[WIP] Gmsh cross-section slicing and modal solver

nbs/modal-sim-cpw/palace.msh

@@ -0,0 +1,155 @@
+$MeshFormat
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+1 13 "air__passive"
+1 14 "airbox__passive"
+1 15 "SiO2__passive"
+1 16 "passive__None"
+1 17 "SiO2__airbox"
+1 18 "SiO2__None"
+1 19 "airbox__None"
+2 8 "air"
+2 9 "passive"
+2 10 "SiO2"
+2 11 "airbox"
+$EndPhysicalNames
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src/gsim/palace/__init__.py

@@ -57,9 +57,11 @@
 from gsim.palace.driven import DrivenSim
 from gsim.palace.eigenmode import EigenmodeSim
 from gsim.palace.electrostatic import ElectrostaticSim
+from gsim.palace.modal import ModalSim
 
 # Mesh utilities
 from gsim.palace.mesh import (
+    CrossSection,
     GroundPlane,
     MeshConfig,
     MeshPreset,
@@ -100,11 +102,12 @@
 )
 
 # Visualization
-from gsim.viz import plot_mesh
+from gsim.viz import plot_mesh, view_mesh
 
 __all__ = [
     "MATERIALS_DB",
     "CPWPortConfig",
+    "CrossSection",
     "DrivenConfig",
     "DrivenSim",
     "EigenmodeConfig",
@@ -123,6 +126,7 @@
     "MeshConfigModel",
     "MeshPreset",
     "MeshResult",
+    "ModalSim",
     "NumericalConfig",
     "PalacePort",
     "PortConfig",
@@ -154,6 +158,7 @@
     "print_stack",
     "print_stack_table",
     "run_simulation",
+    "view_mesh",
 ]
 
 

src/gsim/palace/base.py

@@ -345,8 +345,10 @@ def plot_mesh(
         output: str | Path | None = None,
         show_groups: list[str] | None = None,
         interactive: bool = True,
+        style: str = "wireframe",
+        transparent_groups: list[str] | None = None,
     ) -> None:
-        """Plot the mesh wireframe using PyVista.
+        """Plot the mesh using PyVista.
 
         Requires mesh() to be called first.
 
@@ -356,13 +358,20 @@ def plot_mesh(
                 Example: ["metal", "P"] to show metal layers and ports.
             interactive: If True, open interactive 3D viewer.
                 If False, save static PNG to output path.
+            style: ``"wireframe"`` (default) or ``"solid"``.
+                ``"solid"`` renders faces coloured by physical group
+                with selectable transparent groups.
+            transparent_groups: Physical-group names rendered at low opacity
+                when *style="solid"*.  Defaults to
+                ``["air_none", "air_plastic_enclosure"]``.
 
         Raises:
             ValueError: If output_dir not set or mesh file doesn't exist
 
         Example:
             >>> sim.mesh(preset="default")
             >>> sim.plot_mesh(show_groups=["metal", "P"])
+            >>> sim.plot_mesh(style="solid")
         """
         from gsim.viz import plot_mesh as _plot_mesh
 
@@ -382,4 +391,6 @@ def plot_mesh(
             output=output,
             show_groups=show_groups,
             interactive=interactive,
+            style=style,
+            transparent_groups=transparent_groups,
         )

src/gsim/palace/mesh/__init__.py

@@ -39,6 +39,7 @@
     generate_mesh as generate_mesh_direct,
 )
 from gsim.palace.mesh.pipeline import (
+    CrossSection,
     GroundPlane,
     MeshConfig,
     MeshPreset,
@@ -49,6 +50,7 @@
 from . import gmsh_utils
 
 __all__ = [
+    "CrossSection",
     "GeometryData",
     "GroundPlane",
     "MeshConfig",

src/gsim/palace/mesh/generator.py

@@ -142,6 +142,7 @@ def generate_mesh(
     show_gui: bool = False,
     driven_config: DrivenConfig | None = None,
     write_config: bool = True,
+    cross_section: dict[str, float] | None = None,
     planar_conductors: bool = False,
 ) -> MeshResult:
     """Generate mesh for Palace EM simulation.
@@ -160,6 +161,9 @@ def generate_mesh(
         show_gui: Show gmsh GUI during meshing
         driven_config: Optional DrivenConfig for frequency sweep settings
         write_config: Whether to write config.json (default True)
+        cross_section: Optional cutting plane specification. Pass a dict
+            with exactly one of ``{"x": <value>}`` or ``{"y": <value>}``
+            to slice the 3-D geometry and produce a 2-D mesh instead.
         planar_conductors: If True, treat conductors as 2D PEC surfaces
 
     Returns:
@@ -218,19 +222,33 @@ def generate_mesh(
             planar_conductors,
         )
 
-        # Setup mesh fields
-        logger.info("Setting up mesh refinement...")
-        _setup_mesh_fields(
-            kernel, groups, geometry, stack, refined_mesh_size, max_mesh_size
-        )
+        # Handle optional cross-section cutting plane
+        if cross_section is not None:
+            logger.info("Creating cutting plane for 2-D cross-section...")
+            xmin, ymin, xmax, ymax = geometry.bbox
+            cp_margin = (
+                max(xmax - xmin, ymax - ymin) + margin + air_margin + 500
+            )
+            cut_tag = gmsh_utils.create_cutting_plane(cp_margin, **cross_section)
+            kernel.synchronize()
+            gmsh_utils.slice_with_plane(cut_tag)
+            # Set a reasonable global mesh size for the 2-D case
+            gmsh.option.setNumber("Mesh.MeshSizeMax", max_mesh_size)
+        else:
+            # Setup 3-D mesh fields (not applicable after slicing)
+            logger.info("Setting up mesh refinement...")
+            _setup_mesh_fields(
+                kernel, groups, geometry, stack, refined_mesh_size, max_mesh_size
+            )
 
         # Show GUI if requested
         if show_gui:
             gmsh.fltk.run()
 
-        # Generate mesh
-        logger.info("Generating mesh...")
-        gmsh.model.mesh.generate(3)
+        # Generate mesh (2-D for cross-section, 3-D otherwise)
+        mesh_dim = 2 if cross_section is not None else 3
+        logger.info("Generating %d-D mesh...", mesh_dim)
+        gmsh.model.mesh.generate(mesh_dim)
 
         # Collect mesh statistics
         mesh_stats = collect_mesh_stats()