CGAL users discussion list

[Burak ER <>]

Hi,

I really need an answer urgently, please.

Burak

Cts, 2013-10-26 tarihinde 23:18 +0300 saatinde, Burak ER yazdı:
> Hi,
> 
> Would you please guide me to achieve a meshing procedure where I only
> set the minimum element volume. Therefore, I have the ability to change
> the mesh density with having it uniform with using a single parameter.
> Is it possible? Can you provide me a simple example of code?
> 
> Thank you in advance.
> 
> Burak 
> 
> Cum, 2013-10-25 tarihinde 16:48 +0200 saatinde, Sebastien Loriot
> (GeometryFactory) yazdı:
> > On 10/25/2013 04:44 PM, Burak ER wrote:
> > > Hi Sebastien,
> > >
> > > I am now having difficulties with the space filling tetrahedrons. They
> > > are too small[1] when compared to other tetrahedrons. How can I prevent
> > > this behavior?
> > >
> > > Sorry for these newbie questions.
> > 
> > 
> > I guess it's coming from the way you protected the sharp edges. You need 
> > to reduce the number of protecting balls on the sharp edges.
> > 
> > Sebastien.
> > 
> > 
> > >
> > > Thank you.
> > >
> > > Burak
> > >
> > > [1]http://s10.postimg.org/rblr196hl/Screenshot_from_2013_10_25_17_40_10.png
> > >
> > > Cum, 2013-10-25 tarihinde 16:13 +0300 saatinde, Burak ER yazdı:
> > >> Thank you,
> > >>
> > >> This solved my problem.
> > >>
> > >> Burak ER
> > >>
> > >> Cum, 2013-10-25 tarihinde 12:03 +0200 saatinde, Sebastien Loriot
> > >> (GeometryFactory) yazdı:
> > >>> You need to protect the edges of your box.
> > >>>
> > >>> One solution is to do like this example:
> > >>> http://doc.cgal.org/latest/Mesh_3/index.html#Mesh_3MeshingDomainswithSharpFeatures
> > >>>
> > >>> or to protect them by hand.
> > >>>
> > >>> Sebastien.
> > >>>
> > >>> On 10/25/2013 11:20 AM, Burak ER wrote:
> > >>>> Sorry for the not working link. You can find it here.
> > >>>> <http://s16.postimg.org/pv4ehn3et/Screenshot_from_2013_10_25_12_17_21.png>
> > >>>>
> > >>>> Cum, 2013-10-25 tarihinde 12:14 +0300 saatinde, Burak ER yazdı:
> > >>>>> Dear Sebastian,
> > >>>>>
> > >>>>> This may not be a minimal example. I have created a python interface
> > >>>>> for my application. Within this interface I divide the off file into
> > >>>>> tetrahedrons with CGAL c++ api on the background. I use this
> > >>>>> generation code on the c++ side;
> > >>>>>
> > >>>>> #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
> > >>>>> #include <CGAL/Mesh_triangulation_3.h>
> > >>>>> #include <CGAL/Mesh_complex_3_in_triangulation_3.h>
> > >>>>> #include <CGAL/Mesh_criteria_3.h>
> > >>>>> #include <CGAL/Polyhedral_mesh_domain_3.h>
> > >>>>> #include <CGAL/make_mesh_3.h>
> > >>>>> #include <CGAL/refine_mesh_3.h>
> > >>>>> #include <iostream>
> > >>>>> // IO
> > >>>>> #include <CGAL/IO/Polyhedron_iostream.h>
> > >>>>>
> > >>>>> // Domain
> > >>>>> typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
> > >>>>> typedef CGAL::Polyhedron_3<K> Polyhedron;
> > >>>>> typedef CGAL::Polyhedral_mesh_domain_3<Polyhedron, K> Mesh_domain;
> > >>>>>
> > >>>>> // Triangulation
> > >>>>> typedef CGAL::Mesh_triangulation_3<Mesh_domain>::type Tr;
> > >>>>> typedef CGAL::Mesh_complex_3_in_triangulation_3<Tr> C3t3;
> > >>>>>
> > >>>>> // Criteria
> > >>>>> typedef CGAL::Mesh_criteria_3<Tr> Mesh_criteria;
> > >>>>>
> > >>>>> // To avoid verbose function and named parameters call
> > >>>>> using namespace CGAL::parameters;
> > >>>>>
