrote:
>>
>> Hi everyone,
>>
>> I'd like to implement a particle density plot type, but I'm not familiar
>> enough with the yt/visualization classes. I'm explicitly avoiding particle
>> deposition on the grid (ie, the stuff John ZuHone just PR'd), because even
>> after the particles are assigned to grids, splitting the array for each
>> grid, and then concatenating grid-by-grid is slow. And moving to yt-3.0, we
>> should be able to handle particle as particles not on a grid/oct (right?).
>>
>> To collect all of the particles, project them, and do a 2D histogram is
>> straightforward, but my question is where to do it. I was thinking of
>> imitating the ParticlePlot class, but that basically uses the particle
>> callback that draws a dot for every particle. A histogram'd field is
>> defined everywhere, and is probably not appropriate as a callback.
>>
>> How should I structure this? Which files are the relevant ones?
>>
>> chris
>>
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>
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