Hello Matt, et al.
So maybe this was silly of me, but I decided to try to pursue integrating the cylindrical
coordinates with YTRayBase rather than with YTOrthoRayBase, not realizing that the
implementation wasn't fully there in yt-3.0. So I have updated PR #6 to include these
changes as well as a notably absent RaySelector class in geometry/selection_routines.pyx.
When I do this, however, the _get_data_from_grid() method on YTRayBase never gets
called. This results in tracebacks and missing data when I try to do even simple things
like:
ray = pf.h.ray(E, F)
t = ray['t']
will throw:
Traceback (most recent call last):
File "cylindrical_rays3.py", line 70, in <module>
t = ray['t']
File "/home/scopatz/.local/lib/python2.7/site-packages/yt-3.0dev-py2.7-linux-x86_64.egg/yt/data_objects/data_containers.py", line 196, in __getitem__
self.get_data(key)
File "/home/scopatz/.local/lib/python2.7/site-packages/yt-3.0dev-py2.7-linux-x86_64.egg/yt/data_objects/data_containers.py", line 423, in get_data
fields = self._determine_fields(fields)
File "/home/scopatz/.local/lib/python2.7/site-packages/yt-3.0dev-py2.7-linux-x86_64.egg/yt/data_objects/data_containers.py", line 372, in _determine_fields
finfo = self._get_field_info("unknown", fname)
File "/home/scopatz/.local/lib/python2.7/site-packages/yt-3.0dev-py2.7-linux-x86_64.egg/yt/data_objects/data_containers.py", line 354, in _get_field_info
raise YTFieldNotFound((fname, ftype), self.pf) yt.utilities.exceptions.YTFieldNotFound: Could not find field '('t', 'unknown')' in nif2013_hdf5_plt_cnt_0006.
Any ideas? Thanks in advance.
Be Well
Anthony
On Tue, Sep 11, 2012 at 1:07 PM, Anthony Scopatz
<scopatz@gmail.com> wrote:
On Mon, Sep 10, 2012 at 2:18 PM, Matthew Turk
<matthewturk@gmail.com> wrote:
Hi Anthony,
Sorry for the delay in replying. I'm still pondering the right way to
handle things that are specific to coordinate-systems. There are a
handful:
* Pixelization
* Ray tracing (single ray, ortho and non-ortho)
* Volume rendering
* Ghost zone generation (interpolation, specifically)
There are probably others, too. For ray-tracing I could see value in
either supplying alternate subclasses of YTDataContainer objects or in
abstracting out the bare minimum of routines necessary and putting
those in coordinate_handler.
If we decide to go down the alternate subclasses route, the coordinate_handlers
should have references back to the appropriate YTDataContainers. This might
be the most modular solution...
[snip]
>
> The first question I have is that the rays, unless they begin
> or end on a cell boundary, do not include the start or stop
> points. This seems like the correct behavior to me, but is
> this consistent with the rest of yt?
Hmm, in the past we'd allowed rays that started inside cells to
reflect the partial traversal that entails. I don't think modifying
this behavior should be too big a deal, but that's a refinement for
later.
Well, the rays can start from wherever. It is just that initial and final
segment may or may not be included in the return values. This should
be easy to fix but I agree isn't a high priority for the moment.
> The second, weirder point is as follows. For 2D R,Z data,
> the cell crossings that are calculated *should* be rotationally
> invariant. Take p1 and p2 to be two points in r, z, theta s.t.:
>
> p1 = (r1, z1, theta1)
> p2 = (r2, z2, theta2)
>
> Then the ray should pass through the same cells if instead
> we take q1 and q2 as:
>
> q1 = (r1, z1, theta1 + dtheta)
> q2 = (r2, z2, theta2 + dtheta)
>
> for any constant dtheta and r1, z1, theta1, r2, z2, and theta2
> at the same values in p1 and p2. However, this does not seem
> to be the case. Play around in the notebook and you'll see what
> I mean.
I am also getting this result, which I agree is weird for this data.
It should be invariant. My only thought is that perhaps there's an
issue of rotational invariance we didn't think about when we designed
the system initially. One thought is that the boundary conditions are
*necessarily* important for this data, since a chord running through
the concentric circles that constitute the cells will potentially run
outside 0..2pi unless BCs are taken into effect. This is particularly
true because the initial theta that all of these are set to is pi
(since left edge is 0, right edge is 2pi). I think this would
correlate with a maximum difference at 0 or 2pi and a minimum
difference at pi for the initial theta that gets perturbed. Does that
make sense?
That does make sense. Another, related issue may be that perhaps
the intersection code with respect to theta may only be valid for
small dtheta. This is something else to look into...
[snip]
> I don't think either of the above are deal breakers, but I would like to
> hear other people's thoughts. I will work on integrating this with the
> rest of yt-3.0 next week.
Awesome! Perhaps we should have a discussion here about how best to
organize coordinate handlers. I can lead that, if you'd like.
I would prefer if you lead that discussion as you know the code base much
better than I do ;). Thanks!
Be Well
Anthony