Hypermesh

Local MCP server for driving Altair HyperMesh with generated Tcl scripts.

The MCP is intentionally geometry-rule based. It does not assign mesh strategies by hard-coded component names from one model.

Execution Modes

• Batch mode: run Tcl through hmbatch.exe.
• Visible GUI mode: open HyperMesh, source the generated GUI listener Tcl, then send Tcl into the visible session with execute_tcl_gui.

Visible GUI mode only changes where Tcl is executed. Strategy selection, Tcl generation, and input/output paths remain explicit.

Raw meshing Tcl is guarded by default. execute_tcl and execute_tcl_gui reject direct meshing commands such as *meshdragelements*, *set_meshedgeparams, *meshspinelements*, *defaultmeshsurf_growth, and *tetmesh unless the script was produced by one of the MCP strategy generators. This prevents agents from bypassing balanced drag seeding, cut-section validation, and gear-local refinement rules.

Main Tools

• locate_hypermesh: find candidate HyperMesh batch and GUI executables.
• check_hypermesh_connection: verify batch startup.
• create_gui_listener_tcl: create a Tcl listener for an already opened GUI.
• start_hypermesh_gui_listener: try to launch visible HyperMesh with the GUI listener.
• execute_tcl: run raw Tcl through batch mode.
• execute_tcl_gui: run raw Tcl in the visible GUI listener session.
• get_hypermesh_meshing_strategy: return generic meshing rules and workflows.
• get_meshing_rules: return structured generic tetra/drag/spin rules.
• classify_hypermesh_part_strategy: classify a part by geometry features.
• generate_geometry_probe_tcl: generate a temporary coarse surface-mesh probe for all or selected solids; probe elements and nodes are deleted before return.
• run_geometry_probe_gui: run that temporary probe in the visible GUI and return MCP_PROBE_SOLID lines for per-object sizing/strategy planning.
• recommend_tetra_sizes_from_probe_lines: turn probe lines into per-solid tetra element-size recommendations, reducing size for thin/small bodies.
• generate_surface_automesh_tcl: generate simple surface automesh Tcl.
• generate_surface_deviation_rtrias_tcl: generate surface deviation + R-trias Tcl.
• generate_gear_aware_tetra_tcl: generate gear/tooth local-refinement tetra Tcl.
• generate_guarded_drag_hex_tcl: generate guarded drag-hex Tcl.
• generate_guarded_spin_hex_tcl: generate guarded spin-hex Tcl for a known true section.
• get_cutsection_spin_workflow: explain the generic cut-section spin workflow.
• generate_cutsection_spin_hex_tcl: generate cut-section spin Tcl for stepped or recessed revolved solids.

Generic Strategy Rules

Use classify_hypermesh_part_strategy and geometry facts, not component names. The intended order is:

1. Try the structured hex route that matches the geometry: drag, spin, or cut-section spin.
2. Validate that real 3D hex elements were created. A leftover 2D section mesh by itself is a failure.
3. If the hex route fails, clean up temporary/invalid elements and mesh that object with tetra.
4. For bearing/ring-like revolved bodies, do not stop after direct spin fails. Use a real cut plane through the rotation axis, mesh the true radial section, and spin that section before tetra fallback.

Tetra

Use tetra_surface_deviation_rtrias for:

• flanges or flange-like bodies
• bodies with bolt holes, local holes, bosses, protrusions, ribs, grooves, cutouts, or non-sweepable topology
• ambiguous parts where a clean drag/spin source cannot be proven

Required checks:

• create 2D surface-deviation R-trias mesh first
• clean/check 2D aspect issues
• tetramesh per component/object
• check and locally repair/report volume quality

Drag Hex

Use guarded drag only for simple straight extrusions or tubes with constant section.

Preconditions:

• a real source face exists at one end of the extrusion
• corresponding logical edge groups are forced to matched seed counts
• the source face meshes as 100% quads

Pass solid_id when possible. The generator then validates that the generated hex8 mesh bounding box fits the target solid. If the drag result is missing, non-hex, or poorly fitted, it deletes invalid elements, retries once with the same element size, and then falls back to tetra when fallback_to_tetra is enabled.

Seed policy: if inner/outer preview counts or edge lengths differ greatly, pass preview_edge_seed_counts or source_edge_lengths. When the largest/smallest ratio is at least seed_balance_ratio_threshold (default 1.6), the generator uses a balanced common count instead of forcing all source edges up to the largest outer count.

Do not write naked Tcl with *set_meshedgeparams and *meshdragelements* for drag workflows. The execution tools block that path by default. Use generate_guarded_drag_hex_tcl; otherwise the balanced seed policy cannot be applied.

Spin Hex

Use guarded spin only when the selected source surface is already known to be a true cross-section of a clean revolved solid.

Preconditions:

• source section is a real cross-section
• source section meshes as 100% quads
• spin result contains hex elements only

Pass solid_id when possible so the generated mesh can be checked against the target solid. Failed fit/non-hex results are cleaned, retried once with the same element size, then sent to tetra fallback when enabled.

If the solid is stepped, recessed, grooved, or the source section is ambiguous, use cut-section spin instead.

Cut-Section Spin Hex

Use generate_cutsection_spin_hex_tcl for stepped/recessed/ambiguous revolved solids.

