[yt-users] MultiVariate volume rendering difficulties

[Nathan Goldbaum]

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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