[yt-users] Density/Column density along a ray

Britton Smith brittonsmith at gmail.com
Wed Aug 8 09:09:44 PDT 2012


Hi Thomas,

In addition to ray['t'], which will give you the cumulative distance
traveled at that point in the ray, you can use ray['dts'] to get the just
the distance through each individual cell.  Both of these will be
normalized to the total distance of the ray, but you can use ray['dx'] to
get you the cell size for each cell intersected by the ray, which you can
then use along with 'dts' to calculate the physical distance the ray
travels through each cell.

Britton

On Wed, Aug 8, 2012 at 12:03 PM, j s oishi <jsoishi at gmail.com> wrote:

> Hi Thomas,
>
> Try doing something like
>
> ray = pf.h.ray(start_point,end_point)
>
> density = ray['Density']
> t = ray['t']
>
> where t is the distance along the ray of each sample. It will, by
> default, sample at the highest available resolution. If you need
> subsampling/interpolation, you'll have to wait for someone more
> knowledgeable that I am to jump in.
>
> j
> On Wed, Aug 8, 2012 at 8:56 AM, Thomas Robitaille
> <thomas.robitaille at gmail.com> wrote:
> > Hi
> >
> > I'm still relatively new to yt, and I'm trying to figure out a way to
> > extract the density along a ray joining two points. I've managed to
> > make a plot using PlotCollection.add_ray, but I can't figure out how
> > to get the actual data as a Numpy array. Also, I'd ultimately like to
> > compute the cumulative column density along the ray, so I'd like to
> > ensure that the sampling of distances along the ray is very fine to
> > get an accurate column density. Is there a way to do this?
> >
> > Thanks for any help!
> >
> > Cheers,
> > Tom
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