[yt-dev] Issue #570: Healpix volume rendering produces garbled, artifacted images (yt_analysis/yt)

[Matthew Turk]

Can you attach your image to the issue? On the mailing list you also said
it worked fine I thought.
On May 17, 2013 5:01 PM, "Geoffrey So" <gsiisg at gmail.com> wrote:

> I can confirm, the images I got looks like the grids were not ordered
> correctly, patches of zones looks fine inbetween, but zone and zones do not
> match well at the boundary.
>
> From
> G.S.
>
>
> On Fri, May 17, 2013 at 1:49 PM, Nathan Goldbaum <
> issues-reply at bitbucket.org> wrote:
>
>> New issue 570: Healpix volume rendering produces garbled, artifacted
>> images
>>
>> https://bitbucket.org/yt_analysis/yt/issue/570/healpix-volume-rendering-produces-garbled
>>
>> Nathan Goldbaum:
>>
>> Using the sample script from the docs:
>>
>>
>> ```
>> #!python
>>
>> from yt.mods import *
>> import yt.visualization.volume_rendering.camera as camera
>>
>> pf = load("IsolatedGalaxy/galaxy0030/galaxy0030")
>> image = camera.allsky_projection(pf, [0.5,0.5,0.5], 100.0/pf['kpc'], 64,
>> "Density")
>> camera.plot_allsky_healpix(image, 64, "allsky.png", "Column Density
>> [g/cm^2]")
>> ```
>>
>> Produces the following image:
>>
>> ![](http://i.imgur.com/5wskzay.png)
>>
>> I also tried the manual method described further down in the docs:
>>
>>
>> ```
>> #!python
>>
>> rom yt.mods import *
>> import yt.visualization.volume_rendering.camera as camera
>>
>> Nside = 32
>> pf = load("IsolatedGalaxy/galaxy0030/galaxy0030")
>> cam = camera.HEALpixCamera([0.5,0.5,0.5], 0.2, Nside, pf = pf, log_fields
>> = [False])
>> bitmap = cam.snapshot()
>>
>> import yt.utilities.lib as au
>> from numpy import pi
>> phi, theta = np.mgrid[0.0:2*pi:800j, 0:pi:800j]
>> pixi = au.arr_ang2pix_nest(Nside, theta.ravel(), phi.ravel())
>> img = np.log10(bitmap[:,0,0][pixi]).reshape((800,800))
>>
>> import matplotlib.figure
>> import matplotlib.backends.backend_agg
>>
>> fig = matplotlib.figure.Figure((10, 5))
>> ax = fig.add_subplot(1,1,1,projection='mollweide')
>> image = ax.imshow(img, extent=(-pi,pi,-pi/2,pi/2), clip_on=False,
>> aspect=0.5)
>> cb = fig.colorbar(image, orientation='horizontal')
>>
>>
>> cb.set_label(r"$\mathrm{Column}\/\mathrm{Density}\/[\mathrm{g}/\mathrm{cm}^2]$")
>> canvas = matplotlib.backends.backend_agg.FigureCanvasAgg(fig)
>> canvas.print_figure("allsky.png")
>>
>> ```
>> Note that I had to update this a bit since amr_utils was renamed a while
>> back.  This produces the following image:
>>
>> ![](http://i.imgur.com/Jax1sYB.png)
>>
>> While this looks more sensible, it's not clear to me that it is correct.
>>
>>
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>>
>
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