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Dion Moult
e1be2f208c
Makes large-model streaming over a network actually good — fixing read
amplification, then first-paint latency — building on the byte-range work.
v14 layout + TOC (SidecarLayout, pure + unit-tested)
The loader chunks meshes by spatial Morton order, but the sidecar stored
geometry in mesh-id order, so a chunk's meshes were scattered through the
file: streaming one chunk meant either hundreds of tiny range requests or
reading (and discarding) everything between them — a 113 MB model fetched
~340 MB, a 531 MB model 2.25 GB (4.2x). Fix: at bake, reorder meshes into
the loader's chunk order and rebuild vertex/index(LOD0+LOD1)/instance
sections so each chunk is one CONTIGUOUS byte range, and bake a chunk TOC
({first_mesh, mesh_count}). The loader builds chunks straight from the TOC
rather than re-deriving the plan — the float Morton quantisation isn't
bit-identical across toolchains (x86 baker vs wasm loader), so a re-derived
plan scatters the chunks. Format bumped to v14 (regenerate sidecars). The
reorder buckets instances by per-instance mesh_id (the baker never sets
MeshInfo.first_instance — trusting it scrambled every transform → geometry
at the origin). Multiset-verified on a 28,900-instance model: every
instance's placement + geometry preserved. Result: 531 MB fetches 531 MB
(1.0x) in 72 requests (was 2036).
Progressive streaming (concurrency cap + small chunks)
Even at 1x, geometry appeared only after ~the whole model arrived: the
browser multiplexes every in-flight Range request over one HTTP/2 conn, so
unbounded concurrency (9 in flight) split the bandwidth and nothing finished
until the end (measured: first paint after 113 of 118 MB / 35 s @ 24 Mbps).
Cap concurrent chunk loads (kMaxWebInflightChunks=2): the priority-sorted
top chunks finish and paint first, then the next → first paint 9 s. Chunk
size dropped 16->4 MB (cheap now that each chunk is one read; matches Cesium
3D Tiles / xeokit / SVF2) for smoother progression. First-paint is now
metadata-bound (~10 MB tail) — the next lever.
111/111 unit (new test_sidecar_layout: geometry preserved, contiguous layout,
Morton-identity) + 6/6 web smoke pass; desktop bake (SceneLoader) reorders
before writeSidecar; embedded web sample regenerated to v14.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
IfcOpenShell
IfcOpenShell is an open source (LGPL) software library for working with Industry Foundation Classes (IFC). Complete parsing support is provided for IFC2x3 TC1, IFC4 Add2 TC1, IFC4x1, IFC4x2, and IFC4x3 Add2. Extensive geometric support is implemented for the IFC releases IFC2x3 TC1 and IFC4 Add2 TC1. Extending with support for arbitrary IFC schemas is possible at compile-time when using C++ and at run-time when using Python.
In addition to a C++ and Python API, IfcOpenShell comes with an ecosystem of tools, notably including IfcConvert (an application to convert IFC models to other formats), Bonsai (an add-on to Blender providing a graphical IFC authoring platform), and many other libraries, CLI apps, and more. Support is also provided for auxiliary standards such as BCF and IDS.
For more information, see:
Development is sponsored through your generous donations!
Contents
| Name | Description | License | Service |
|---|---|---|---|
| bcf | Library to read and write BCF-XML and query OpenCDE BCF-API modules | LGPL-3.0-or-later |   |
| bonsai | Add-on to Blender providing a graphical native IFC authoring platform | GPL-3.0-or-later |    |
| bsdd | Library to query the bSDD API | LGPL-3.0-or-later |  |
| ifc2ca | Utility to convert IFC structural analysis models to Code_Aster | LGPL-3.0-or-later | |
| ifc4d | Convert to and from IFC and project management software | LGPL-3.0-or-later |  |
| ifc5d | Report and optimise cost information from IFC | LGPL-3.0-or-later |  |
| ifcbimtester | Wrapper for Gherkin based unit testing for IFC models | LGPL-3.0-or-later | |
| ifcblender | Historic Blender IFC import add-on | LGPL-3.0-or-later* | |
| ifccityjson | Convert CityJSON to IFC | LGPL-3.0-or-later |  |
| ifcclash | Clash detection library and CLI app | LGPL-3.0-or-later |  |
| ifcconvert | CLI app to convert IFC to many other formats | LGPL-3.0-or-later* |   |
| ifccsv | Library and CLI app to export and import schedules from IFC | LGPL-3.0-or-later |  |
| ifcdiff | Compare changes between IFC models | LGPL-3.0-or-later |  |
| ifcedit | CLI wrapper for ifcopenshell.api IFC model mutation functions | LGPL-3.0-or-later |  |
| ifcfm | Extract IFC data for FM handover requirements | LGPL-3.0-or-later |  |
| ifcmax | Historic extension for IFC support in 3DS Max | LGPL-3.0-or-later* | |
| ifcmcp | MCP server for querying and editing IFC building models | LGPL-3.0-or-later |  |
| ifcopenshell-python | Python library for IFC manipulation | LGPL-3.0-or-later* |         |
| ifcpatch | Utility to run pre-packaged scripts to manipulate IFCs | LGPL-3.0-or-later |  |
| ifcquery | CLI tool for querying and inspecting IFC building models | LGPL-3.0-or-later |  |
| ifcsverchok | Blender Add-on for visual node programming with IFC | GPL-3.0-or-later |  |
| ifctester | Library, CLI and webapp for IDS model auditing | LGPL-3.0-or-later |  |
The IfcOpenShell C++ codebase is split into multiple interal libraries:
| Name | Description | License |
|---|---|---|
| ifcgeom | Internal library for IfcOpenShell | LGPL-3.0-or-later* |
| ifcgeom_schema_agnostic | Internal library for IfcOpenShell | LGPL-3.0-or-later* |
| ifcgeomserver | Internal library for IfcOpenShell | LGPL-3.0-or-later* |
| ifcjni | Internal library for IfcOpenShell | LGPL-3.0-or-later* |
| ifcparse | Internal library for IfcOpenShell | LGPL-3.0-or-later* |
| ifcwrap | Internal library for IfcOpenShell | LGPL-3.0-or-later* |
| qtviewer | Internal library for IfcOpenShell | LGPL-3.0-or-later* |
| serializers | Internal library for IfcOpenShell | LGPL-3.0-or-later* |