[vtkusers] Design question (dataset relationship)

Gerald Dalley dalleyg at []
Fri Sep 8 07:57:58 EDT 2000

> -----Original Message-----
> From: Will Schroeder [mailto:will.schroeder at kitware.com]
> Sent: Thursday, 07 September, 2000 8:50 PM
> To: Sebastien BARRE; dalleyg at dma.org
> Cc: VTK Users
> Subject: RE: [vtkusers] Design question (dataset relationship)
> At 05:29 PM 9/7/2000 +0200, Sebastien BARRE wrote:
> >At 10:35 07/09/00 -0400, Gerald Dalley a écrit:
> >
> >>For some range image registration work I've been doing, yes,
> I've done that.
> >>I tried using some of the built-in locators, but found one of the
> >>fundamental requirements of the base classes to be too
> stringent: the search
> >>point must be inside the bounding box of the dataset being searched.
> >
> >Wow. Do the VTK gurus confirm ?
> >
> >I see : "vtkPointLocator works by dividing a specified region of space
> >into a regular array of "rectangular" buckets, and then keeping
> a list of
> >points that lie in each bucket.".
> >Thus I guess if the search point is not in the dataset, it has no chance
> >to fall in a bucket :(
> There is a lot of room for improvement in the locators. Not only do they
> need to know the initial bounding box prior to point insertion, but they
> are not good in situations requiring adaptive behavior (i.e., the
> subdivision of the locators is uniform). For example, if you have an
> unstructured grid with 90% of the mesh in a thin boundary layer,
> and try to
> contour it, you start getting very bad performance. You can
> always increase
> the resolution of the locator but this takes up a ton of memory.
> What would
> be better would be an adaptive scheme like a non-uniform octree
> or kd tree.
> It's open-source...volunteers?

Right now, I'm temporarily off the project that I was working on when I
implemented a FindClosestPoint method that uses kd trees.  If I start back
up on that project, I might be able to do some extra work on it.  No
promises though :)  If you happen to bump into anyone that does want to do a
kd tree point locator, I'd be more than happy to share the source that I've
developed so far.

> Will
> ------------------------------------
> Dr. William J. Schroeder
> VTK-Based Visualization Solutions, Kitware, Inc.
> 469 Clifton Corporate Parkway
> Clifton Park, NY 12065 USA
> will.schroeder at kitware.com
> http://www.kitware.com
> 1-518-371-3971 x102

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