[Paraview] Delaunay 3D filter too slow

[庞庆源]

I have an extra question.Both my reader and Delaunay3D filter are subclass
from vtkUnstructuredGridAlgorithm.But when I test with 8 vertices of a
cube,my reader renders a hollow cube.But why can Delaunay3D filter render a
solid cube?I have checked the Delaunay3D source file,but can not find the
answer.


2013/9/29 Karl König <kkoenig11 at web.de>

> 庞庆源,
>
> I found some spare time to look into this.
>
> The test data set you provided defines a point cloud with spherical
> topology. Your reader does import this geometric information (as
> points), but provides no topology. In order for VTK and hence ParaView
> to display anything, some kind of topology is needed. The simplest being
> vertices as 0D topology, i.e. a dot per point. The patch attached does
> exactly add that. With this, you can already see something in ParaView
> when using your reader plugin to import the test data set.
>
> You've been trying to triangulate your point cloud with spherical
> topology with Delaunay3D, in vain. I could reproduce that. With a debug
> build of ParaView, one notices thousands of warnings of kind "Unable to
> factor linear system" being issued when trying to apply Delaunay3D
> filter to your input.
>
> The same actually happens when applying Delaunay3D filter to a sphere
> source created with theta resolution 180 and phi resolution 90.
> A few dozen warnings about being unable to factor a linear system are
> raised. (On a side node: a debug build of ParaView master branch with
> CMake option VTK_DEBUG_LEAKS:BOOL=ON reveals a memory leak in Delaunay3D
> when applied to this densely meshed sphere.) The result, however, is
> disappointing as the volume mesh has some gaps and rifts, not really a
> smooth surface any more. So, you need to pursue another triangulation
> approach.
>
> Applying Delaunay2D filter instead produces at least a hemisphere,
> almost instantly. I suspect, however, that a hemisphere is not good
> enough.
>
> You could resort to applying a Glyph filter with Glyph type "Sphere" and
> otherwise default settings. That yields a coarse approximation of what I
> guess you would like to achieve.
>
> It might also be that class vtkSurfaceReconstructionFilter or class
> vtkMarchingCubes or one of the filters from the pv-meshless plugin are
> able to create the surface mesh, but I'm not too familiar with them to
> say this with confidence or provide additional advice.
>
> There have recently even been a few discussions on the VTK mailing list
> regarding the general problem of triangulating point clouds with
> spherical topology, see e.g.
> http://markmail.org/message/fc3kjifkwtpggqai
>
> But given that your points are not arbitrarily distributed over the
> sphere, but in fact stored in your input file in a very regular and pre-
> sorted way (180 points per latitude, latitude after latitude from pole
> to pole) and given that the implied topology is very simple too (every
> vertex has exactly 4 neighbors), it is not too hard to extend your
> reader to have it create a smooth triangulation of the surface by simple
> quads (connecting vertex i with i+1, i+181 and i+180) without involving
> the help from additional VTK meshing classes.
>
> Maybe someone else on the list can even tell you how to re-arrange your
> data to fulfill the prerequisites for a structured grid data set for
> which the triangulation is implicitly done by VTK.
>
> Hope this helps,
> Karl
>
>
>
> 庞庆源 wrote, On 27.09.2013 02:46:
> > This is the source of my test plugin.Could you have a try?
> > My paraview version is 4.0.1 ,built from source.
> >
> >
> > 2013/9/27 Moreland, Kenneth <kmorel at sandia.gov <mailto:kmorel at sandia.gov
> >>
> >
> >     I doubt that would make a difference. I just tried a bimodal
> >     distribution using two point sources, and the filter still executed
> >     in about the same amount of time.
> >
> >     So what version of ParaView are you using? Are you using a binary
> >     downloaded from paraview.org <http://paraview.org> or did you build
> >     your own?
> >
> >     -Ken
> >
> >     From: 庞庆源 <pangqingyuan1991 at gmail.com
> >     <mailto:pangqingyuan1991 at gmail.com>>
> >     Date: Thursday, September 26, 2013 3:05 AM
> >     To: Kenneth Moreland <kmorel at sandia.gov <mailto:kmorel at sandia.gov>>
> >     Cc: "paraview at paraview.org <mailto:paraview at paraview.org>"
> >     <paraview at paraview.org <mailto:paraview at paraview.org>>
> >
> >     Subject: [EXTERNAL] Re: [Paraview] Delaunay 3D filter too slow
> >
> >     My points are not Uniform distribution.They take from intersections
> >     of 89 wefts and 180 warps.So the points are intensive at poles and
> >     sparse at equator.Is this the problem?
> >
> >
> >     2013/9/25 Moreland, Kenneth <kmorel at sandia.gov
> >     <mailto:kmorel at sandia.gov>>
> >
> >         That is strange. I cannot replicate your problem. I used a point
> >         source to create 16020 random points in a sphere, and the
> >         Delaunay triangulation took only about 2 seconds. My processor
> >         might be a bit better than yours, but not anywhere near enough
> >         to explain the difference.
> >
> >         What version of ParaView are you using? Are you a binary
> >         downloaded from paraview.org <http://paraview.org> or did you
> >         build your own?
> >
> >         -Ken
> >
> >         From: 庞庆源 <pangqingyuan1991 at gmail.com
> >         <mailto:pangqingyuan1991 at gmail.com>>
> >         Date: Tuesday, September 24, 2013 10:29 PM
> >         To: Kenneth Moreland <kmorel at sandia.gov <mailto:
> kmorel at sandia.gov>>
> >         Subject: [EXTERNAL] Re: [Paraview] Delaunay 3D filter too slow
> >
> >         in fact,I have only 16020 points for test.My cpu is AMD
> >         Athlon(tm) II P320 Dual-Core Processor with 2.1GHz.How long will
> >         it take in this case if I use one cpu to calculate?I have wait
> >         for more than 10 minutes before stopping it.
> >
> >
> >         2013/9/24 Moreland, Kenneth <kmorel at sandia.gov
> >         <mailto:kmorel at sandia.gov>>
> >
> >             Your options are probably either to wait or do something
> >             else. Delaunay triangulation is a pretty heavyweight
> >             operation and in general it is not trivial to impose a
> >             topology on a collection of points.
> >
> >             You might rethink whether you really need to create a solid
> >             sphere in the first place. I'm guessing you have at least
> >             around 100,000 points (or else Delaunay probably would not
> >             be that slow). If you just render these points as a cloud of
> >             points, you should get enough occlusion for it to look
> >             pretty much like a sphere.
> >
> >             -Ken
> >
> >             From: 庞庆源 <pangqingyuan1991 at gmail.com
> >             <mailto:pangqingyuan1991 at gmail.com>>
> >             Date: Tuesday, September 24, 2013 5:01 AM
> >             To: paraview <paraview at paraview.org
> >             <mailto:paraview at paraview.org>>
> >             Subject: [EXTERNAL] [Paraview] Delaunay 3D filter too slow
> >
> >             I have a lot of points taking sample from a solid sphere.So
> >             I want to use Delaunay 3D filter to render the shpere with
> >             known scalars of the points.But it took me so much time.What
> >             should I do?
>
>


-- 
庞庆源 <pangqingyuan1991 at gmail.com>
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