Regional attributes

General Discussion
1

Hello everyone, may I ask how the Regional attributes in the regionlist are generated when using Tetgen to generate mesh? how to get “145” as follow?

real[int] domain =[1.5,pi,0.75,145,0.0025];
mesh3 Thfinal = tetg(Th33,switch=“paAAQY”,regionlist=domain);

2

I think you get a region number = 145 if the point [1.5,pi,0.75] is in the discrete domain , Pay attention to curved domain.

3

Thank you for your reply, Professor.
I tested using a simple case in the manual, where regional attributes=Th (x, y, z). region, but the results did not match the region list. I hope to receive your further explanation.
tet.edp (9.8 KB)

4

Some correction, remark the region number od meshS is the surface number non a volume number.


 load "tetgen" 
  {   
    real hs = 0.1;  // mesh size on sphere 
    int[int]  N=[20,20,20];
    real [int,int]  B=[[-1,1],[-1,1],[-1,1]];
    int [int,int]  L=[[1,2],[3,4],[5,6]];
    
    ////////////////////////////////
    meshS ThH = SurfaceHex(N,B,L,1);
    meshS ThS =Sphere(0.5,hs,7,1); // "gluing" surface meshs to tolat boundary meshes
    cout << " xxxx" << ThH.nv << " " << ThS.nv << endl;
    
    meshS ThHS=ThH+ThS;
    plot(ThHS);
// soory MeshS no mesh3 wrong ..
   real voltet=(hs^3)/6.;
    cout << " voltet = " << voltet << endl;
    real[int] domaine = [0,0,0,1,voltet,0,0,0.7,2,voltet];
  
    mesh3 Th = tetg(ThHS,switch="pqaAAYYQ",nbofregions=2,regionlist=domaine);    
    cout << "3d regions " << regions(Th) << endl; 
   cout << " Th 3d = (0,0,0) " << Th(0,0,0).region<< endl;
  cout << " Th 3d = (0,0,0.7)" << Th(0,0,0.7).region<< endl;
   plot(Th,wait=1);
  }
5

Thank you for your reply, Professor. If this number comes from a 3D mesh, but the 3D mesh requires this number to be generated, is this contradictory? For example, in the following case, how to determine this number in “int [int] domain”?
test.edp (2.1 KB)

6

The 4th argument (out of 5) of each region description in “regionlist” sets the label. You can choose it as you like!
If you define as in your file
real[int] domaine = [0.2,0.2,1,0,voltet];
then the label of the region will be 0.
If you set
real[int] domaine = [0,0,0,1,voltet,0,0,0.7,2,voltet];
then you will have two regions, the first with region label 1, and the second with region label 2.

8

Thank you for your help, Professor. In the following case, I did this, but the program process was killed without any errors，can you help me? please
test.edp (2.2 KB)

9

I don’t see any problem in your code, it terminates normally after doing what it is asked to do!

10

Thank you, professor. I am looking for the reason for its abnormal termination. Have a good day

11

Make a brief mark here so that friends who have the same questions as me can refer to it. Thank you again to the two professors.
Solution: 1. The number in the region list {4th} can be given freely by oneself; 2. If the program terminates inexplicably, check if (x, y, z) in the regionlist exceeds the limit