Function build_geometry_data_export 

pub fn build_geometry_data_export(
    meshes: &[MeshData],
    rtc_offset: [f64; 3],
    site_rotation: Option<&[f64]>,
) -> GeometryDataExport

Build the geometry-data export from a processed model’s meshes.

rtc_offset is ProcessingResult.metadata.coordinate_info.origin_shift.

site_rotation is the IfcSite placement (column-major 4x4) only when the model was processed into the site_local coordinate space — there the pipeline inverse-rotates positions + origin into site-local axes, so to emit true IFC world coordinates we reapply the forward 3x3 rotation: world = R * (position + origin) + rtc_offset. Pass None for the model_rtc / raw_ifc spaces (R = identity), which is the common case.