Common Issues (+1)
Common Issues
| Problem |
Cause |
Solution |
| Empty mesh output |
Missing synchronize() |
Call gmsh.model.geo.synchronize() or gmsh.model.occ.synchronize() before meshing |
| Wrong element types |
Default is triangles |
Use setRecombine() for quads, or RecombineAll option |
| Poor quality at corners |
Sharp angles |
Add local refinement or increase Mesh.Smoothing |
| STEP import fails |
Topology issues |
Enable Geometry.OCCFixDegenerated, OCCFixSmallEdges, OCCSewFaces |
| MSH format not recognized |
Wrong version |
Set Mesh.MshFileVersion to 2.2 for BEM tools |
| Physical groups empty |
Not assigned |
Must define physical groups before write() |
| Transfinite fails |
Incompatible topology |
Surface must be 3 or 4-sided, curves must have matching node counts |
| Size fields ignored |
Other size sources active |
Disable MeshSizeExtendFromBoundary, MeshSizeFromPoints, MeshSizeFromCurvature |
| Crash on large models |
Memory |
Use -nt for parallel meshing, increase verbosity to find bottleneck |
gmsh CLI: /usr/bin/env: 'python': No such file or directory |
pip-installed gmsh wrapper uses #!/usr/bin/env python shebang |
Fix shebang: sed -i 's|python$|python3|' ~/.local/bin/gmsh; or use /usr/bin/gmsh (system binary) |
| pip gmsh shadows system gmsh |
~/.local/bin/gmsh (pip wrapper) takes precedence over /usr/bin/gmsh (native) |
Check type -a gmsh; pip version is Python-only (no GUI), system version has FLTK GUI |
Debugging Tips
# Enable verbose output
gmsh.option.setNumber("General.Verbosity", 99)
# Check model entities
print(gmsh.model.getEntities()) # All entities
print(gmsh.model.getEntities(dim=2)) # Surfaces only
# Check bounding box
xmin, ymin, zmin, xmax, ymax, zmax = gmsh.model.getBoundingBox(-1, -1)
# Visualize interactively
gmsh.fltk.run() # Opens GUI
# Check mesh statistics
gmsh.model.mesh.generate(2)
node_tags, _, _ = gmsh.model.mesh.getNodes()
print(f"Number of nodes: {len(node_tags)}")
elem_types, elem_tags, _ = gmsh.model.mesh.getElements(dim=2)
total_elems = sum(len(t) for t in elem_tags)
print(f"Number of elements: {total_elems}")
1---2name: gmsh-meshing-common-issues3description: Sub-skill of gmsh-meshing: Common Issues (+1).4---56# Common Issues (+1)78## Common Issues91011| Problem | Cause | Solution |12|---------|-------|----------|13| Empty mesh output | Missing `synchronize()` | Call `gmsh.model.geo.synchronize()` or `gmsh.model.occ.synchronize()` before meshing |14| Wrong element types | Default is triangles | Use `setRecombine()` for quads, or `RecombineAll` option |15| Poor quality at corners | Sharp angles | Add local refinement or increase `Mesh.Smoothing` |16| STEP import fails | Topology issues | Enable `Geometry.OCCFixDegenerated`, `OCCFixSmallEdges`, `OCCSewFaces` |17| MSH format not recognized | Wrong version | Set `Mesh.MshFileVersion` to 2.2 for BEM tools |18| Physical groups empty | Not assigned | Must define physical groups before `write()` |19| Transfinite fails | Incompatible topology | Surface must be 3 or 4-sided, curves must have matching node counts |20| Size fields ignored | Other size sources active | Disable `MeshSizeExtendFromBoundary`, `MeshSizeFromPoints`, `MeshSizeFromCurvature` |21| Crash on large models | Memory | Use `-nt` for parallel meshing, increase verbosity to find bottleneck |22| `gmsh` CLI: `/usr/bin/env: 'python': No such file or directory` | pip-installed gmsh wrapper uses `#!/usr/bin/env python` shebang | Fix shebang: `sed -i 's\|python$\|python3\|' ~/.local/bin/gmsh`; or use `/usr/bin/gmsh` (system binary) |23| pip gmsh shadows system gmsh | `~/.local/bin/gmsh` (pip wrapper) takes precedence over `/usr/bin/gmsh` (native) | Check `type -a gmsh`; pip version is Python-only (no GUI), system version has FLTK GUI |242526## Debugging Tips272829```python30# Enable verbose output31gmsh.option.setNumber("General.Verbosity", 99)3233# Check model entities34print(gmsh.model.getEntities()) # All entities35print(gmsh.model.getEntities(dim=2)) # Surfaces only3637# Check bounding box38xmin, ymin, zmin, xmax, ymax, zmax = gmsh.model.getBoundingBox(-1, -1)3940# Visualize interactively41gmsh.fltk.run() # Opens GUI4243# Check mesh statistics44gmsh.model.mesh.generate(2)45node_tags, _, _ = gmsh.model.mesh.getNodes()46print(f"Number of nodes: {len(node_tags)}")47elem_types, elem_tags, _ = gmsh.model.mesh.getElements(dim=2)48total_elems = sum(len(t) for t in elem_tags)49print(f"Number of elements: {total_elems}")50```