Hi Kassandra,
The process described above using alphaShape and triangulation is intended to create a surface mesh, not a volumetric mesh. Here's how you can confirm and understand the distinction:
Surface Mesh vs. Volumetric Mesh
- Surface Mesh: Represents only the outer boundary of a 3D object. It consists of vertices, edges, and faces (usually triangles), and is typically used for visualization, rendering, and surface analysis.
- Volumetric Mesh: Represents the entire volume of a 3D object, including its interior. It consists of elements like tetrahedra or hexahedra and is used for simulations such as finite element analysis (FEA).
Confirmation Steps
- Examine the Output Structure:
- The triangulation object created from boundaryFacets contains only vertices and triangular faces, indicating a surface mesh.
- You can inspect the TR object in MATLAB to see that it only includes surface information:
TR.Points % Lists vertices
TR.ConnectivityList % Lists triangular faces
2. Visual Inspection:
- Visualize the mesh using MATLAB's plotting functions to confirm it's a surface:
trisurf(TR, 'FaceColor', 'cyan', 'EdgeColor', 'none');
axis equal;
camlight;
lighting gouraud;
- This visualization will show only the outer shell of the object, characteristic of a surface mesh.
3. STL File Format:
- The STL file format itself is inherently a surface representation format. It describes 3D geometries using only triangular facets without any volumetric information.
Creating a Volumetric Mesh
If you need a volumetric mesh, you would typically use software or libraries specifically designed for this purpose, such as:
- TetGen: For generating tetrahedral meshes.
- Gmsh: A 3D finite element mesh generator with built-in pre- and post-processing facilities.
- CGAL: The Computational Geometry Algorithms Library for more complex meshing tasks.
These tools take a surface mesh and fill the interior with volumetric elements, which can then be used for simulations or analyses that require volumetric data.
