[yt-users] MultiVariate volume rendering difficulties

[Sam Skillman]

Hi all,
The multivariate tf could use both some updating and documentation. I'm
offline for the next few days but if it hasn't been fixed by next week I
can take a look.

Sam
On Jul 30, 2013 8:40 AM, "Nathan Goldbaum" <nathan12343 at gmail.com> wrote:

> Hi Noel,
>
> I believe this is a bug that needs to be fixed.  It seems
> MultiVariateTransferFunction was never updated after opaque volume
> rendering was added.
>
> Can you please open a new issue about this?
>
> Nathan
>
> On Tuesday, July 30, 2013, Noel Scudder wrote:
>
>> Hi all,
>>
>> I'm attempting to visualize multiple variables in the same volume
>> rendering. For instance, I'd like to show some density surfaces of a star
>> and then get temperature overlayed to show hotspots. I found the
>> MultiVariateTransferFunction, but it is unfortunately not particularly well
>> documented yet, and I'm being repeatedly thwarted. I'm not sure if I've set
>> it up correctly, or how to go from the transfer function to an image.
>> Here's my current script, using just one variable for now:
>>
>> #----------------------------------
>> from yt.mods import *
>> pf = load('plt00100')
>>
>> #<some constants>
>>
>> pf.h
>> pf.field_info['density'].take_log=True
>>
>> mv = MultiVariateTransferFunction()
>>
>> tf = TransferFunction((mi-1, ma+1), nbins=1.0e6)
>> tf.add_gaussian(np.log10(9.0e5), 0.01, 1.0)
>>
>> mv.add_field_table(tf, 0)
>> mv.link_channels(0, [0,1,2,3])
>>
>> c = [5.0e9, 5.0e9, 5.0e9]
>> L = [0.15, 1.0, 0.40]
>> W = wi*0.7
>> Nvec = 1024
>>
>> cam = pf.h.camera(c, L, W, (Nvec,Nvec), transfer_function = mv,
>>                              fields=['density'], pf=pf, no_ghost=True)
>>
>> im = cam.snapshot(num_threads=4)
>>
>> im.write_png('plt00100.png' )
>> #----------------------------------
>>
>> I checked to make sure density is indeed my 0-index field. I get the
>> following error after ray casting:
>>
>> Traceback (most recent call last):
>>   File "<stdin>", line 1, in <module>
>>   File "multivol.py", line 153, in <module>
>>     im = cam.snapshot(num_threads=4)
>>   File
>> "/home/noel/shocks/yt-x86_64/src/yt-hg/yt/visualization/volume_rendering/camera.py",
>> line 742, in snapshot
>>     image, sampler),
>>   File
>> "/home/noel/shocks/yt-x86_64/src/yt-hg/yt/visualization/volume_rendering/camera.py",
>> line 632, in _render
>>     image = self.finalize_image(image)
>>   File
>> "/home/noel/shocks/yt-x86_64/src/yt-hg/yt/visualization/volume_rendering/camera.py",
>> line 611, in finalize_image
>>     if self.transfer_function.grey_opacity is False:
>> AttributeError: 'MultiVariateTransferFunction' object has no attribute
>> 'grey_opacity'
>>
>>
>> Can I not use snapshot in this case, or is something else the matter
>> entirely?
>>
>> Thanks,
>> Noel Scudder
>>
>
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