[yt-dev] Gadget status

Nathan Goldbaum nathan12343 at gmail.com
Tue Jul 15 15:00:34 PDT 2014


On Tue, Jul 15, 2014 at 2:56 PM, Chris Malone <chris.m.malone at gmail.com>
wrote:

> Thanks for the feedback, Nathan.
>
> In slices, I was plotting 'all_density', which is a 'deposit' field.  I'll
> try looking at 'Gas_smoothed_density' ...
>
>
('deposit', 'all_density') uses nearest neighbor deposition.  There's also
('deposit', 'all_cic') which does cloud-in-cell.

('deposit', 'Gas_smoothed_density') is aliased to ('gas', 'density') or
just 'density'.  This way we can access gas fields in an SPH dataset just
like with a grid dataset.


> I'll see about getting permission to pass along the dataset.  For the time
> being, do you know of any notebook or cookbook recipe that shows how to do
> this for particle data?  I couldn't seem to find anything.
>

Yes, there's an example in the docs using tipsy data:
http://yt-project.org/docs/dev-3.0/examining/loading_data.html#tipsy-data

I also went into a bit of depth about working with SPH data in my scipy
talk: www.youtube.com/watch?v=sNkN7nyj4nE

I don't think there's an example of volume rendering SPH data floating
around, thus my uncertainty about it working or not.


>
>
> Chris
>
>
> On Tue, Jul 15, 2014 at 3:43 PM, Nathan Goldbaum <nathan12343 at gmail.com>
> wrote:
>
>>
>>
>>
>> On Tue, Jul 15, 2014 at 2:35 PM, Chris Malone <chris.m.malone at gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> Caveat: I'm not that familiar with particle-based datasets/codes.
>>>
>>> I'm unsuccessfully trying to help a summer student do some visualization
>>> of someone else's Gadget binary data dump.  What is the status of volume
>>> rendering SPH/Gadget data in 3.0?
>>>
>>
>> Not sure about volume rendering.  I believe it should work for
>> particle/octree data but haven't tried it recently.
>>
>>
>>>
>>> When I've tried what I know works for grid-based data, the returned
>>> image is simply empty.  Projections look okay (for some variables), and
>>> Slices look worse as there are blank splotches, likely due to emptiness in
>>> the tree.
>>>
>>>
>> What field are you slicing?  There shouldn't be empty spots for SPH
>> smoothed fields.
>>
>>
>>> Also, is there a list somewhere that describes/defines what the various
>>> fluid types mean (e.g. 'all', 'gas', 'deposit', etc)?  If not, it might be
>>> nice to have somewhere in the docs.
>>>
>>>
>> There are several open issues about this. We won't be releasing yt-3.0
>> until these docs are written.
>>
>> 'all' is the union that contains all particle data.
>>
>> 'gas' (lowercase g) corresponds to SPH smoothed quantities for Gadget.
>>  In binary datasets, the Gas particle type corresponds to the gas particles.
>>
>> 'deposit' corresponds to fields that are deposited onto the octree mesh
>> using a particle type. The SPH smoothed fields are actually defined here,
>> 'gas' is just an alias to the smoothed deposition fields.
>>
>> If you have more specific questions (even better if you have an example
>> script and a dataset) one of us should be able to help you out more.
>>
>> -Nathan
>>
>>
>>> Chris
>>>
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