[yt-users] question about transfer function colorbar

[Michael Zingale]

I haven't explored this in any detail yet (still dealing with the end of
the semester here)


On Wed, May 21, 2014 at 8:38 PM, Sam Skillman <samskillman at gmail.com> wrote:

> Hi Michael,
>
> That looks like a bug to me. I'll take a look at it in more detail
> tomorrow.  If you have a fix that works, let us know...
>
> Sam
>
>
> On Wed, May 21, 2014 at 8:17 AM, Michael Zingale <
> michael.zingale at stonybrook.edu> wrote:
>
>> I looked at this some more.  It is this line in vert_cbar that adds the
>> odd-valued colorbar label:
>>
>> xticks = np.append(visible[-1], xticks)
>>
>> in particular, that adds the "255" value into the xticks array.
>>  Interestingly, xticks has a 256 value with the correct x_format() behavior
>> (mapping to 1.e7, the upper limit of my transfer function), but that is
>> ignored, since it is outside of the bounds of the color bar.
>>
>> So the question then is why when I setup a transfer function via:
>>
>>     tf =
>>  yt.visualization.volume_rendering.api.ColorTransferFunction((mi, ma))
>>
>> with mi = -1.e7 and ma = 1.e7, does it map -1.e7 into index 0 in the
>> palette and 1.e7 into 256 in the palette, instead of 255?
>>
>>
>> On Sun, May 11, 2014 at 6:03 PM, Michael Zingale <
>> michael.zingale at stonybrook.edu> wrote:
>>
>>> I poked around that code earlier but didn't see anything odd.  I'll look
>>> some more at it tomorrow.
>>>
>>>
>>> On Sat, May 10, 2014 at 11:31 AM, Chris Malone <chris.m.malone at gmail.com
>>> > wrote:
>>>
>>>> Hi Mike,
>>>>
>>>> The number that is getting set (~9.92e6) is just one bin off from the
>>>> maximum value (you have a range of 2e7 and the default is 256 bins).  The
>>>> code that displays the colorbar, as best I can tell, occurs when you call
>>>> save_annotated.  This method eventually calls
>>>> ColorTransferFunction.vert_cbar where the ticks and limits are applied to
>>>> the colorbar axes object.
>>>>
>>>> Looking over the logic in that code, it is not immediately obvious to
>>>> me why the index is off.  I suspect is has something to do with how the
>>>> `visible` variable is defined, but I'd need to play with a dataset and some
>>>> print statements...
>>>>
>>>> Chris
>>>>
>>>>
>>>> On Wed, May 7, 2014 at 8:17 PM, Michael Zingale <
>>>> michael.zingale at stonybrook.edu> wrote:
>>>>
>>>>> I'm trying to show the transfer function on a volume render.  Plotting
>>>>> a velocity component, I set the transfer function with 4 Gaussians all with
>>>>> the same width.  The range of the transfer function is -1.e7 to 1.e7, but
>>>>> for some reason, when output, the upper label in the colorbar is not 1.e7
>>>>> but a bit lower (9.92e6).  I am not sure where the code is that draws this,
>>>>> and I am confused why it is not setting the tick at 1.e7. It gets the
>>>>> bottom tick right.
>>>>> Here's an image:
>>>>>
>>>>> http://bender.astro.sunysb.edu/random/test_0000.png
>>>>>
>>>>> and the script:
>>>>>
>>>>> http://bender.astro.sunysb.edu/random/vol_rotate.py
>>>>>
>>>>> any pointers are appreciated.
>>>>>
>>>>> Mike
>>>>> --
>>>>> Michael Zingale
>>>>> Associate Professor
>>>>>
>>>>> Dept. of Physics & Astronomy • Stony Brook University • Stony Brook,
>>>>> NY 11794-3800
>>>>> *phone*:  631-632-8225
>>>>> *e-mail*: Michael.Zingale at stonybrook.edu
>>>>> *web*: http://www.astro.sunysb.edu/mzingale
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>
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>>>
>>>
>>> --
>>> Michael Zingale
>>> Associate Professor
>>>
>>> Dept. of Physics & Astronomy • Stony Brook University • Stony Brook, NY
>>> 11794-3800
>>> *phone*:  631-632-8225
>>> *e-mail*: Michael.Zingale at stonybrook.edu
>>> *web*: http://www.astro.sunysb.edu/mzingale
>>>
>>
>>
>>
>> --
>> Michael Zingale
>> Associate Professor
>>
>> Dept. of Physics & Astronomy • Stony Brook University • Stony Brook, NY
>> 11794-3800
>> *phone*:  631-632-8225
>> *e-mail*: Michael.Zingale at stonybrook.edu
>> *web*: http://www.astro.sunysb.edu/mzingale
>>
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>>
>>
>
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-- 
Michael Zingale
Associate Professor

Dept. of Physics & Astronomy • Stony Brook University • Stony Brook, NY
11794-3800
*phone*:  631-632-8225
*e-mail*: Michael.Zingale at stonybrook.edu
*web*: http://www.astro.sunysb.edu/mzingale
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