Module mesh 

Mesh data structures

Structs

InstanceMeta

Side-channel instancing metadata, attached only when GPU instancing is enabled (the IFC_LITE_INSTANCING flag). NEVER read by geometry processing and excluded from compute_mesh_hash / meshes_equal, so content-dedup and the default flat path are unaffected. The native helper collates occurrences into unique geometry + per-instance transforms. Reconstruction contract: world = (transform . local_transform) * canonical_local_vertex - rtc_offset.

Mesh

Triangle mesh

PlaneTag

The kernel’s f64 supporting plane for one output triangle, carried forward from kernel::mesh_bridge::tris_to_mesh (issue #3914). consolidate_coplanar buckets triangles into coplanar groups by re-deriving a plane from each triangle’s f32-ROUNDED vertices; on a rotated/tilted face this can straddle the bucket’s quantization boundary and split one physical plane into two adjacent buckets that its cross-bucket seam-conform pass (tangential-only) cannot stitch back together, tearing the mesh. The kernel already computes each output triangle’s plane in f64, BEFORE that f32 cast — carrying it forward gives consolidate_coplanar the same plane identity for both triangles without inventing a new tolerance or clustering pass.

SubMesh

A sub-mesh with its source geometry item ID. Used to track which geometry items contribute to an element’s mesh, allowing per-item color/style lookup.

SubMeshCollection

Collection of sub-meshes from an element, preserving per-item identity