[yt-dev] Boolean data objects in yt-3

[Brian O'Shea]

>
> I've stumbled across across a research task that could really use yt's
>>>> Boolean data object feature, and according to the documentation it is not
>>>> implemented in yt-3.  Have boolean data objects been replaced by something
>>>> else?  I know there are various filtering methods in yt, but what I really
>>>> need to do is spatial filtering (i.e., data in a sphere with some chunks of
>>>> the sphere excised).
>>>>
>>>
>>> This hasn't been implemented.
>>>
>>>
>>>>
>>>> In principle I'd be happy to take a crack at re-implementing it,
>>>> although I might need some help.  Could somebody give me a sense of why it
>>>> wasn't ported to yt-3 when the changeover was made?
>>>>
>>>
>>> The data selection API was completely rewritten.
>>>
>>
>> How difficult might it be to re-implement the boolean data objects in the
>> new data selection API?  (I suppose the question is really "how difficult
>> might it be for somebody who is a decent programmer but not an expert in
>> yt's internals to do so"?)
>>
>
> I'm not sure, offhand. Probably very hard if you want to use the
> eval-style way of contrusting the data objects using a string written in
> Python, since data selection happens at a lower level in yt now. See
> selection_routines.pyx for more details about how this works.
>
> It is possible to combine data objects by chaining data_source keyword
> arguments, (e.g. one can create a half-sphere data object by chaining a
> region that selects only half a sphere with a sphere data object). It may
> be possible to generalize that somehow.
>

OK, this is useful.  I will think about it a bit.  Thanks!
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