# Level-set with parmmg3d

**URL:** <https://community.freefem.org/t/level-set-with-parmmg3d/4257>\
**Category:** General Discussion\
**Created:** [April 18, 2026, 2:08pm UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257 "2026-04-18T14:08:28Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![GiacomoSperoni97](https://avatars.discourse-cdn.com/v4/letter/g/ecc23a/32.png) [@GiacomoSperoni97](https://community.freefem.org/u/GiacomoSperoni97)\
**Post date:** [April 18, 2026, 2:08pm UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257/1 "2026-04-18T14:08:28Z")

</div>

Dear FreeFem users,

I am trying to use `parmmg3d` from FreeFEM in level-set mode, but I am not sure whether this functionality is actually supported by the current FreeFEM interface to ParMmg.

From reading the `parmmg.cpp` plugin source in FreeFEM, it seems that the parameters

- `iso`
- `ls`

do exist and are forwarded to the ParMmg API. However, in practice, the call does not seem to modify the mesh. So, is ParMmg level-set mode really supported through `parmmg3d` in FreeFEM?

In a minimal test, if I run ParMmg externally from the shell with something like

```bash
parmmg_O3 -in mesh.mesh -sol phi.sol -ls 0 -out out.mesh

```

the level-set mode seems to be available.

But when I call it from FreeFEM with `parmmg3d(..., metric=..., ls=0)`, the mesh does not change, and I also get the message

```plaintext
## Error: MMG5_scale_scalarMetric: at least 1 wrong metric.

```

Here is a minimal example:

```bash
load "mshmet"
load "PETSc"
load "parmmg"
load "medit"
macro dimension()3// EOM
include "macro_ddm.idp"

func real Heav(real x, real beta, real eta)
{
  return (tanh(beta*eta) + tanh(beta*(x-eta))) /
         (tanh(beta*eta) + tanh(beta*(1.0-eta)));
}

int[int] fforder = [1];
real err = 0.05;
int n = 15;

mesh3 Th3=cube(n,n,n);
mesh3 ThBackup = Th3;

Mat A;
int[int] n2o;
NewMacro Th3N2O() n2o EndMacro
DmeshCreate(Th3);

MatCreate(Th3, A, P1);
fespace Vh(Th3, P1);
Vh u;
plotDmesh(Th3, cmm = "Th3");

Vh uh = sqrt((x-0.5)^2 + (y-0.5)^2 + (z-0.5)^2) - 0.3;
// Smooth
uh[] += 0.5;
uh = Heav(uh, 40, 0.5) - 0.5;

fespace VhBackup(ThBackup, P1);
VhBackup h, hReduced;
uh[] .*= A.D;
int[int] rest = restrict(Vh, VhBackup, n2o);
for[i, v : rest] h[][v] = uh[][i];
mpiAllReduce(h[], hReduced[], mpiCommWorld, mpiSUM); // centralize distributed solution

// real[int] met = mshmet(ThBackup, hReduced, aniso = 0, hmin = 1.0e-3, hmax = 2.0e-1, err = err);
ThBackup = parmmg3d(ThBackup, metric = uh[], hgrad = 2.3, verbose=3, ls=0);
Th3 = ThBackup;
Mat Adapt;
MatCreate(Th3, Adapt, P1);
A = Adapt;
cout << "mpirank # " << mpirank << " : Th3.nv " << Th3.nv << ", Th3.nt " << Th3.nt << endl;
plotDmesh(Th3, cmm = "Th3Adapt");

```

Thank you

---

<div class="post-metadata">

**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [April 20, 2026, 6:34am UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257/2 "2026-04-20T06:34:38Z")

</div>

You are missing the `iso = 1` parameter to make this work with `mmg3d`. It still doesn’t work with `parmmg3d`, though. Where are the `mesh.mesh`, `phi.sol`, and `out.mesh` coming from in your test?