> > >>>>> class MeshElement;
> > >>>>>
> > >>>>> void Mesh(void)
> > >>>>> {
> > >>>>>
> > >>>>>    boost::filesystem::path mypath(filename);
> > >>>>>    std::ifstream input(filename.data());
> > >>>>>
> > >>>>>    if(mypath.extension()!=boost::filesystem::path(".off")){
> > >>>>>    std::string errormessage ="Invalid extension is specified with 
> > >>>>> the
> > >>>>> mesh file";
> > >>>>>    throw std::invalid_argument(errormessage);
> > >>>>>    }
> > >>>>>
> > >>>>>    // Create input polyhedron
> > >>>>>    Polyhedron polyhedron;
> > >>>>>
> > >>>>>    input >> polyhedron;
> > >>>>>
> > >>>>>    // Create domain
> > >>>>>    Mesh_domain domain(polyhedron);
> > >>>>>
> > >>>>>    // Mesh criteria (no cell_size set)
> > >>>>>    Mesh_criteria criteria(facet_angle, facet_size,
> > >>>>> facet_distance,/*facet_topology*/
> > >>>>>                           cell_radius_edge_ratio, cell_size);
> > >>>>>
> > >>>>>    // Mesh generation
> > >>>>>    c3t3.clear();
> > >>>>>
> > >>>>>    c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria, no_perturb(),
> > >>>>> no_exude());
> > >>>>>
> > >>>>>    elems.clear();// clear our vector
> > >>>>>
> > >>>>>    interfacingpairs.clear();
> > >>>>>
> > >>>>>    handlemap.clear();
> > >>>>>
> > >>>>>    elems.resize(c3t3.number_of_cells_in_complex()); // resize it as 
> > >>>>> the
> > >>>>> new number of elements
> > >>>>>
> > >>>>>    size_t i=0;
> > >>>>>    /*
> > >>>>>     * This is not a nice way to index elements
> > >>>>>     * we could use cell_with_info structure of cgal but really how 
> > >>>>> to
> > >>>>> use that? No tutorial, no example at all on its document!!!
> > >>>>>     *
> > >>>>>     * */
> > >>>>>    for(C3t3::Cells_in_complex_iterator
> > >>>>> it=c3t3.cells_begin();it!=c3t3.cells_end();it++){
> > >>>>>
> > >>>>>    //Create new elements
> > >>>>>
> > >>>>>    //share_ptr handles deletion of the newly created element
> > >>>>>    elems[i]=shared_ptr<MeshElement>(new Linear4NodeTetMeshElem(it));
> > >>>>>
> > >>>>>    //Give an index to handle
> > >>>>>    handlemap[it]=i;
> > >>>>>    i++;
> > >>>>>    }
> > >>>>>    // Add interactions
> > >>>>>    for(C3t3::Cells_in_complex_iterator
> > >>>>> it=c3t3.cells_begin();it!=c3t3.cells_end();it++){
> > >>>>>
> > >>>>>              //For each neighbor of the currrent iterator
> > >>>>> for(int j=0;j<4;j++)
> > >>>>>          {
> > >>>>>
> > >>>>>       C3t3::Cell_handle neigh=it->neighbor(j);
> > >>>>>
> > >>>>> /*Check if we have this neighbor handle*/
> > >>>>> if(c3t3.is_in_complex(neigh))
> > >>>>> {
> > >>>>> size_t indexel=handlemap[it];
> > >>>>> size_t indexneigh=handlemap[neigh];
> > >>>>>
> > >>>>> //Get element and its neighbors from element list
> > >>>>> shared_ptr<MeshElement> el;
> > >>>>> shared_ptr<MeshElement> neighel;
> > >>>>>         //Change the ordering of the elements
> > >>>>>          if(indexel<indexneigh){
> > >>>>> el=elems[indexel];
> > >>>>> neighel=elems[indexneigh];}
> > >>>>>           else{
> > >>>>> neighel=elems[indexel];
> > >>>>>          el=elems[indexneigh];
> > >>>>> }
> > >>>>>
> > >>>>>
> > >>>>> nodePairsIndices indiceofpairs;
> > >>>>>
> > >>>>> //Get shared node list
> > >>>>> indiceofpairs=getNodeCon(el,neighel);
> > >>>>>
> > >>>>>         //check if there is a face share
> > >>>>>           if(indiceofpairs.size()>=3)
> > >>>>> {
> > >>>>> //Create the pair
> > >>>>> ElementPair pair(el,neighel,indiceofpairs);
