OpenUSD model pack specification

This document defines the OpenUSD model pack: the single .usdc file that represents one MDCX product model — or one partner unit such as a chiller, BESS or switchgear — in the CIOS digital twin, in design coordination and in public downloads. The same rules apply to MDCX exports and to supplier deliveries; there is no separate "marketing" USD format.

Status: v1.0 · 2026-09-22 · Supersedes the public draft v0.1 of 2026-08-10 (Y-up, /MDCX/<SKU_ID> root, LOD tiers — all withdrawn). Every public download listed in §11 is byte-identical to the pack the CIOS twin loads.

1. What a model pack is

• One model = one self-contained .usdc file (USD binary crate). No sublayers, no external references, no texture files beside it. If a look needs image textures, use plain material colors — the twin is a monitoring view, not a render.
• File name = <ALIAS>.usdc, where <ALIAS> is the short model alias from the product matrix (e.g. L1240C45.usdc). The full SKU ID is for display, not for file names.
• The pack is loaded read-only and instantiated many times per site. It shows one unit at true scale — nothing else: no room, floor, sky, people or neighbouring equipment.
• A component manifest (spreadsheet or PDF) accompanies every supplier delivery: one row per named component and per sensor marker, mapped to the physical part or datasheet measuring point.

2. Identity binding

3. Stage settings (required)

Stage customLayerData must carry four keys:

4. Prim hierarchy (required)

/root                 Xform, default prim — cios:type, cios:model
├── geo/              all visible geometry
│   ├── rack000/      one group per functional component (§5)
│   │   └── rdhx000/  nesting mirrors physical parentage
│   └── frame/        enclosure, doors, cable dressing, labels
├── sen/              sensor location markers (§6); may be empty
└── _materials        materials (Scope)

No meshes directly under /root, and no other direct children of /root.

5. Naming (required)

• Charset: every prim under geo/ and sen/ — frame/ included — matches [a-z0-9]+: lowercase letters and digits only. No underscores, spaces, capitals, non-ASCII or tool-generated duplicate suffixes (.001, _001). Material and shader prims under _materials may use _ but must be lowercase.
• Functional components use the CIOS type vocabulary plus a 3-digit index from 000 (chip-level items use a natural index, e.g. gpu0). Components relevant to container models: rack tank node cdu rdhx manifold ceilair ups pdu pdc busbar tou ats valve pump fan switch. Supplier units: chiller drycooler compressor watermeter bess battery cell pcs switchgear breaker transformer meter genset.
• Dressing (panels, brackets, piping runs, doors) goes inside the owning component's group or under geo/frame/. Name it by role with the owner as prefix (battery000body, ceilair002label). Two traps: never a vendor product designation as a prim name (EATON_93Li, CRAH3), and never a plain letters-then-digits name (cube019) — it reads as a component and is rejected.
• Never invent vocabulary. If a category is missing, flag it in the manifest; MDCX extends the vocabulary through its own controlled process.

6. Attributes and sensor markers

• /root carries cios:type and cios:model; each functional component carries cios:type.
• Each measuring point (temperature, pressure, flow, level, gas) gets a small locator prim under sen/, named mon000, mon001, … — not sensor000, which is a component name and illegal under sen/. Marker meshes follow the same charset (mon026base).
• Markers are bound to live telemetry through cios:relpath, written at intake. Live values (cios:tlm:*, cios:unit:*) are written by the twin at runtime — packs must not pre-bake them, and no other cios: attribute may be invented.

7. Materials and colours

Colours in a pack describe the physical appearance of the unit only; status, temperature and alarm visuals are added by the twin at runtime and are never baked into a pack.

8. Not allowed

Deliveries are rejected if they contain any of:

1. Lights or cameras.
2. Animation, time samples, rigs, physics or audio.
3. Surroundings — rooms, floors, ground planes, neighbouring units (the unit's own enclosure belongs in geo/frame/).
4. External file dependencies, including asset paths such as ./textures/*.png.
5. Any transform on /root.
6. Pre-baked telemetry values or invented cios: attributes.

9. Size budget

File ≤ 50 MB · ≤ 500 k triangles · ≤ 64 materials · ≤ 5 000 prims. Budgets are warnings, not hard failures; exceeding one needs a written reason. Target detail: recognisable at 2 m, not photorealistic close-up. Decimate CAD tessellation and drop fasteners and hidden internals.

10. Conformance check

Every pack passes an automated check before it is accepted or published: stage settings (§3), hierarchy (§4), naming and vocabulary (§5), attributes and markers (§6), materials (§7), prohibitions (§8) and budgets (§9, warning). A manual self-containment check and a visual review of scale, origin and orientation follow. Before sending a file, open it in NVIDIA USD Composer or any USD viewer and confirm it sits on the ground plane at the origin, faces +X, and measures correctly.

Web presentation is separate from the pack: product pages show a poster first and load web 3D (glTF) only on request. The USD pack is always an explicit download, never fetched on page load.

11. Public downloads

Each download is a .zip containing exactly one <ALIAS>.usdc, byte-identical to the pack used by the CIOS twin.

Multi-container arrangements are not model packs; they are built by placing packs in a site layout.

12. Changelog