[vtk-developers] Cell location for unstructured grids - Plan

Andy Bauer andy.bauer at kitware.com
Tue Jul 12 11:04:34 EDT 2011


Hi Tharindu,

I'm also sending this email to the vtk developers list in case other people
have insight into your work.

I'm not sure I completely understand the problem.  Can you just replace the
implementation for FindCell() with a better implementation without affecting
other class methods?  If you can do that, I'd just worry about that first
and then do some profiling/performance testing to see where it's at.  After
that it may be worthwhile to see if some of the other class methods can be
improved too.  If a decent amount of changes have to be made in order to
implement that algorithm though then it may make sense to subclass from an
existing concrete cell locator class.

HTH,
Andy

On Mon, Jul 11, 2011 at 11:54 PM, Tharindu De Silva <tsameera1 at gmail.com>wrote:

> Hi Andy,
>
>        When I go through *vtkCellLocator* and *vtkModifiedBSPTree*classes, I find that in addition to finding the containing-cell of a given
> point (findCell method), they have some extra functionality (e.g. Finding
> cells which intersect a given line, closest cell within a radius). With what
> I understood from the paper, it describes an efficient method to locate the
> cell given a point.  I am not sure at this point, whether that algorithm can
> be extended to improve  other functionality such as line intersection.  At
> this point, I can subclass *vtkCellLocator* and implement FindCell method
> in that subclass according to the algorithm given in the paper.  This is in
> contrast to the initial idea I had to have another class like *vtkCellLocator
> *to implement the given algorithm.  Please let me know, what you think
> about subclassing vtkCellLocator and implementing the FindCell method.
>
> Thank you,
>
> Regards,
>
> Tharindu
>
>
> On Fri, Jul 8, 2011 at 9:18 AM, Andy Bauer <andy.bauer at kitware.com> wrote:
>
>> There's a list of examples at http://www.vtk.org/Wiki/VTK/Examples
>>
>> Doing "ctest -R CellLocator -N" gives me one cell locator test.
>>
>> I'm not sure if any of them are specific to unstructured grids but since
>> any VTK grid can be converted to an unstructured grid you should be able to
>> modify them to work as desired.
>>
>> Andy
>>
>>
>> On Thu, Jul 7, 2011 at 4:17 PM, Tharindu De Silva <tsameera1 at gmail.com>wrote:
>>
>>> Hi Andy,
>>>
>>>      Could you please point out to me if there is any existing example
>>> that tests cell location in unstructured grids.  If there is, I can use that
>>> as an initial check during my implementation.
>>>
>>> Thank you very much,
>>>
>>> Tharindu
>>>
>>> On Thu, Jul 7, 2011 at 11:00 AM, Andy Bauer <andy.bauer at kitware.com>wrote:
>>>
>>>> Hi Tharindu,
>>>>
>>>> I'd be interested in taking a look at what you're doing.  Is
>>>> www.idav.ucdavis.edu/~garth/pdfs/vis10a.pdf<http://www.idav.ucdavis.edu/%7Egarth/pdfs/vis10a.pdf>the paper you're talking about?  I haven't gone through it yet so I can't
>>>> give much feedback now.  I'll try to answer any questions you have and if
>>>> you want me to review your code, feel free to push it to gerrit and add me
>>>> as a reviewer.
>>>>
>>>> Andy
>>>>
>>>>
>>>> On Thu, Jul 7, 2011 at 10:50 AM, Berk Geveci <berk.geveci at kitware.com>wrote:
>>>>
>>>>> That sounds like a good plan. I included Will and Andy. They probably
>>>>> know most about locators and can provide some additional guidance.
>>>>> What do you think guys?
>>>>>
>>>>> PS: Tharindu is the Google Summer of Code student working on
>>>>> implementing 2 papers from last VisWeek in VTK.
>>>>>
>>>>> On Fri, Jul 1, 2011 at 3:12 PM, Jeff Baumes <jeff.baumes at kitware.com>
>>>>> wrote:
>>>>> > Berk may have some guidance on the cell locator, or may direct you
>>>>> someone
>>>>> > else who can help.
>>>>> > Jeff
>>>>> >
>>>>> > On Mon, Jun 27, 2011 at 4:17 PM, Tharindu De Silva <
>>>>> tsameera1 at gmail.com>
>>>>> > wrote:
>>>>> >>
>>>>> >> HI Jeff and Marcus,
>>>>> >>      I started with the second paper, "Fast memory efficient cell
>>>>> location
>>>>> >> in unstructered grids for visualization" paper.  I have been going
>>>>> through
>>>>> >> vtkCellLcoator and vtkModifiedBSPTree classes.  My plan is to
>>>>> implement
>>>>> >> another class like this subclassing vtkAbstractCellLocator class. I
>>>>> am
>>>>> >> sorry, that I was a little slow in understanding the paper due to my
>>>>> lack of
>>>>> >> background in especially the data structures being used.  Now, I
>>>>> understand
>>>>> >> most of the paper, but there is still more to be done.  In the next
>>>>> couple
>>>>> >> of weeks I will implement that paper.
>>>>> >>   Meanwhile, I requested the author of tick label paper for the data
>>>>> that
>>>>> >> he used to try an replicate all the results he got.  But he didn't
>>>>> get back
>>>>> >> to me yet.  Some figures have a lot of tiny data points that it is
>>>>> hard to
>>>>> >> trace it visually.  I will write an interface that I can trace that
>>>>> data by
>>>>> >> clicking points and replicate all the results in the paper.
>>>>> >> Thank you,
>>>>> >> Tharindu
>>>>> >
>>>>>
>>>>
>>>>
>>>
>>
>
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