EN docs assembly mass

Revision-bound assembly mass and inertia

Полный русский перевод

Русский обзор · English reference

Русский обзор

Масса и инерция сборки

Документ v11 ввёл явные материалы, граф сборки v3 сохраняется в текущем v12. set_assembly_part_material принимает название, положительную плотность в кг/м³ и источник либо null. cadyx_measure_assembly_mass_properties рассчитывает массу, центр масс и тензор инерции по подходящим OCCT B-rep с привязкой к ревизии. Единицы результата — кг, мм и кг·мм². Массы экземпляров суммируются, пересечения автоматически не вычитаются. Неизвестная плотность, сеточная геометрия и устаревшая ревизия вызывают явную ошибку.

Это обзор, не полный перевод. Полные схемы, примеры и подробности контракта приведены на английском ниже.

English reference

Persisted schema

Document v11 introduced assembly v2 → v3 material fields; the current document schema is v12 and continues to use assembly graph v3. Each part definition has a material field which is either null (not assigned, the migration default) or exactly:

{"name":"Declared alloy","density_kg_m3":2700,"source":"Supplier material specification"}

name and source are mandatory nonblank strings (up to 256 characters). Density is a positive, finite number at most 1e9 kg/m³. It is an explicitly supplied nominal density, not a lookup, default, measured property or manufacturing certification. Previous v10 part records upgrade to material:null on isolated document reads; a read alone never rewrites data. The v10→v11 document migration preserves part, instance, mate and body IDs.

Use the ordinary revision- and lease-protected Command System: {"type":"set_assembly_part_material","part_id":"part:...","material":{...}}. Pass null to clear a material. The material belongs to the source part, so every reused instance receives the same source material. The browser stays read-only; commands animate through the ordinary Core activity path.

Read-only calculation contract

POST /api/v1/agent/projects/{id}/validations/mass-properties uses {"expected_revision":<saved document revision>,"persist":false}. Equivalent MCP tool: cadyx_measure_assembly_mass_properties. No edit lease is needed. persist:true records the report in the existing project-local validation sidecar without changing the document revision.

The response provides:

• status:"pass", revision, geometry_sha256 over saved assembly graph, materials and referenced body descriptors, method and explicit units;
• parts[]: distinct source part IDs, original body IDs, material+provenance, exact volume in mm³, mass in kg, local COM in mm, and symmetric 3×3 center-of-mass inertia in kg·mm²;
• instances[]: flattened nested leaf path, source ID, global translation and quaternion, world COM and rotated 3×3 inertia at its own COM;
• assembly: sum of placed instance mass, mass-weighted world COM, central inertia via the parallel-axis theorem, and leaf count.

Only valid closed, single-solid OCCT B-reps are authoritative production geometry; the existing native cadyx_brep_metrics integrates BRepGProp::VolumeProperties once per distinct source part at unit density and now returns centroid and full inertia matrix alongside its prior volume field. The bridge must be rebuilt on Windows before use. For a supplied density (\rho) in kg/m³ and a geometric volume (V) in mm³, (m=\rho V 10^{-9}) kg; the same factor converts the native mm⁵ inertia integral to kg·mm². All placements are in explicitly declared assembly mm, and quaternion transforms rotate tensors rather than copy solids.

Unknown material density or provenance, unsupported graph/units, mesh-only source, invalid native physical properties, or stale revision raises an explicit error instead of returning fabricated mass. The current contract supports up to 128 distinct source parts and 256 flattened leaf instances; empty/unplaced assemblies do not yield an aggregate report. Aggregates are additive: if parts overlap, overlapping volume is counted once for each physical instance, not Boolean-unioned or automatically subtracted. There is no physical tolerance stack, stiffness, contact stress, interference clearance or continuous-motion certificate. Use separate assembly-fit validation for collision checks.

Regression fixtures in tests/test_assembly_mass.py cover cuboid moments, centroid shifts, rotation, repeated instances, unknown density, invalid inputs, migration and stale-revision behavior using a native-free analytic primitive fixture. They are checked into source but intentionally not executed locally; authoritative OCCT/Windows checks remain CI work.