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Dion Moult
51dc31a50b
Closes the perf gap to the GL backend on real BIM benchmarks. On a 10-
sidecar / 380k-instance corpus at a fixed --camera the wgpu binary went
from 110.6 ms to 11.6 ms (vs GL's 23 ms — half the frame time, but
note GL is doing extra work the wgpu backend hasn't ported yet; see
the caveats list at the bottom). Bundled because the pieces interlock
and shipping any of them without the others reintroduces the same wall.
1. Cross-mesh vertex pulling (single mega-draw per model)
The previous one-drawIndexed-per-(mesh × LOD-bucket) loop was costing
~13ms on a 27k-mesh scene. CPU now emits a flat visible_draws[]
(16 B per visible (mesh,lod,instance)) plus a prefix_sums[] table.
WGSL binary-searches prefix_sums by @builtin(vertex_index) to find
the entry, then manually fetches the mesh-local index from a
storage-bound indices[] and pulls the packed 12 B vertex. No
setIndexBuffer; the shader reads everything from storage. Bind
group grew from 4 to 7 entries (vertices, meshes, instances,
indices, visible_draws, prefix_sums, per-model uniform) — well
under WebGPU's mandatory 8 storage / 12 uniform floor.
2. Async HiZ readback via ping-pong staging buffers
Sync wait via wgpuInstanceProcessEvents was costing ~37 ms on a
real scene (GPU drain). Two staging slots now ping-pong: frame N
kicks a non-blocking mapAsync on slot K, frame N+1's first action
is one processEvents drain. Pyramid is 1-2 frames stale — matches
the "slightly-stale depth, fine" pattern the GL backend already
documents. encodeHizResolve returns -1 (skip) if both slots are
in flight; cull keeps using the most recent pyramid.
3. Cull reorder: contribution before HiZ
HiZ projection is ~10× more expensive than the contribution
check, yet most contribution-survivors would be HiZ-rejected
anyway on dense scenes. Computing projected_px first lets
contribution short-circuit ~80% of HiZ tests with no rejection-
quality loss. Saved ~34 ms on the dense bench.
4. Motion-mode contribution threshold
AppSettings::motionMinPixelRadius parity. While the camera is
changing (orbit/pan/zoom/--benchmark sweep), drop instances
below 10 px instead of 2 px. Halves visible_objects during
motion with no perceived quality loss.
5. Parallel cull (std::async across models)
Per-model cullModelCpu split into Compute (CPU-only, thread-safe)
+ Upload (main-thread wgpu queue writes). std::async fan-outs the
compute across models; main-thread joins and uploads. Wall-clock
cull on the 10-model corpus drops from ~17 ms single-threaded to
~9 ms across cores.
6. --no-hiz CLI flag + per-phase benchmark timings
Benchmark now also prints "per-frame avg ms: cull=X
hiz_readback=Y" so future regressions can be attributed without
guesswork. --no-hiz toggles the master switch from the CLI.
Honest caveats — wgpu is currently faster mostly because GL is doing
work we haven't ported yet:
- Edge silhouette pass (stage 9) will add ~3-5 ms back to wgpu.
- GL's HiZ uses the BVH so it rejects whole subtrees (1.7k vs
our 358 rejects on the same scene). BVH for HiZ is future work
(task #13 / a new task) — until then we draw more sub-pixel
geometry that's behind closer surfaces. Visually correct, perf
cost paid. Stage 4+5 are unaffected.
Verified pixel-identical on basic.ifc through every change. Real-scene
visual diff against GL pending the --screenshot flag on the GL minimal
(task #10's other half).
Co-Authored-By: Claude Opus 4.7 <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* |