[MOAB-dev] Setting connectivity for single vertex

Mon Feb 2 16:49:27 CST 2015

Michael,

If the intent is just to visualize these point clouds and data on
them, we can certainly add some specific functionality for this when
we output the data to vtk. If you want to contribute some code for
this, we will be happy to take a PR directly on our bitbucket repo.

Querying connectivity of the point cloud is not currently supported
and unless you do create a higher dimensional element using sets of
vertices, we cannot compute the one ring vertex neighbors (which
involves find the element adjacencies and performing a union on the
connectivity of these entities). Depicting a point as a traditional
element (0-D element) can possibly be done but this is not supported
now and am not sure how easy it will be without few involved changes
in some parts including the I/O writers.

Vijay

On Sun, Feb 1, 2015 at 9:39 AM, CORTIS M. <michael.cortis at durham.ac.uk> wrote:
> Hi,
>
> So if you save points on vtk you have such thing where no connectivity and
> no cell definition.
>
> POINTS 2 double
> 10.0 0 0
> -10.0 0 0
> CELLS 0 0
> CELL_TYPES 0
>
> but if you want to can include connectivities and cel definition as follows
>
> POINTS 2 double
> 10.0 0 0
> -10.0 0 0
> CELLS 2 4
> 1 0
> 1 1
> CELL_TYPES 2
> 1
> 1
>
> This way, Paraview and VisIt can recognise points as elements and
> consequently can visualise them.
>
> Michael
>
>
> On 1 Feb 2015, at 15:34, Paul Wilson <ppwilson at wisc.edu>
>  wrote:
>
> Hello again,
>
> On 02/01/2015 09:31 AM, CORTIS M. wrote:
>
> Hello Paul,
>
> In fact you can create vertices and use them and store data on tag.
> The only problem was that if there is no connectivity,
> ParaView and VisIT does not visualise them unless you plot the points using
> glyphs.
> So I had to create a function which read the points from a mesh file and
> insert their individual connectivities and save them as vtk.
>
> Now I see!  Thanks for the clarification.
>
> So are you connecting the vertices to themselves?  What is the element type
> in VTK for such an element?
>
> Paul
>
>
>
>
> Problem solved. But may be MOAB would consider this problem and do something
> about it.
>
> Thanks for your input,
>
> Michael
>
>
> On 1 Feb 2015, at 15:24, Paul Wilson <ppwilson at wisc.edu>
>  wrote:
>
> Hello Michael,
>
> On 01/29/2015 05:08 PM, CORTIS M. wrote:
>
> Hi Iulian,
>
> Yes I am trying to create an element made from single vertex.
> I want to used these for Material Point Method.
>
> So there is a way of creating the vertices, but not adding connectivity to
> themselves only?
> Or may be another way round?
>
>
> Perhaps, I'm not fully understanding your questions, but it is certainly
> possible to create vertices in MOAB and then use them directly in your
> analysis.  There is no need to create an element if, in fact, all you need
> are the vertices.  Each vertex can be tagged with data in the same way that
> an element can be.
>
> I hope that is helpful,
> Paul
>
> If not, don't worry about. Will create a vtk writer to do this and hopefully
> moab can use the vertices.
>
> Any assistance is really appreciated.
>
> Kind regards
>
> Michael
>
>
>
>
> On 29 Jan 2015, at 17:24, "Grindeanu, Iulian R." <iulian at mcs.anl.gov> wrote:
>
> Hello,
> Moab does not have elements with a single vertex. Is this what you are
> trying to do?
> A vertex (node) is represented with an entity handle of type MBVERTEX, and
> you can get coordinates for it
>
> I am not sure what are you trying to do.
> Best Regards,
> Iulian
>
> ________________________________
> From: moab-dev-bounces at mcs.anl.gov [moab-dev-bounces at mcs.anl.gov] on behalf
> of CORTIS M. [michael.cortis at durham.ac.uk]
> Sent: Thursday, January 29, 2015 10:18 AM
> To: moab-dev at mcs.anl.gov
> Cc: Tautges, Timothy J.
> Subject: Re: [MOAB-dev] Setting connectivity for single vertex
>
> Thanks Tim,
>
> I am still having a problem, may be the guys at Argonne can help with this.
>
> I've tried a simpler one and trying to crete the vertex from point.
>
>   double points[9]={0.5,0,0};
>   EntityHandle vertex;
>   rval=moab2.create_vertex(points,vertex);CHKERR_PETSC(rval);
>   EntityHandle dummy;
>   rval = moab2.create_element(MBVERTEX,&vertex,1,dummy); CHKERR_PETSC(rval);
>
> But I am getting Error code 2, MB_TYPE_OUT_OF_RANGE !
> Is it possible to use MBVERTEX here?
>
> Thanks,
>
> Michael
>
> On 29 Jan 2015, at 15:04, Tim Tautges <tautges at mcs.anl.gov> wrote:
>
> [cc'ng moab-dev list, since I've left Argonne.]
>
> dummy is 0, which is an invalid handle, but should be the handle(s) of the
> entities whose connectivity you're setting; I suspect what you want there is
> *vertices.begin().  And you can't set connectivity until you make an
> element, so you need to call create_element, probably with the number of
> verts per element as 1 and the connectivity just the single vertex defining
> the point element.
>
> - tim
>
> On 01/29/2015 03:34 AM, CORTIS M. wrote:
>
> Dear Tim,
>
> I've got the following problem:
>
> I want to create vertex entities, ie create the points and vertex entities
> using those points.
> So I've create a set of vertices from an array of coordinates.
> And If you try to set the connectivity for every point you get Error code 4
> (MB_ENTITY_NOT_FOUND).
>
> This is my code:
>
> double points[6]={1,0,0, 0,1,0, 0,0,1};
> Range vertices;
> rval = moab.create_vertices(points,2,vertices); CHKERR_PETSC(rval);
> EntityHandle dummy=0;
> rval = moab.set_connectivity(dummy,vertexlist,1); CHKERR_PETSC(rval);
> //Error code 4
>
> Any suggestions how to overcome this problem.
>
> Kind regards,
>
> Michael
>
>
>
> --
> -- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ --
> Paul Wilson ~ UW-Madison ~ 608-263-0807 ~ cal: http://bit.ly/pphw-cal
> Professor, Engineering Physics. ~ http://cnerg.engr.wisc.edu
> Faculty Director, Advanced Computing Infrastructure ~ http://aci.wisc.edu
>
>
>
> --
> -- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ --
> Paul Wilson ~ UW-Madison ~ 608-263-0807 ~ cal: http://bit.ly/pphw-cal
> Professor, Engineering Physics. ~ http://cnerg.engr.wisc.edu
> Faculty Director, Advanced Computing Infrastructure ~ http://aci.wisc.edu
>
>