Tetrahedral Mesh¶

The tetrahedral mesh is the basis for most simulated object types in Mesh Deformations.

MAGES uses tetrahedral meshes stored in .msh files. If you already have an .msh file, drag and drop it into the project’s Assets folder. The mesh will be imported automatically and will be ready to use in the next steps of the workflow.

If your starting point is a surface mesh (an .stl file, or any mesh already imported into Unity), you must first convert it into a tetrahedral volumetric mesh. You can do this inside the Unity editor with the Tetrahedralize window, or externally with third-party tools such as Salome-Meca and Gmsh.

Tetrahedralizing in the Unity Editor¶

The Tetrahedralize window converts a Unity Mesh directly into a .msh asset, without leaving the editor. Open it from ORamaVR Creator > Mesh Deformations > Tetrahedralize…, or right-click a mesh asset and choose ORamaVR Creator > Tetrahedralize… to pre-fill the mesh field.

1. Assign the Mesh to tetrahedralize.

2. Pick a Tetrahedralizer:

   • NetGen — a full NetGen-based mesher with detailed controls (mesh size, fineness, grading, optimization steps, and so on). Best quality and control.

   • Simple — a lightweight built-in tetrahedralizer with a couple of parameters (interior spacing, weld distance). Handy for quick tests.

3. Adjust the tetrahedralizer’s parameters as needed.

4. (Optional) Enable Also bake wedge UVs (.tetuv). When the input mesh is UV-mapped and the selected tetrahedralizer supports it, this also writes a per-wedge UV (.tetuv) sidecar beside the .msh, sourced from the input mesh’s UV seams. That sidecar can be assigned straight to a dynamic softbody — see Texturing.

5. Click Run and choose a save location inside the project’s Assets folder. The resulting .msh is imported automatically.

Tetrahedralizing with External Tools¶

Use this route when you need a mesher outside of Unity. It converts an .stl into a .msh using Salome-Meca and Gmsh. The steps below cover preparing the input, tetrahedralizing single or multiple regions, and exporting the result for Unity.

Before You Start¶

For tetrahedralization, the input .stl should be:

• enclosed (watertight)

• triangulated

• free of self-intersections

The result of this process is a tetrahedral volumetric mesh that can be exported as an .msh file and imported into Unity.

Tetrahedralizing a Single Region¶

Use this workflow when the model should become one tetrahedral volume.

1. Open Salome-Meca.

2. Switch to the Geometry module.

   

3. Import the .stl file.

   

4. Click New Entity > Build > Solid and create a solid from the imported STL geometry.

   

5. Switch to the Mesh module.

   

6. Click Mesh > Create Mesh.

   

7. For Geometry, select the solid you created.

   

8. Set the algorithm to NetGen 1D-2D-3D and create a hypothesis with the default values and click Apply and Close.

   

9. In the Object Browser, right-click the created mesh and select Compute Mesh.

The tetrahedral mesh may appear with a warning icon before computation. This is expected.

If you need a finer or coarser result:

1. Right-click the hypothesis and select Edit Hypothesis.

2. Adjust the values and click OK.

3. Right-click the mesh and select Clear Mesh Data.

4. Right-click the mesh again and select Compute Mesh.

Tetrahedralizing Multiple Regions¶

Use this workflow when the model contains multiple regions that you want to preserve in the tetrahedral mesh.

1. Open Salome-Meca.

2. Switch to the Geometry module.

   

3. Import the .stl file.

   

4. Click New Entity > Build > Solid and create solids from the imported geometry.

   

5. Select the objects that should be combined and click Operations > Partition.

   

6. Use Explode with Solid as the type so the partitioned result is split into separate solid regions.

7. Switch to the Mesh module.

   

8. Click Mesh > Create Mesh.

   

9. For Geometry, select the solid or partitioned result you want to tetrahedralize.

10. Set the algorithm to NetGen 1D-2D-3D and create a hypothesis with the default values and click Apply and Close.

    

11. In the Object Browser, right-click the created mesh and select Compute Mesh.

You can refine the result in the same way as in the single-region workflow by editing the hypothesis, clearing the mesh data, and computing the mesh again.

Exporting for Unity¶

After tetrahedralization is complete, export the mesh from Salome-Meca and then convert it in Gmsh.

Salome-Meca¶

1. In Salome-Meca, right-click the mesh and select Export Mesh.

2. Export the mesh as either GMF or MED.

3. Close Salome-Meca once the export is complete.

Gmsh¶

1. Open Gmsh.

2. Click File > Open and load the exported mesh.

3. Click File > Export and export it as an .msh file.

4. When exporting from Gmsh, choose Version 2 ASCII.

5. Drag and drop the resulting .msh file into your Unity project’s Assets folder.