Extra nodes that do not belong to any element

[Kodanda Ram Mangipudi]

Hi Dr. Fang,

I use a binary volume to get a mesh using 'cgalmesh' option.

I found several (on the order of 2000 nodes in a total of 40K nodes) that do not belong to any elements in the mesh. The mesh appears good though.

I do have some very small islands (a few pixels in diameter). 

Having these "free" nodes is known? Do you think it is related to the small islands? I expected missing these tiny islands but not these "free" nodes. Your help is greatly appreciated.

Thanks and regards,

Kodanda

[Qianqian Fang]

On 04/27/2015 11:12 AM, Kodanda Ram Mangipudi wrote:

Hi Dr. Fang,

I use a binary volume to get a mesh using 'cgalmesh' option.

I found several (on the order of 2000 nodes in a total of 40K nodes) that do not belong to any elements in the mesh. The mesh appears good though.

hi Kodanda

This is new to me, although I have to admit I haven't paid close attention
to the mesh produced by cgalmesh. My impression for the tetgen-generated
meshes are free of isolated nodes, but again, I did not test every case.

I do have some very small islands (a few pixels in diameter).

that should not be part of these isolated nodes as they do
belong to the elements in those small islands.

Having these "free" nodes is known? Do you think it is related to the small islands? I expected missing these tiny islands but not these "free" nodes. Your help is greatly appreciated.

you can always remove redundant isolated nodes by calling
function removeisolatednode().

for the small islands, I have a function called removeisolatedsurf()
where you can specify a min surface diameter. below that threshold,
the islands will be removed.

let me know if this solves the issues you have.

Qianqian

Thanks and regards,

Kodanda

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[Kodanda Ram Mangipudi]

Dear Dr. Fang,

Thanks you very much for your reply.

I think I will just remove these "extra" nodes and continue. 

Regarding the islands, I do not have any "unwanted" islands after meshing. So the mesh seems fine for the input geometry and for my purposes. 

Just did not understand these extra nodes as they appeared in the boundary node set in the ABAQUS inp file. ( I have a function  which creates boundary node sets that identifies all the nodes on the 6 boundary faces of a rectangular prism.)  

[Qianqian Fang]

On 4/27/2015 3:18 PM, Kodanda Ram Mangipudi wrote:

Dear Dr. Fang,

Thanks you very much for your reply.

I think I will just remove these "extra" nodes and continue. 

Regarding the islands, I do not have any "unwanted" islands after meshing. So the mesh seems fine for the input geometry and for my purposes. 

Just did not understand these extra nodes as they appeared in the boundary node set in the ABAQUS inp file. ( I have a function  which creates boundary node sets that identifies all the nodes on the 6 boundary faces of a rectangular prism.) 

this should be a good question to the CGAL developers, as the option
"cgalmesh" calls one of the CGAL tools to produce the mesh. I believe
some of the CGAL developers are subscribing to this list, love to hear
what they think. Alternatively, feel free to post your question on the
cgal-discuss mailing list:

http://www.cgal.org/mailing_list.html

there is a very actively supported community there.

Qianqian