[vtk-developers] Better than O(n) prop operations on vtkRenderer

[Bill Lorensen]

Do you have benchmarks that show the differences?

On Thu, Dec 13, 2018, 3:47 PM Paul Harris <harris.pc at gmail.com wrote:

> I had to hack vtkCollection for this exact reason.
>
> It keeps an ordered linked list because its design allows for the same
> element to be added multiple times.
>
> I replaced that ordered linked list with a boost::multi_index, so it kept
> the old interface, multiple-entry feature, and addition-order,
> but also added fast lookups and fast removal.
>
> I'm happy to share the code.  It was hacked into an older VTK version, and
> added a boost dependency, so it'll need some cleanup in that respect.  But
> I did check the newer VTK code when I hacked it in July and it didn't look
> like it had changed much.  So apart from the boost dependency, it might be
> easy to bring into the latest VTK.
>
>
> On Fri, 14 Dec 2018 at 07:19, Todd Martin via vtk-developers <
> vtk-developers at public.kitware.com> wrote:
>
>> My solution to this kind of problem in the past has been to build a
>> (non-clustered) sorted index for fast lookup on the collection, without
>> changing the underlying collection itself. In fact multiple indicies could
>> be built and (if desired) attached to the collection in a list. Of course
>> it means that each index needs to be rebuilt, when anything is added to or
>> removed from the collection. The most efficient way to do that is to set a
>> flag when anything changes and then only rebuild the index the next time it
>> is accessed.
>>
>>
>>
>> Todd Martin, PhD.
>> *Freelance Engineer/Software Architect.*
>>
>>
>>
>> On Friday, 14 December 2018, 12:06:59 PM NZDT, David Gobbi <
>> david.gobbi at gmail.com> wrote:
>>
>>
>> Hi Elvis,
>>
>> I don't think there are any fans of vtkCollection, but replacing it
>> with something modern would be lot of work and would provide
>> far less benefit than e.g. the recent reworking of the VTK data
>> arrays to provide flexible memory access patterns.
>>
>> Also, given the cost for vtkRenderer to render a bunch of props,
>> you would have to be doing many hundreds (thousands?) of
>> insertions/removals per render before the time required for those
>> operations becomes significant to overall app performance.
>>
>>   David
>>
>>
>> On Thu, Dec 13, 2018 at 3:33 PM Elvis Stansvik <
>> elvis.stansvik at orexplore.com> wrote:
>>
>> Hi all,
>>
>> The props of a vtkRenderer are kept in a vtkCollection (and probably
>> have been since VTKs childhood), meaning linear time
>> search/insert/remove.
>>
>> I realize the use of vtkCollection is pervasive in these classes, and
>> also shines through in their API, so this is a bit of a long shot,
>> but, is there any chance that it'll at some point be converted to use
>> a sorted data structure, to permit logarithmic operations?
>>
>> Has anyone else had the need to rapidly insert/remove/check for props
>> in a renderer with a large amounts of props in it? Has the idea of
>> having vtkRenderer backed by something else been discussed before?
>>
>> Cheers,
>> Elvis
>>
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