[yt-users] RAMSES MHD visualisation weirdness

[Sam Geen]

Thanks Romain - this ordering should already be implemented in the 
frontend. I've just checked the code and RAMSES MHD does indeed add 3 to 
nvar before outputting - in this case I have no idea what caused the bug 
in the previous outputs, unless an older version doesn't do this. Will 
take another look tomorrow.

Sam

On 11/02/14 22:31, Romain Teyssier wrote:
> Hi all,
>
> The RAMSES MHD output is indeed different than the hydro outputs.
>
> What is stored is in order:
> 1- density
> 2- x-velocity
> 3- x-velocity
> 4- x-velocity
> 5- Left Bx field
> 6- Left By field
> 7- Left Bz field
> 8- Right Bx field
> 9- Right By field
> 10- Right Bz field
> 11- Thermal pressure
> 12 and beyond: Passive scalars
>
>
> The left and right B fields means that in Ramses the magnetic field is face centred.
> So for each cell, you have a left-face and right-face centred quantity.
>
> Romain
>
>
>
>
> On 11 Feb 2014, at 19:27, Sam Geen <samgeen at astro.ox.ac.uk> wrote:
>
>> Hi Nathan,
>>
>> Ah, thanks, you just gave me an idea - the MHD code (for some reason, I've no idea why) has 3 extra variables than NVAR, and the RAMSES frontend currently assumes that the output is reliably reporting the number of variables, so it could be getting confused. I'll try that tomorrow; you're right that this could be causing the visualisation to wig out. This could be a bug/feature that's worth changing in RAMSES itself as it's quite confusing, but since it's existed for a while now it might be simpler just to work around it in YT somehow.
>>
>> I'll look at getting together some simple MHD test problems and making some outputs, too - there's at least one included with RAMSES so I'll try running that now and contact you once I'm done.
>>
>> Sam
>>
>> On 11/02/14 19:02, Nathan Goldbaum wrote:
>>> Hi Sam,
>>>
>>> Can you share the script you're using to make that plot?  In
>>> particular I'd like to see the call you use to load the dataset, since
>>> the number of fields you request and their order can matter a lot for
>>> the RAMSES data format.
>>>
>>> It would also be nice to have a public RAMSES MHD test dataset - there
>>> doesn't appear to be one on yt-project.org. If you (or anyone else on
>>> the list) has one to share, that should help in debugging RAMSES MHD
>>> issues in the future. If so, contact me off-list and we can work out
>>> how to share the data.
>>>
>>> -Nathan
>>>
>>>
>>> On Tue, Feb 11, 2014 at 7:58 AM, Sam Geen <samgeen at astro.ox.ac.uk> wrote:
>>>> Hi,
>>>>
>>>> I tried visualising a RAMSES MHD output in YT and got this weird effect:
>>>> http://i.imgur.com/abjRorm.png (this happens for slices and projections)
>>>>
>>>> Any idea what could be causing this? Nearly-identical non-MHD simulations
>>>> seem to visualise fine, and it happened for every MHD output I've looked at.
>>>> I can give more info if you like, although I'm not sure what diagnostics to
>>>> check for, so pointers on how to hunt this down would be appreciated as
>>>> well! It's entirely possible it's a bug/side-effect of the MHD solver,
>>>> although I'm not sure what, and other visualisation routines (in
>>>> IDL/Fortran) seem to work fine with some of the outputs I've tried on it.
>>>>
>>>> Thanks,
>>>>
>>>> Sam
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