BIM + IoT: your building as a 3D digital twin

BIM (Building Information Modeling) is the 3D and semantic modelling of a building, standard in construction for 15 years. The pivotal format is IFC (Industry Foundation Classes), maintained by buildingSMART.

Connecting your BIM to your IoT creates a digital twin: the 3D model stays static, IoT sensors inject the real-time state. You see where your sensors are in space, you see their values overlaid, you understand alarms in spatial context. SensIa does this plug-and-play from your IFC without an intermediary.

The import workflow is entirely client-side — not a byte of IFC transits through our backend.

1. You upload your IFC from the building inventory
2. Web Worker parsing via @thatopen/fragments::IfcImporter, WASM served locally
3. IFC → .frag conversion (lightweight Fragments format, ~10× smaller)
4. Direct browser → MinIO upload via 15-min presigned URLs
5. Automatic Floor/Room spatial typology generation from IFCBUILDINGSTOREY and IFCSPACE
6. Backend persists lightweight attributes (fragments_url, ifc_last_imported_at) on the building

Once the BIM is imported, the 3D viewer opens in the IoT inventory. Your unlocated sensors appear in a side panel. You drag-and-drop each sensor onto the right room in the 3D model — SensIa resolves the ifc_global_id of the targeted IFCSPACE and persists the attachment.

The sensor now appears at its 3D position in every view (map, supervision, BIM 3D). For 100 sensors, plan 15 to 30 minutes of placement.

.frag files range from 5 to 50 MB depending on building size. Systematic reloads would be slow. SensIa implements a multi-tier cache:

• L1 memory: LRU 3 models, ~150 MB max
• L2 persistent IndexedDB: 500 MB max

Re-opening after F5, building switch or session return is instant. Invalidation goes through the ifc_last_imported_at attribute — re-importing an updated IFC properly invalidates the cache, zero stale.

The 3D BIM integrates into the SensIa supervision canvas. You navigate Site → Building → Floor → Room via a clickable breadcrumb.

At each level you see the current sub-tree (auto-computed KPIs: sensor count, % online, active alerts), direct children (cards or compact table), and scoped analytics sections (measurements, fleet health, alarms, trends). The URL is shareable — ?path=site:UUID/building:UUID/floor:UUID sends a colleague directly to your visualisation level.

BIM models are stored on MinIO with a forced org-{org_id}/ prefix — no cross-tenant leak possible. The bim_models table is FORCE Row Level Security, each organisation only sees its buildings.

The audit log traces every IFC import and every sensor placement modification. GDPR-compliant: BIM models may contain confidential architectural plans, the confidentiality chain is honoured all the way to at-rest encrypted storage.