> > >>>>>
> > >>>>> //Add it into the interfacing pair list
> > >>>>>          if(!interfacingpairs[pair])
> > >>>>> {
> > >>>>>
> > >>>>> interfacingpairs[pair]=shared_ptr<ElementPair>(new
> > >>>>> ElementPair(el,neighel,indiceofpairs));
> > >>>>>
> > >>>>> }
> > >>>>> }
> > >>>>>    }
> > >>>>>                    }
> > >>>>>
> > >>>>> }
> > >>>>>    std::cout<<"Meshing is complete "<<std::endl;
> > >>>>>    std::cout<<"Number of tetrahedral elements 
> > >>>>> "<<elems.size()<<std::endl;
> > >>>>>    std::cout<<"Number of interaction elements
> > >>>>> "<<interfacingpairs.size()<<std::endl;
> > >>>>> }
> > >>>>>
> > >>>>> Using this function and the  off file in the attachment;
> > >>>>>
> > >>>>> When I use the parameters as
> > >>>>> facet_angle=33,
> > >>>>> facet_distance=.6,
> > >>>>> facet_size=0.6,
> > >>>>> cell_radius_edge_ratio=0.11,
> > >>>>> cell_size=1e-3
> > >>>>>
> > >>>>> The result is 5580 elements and they are distributed as here 
> > >>>>> <http://>
> > >>>>> where you can see the empty parts on the boundary of the plate.
> > >>>>>
> > >>>>> Also slight change on the cell_radius_edge_ratio=0.15 makes it even
> > >>>>> worser as here.
> > >>>>> <http://s14.postimg.org/o8j6yl07l/Screenshot_from_2013_10_25_12_08_06.png>
> > >>>>>
> > >>>>> What do you think the problem is?
> > >>>>>
> > >>>>> Burak
> > >>>>>
> > >>>>> Cum, 2013-10-25 tarihinde 09:28 +0200 saatinde, Sebastien Loriot
> > >>>>> (GeometryFactory) yazdı:
> > >>>>>> It might help if you share a minimal example showing the pb.
> > >>>>>>
> > >>>>>> Sebastien.
> > >>>>>>
> > >>>>>> On 10/25/2013 09:26 AM, Burak ER wrote:
> > >>>>>>> Dear Cgal Users,
> > >>>>>>>
> > >>>>>>> I really need help on this problem. Still waiting for an answer.
> > >>>>>>>
> > >>>>>>> Thank you in advance.
> > >>>>>>>
> > >>>>>>> Burak ER
> > >>>>>>>
> > >>>>>>> Pzt, 2013-10-21 tarihinde 18:40 +0300 saatinde, Burak ER yazdı:
> > >>>>>>>> Dear Cgal Users,
> > >>>>>>>>
> > >>>>>>>> I am trying to mesh a rectengular prism domain from an off file 
> > >>>>>>>> into
> > >>>>>>>> tetrahedral elements using cgal. But whatever parameters I use 
> > >>>>>>>> within
> > >>>>>>>> criteria structure, I get a mesh where the boundaries are not 
> > >>>>>>>> conserved
> > >>>>>>>> rather they are "uneven".
> > >>>>>>>>
> > >>>>>>>> What may cause that? How to force keeping boundaries exact while
> > >>>>>>>> meshing?
> > >>>>>>>>
> > >>>>>>>> Thank you in advance.
> > >>>>>>>>
> > >>>>>>>> --
> > >>>>>>>> Burak ER
> > >>>>>>>>
> > >>>>>>>> Research Assistant
> > >>>>>>>> Mechanical Engineering Department
> > >>>>>>>> Bursa Technical University
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>> --
> > >>>> Burak ER 
> > >>>> <
> > >>>>  
> > >>>> <mailto:>>
> > >>>>
> > >>>>
> > >>>> Bu elektronik posta ve ekleri sadece adreste belirtilen kisi veya
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> > >>>> mesaji
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> > >>>> ne
> > >>>> sekilde olursa olsun ucuncu kisiler ile paylasilmasi hukuki ve cezai
> > >>>> sorumluluk dogurabilir. Bursa Teknik Universitesi'nin, bu mesaj ve
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> > >>>>
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> > >>>
> > >>>
> > >>
> > >> --
> > >> Burak ER 
> > >> <>
> > >>
> > >>
> > >>
> > >
> > 
> > 
> 
> -- 
> Burak ER 
> <>
> 
> 
> 

-- 
Burak ER 
<>