Storey plans

BuildImport pre-bakes one StoreyPlan per IfcBuildingStorey, so a renderable floor plan comes out of the import with no second pass over the geometry.

m, err := ifc.BuildImport(f)
if err != nil {
    panic(err)
}
for _, plan := range m.StoreyPlans {
    fmt.Printf("storey %s at %.2f m — %d entities\n",
        plan.StoreyGlobalID, plan.Elevation, len(plan.Entities))

    for _, ent := range plan.Entities {
        for _, loop := range ent.Loops {
            _ = ent.GlobalID // your own domain object id
            _ = ent.IFCClass // "IfcWall", "IfcDoor", ...
            _ = loop.Role    // LoopCut (poché) or LoopSilhouette (context)
            _ = loop.Points  // [][2]float64, world XY metres
        }
    }
}

Each StoreyPlan carries its storey's GlobalID, an Elevation, and the StoreyEntity values that draw on it. Loops are the same geometry.Loop described in sections and floor plans — same roles, same winding, same hole convention.

The rest of this page is the part godoc cannot tell you: where the cut height comes from, and which storeys silently produce nothing.

The cut height

Each storey is cut at floorZ + 1.2 m, the architectural convention for a plan cut: above the door handles, below the window heads.

floorZ is seeded from the minimum world Z of the mesh elements spatially contained in that storey. Seeded, not decided — spatial containment picks the band, and then geometry decides membership. An element assigned to storey 2 in the IFC hierarchy but physically sitting on storey 1 draws where it actually is. This matters on real exports, where containment is frequently wrong.

Storeys that get skipped

A storey with no contained mesh element is omitted from StoreyPlans entirely — there is no reliable way to place its cut plane, so it produces no plan rather than an empty or arbitrarily-placed one.

Do not assume len(m.StoreyPlans) equals the number of IfcBuildingStorey nodes in the tree. Iterate the plans, or join back on StoreyGlobalID.

Elevation comes from the storey's own IfcBuildingStorey elevation attribute and is 0 when absent — it is for ordering the storeys in a UI, not for positioning geometry. The geometry is already in world coordinates.

Determinism

Identical input yields an identical slice — same storeys, same order, same entities, same loops. You can golden-diff storey plans across releases and a change in the output means a change in behaviour.