[vtk-developers] vtkPointCloud remote module

Shawn Waldon shawn.waldon at kitware.com
Fri Jan 29 12:23:27 EST 2016 

Ken,

What you are wanting sounds very similar to how the streaming particles
plugin in ParaView works.  In this case it is the representation that is
deciding what data to request from the upstream pipeline.  I have an
example source in there [1] that randomly generates an octree-like
structure that it expects (of vtkMultiBlockDataset).  Either you or Will
may want to look at how that is working while you are tackling this.

Shawn

[1]:
ParaView-src/Plugins/StreamingParticles/vtkPVRandomPointsStreamingSource.{h,cxx}.

On Fri, Jan 29, 2016 at 12:15 PM, Ken Martin <ken.martin at kitware.com> wrote:

> Thanks Will. I promise I'll write the mapper :-) The PTS reader is a
> simple ascii X Y Z R G B type format that I usually immediately convert to
> VTK XML format as that is far faster and more compact. So unfortunately PTS
> is not it. I am thinking a vtkXMLPolyDataWriter subclass that adds some
> bounding box metadata.
>
> Ken
>
> On Fri, Jan 29, 2016 at 11:08 AM, Will Schroeder <
> will.schroeder at kitware.com> wrote:
>
>> Ken-
>>
>> I am totally with you. I am writing some simple stuff at the moment like
>> VoxelGrid as sort of a "drop-in" replacements for PCL workflows; mostly to
>> get my head around the challenges and serve as a stop gap until our better
>> stuff comes along. I really like your idea and I do plan to implement this;
>> it's really not too hard to do from what I understand and given the pieces
>> available in VTK.
>>
>> So I'll wrap up this simple VoxelGrid and then take a crack at the beast
>> you've envisioned. The two major pieces seems to be 1) create a class that
>> builds the hierarchical structure, and 2) write a reader/writer pair that
>> can perform associated IO. In an earlier email you mentioned a PTS reader
>> that you made improvement to; is this a good exemplar data format or do you
>> have a better starting point?
>>
>> It seems I have a homework assignment for the weekend :-)
>>
>> Best,
>> W
>>
>> On Fri, Jan 29, 2016 at 10:42 AM, Ken Martin <ken.martin at kitware.com>
>> wrote:
>>
>>> Nice, can I make a specific request Will? :-) Part of what I want to do
>>> for large point clouds is something like the following:
>>>
>>> 1) Open a VTK multipiece file and read in the bounding boxes of the
>>> pieces (but not the data)
>>>
>>> 2) Read in the first piece and use it for rendering
>>>
>>> 3) In the background read in more pieces, as they are loaded make them
>>> available to the mapper
>>>
>>> 4) The mapper based on the current camera parameters and bounding boxes
>>> of the pieces intelligently selects what pieces to render. This provides a
>>> happy fast interactive experience leading to world peace.
>>>
>>> For this to work well my thought was to have the pieces be broken up in
>>> a special way sort of like an octree but a spatial hash etc would be just
>>> as good as long as it is hierarchical and structured. Think of breaking up
>>> the volume into 1 + 8 + 64 pieces. The first piece contains ~1/73 of the
>>> data covering the entire bounding box. The next eight pieces also each
>>> contain  about 1/73 of the data each constrained by their octant of the
>>> bounding box. Same idea for the next 64 boxes, they are just one level
>>> further down.  This would work really well for a smart mapper providing
>>> fast first render plus fast LOD/subsequent renders. I can implement 1-4
>>> pretty quickly.
>>>
>>> But .... for it to work I need someone to create the 73 piece file the
>>> right way. (it does not have to be 73, and clearly some of those 73 will be
>>> empty, it just needs to be hierarchical and structured so that a group of
>>> pieces can be represented at a lower level of detail by some other piece)
>>> My gut feeling was to have the LOD pieces use actual points of the dataset
>>> (not centroids or similar) that way as more pieces are loaded we are just
>>> providing more detail, not replacing fake data (centroids) with real data.
>>> But really either approach is pretty easy to implement in the mapper. The
>>> latter approach just means the entire dataset footprint is larger because
>>> some of the points are not part of the full res dataset because you
>>> generated them.
>>>
>>> I could be totally off base but that was my gut feeling on rendering >
>>> 2GB point clouds in a nice zippy manner.
>>>
>>> TLDR: I want someone to write a filter/writer subclass to create a
>>> special 73 piece vtk file :-)
>>>
>>> Ken
>>>
>>>
>>>
>>>
>>>
>>> On Fri, Jan 29, 2016 at 10:06 AM, Will Schroeder <
>>> will.schroeder at kitware.com> wrote:
>>>
>>>> Geoff-
>>>>
>>>> I knocked out a vtkVoxelGrid last night, it seems to work great. It's
>>>> threaded and seems to be fast.
>>>>
>>>> Question for you before I push the work to the repository: averaging
>>>> points in each bin provides a nice subsampled point position. But what do
>>>> you think we should do for attributes (e.g., scalars, vector, etc.)? These
>>>> could be averaged too. There are however other options like finding the
>>>> closest point to the subsampled point and using those attribute values, or
>>>> if you want to get really fancy, using an interpolation kernel to
>>>> interpolate to the subsampled point.
>>>>
>>>> Thoughts?
>>>> W
>>>>
>>>> On Thu, Jan 28, 2016 at 10:03 AM, Will Schroeder <
>>>> will.schroeder at kitware.com> wrote:
>>>>
>>>>> Thanks for the feedback. I have some downsampling filters in the works
>>>>> now, I'll let you know when I have something ready.
