Re: [deal.II] Strategy to snap the boundary of a triangulation to a manifold

[heena patel]

Dear Bruno,
   I am not expert, but OpenFoam has Snappyhex mesh
feature that might help you. Check the link below.
http://www.wolfdynamics.com/wiki/meshing_OF_SHM.pdf

Regards,
Heena

On Mon, Jun 8, 2020 at 6:22 PM Bruno Blais  wrote:

> Dear all,
> I hope you are doing well.
>
> In my endless quest for robust mesh generation of hex meshes using GMSH, I
> have managed to come up with a very robust strategy to generate hex-only
> meshes
> My only issue (which is a major one) is that this implies that my
> decomposition from tet to hex adds nodes that are not "snapped" to the
> boundary, but that are only linear interpolation of the other node on the
> triangular faces.
> Consequently, my quest remains unfulfilled.
>
> Meshing through high-order and snapping the additional node to a
> high-order mesh from within GMSH is very troublesome and not very robust
> (and also very time consuming). However, an idea came to mind.
> I was wondering if there could be an easy way to "snap" my faces to the
> manifold to which they belong.
>
> My problem is thus the following:
> - Given a triangulation and a manifold
> - Some nodes are exactly on the manifolds (the original nodes of the tets)
> and some are not (the added nodes in the subdivision)
> - What would be the best way to deform mesh so that the non-conforming
> node get deformed to the position which would be implied by the manifold? I
> think I could also make the process more robust by solving an additional
> elasticity equation during the deformation to deform the entire mesh
> instead of just the nodes close to the manifold.
>
>
> Would any of you have a suggestion on how best to achieve the deformation
> of the nodes to match the manifold?
>
>
> --
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> 
> .
>

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Re: [deal.II] Strategy to snap the boundary of a triangulation to a manifold

[Wolfgang Bangerth]

On 6/8/20 10:22 AM, Bruno Blais wrote:



Would any of you have a suggestion on how best to achieve the deformation of 
the nodes to match the manifold?


I suspect that this depends a lot on how exactly your manifold is given. You 
need some projection onto the manifold. If you used IGES CAD files, such 
projections are built-in with OpenCASCADE. For constructive solid geometry 
cases, it may be possible to build the project from known normal vectors. I 
expect that the situation becomes complicated in the "creases" where two 
boundary patches come together.


Best
 W.


--

Wolfgang Bangerth  email: bange...@colostate.edu
   www: http://www.math.colostate.edu/~bangerth/

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[deal.II] Strategy to snap the boundary of a triangulation to a manifold

[Bruno Blais]

Dear all,
I hope you are doing well.

In my endless quest for robust mesh generation of hex meshes using GMSH, I 
have managed to come up with a very robust strategy to generate hex-only 
meshes
My only issue (which is a major one) is that this implies that my 
decomposition from tet to hex adds nodes that are not "snapped" to the 
boundary, but that are only linear interpolation of the other node on the 
triangular faces.
Consequently, my quest remains unfulfilled.

Meshing through high-order and snapping the additional node to a high-order 
mesh from within GMSH is very troublesome and not very robust (and also 
very time consuming). However, an idea came to mind.
I was wondering if there could be an easy way to "snap" my faces to the 
manifold to which they belong.

My problem is thus the following:
- Given a triangulation and a manifold
- Some nodes are exactly on the manifolds (the original nodes of the tets) 
and some are not (the added nodes in the subdivision)
- What would be the best way to deform mesh so that the non-conforming node 
get deformed to the position which would be implied by the manifold? I 
think I could also make the process more robust by solving an additional 
elasticity equation during the deformation to deform the entire mesh 
instead of just the nodes close to the manifold.


Would any of you have a suggestion on how best to achieve the deformation 
of the nodes to match the manifold?


-- 
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