[yt-users] chombo/orion2 projection issue

[William Gray]

Hi Nathan,

Thanks for your response. I tried a variety of render options and was
unable to produce a 'correct' plot.

First, as a sanity check I tried a simple volume rendering just to see if
that would work, the important calls were:

mi,ma = data.quantities["Extrema"]("Density")[0]
tf = ColorTransferFunction((np.log10(mi)+1,np.log10(ma)))
tf.add_layers(5,w=0.02,colormap="spectral")
cam = pf.h.camera(c,L,W,N,tf,no_ghost=False)
den = cam.snapshot()

where c is centered on some particle, L is is angular momentum vector of
said particle, W =[1.5e15,1.5e15,1.5e15] and N is 512. This works and gives
a nice volume render.

Next I tried:

tf = ProjectionTransferFunction()
cam = pf.h.camera(c,L,W,N,tf,fields=[field],log_fields,
[use_log],no_ghost=False)
den = cam.snapshot()

Which is the same as above except with a different transfer function. This
gives a blank/black projection image. I also retried both
off_axis_projection and OffAxisProjectionPlot. Both give blank images, as
expected.

I am working on a test problem to see if I can reproduce this problem. If I
get one working I will send it along.

Please let me know if there is some other info that may be of importance
and if there is something else you want me to try.

-Will



On Thu, Oct 31, 2013 at 10:57 AM, Nathan Goldbaum <nathan12343 at gmail.com>wrote:

> Hi William,
>
> Both OffAxisProjectionPlot and off_axis_projection are just wrappers
> around yt's volume renderer using the ProjectionTransferFunction.
>
> I’m not sure why you’re not getting good data with narrow depths, but you
> might try again by directly calling the volume renderer.  In any case, if
> you see the same thing it would give us more clues to figure out what is
> going wrong.
>
> Also, if you have a test dataset that exhibits this behavior and you
> wouldn’t mind sharing, that would also be useful for us to debug this.
>
> -Nathan
>
> On October 31, 2013 at 10:52:29 AM, William Gray (graywilliamj at gmail.com<//graywilliamj at gmail.com>)
> wrote:
>
> Hello yt-users,
>
> I am having an issue in creating off axis projection plots with short
> depths in yt. I am looking for disks around particles which necessitates
> using the off axis projection functionality. What I want to do is create a
> projection where the depth is the same as or similar to the width of the
> plot. However, I am finding that unless the depth is orders of magnitude
> larger than the width I will always create a blank plot (for example, the
> width is ~100 au, the depth to get a plot has to be ~1000xwidth, I want a
> plot where the width and depth are ~100 au). I have tried using both
> off_axis_projection and the OffAxisProjection methods with similar (bad)
> results.
>
> As a comparison, I ran a low resolution FLASH simulation that did not seem
> to have this problem. I also know that such a plot was possible with ORION2
> data in the recent past (spring of this year) since a colleague was able
> produce such a plot. That same script now also fails.
>
> Does anyone know of a way around this problem? Has there been any recent
> changes that broke volume rendering for chombo/orion2 data?
>
> Thanks,
> William Gray
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