Workflow:

1. Split the actual solid with *body_splitmerge_with_plane using a middle plane.
2. Detect newly created surfaces from the split.
3. Temporarily mesh each new surface.
4. Accept only all-quad surfaces whose shell nodes lie on the split plane.
5. Spin the accepted 2D section shells into 3D hex elements.
6. Delete only the temporary 2D seed shells.

Required inputs:

• solid_id
• component_name
• split plane normal and point
• spin axis and a point on the spin axis; this is required and must be on the real rotation axis, not merely any point on the split plane
• element size and spin density

The split plane must contain the spin axis. In practical terms, the split plane normal should be nearly perpendicular to the spin axis. If the cut plane is perpendicular to the axis and creates an annular transverse section, that is a drag-style source section for a constant-section body, not a spin section.

The generator validates the spin result. If no valid 3D hex8 elements are created, it deletes temporary section/invalid elements and retries once with the same requested element size. It does not shrink/refine the hex mesh for the retry. If the second attempt still fails, it falls back to tetra when fallback_to_tetra is enabled.

The cut-section generator also considers existing section surfaces on the target solid after a split. This helps when a model has already been split or when HyperMesh does not create new surface IDs. If mapped quads fail, it can try a quad-only section mesh mode with the same element size before falling back.

Gear-Aware Tetra

Use classify_hypermesh_part_strategy from geometry facts only. Do not classify gear regions from component names, file names, or natural-language labels. Set one or more of these when geometry inspection shows a gear-like region: has_gear_teeth, has_helical_teeth, has_twisted_tooth_faces, has_many_repeated_radial_teeth, has_periodic_outer_radius_variation, has_outer_tooth_band, has_repeated_tooth_flanks, tooth_count, or outer_radius_variation_ratio.

Negative bearing/ring evidence wins over gear hints. If the part is a smooth concentric ring, bearing race, or annular-groove-only body, set is_smooth_concentric_ring, has_bearing_race_grooves, or has_annular_grooves_only; the classifier must not treat it as a gear.

As a last-resort workflow aid, callers may set name_hint_indicates_gear=True when the user has intentionally named a part as gear. This hint only asks the MCP to inspect/refine possible tooth geometry; it does not replace geometry checks, and it is still overridden by bearing/ring evidence.

Then use generate_gear_aware_tetra_tcl:

• pass solid_id and component_name
• pass base_element_size for shaft/hub surfaces
• pass gear_surface_ids for repeated tooth, flank, and root surfaces
• optionally pass gear_element_size; otherwise it uses base_element_size * gear_size_factor
• pass gear_axis (x, y, or z) so automatic tooth-band detection uses the correct shaft axis

If gear_surface_ids are not supplied, the script auto-detects the outer gear band from surface radii using gear_outer_band_fraction and meshes that band finer. This is meant to catch helical gears where tooth surfaces are oblique/twisted rather than simple radial faces. If auto-detection finds nothing, it falls back to uniform base-size tetra.

For automatic detection, prefer passing geometry_confirms_gear_teeth=True only after geometry inspection sees tooth peaks/roots, repeated flanks, or twisted helical tooth faces. If only the last-resort name hint is available, pass name_hint_indicates_gear=True; the script will run cautious outer-band detection, but this should not be used for bearing/ring geometry.

The intended behavior is local refinement only: tooth, flank, root, or detected outer gear-band faces use gear_element_size; shaft, bore, hub, and non-tooth faces keep base_element_size.

Do not run a raw uniform *defaultmeshsurf_growth + *tetmesh script for a part whose geometry inspection indicates gear features. The execution tools block raw tetra/surface-growth meshing by default; use generate_gear_aware_tetra_tcl for gear-like geometry so the local tooth-band refinement rule is applied.

Known Limitations

• Some bearing/ring solids still fall back to tetra even though a human can see they should be sweepable by cutting a radial section and spinning it. The current generate_cutsection_spin_hex_tcl requires HyperMesh to expose a usable all-quad true section after *body_splitmerge_with_plane; on some recessed bearing geometry it only produces invalid/non-quad sections, so the guarded workflow correctly falls back to tetra. Future work: add a more robust profile extraction path that derives ordered radial profile loops from solid edges instead of relying only on newly split surfaces.

Quality Policy

Do not blindly refine the whole mesh to fix quality.

Preferred order:

1. Change strategy if the topology is wrong.
2. Try local 3D smooth/remesh.
3. Try sliver repair where applicable.
4. If bad volume elements remain, keep them and report their IDs.

Do not automatically delete unfixable quality-failed volume elements unless the user explicitly asks.

Configuration Example

{
  "mcpServers": {
    "hypermesh": {
      "command": "python",
      "args": ["F:\\mcp\\hypermesh_mcp_server.py"],
      "env": {
        "HYPERMESH_BATCH_EXE": "F:\\Program Files\\Altair\\2020\\hwdesktop\\hw\\bin\\win64\\hmbatch.exe",
        "HYPERMESH_GUI_EXE": "F:\\Program Files\\Altair\\2020\\hwdesktop\\hw\\bin\\win64\\hw.exe"
      }
    }
  }
}

Adjust paths for your workstation.