>>>>>
>>>>> BTW we are on a similar path. PCL is awesome, but we have some common
>>>>> workflows that would be better served with more compact software
>>>>> environments, and with minimal IO and/or data transfer. So we're trying to
>>>>> knock of a small kernel of capability to achieve this.
>>>>>
>>>>> Best,
>>>>> W
>>>>>
>>>>> On Thu, Jan 28, 2016 at 9:56 AM, Geoff Wright <gpwright at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hi Will,
>>>>>>
>>>>>> This is good to see.  I'm currently using VTK to generate surfaces
>>>>>> from some point cloud data.  I have some initial pre processing steps that
>>>>>> I use PCL (point cloud library) for, and then a vtk stage that converts PCL
>>>>>> point cloud into vtkPolyData/vtkPoints.  It would be great to
>>>>>> eliminate the PCL dependency and use exclusively vtk.  My point
>>>>>> cloud data grows very large over time with a lot of redundant points so its
>>>>>> very important to downsample them onto uniform spacing (
>>>>>> http://docs.pointclouds.org/trunk/classpcl_1_1_voxel_grid.html )
>>>>>> before processing them in vtk.  Would it make sense to add something like
>>>>>> this to your library?
>>>>>>
>>>>>> Geoff
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Thu, Jan 28, 2016 at 9:12 AM Will Schroeder <
>>>>>> will.schroeder at kitware.com> wrote:
>>>>>>
>>>>>>> FYI- I have committed an initial set of filters for performing point
>>>>>>> cloud processing. Any feedback or suggestions are welcome as this is an
>>>>>>> initial prototype. The work is currently available as a remote module to
>>>>>>> VTK (vtkPointCloud) via this repository:
>>>>>>> https://gitlab.kitware.com/vtk/point-cloud.git
>>>>>>>
>>>>>>> A couple of notes:
>>>>>>> + Right now I am using vtkPolyData to represent the point cloud via
>>>>>>> a vtkPoints instance. There are no vtkVertex, vtkPolyVertex cells created
>>>>>>> to save on memory.
>>>>>>> + The classes will process as input any vtkPointSet dataset
>>>>>>> + There is a general framework for filtering point clouds via the
>>>>>>> class vtkPointCloudFilter. Besides their filtered cloud output, these
>>>>>>> filters also have an optional, second output which contains any points
>>>>>>> removed from the input.
>>>>>>> + Current filters include vtkRadiusOutlierRemoval,
>>>>>>> vtkStatisticalOutlierRemoval, vtkExtractPoints (extract points using an
>>>>>>> implicit function). Some of  these names are inspired by PCL
>>>>>>> <http://pointclouds.org/> names.
>>>>>>> + All filters are threaded using vtkSMPTools using a threaded
>>>>>>> locator (vtkStaticPointLocator) so I believe that this is relatively fast,
>>>>>>> although I have not done much testing.
>>>>>>> + I'm using vtkPointGaussianMapper in the tests, a class that Ken
>>>>>>> wrote that is very fast.
>>>>>>>
>>>>>>> As usual comments and suggestions are requested. In particular any
>>>>>>> suggestions for other filters to write are welcome (to round out some of
>>>>>>> the core functionality). The repository is in flux as I try crazy ideas and
>>>>>>> try to educate myself, so be forewarned.
>>>>>>>
>>>>>>> Best,
>>>>>>> W
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Powered by www.kitware.com
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>>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> William J. Schroeder, PhD
>>>>> Kitware, Inc. - Building the World's Technical Computing Software
>>>>> 28 Corporate Drive
>>>>> Clifton Park, NY 12065
>>>>> will.schroeder at kitware.com
>>>>> http://www.kitware.com
>>>>> (518) 881-4902
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> William J. Schroeder, PhD
>>>> Kitware, Inc. - Building the World's Technical Computing Software
>>>> 28 Corporate Drive
>>>> Clifton Park, NY 12065
>>>> will.schroeder at kitware.com
>>>> http://www.kitware.com
>>>> (518) 881-4902
>>>>
>>>> _______________________________________________
>>>> Powered by www.kitware.com
>>>>
>>>> Visit other Kitware open-source projects at
>>>> http://www.kitware.com/opensource/opensource.html
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>>>>
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>>>>
>>>>
>>>
>>>
>>> --
>>> Ken Martin PhD
>>> Chairman & CFO
>>> Kitware Inc.
>>> 28 Corporate Drive
>>> Clifton Park NY 12065
>>> 518 371 3971
>>>
>>> This communication, including all attachments, contains confidential and
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>>>
>>
>>
>>
>> --
>> William J. Schroeder, PhD
>> Kitware, Inc. - Building the World's Technical Computing Software
>> 28 Corporate Drive
>> Clifton Park, NY 12065
>> will.schroeder at kitware.com
>> http://www.kitware.com
>> (518) 881-4902
>>
>
>
>
> --
> Ken Martin PhD
> Chairman & CFO
> Kitware Inc.
> 28 Corporate Drive
> Clifton Park NY 12065
> 518 371 3971
>
> This communication, including all attachments, contains confidential and
> legally privileged information, and it is intended only for the use of the
> addressee.  Access to this email by anyone else is unauthorized. If you are
> not the intended recipient, any disclosure, copying, distribution or any
> action taken in reliance on it is prohibited and may be unlawful. If you
> received this communication in error please notify us immediately and
> destroy the original message.  Thank you.
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Search the list archives at: http://markmail.org/search/?q=vtk-developers
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> Follow this link to subscribe/unsubscribe:
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