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

[Todd Martin]

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 itwith something modern would be lot of work and would providefar less benefit than e.g. the recent reworking of the VTK dataarrays 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?) ofinsertions/removals per render before the time required for thoseoperations 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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