---

<div class="post-metadata">

**Author:** ![GiacomoSperoni97](https://avatars.discourse-cdn.com/v4/letter/g/ecc23a/32.png) [@GiacomoSperoni97](https://community.freefem.org/u/GiacomoSperoni97)\
**Post date:** [April 23, 2026, 8:25am UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257/3 "2026-04-23T08:25:35Z")

</div>

Dear @prj, thank you!  
I called `parmmg` from the terminal with the centralized saved mesh `ThBackup` and the solution `hReduced`, by just including

```auto
if(mpirank == 0){
    savemesh(ThBackup, "mesh.mesh");
    savesol("phi.sol", ThBackup, hReduced);
}

```

before the FreeFem call to parmmg.  
I attach here the full code

```auto
load "mshmet"
load "PETSc"
load "parmmg"
load "medit"
macro dimension()3// EOM
include "macro_ddm.idp"

func real Heav(real x, real beta, real eta)
{
  return (tanh(beta*eta) + tanh(beta*(x-eta))) /
         (tanh(beta*eta) + tanh(beta*(1.0-eta)));
}

int[int] fforder = [1];
real err = 0.05;
int n = 15;

mesh3 Th3=cube(n,n,n);
mesh3 ThBackup = Th3;

Mat A;
int[int] n2o;
NewMacro Th3N2O() n2o EndMacro
DmeshCreate(Th3);

MatCreate(Th3, A, P1);
fespace Vh(Th3, P1);
Vh u;
plotDmesh(Th3, cmm = "Th3");

Vh uh = sqrt((x-0.5)^2 + (y-0.5)^2 + (z-0.5)^2) - 0.3;
// Smooth
uh[] += 0.5;
uh = Heav(uh, 40, 0.5) - 0.5;

fespace VhBackup(ThBackup, P1);
VhBackup h, hReduced;
uh[] .*= A.D;
int[int] rest = restrict(Vh, VhBackup, n2o);
for[i, v : rest] h[][v] = uh[][i];
mpiAllReduce(h[], hReduced[], mpiCommWorld, mpiSUM); // centralize distributed solution

// real[int] met = mshmet(ThBackup, hReduced, aniso = 0, hmin = 1.0e-3, hmax = 2.0e-1, err = err);

if(mpirank == 0){
    savemesh(ThBackup, "mesh.mesh");
    savesol("phi.sol", ThBackup, hReduced);
}

ThBackup = parmmg3d(ThBackup, metric = uh[], hgrad = 2.3, verbose=3, ls=0);
Th3 = ThBackup;
Mat Adapt;
MatCreate(Th3, Adapt, P1);
A = Adapt;
cout << "mpirank # " << mpirank << " : Th3.nv " << Th3.nv << ", Th3.nt " << Th3.nt << endl;
plotDmesh(Th3, cmm = "Th3Adapt");

```

Thanks, Giacomo

---

<div class="post-metadata">

**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [April 23, 2026, 1:33pm UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257/4 "2026-04-23T13:33:04Z")

</div>

Thanks, I have reproduced the issue and I’m working on a fix. Should be good in a couple of minutes.

---

<div class="post-metadata">

**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [April 23, 2026, 1:47pm UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257/5 "2026-04-23T13:47:35Z")

</div>

Fixed in [Fix ParMmg in level-set mode · FreeFem/FreeFem-sources@2cb676e · GitHub](https://github.com/FreeFem/FreeFem-sources/commit/2cb676e86f1ed5a78279791eb476d94dbf71b0ce). You also need to fix your `.edp`: you are missing the `iso = 1` parameter, and you should use `hReduced[]` instead of `uh[]` for the `metric` argument. Let me know if you run into other issues. Thanks for the report.

---

<div class="post-metadata">

**Author:** ![GiacomoSperoni97](https://avatars.discourse-cdn.com/v4/letter/g/ecc23a/32.png) [@GiacomoSperoni97](https://community.freefem.org/u/GiacomoSperoni97)\
**Post date:** [April 25, 2026, 1:26pm UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257/6 "2026-04-25T13:26:05Z")

</div>

Wow, thanks a lot!  
Yes, you are right, I need to call parmmg as  
`ThBackup = parmmg3d(ThBackup, metric = hReduced[], hgrad = 2.3, verbose=3, ls=0, iso=1); `

I’ve recompiled FreeFem, in the `develop` branch, but the error `## Error: MMG5_scale_scalarMetric: at least 1 wrong metric.` persists.

