LOD and closest neighbour with vtk octree

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1

Hello :smiley:
I am creating a 3D viewer to display large point cloud, I want to add octree structure to my viewer. This octree must allow me :

  • To display the number of level I want
  • To find the closest neighbour point

Is there a vtk class that allows me to have this both functionnality in a single octree structure (according to what I found vtk octree is used to find closest neighbour) or should I use potree library ( or create my own octree algorithm and data structure) ?

Thanks for your help

2

vtkStaticPointLocator ?

3

@mwestphal with vtkStaticPointLocator you can locate a point but I also want to choose de LOD to render to optimize performance and according to the documentation this class does not have such a functionnality or maybe I donā€™t look at the doc correctly

4

Indeed, LOD would need to be performed using a dedicated filter for LOD.

5

@mwestphal do you know what kind of filter ? Could I use the same octree with this filter that I create with vtkStaticPointLocator? I am starting to use vtk, itā€™s not easy to see the power of filters

6

https://vtk.org/doc/nightly/html/classvtkDecimatePro.html#details

7

There are several decimators. Also check out vtkBinnedDecimation (which is similar to what ParaView uses).

8

Paraview uses vtkBinnedDecimation as filter to display LOD ? Because Paraview octrees seem to be very efficient. I should maybe go deeper inside the paraview source code to see how octrees are managed

9

ParaView use VTKm provided decimator.

10

@mwestphal So with a decimator filter, LODMapper and LODActor I should be able to have performance equivalent to paraview octree ?

11

Probable a bit basic for you but some of the octree examples may help e.g. OctreeVisualize, there are nine other examples there.

12

Yes Iā€™ve already seen this example, it displays an octree representation according to the choosen level but you canā€™t display the corresponding point. I am running through the vtk documentation and examples and honestly for now Iā€™m not totally convinced that using the vtk classes allows me to generate a real octree structure for displaying and finding points.

13

When I use vtkBinnedDecimation, I get the error ā€œno data to decimateā€, is it posible to apply such a decimator with vtkPoints ?

14

No, itā€™s a mesh decimation algorithm

15

If I want to decimate a pointcloud (vtkpoints), is there some vtk tools to do that or should I do that by my own ?