[Paraview] Delaunay3D

Tue May 22 16:15:50 EDT 2018

Weiguang,

I just want to clarify something quickly with your question. When you say “some of the points are ignored in the process of Delauney triangulation” and “dangling points,” do you mean that you can see some spheres that are inside the rest of the spheres?

I note in your description that you said you are looking at the wireframe of the Delaunay triangulation. The wireframe representation actually only shows the wireframe of the surface. You will not see the edges on the interior of the mesh, so any points that are on the interior will not look connected even if they are.

Instead of showing the wireframe, run the Extract Edges filter (which will show a wireframe of all edges). Does that connect the points like you expect?

-Ken

From: ParaView [mailto:paraview-bounces at public.kitware.com] On Behalf Of Weiguang Guan
Sent: Tuesday, May 22, 2018 1:58 PM
To: Will Schroeder <will.schroeder at kitware.com>
Cc: paraview at public.kitware.com
Subject: [EXTERNAL] Re: [Paraview] Delaunay3D

Hi Will,

Thank you very much for your time. I've tried v5.5 and v5.2. This "issue" doesn't seem to have anything to do with the versions.

First of all, I would like to change my words for the N=5 case, where there might be 2, 3, or even 4 terahedra depending on the relative locations of the 5 points.

However, the question for the N=20 case is still pending one. You can see the dangling points if you change the representation from "surface" to "wireframe". I basically have similar result as yours. Because the point source generates point cloud with random positions of points, you will see different results each time you change the parameters of Point Source (either number of point or the radius).

Another question: is there another filter that constructs a grid from a set of points?

Weiguang

On 5/22/2018 3:42 PM, Will Schroeder wrote:
What version of ParaView? Mine works just fine..... 5.5.0-323-g37ce137a21 64-bit

[image.png][image.png]

On Tue, May 22, 2018 at 3:05 PM Weiguang Guan <guanw at rhpcs.mcmaster.ca<mailto:guanw at rhpcs.mcmaster.ca>> wrote:
Dear Paraview users,

Based on the documentation, Delaunay3D will construct a 3D Delaunay triangulation from a list of input points if alpha=0. But I did an experiment that gave a different result. Here are the steps:
(1) Sources->Point source, and set Number of points to N (I experiment with different N=5 and N=20)
(2) Using sphere glyph to display these points
(3) Apply filter "Delaunay 3D" to the points with alpha=0 and display the resultant unstructured grid as wireframe.

When N=20, I can see some of the points are ignored in the process of Delauney triangulation.
When N=5, The resultant unstructured grid has 3 cells while I think it should have only 2 tetrahedra.

Can someone explain it? Thanks a lot.

Weiguang
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William J. Schroeder, PhD
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Weiguang Guan

Research Scientist

RHPCS, McMaster University

Phone: 905-525-9140 x22540
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