I also notice that by calling parmmg with a metric (computed e.g. with meshmet) instead of `hReduced` and `iso=1`, and looking at the output of parmmg, the isovalue discretization option seems to be activated:

```auto
  &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
   MODULE PARMMGLIB_CENTRALIZED: IMB-LJLL : 1.5.0 (Nov. 01, 2024)
  &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
     git branch: HEAD
     git commit: cd8a6e340e466e857b0bb9952f115d8999337167
     git date: 2024-11-01 09:12:00 +0100

  -- PMMG: CHECK INPUT DATA
  -- CHECK INPUT DATA COMPLETED. 0.000s

  -- PHASE 1 : ANALYSIS AND MESH DISTRIBUTION

  -- ANALYSIS
  -- PARALLEL MESH QUALITY 4096 20250
     BEST 0.657267 AVRG. 0.657267 WRST. 0.657267 (ELT 251)
     HISTOGRAMM: 100.00 % > 0.12

  -- PHASE 1a: ISOVALUE DISCRETIZATION     

 Unexpected error: Segmentation fault

```

I know that the metric information and the iso-requirement are not compatible in this case, it was only a test. Hope that it helps.

Thank you again,  
Giacomo

---

<div class="post-metadata">

**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\
**Post date:** [April 25, 2026, 7:15pm UTC](https://community.freefem.org/t/level-set-with-parmmg3d/4257/7 "2026-04-25T19:15:45Z")

</div>

I cannot reproduce the error.

```auto
'/Volumes/Data/repositories/petsc/arch-darwin-c-opt-real/bin/mpiexec' -n 4 /Volumes/Data/repositories/FreeFem-sources-opt/src/mpi/FreeFem++-mpi -nw 'parmmg.edp' -v 0

  &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
   MODULE PARMMGLIB_CENTRALIZED: IMB-LJLL : 1.5.0 (Nov. 01, 2024)
  &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
     git branch: HEAD
     git commit: cd8a6e340e466e857b0bb9952f115d8999337167
     git date: 2024-11-01 09:12:00 +0100

  -- PMMG: CHECK INPUT DATA
  -- CHECK INPUT DATA COMPLETED. 0.000s

  -- PHASE 1 : ANALYSIS AND MESH DISTRIBUTION

  -- ANALYSIS
  -- PARALLEL MESH QUALITY 4096 20250
     BEST 0.657267 AVRG. 0.657267 WRST. 0.657267 (PROC 0 - ELT 251)
     HISTOGRAMM: 100.00 % > 0.12

  -- PHASE 1a: ISOVALUE DISCRETIZATION     
  -- PHASE 1a COMPLETED 0.037s
       LS discretization OK: no non-manifold topology.

  -- ANALYSIS COMPLETED 0.067s

  -- PARTITIONING
  -- PARTITIONING COMPLETED 0.021s
  -- PHASE 1 COMPLETED. 0.088s

  -- PHASE 2 : ISOTROPIC MESHING

  ## Warning: MMG3D_chkmani: at least 1 tetra with 4 boundary faces.

  -- PARALLEL MESH QUALITY 1087 5890
     BEST 0.993480 AVRG. 0.652338 WRST. 0.089281 (PROC 1 - ELT 1111)
     HISTOGRAMM: 99.90 % > 0.12
  -- PHASE 2 COMPLETED. 0.768s

  -- PHASE 3 : MERGE MESHES OVER PROCESSORS
  -- PHASE 3 COMPLETED. 0.001s

  -- PHASE 4 : MESH PACKED UP
  -- PHASE 4 COMPLETED. 0.000s

   PARMMGLIB_CENTRALIZED: ELAPSED TIME 0.858s

  &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
   END OF MODULE PARMMGLIB_CENTRALIZED: IMB-LJLL 
  &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
mpirank # 0 : Th3.nv 507, Th3.nt 2312
mpirank # 1 : Th3.nv 524, Th3.nt 2375
mpirank # 2 : Th3.nv 534, Th3.nt 2375
mpirank # 3 : Th3.nv 557, Th3.nt 2491

```