Hi Brendan, On Fri, Aug 8, 2014 at 1:47 PM, Brendan Griffen <brendan.f.griffen@gmail.com> wrote:

Hi,

As I understand yt is able to construct an array based on cloud-in-cell assignment but not using sph assignment. Each particle must have their own smoothing lengths. Could a rudimentary smoothing length be assigned within yt if particles don't already have a smoothing length? The volume rendering looks great for gas with a 'density' field but if I want to create a sph smoothed field also called 'density' for the dark matter particles, my only option for particle data at this point is cloud in cell assignment? This looks OK for large scale full homogeneous runs but for zoom-ins cloud in cell looks pretty terrible.

This can definitely be done! (Amos Manneschmidt wrote to the list today with a related question, which I will reply to as soon as I can.) Right now, the smoothing length is assumed to be provided, but the field definition looks like this: https://bitbucket.org/yt_analysis/yt/src/d0ec6bb3dbf2455e05e565f1d862a294281... Note that "smoothing length" is an input field. One can then do any other derived field in a similar way. If you're looking for, say, the distance to the Nth nearest neighbor, that is relatively simple to implement, and I was planning on doing that shortly.

Or could you even feed yt the smoothing lengths (say output from subfind) as a vector which yt then uses for the sph assignment? This might be a good first step as I already have the smoothing lengths pre-calculated in hsml files from subfind.

This is also totally feasible. What you'd want to do is make a derived field like the one described above, but specify your smoothing length differently. -Matt

Thanks.

Brendan

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