feat: add MeepMeshSim for GMSH mesh-based photonic simulations#39
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feat: add MeepMeshSim for GMSH mesh-based photonic simulations#39
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Add an alternative mesh-based workflow for Meep that mirrors Palace's mesh() → write_config() pattern. Produces a GMSH .msh + mesh_config.json that fully describes a photonic problem. - MeepMeshSim class with geometry/source/domain/solver setters - mesh_config.py writer for JSON problem definition - include_airbox flag on generate_mesh (default False for photonics) - gsim.common.mesh module for solver-agnostic GMSH mesh generation - 21 new tests + notebook demo
Palace mesh modules import shared utilities from gsim.common.mesh instead of duplicating them. Also includes auto-generated api.md.
After fragmentation, identify waveguide boundary faces at each gdsfactory port location and assign them as named surface physical groups (port_<name>). Port metadata (center, width, orientation, layer, z_range) is serialized into mesh_config.json. Also hardcode mesh filename to mesh.msh for consistent cloud runner expectations.
…ation The previous truncation `[:len(tags)]` dropped dielectric volume fragments when fragmentation split boxes into more pieces than the original count. Now layer/metal volume tags are collected first and excluded from dielectric groups, ensuring all fragments are assigned without double-counting. Also improved plot_mesh to render per-group with colors by default, with the largest volume (e.g. cladding) as a transparent wireframe so inner structures like waveguide cores are visible.
Adjacent dielectric boxes of the same material are now merged into a single GMSH box (e.g. box+clad SiO2 → one volume), eliminating coincident faces and sliver tets. Different-material boxes sharing a z-boundary use removeAllDuplicates() to cleanly resolve the shared face. Also adds a regression test verifying box/clad XY consistency, improves the mesh summary in notebooks, and removes the plot_mesh_slice feature.
Add mesh_scale param to generate_mesh() for post-generation coordinate scaling. MeepMeshSim passes 1000.0 to convert um→nm. mesh_config.json now includes length_scale (1e-9) and nanometers_per_cell instead of resolution in pixels/um.
Port centers, widths, z_ranges, wavelengths, and domain margins are now written in nm, consistent with length_scale=1e-9 and the mesh coordinates.
- Port normals now computed at mesh generation (generator.py) as 3D unit vectors in the global mesh frame; serializer passes them through verbatim. When ports gain out-of-plane tilt, only the upstream computation changes. - port_surfaces JSON trimmed to the minimum-sufficient contract (phys_group + normal + layer). Center/width/z_range are recoverable from the mesh triangles, so keeping them in JSON duplicated the source of truth. - domain.pml now serialized as integer pml_cells (pml x resolution) instead of a micron value, matching what the solver actually consumes. - mesh_priority added to volumes/layer_volumes, ranked by refractive index (highest n -> priority 1), matching gplugins/femwell/meshwell convention. Adds a port-surfaces pass-through test covering both axis-aligned and out-of-plane-tilted normals.
single-clad notebook uses one dielectric box wrapping the core above and below (one SiO2 physical group); split-clad was re-executed to refresh outputs against the new mesh_config.json schema.
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Summary
MeepMeshSimclass — alternative mesh-based workflow for Meep that mirrors Palace'smesh()→write_config()pattern.msh+mesh_config.jsonthat fully describes a photonic problem (materials, source, monitors, domain, solver)include_airboxflag togenerate_mesh()/add_dielectrics()— defaults toTruefor Palace (RF),Falsefor Meep (photonics)materialfield to volume groups in mesh config JSON for consistency with layer_volumesgsim.common.meshmodule for solver-agnostic GMSH mesh generationTest plan
uv run pytest tests/meep/test_mesh_sim.py -v— 21 new tests passuv run pytest tests/common/test_mesh.py -v— common mesh tests passuv run pytest tests/— all existing tests still passnbs/mesh_ybranch.ipynbproduces.msh+mesh_config.json